| /* |
| * linux/fs/buffer.c |
| * |
| * Copyright (C) 1991, 1992, 2002 Linus Torvalds |
| */ |
| |
| /* |
| * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95 |
| * |
| * Removed a lot of unnecessary code and simplified things now that |
| * the buffer cache isn't our primary cache - Andrew Tridgell 12/96 |
| * |
| * Speed up hash, lru, and free list operations. Use gfp() for allocating |
| * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM |
| * |
| * Added 32k buffer block sizes - these are required older ARM systems. - RMK |
| * |
| * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de> |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/syscalls.h> |
| #include <linux/fs.h> |
| #include <linux/mm.h> |
| #include <linux/percpu.h> |
| #include <linux/slab.h> |
| #include <linux/capability.h> |
| #include <linux/blkdev.h> |
| #include <linux/file.h> |
| #include <linux/quotaops.h> |
| #include <linux/highmem.h> |
| #include <linux/export.h> |
| #include <linux/writeback.h> |
| #include <linux/hash.h> |
| #include <linux/suspend.h> |
| #include <linux/buffer_head.h> |
| #include <linux/task_io_accounting_ops.h> |
| #include <linux/bio.h> |
| #include <linux/notifier.h> |
| #include <linux/cpu.h> |
| #include <linux/bitops.h> |
| #include <linux/mpage.h> |
| #include <linux/bit_spinlock.h> |
| |
| static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); |
| |
| #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) |
| |
| inline void |
| init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private) |
| { |
| bh->b_end_io = handler; |
| bh->b_private = private; |
| } |
| EXPORT_SYMBOL(init_buffer); |
| |
| static int sleep_on_buffer(void *word) |
| { |
| io_schedule(); |
| return 0; |
| } |
| |
| void __lock_buffer(struct buffer_head *bh) |
| { |
| wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer, |
| TASK_UNINTERRUPTIBLE); |
| } |
| EXPORT_SYMBOL(__lock_buffer); |
| |
| void unlock_buffer(struct buffer_head *bh) |
| { |
| clear_bit_unlock(BH_Lock, &bh->b_state); |
| smp_mb__after_clear_bit(); |
| wake_up_bit(&bh->b_state, BH_Lock); |
| } |
| EXPORT_SYMBOL(unlock_buffer); |
| |
| /* |
| * Block until a buffer comes unlocked. This doesn't stop it |
| * from becoming locked again - you have to lock it yourself |
| * if you want to preserve its state. |
| */ |
| void __wait_on_buffer(struct buffer_head * bh) |
| { |
| wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE); |
| } |
| EXPORT_SYMBOL(__wait_on_buffer); |
| |
| static void |
| __clear_page_buffers(struct page *page) |
| { |
| ClearPagePrivate(page); |
| set_page_private(page, 0); |
| page_cache_release(page); |
| } |
| |
| |
| static int quiet_error(struct buffer_head *bh) |
| { |
| if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) |
| return 0; |
| return 1; |
| } |
| |
| |
| static void buffer_io_error(struct buffer_head *bh) |
| { |
| char b[BDEVNAME_SIZE]; |
| printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", |
| bdevname(bh->b_bdev, b), |
| (unsigned long long)bh->b_blocknr); |
| } |
| |
| /* |
| * End-of-IO handler helper function which does not touch the bh after |
| * unlocking it. |
| * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but |
| * a race there is benign: unlock_buffer() only use the bh's address for |
| * hashing after unlocking the buffer, so it doesn't actually touch the bh |
| * itself. |
| */ |
| static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) |
| { |
| if (uptodate) { |
| set_buffer_uptodate(bh); |
| } else { |
| /* This happens, due to failed READA attempts. */ |
| clear_buffer_uptodate(bh); |
| } |
| unlock_buffer(bh); |
| } |
| |
| /* |
| * Default synchronous end-of-IO handler.. Just mark it up-to-date and |
| * unlock the buffer. This is what ll_rw_block uses too. |
| */ |
| void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
| { |
| __end_buffer_read_notouch(bh, uptodate); |
| put_bh(bh); |
| } |
| EXPORT_SYMBOL(end_buffer_read_sync); |
| |
| void end_buffer_write_sync(struct buffer_head *bh, int uptodate) |
| { |
| char b[BDEVNAME_SIZE]; |
| |
| if (uptodate) { |
| set_buffer_uptodate(bh); |
| } else { |
| if (!quiet_error(bh)) { |
| buffer_io_error(bh); |
| printk(KERN_WARNING "lost page write due to " |
| "I/O error on %s\n", |
| bdevname(bh->b_bdev, b)); |
| } |
| set_buffer_write_io_error(bh); |
| clear_buffer_uptodate(bh); |
| } |
| unlock_buffer(bh); |
| put_bh(bh); |
| } |
| EXPORT_SYMBOL(end_buffer_write_sync); |
| |
| /* |
| * Various filesystems appear to want __find_get_block to be non-blocking. |
| * But it's the page lock which protects the buffers. To get around this, |
| * we get exclusion from try_to_free_buffers with the blockdev mapping's |
| * private_lock. |
| * |
| * Hack idea: for the blockdev mapping, i_bufferlist_lock contention |
| * may be quite high. This code could TryLock the page, and if that |
| * succeeds, there is no need to take private_lock. (But if |
| * private_lock is contended then so is mapping->tree_lock). |
| */ |
| static struct buffer_head * |
| __find_get_block_slow(struct block_device *bdev, sector_t block) |
| { |
| struct inode *bd_inode = bdev->bd_inode; |
| struct address_space *bd_mapping = bd_inode->i_mapping; |
| struct buffer_head *ret = NULL; |
| pgoff_t index; |
| struct buffer_head *bh; |
| struct buffer_head *head; |
| struct page *page; |
| int all_mapped = 1; |
| |
| index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); |
| page = find_get_page(bd_mapping, index); |
| if (!page) |
| goto out; |
| |
| spin_lock(&bd_mapping->private_lock); |
| if (!page_has_buffers(page)) |
| goto out_unlock; |
| head = page_buffers(page); |
| bh = head; |
| do { |
| if (!buffer_mapped(bh)) |
| all_mapped = 0; |
| else if (bh->b_blocknr == block) { |
| ret = bh; |
| get_bh(bh); |
| goto out_unlock; |
| } |
| bh = bh->b_this_page; |
| } while (bh != head); |
| |
| /* we might be here because some of the buffers on this page are |
| * not mapped. This is due to various races between |
| * file io on the block device and getblk. It gets dealt with |
| * elsewhere, don't buffer_error if we had some unmapped buffers |
| */ |
| if (all_mapped) { |
| char b[BDEVNAME_SIZE]; |
| |
| printk("__find_get_block_slow() failed. " |
| "block=%llu, b_blocknr=%llu\n", |
| (unsigned long long)block, |
| (unsigned long long)bh->b_blocknr); |
| printk("b_state=0x%08lx, b_size=%zu\n", |
| bh->b_state, bh->b_size); |
| printk("device %s blocksize: %d\n", bdevname(bdev, b), |
| 1 << bd_inode->i_blkbits); |
| } |
| out_unlock: |
| spin_unlock(&bd_mapping->private_lock); |
| page_cache_release(page); |
| out: |
| return ret; |
| } |
| |
| /* |
| * Kick the writeback threads then try to free up some ZONE_NORMAL memory. |
| */ |
| static void free_more_memory(void) |
| { |
| struct zone *zone; |
| int nid; |
| |
| wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM); |
| yield(); |
| |
| for_each_online_node(nid) { |
| (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), |
| gfp_zone(GFP_NOFS), NULL, |
| &zone); |
| if (zone) |
| try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, |
| GFP_NOFS, NULL); |
| } |
| } |
| |
| /* |
| * I/O completion handler for block_read_full_page() - pages |
| * which come unlocked at the end of I/O. |
| */ |
| static void end_buffer_async_read(struct buffer_head *bh, int uptodate) |
| { |
| unsigned long flags; |
| struct buffer_head *first; |
| struct buffer_head *tmp; |
| struct page *page; |
| int page_uptodate = 1; |
| |
| BUG_ON(!buffer_async_read(bh)); |
| |
| page = bh->b_page; |
| if (uptodate) { |
| set_buffer_uptodate(bh); |
| } else { |
| clear_buffer_uptodate(bh); |
| if (!quiet_error(bh)) |
| buffer_io_error(bh); |
| SetPageError(page); |
| } |
| |
| /* |
| * Be _very_ careful from here on. Bad things can happen if |
| * two buffer heads end IO at almost the same time and both |
| * decide that the page is now completely done. |
| */ |
| first = page_buffers(page); |
| local_irq_save(flags); |
| bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
| clear_buffer_async_read(bh); |
| unlock_buffer(bh); |
| tmp = bh; |
| do { |
| if (!buffer_uptodate(tmp)) |
| page_uptodate = 0; |
| if (buffer_async_read(tmp)) { |
| BUG_ON(!buffer_locked(tmp)); |
| goto still_busy; |
| } |
| tmp = tmp->b_this_page; |
| } while (tmp != bh); |
| bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| local_irq_restore(flags); |
| |
| /* |
| * If none of the buffers had errors and they are all |
| * uptodate then we can set the page uptodate. |
| */ |
| if (page_uptodate && !PageError(page)) |
| SetPageUptodate(page); |
| unlock_page(page); |
| return; |
| |
| still_busy: |
| bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| local_irq_restore(flags); |
| return; |
| } |
| |
| /* |
| * Completion handler for block_write_full_page() - pages which are unlocked |
| * during I/O, and which have PageWriteback cleared upon I/O completion. |
| */ |
| void end_buffer_async_write(struct buffer_head *bh, int uptodate) |
| { |
| char b[BDEVNAME_SIZE]; |
| unsigned long flags; |
| struct buffer_head *first; |
| struct buffer_head *tmp; |
| struct page *page; |
| |
| BUG_ON(!buffer_async_write(bh)); |
| |
| page = bh->b_page; |
| if (uptodate) { |
| set_buffer_uptodate(bh); |
| } else { |
| if (!quiet_error(bh)) { |
| buffer_io_error(bh); |
| printk(KERN_WARNING "lost page write due to " |
| "I/O error on %s\n", |
| bdevname(bh->b_bdev, b)); |
| } |
| set_bit(AS_EIO, &page->mapping->flags); |
| set_buffer_write_io_error(bh); |
| clear_buffer_uptodate(bh); |
| SetPageError(page); |
| } |
| |
| first = page_buffers(page); |
| local_irq_save(flags); |
| bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
| |
| clear_buffer_async_write(bh); |
| unlock_buffer(bh); |
| tmp = bh->b_this_page; |
| while (tmp != bh) { |
| if (buffer_async_write(tmp)) { |
| BUG_ON(!buffer_locked(tmp)); |
| goto still_busy; |
| } |
| tmp = tmp->b_this_page; |
| } |
| bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| local_irq_restore(flags); |
| end_page_writeback(page); |
| return; |
| |
| still_busy: |
| bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
| local_irq_restore(flags); |
| return; |
| } |
| EXPORT_SYMBOL(end_buffer_async_write); |
| |
| /* |
| * If a page's buffers are under async readin (end_buffer_async_read |
| * completion) then there is a possibility that another thread of |
| * control could lock one of the buffers after it has completed |
| * but while some of the other buffers have not completed. This |
| * locked buffer would confuse end_buffer_async_read() into not unlocking |
| * the page. So the absence of BH_Async_Read tells end_buffer_async_read() |
| * that this buffer is not under async I/O. |
| * |
| * The page comes unlocked when it has no locked buffer_async buffers |
| * left. |
| * |
| * PageLocked prevents anyone starting new async I/O reads any of |
| * the buffers. |
| * |
| * PageWriteback is used to prevent simultaneous writeout of the same |
| * page. |
| * |
| * PageLocked prevents anyone from starting writeback of a page which is |
| * under read I/O (PageWriteback is only ever set against a locked page). |
| */ |
| static void mark_buffer_async_read(struct buffer_head *bh) |
| { |
| bh->b_end_io = end_buffer_async_read; |
| set_buffer_async_read(bh); |
| } |
| |
| static void mark_buffer_async_write_endio(struct buffer_head *bh, |
| bh_end_io_t *handler) |
| { |
| bh->b_end_io = handler; |
| set_buffer_async_write(bh); |
| } |
| |
| void mark_buffer_async_write(struct buffer_head *bh) |
| { |
| mark_buffer_async_write_endio(bh, end_buffer_async_write); |
| } |
| EXPORT_SYMBOL(mark_buffer_async_write); |
| |
| |
| /* |
| * fs/buffer.c contains helper functions for buffer-backed address space's |
| * fsync functions. A common requirement for buffer-based filesystems is |
| * that certain data from the backing blockdev needs to be written out for |
| * a successful fsync(). For example, ext2 indirect blocks need to be |
| * written back and waited upon before fsync() returns. |
| * |
| * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), |
| * inode_has_buffers() and invalidate_inode_buffers() are provided for the |
| * management of a list of dependent buffers at ->i_mapping->private_list. |
| * |
| * Locking is a little subtle: try_to_free_buffers() will remove buffers |
| * from their controlling inode's queue when they are being freed. But |
| * try_to_free_buffers() will be operating against the *blockdev* mapping |
| * at the time, not against the S_ISREG file which depends on those buffers. |
| * So the locking for private_list is via the private_lock in the address_space |
| * which backs the buffers. Which is different from the address_space |
| * against which the buffers are listed. So for a particular address_space, |
| * mapping->private_lock does *not* protect mapping->private_list! In fact, |
| * mapping->private_list will always be protected by the backing blockdev's |
| * ->private_lock. |
| * |
| * Which introduces a requirement: all buffers on an address_space's |
| * ->private_list must be from the same address_space: the blockdev's. |
| * |
| * address_spaces which do not place buffers at ->private_list via these |
| * utility functions are free to use private_lock and private_list for |
| * whatever they want. The only requirement is that list_empty(private_list) |
| * be true at clear_inode() time. |
| * |
| * FIXME: clear_inode should not call invalidate_inode_buffers(). The |
| * filesystems should do that. invalidate_inode_buffers() should just go |
| * BUG_ON(!list_empty). |
| * |
| * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should |
| * take an address_space, not an inode. And it should be called |
| * mark_buffer_dirty_fsync() to clearly define why those buffers are being |
| * queued up. |
| * |
| * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the |
| * list if it is already on a list. Because if the buffer is on a list, |
| * it *must* already be on the right one. If not, the filesystem is being |
| * silly. This will save a ton of locking. But first we have to ensure |
| * that buffers are taken *off* the old inode's list when they are freed |
| * (presumably in truncate). That requires careful auditing of all |
| * filesystems (do it inside bforget()). It could also be done by bringing |
| * b_inode back. |
| */ |
| |
| /* |
| * The buffer's backing address_space's private_lock must be held |
| */ |
| static void __remove_assoc_queue(struct buffer_head *bh) |
| { |
| list_del_init(&bh->b_assoc_buffers); |
| WARN_ON(!bh->b_assoc_map); |
| if (buffer_write_io_error(bh)) |
| set_bit(AS_EIO, &bh->b_assoc_map->flags); |
| bh->b_assoc_map = NULL; |
| } |
| |
| int inode_has_buffers(struct inode *inode) |
| { |
| return !list_empty(&inode->i_data.private_list); |
| } |
| |
| /* |
| * osync is designed to support O_SYNC io. It waits synchronously for |
| * all already-submitted IO to complete, but does not queue any new |
| * writes to the disk. |
| * |
| * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as |
| * you dirty the buffers, and then use osync_inode_buffers to wait for |
| * completion. Any other dirty buffers which are not yet queued for |
| * write will not be flushed to disk by the osync. |
| */ |
| static int osync_buffers_list(spinlock_t *lock, struct list_head *list) |
| { |
| struct buffer_head *bh; |
| struct list_head *p; |
| int err = 0; |
| |
| spin_lock(lock); |
| repeat: |
| list_for_each_prev(p, list) { |
| bh = BH_ENTRY(p); |
| if (buffer_locked(bh)) { |
| get_bh(bh); |
| spin_unlock(lock); |
| wait_on_buffer(bh); |
| if (!buffer_uptodate(bh)) |
| err = -EIO; |
| brelse(bh); |
| spin_lock(lock); |
| goto repeat; |
| } |
| } |
| spin_unlock(lock); |
| return err; |
| } |
| |
| static void do_thaw_one(struct super_block *sb, void *unused) |
| { |
| char b[BDEVNAME_SIZE]; |
| while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) |
| printk(KERN_WARNING "Emergency Thaw on %s\n", |
| bdevname(sb->s_bdev, b)); |
| } |
| |
| static void do_thaw_all(struct work_struct *work) |
| { |
| iterate_supers(do_thaw_one, NULL); |
| kfree(work); |
| printk(KERN_WARNING "Emergency Thaw complete\n"); |
| } |
| |
| /** |
| * emergency_thaw_all -- forcibly thaw every frozen filesystem |
| * |
| * Used for emergency unfreeze of all filesystems via SysRq |
| */ |
| void emergency_thaw_all(void) |
| { |
| struct work_struct *work; |
| |
| work = kmalloc(sizeof(*work), GFP_ATOMIC); |
| if (work) { |
| INIT_WORK(work, do_thaw_all); |
| schedule_work(work); |
| } |
| } |
| |
| /** |
| * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers |
| * @mapping: the mapping which wants those buffers written |
| * |
| * Starts I/O against the buffers at mapping->private_list, and waits upon |
| * that I/O. |
| * |
| * Basically, this is a convenience function for fsync(). |
| * @mapping is a file or directory which needs those buffers to be written for |
| * a successful fsync(). |
| */ |
| int sync_mapping_buffers(struct address_space *mapping) |
| { |
| struct address_space *buffer_mapping = mapping->assoc_mapping; |
| |
| if (buffer_mapping == NULL || list_empty(&mapping->private_list)) |
| return 0; |
| |
| return fsync_buffers_list(&buffer_mapping->private_lock, |
| &mapping->private_list); |
| } |
| EXPORT_SYMBOL(sync_mapping_buffers); |
| |
| /* |
| * Called when we've recently written block `bblock', and it is known that |
| * `bblock' was for a buffer_boundary() buffer. This means that the block at |
| * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's |
| * dirty, schedule it for IO. So that indirects merge nicely with their data. |
| */ |
| void write_boundary_block(struct block_device *bdev, |
| sector_t bblock, unsigned blocksize) |
| { |
| struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); |
| if (bh) { |
| if (buffer_dirty(bh)) |
| ll_rw_block(WRITE, 1, &bh); |
| put_bh(bh); |
| } |
| } |
| |
| void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) |
| { |
| struct address_space *mapping = inode->i_mapping; |
| struct address_space *buffer_mapping = bh->b_page->mapping; |
| |
| mark_buffer_dirty(bh); |
| if (!mapping->assoc_mapping) { |
| mapping->assoc_mapping = buffer_mapping; |
| } else { |
| BUG_ON(mapping->assoc_mapping != buffer_mapping); |
| } |
| if (!bh->b_assoc_map) { |
| spin_lock(&buffer_mapping->private_lock); |
| list_move_tail(&bh->b_assoc_buffers, |
| &mapping->private_list); |
| bh->b_assoc_map = mapping; |
| spin_unlock(&buffer_mapping->private_lock); |
| } |
| } |
| EXPORT_SYMBOL(mark_buffer_dirty_inode); |
| |
| /* |
| * Mark the page dirty, and set it dirty in the radix tree, and mark the inode |
| * dirty. |
| * |
| * If warn is true, then emit a warning if the page is not uptodate and has |
| * not been truncated. |
| */ |
| static void __set_page_dirty(struct page *page, |
| struct address_space *mapping, int warn) |
| { |
| spin_lock_irq(&mapping->tree_lock); |
| if (page->mapping) { /* Race with truncate? */ |
| WARN_ON_ONCE(warn && !PageUptodate(page)); |
| account_page_dirtied(page, mapping); |
| radix_tree_tag_set(&mapping->page_tree, |
| page_index(page), PAGECACHE_TAG_DIRTY); |
| } |
| spin_unlock_irq(&mapping->tree_lock); |
| __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
| } |
| |
| /* |
| * Add a page to the dirty page list. |
| * |
| * It is a sad fact of life that this function is called from several places |
| * deeply under spinlocking. It may not sleep. |
| * |
| * If the page has buffers, the uptodate buffers are set dirty, to preserve |
| * dirty-state coherency between the page and the buffers. It the page does |
| * not have buffers then when they are later attached they will all be set |
| * dirty. |
| * |
| * The buffers are dirtied before the page is dirtied. There's a small race |
| * window in which a writepage caller may see the page cleanness but not the |
| * buffer dirtiness. That's fine. If this code were to set the page dirty |
| * before the buffers, a concurrent writepage caller could clear the page dirty |
| * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean |
| * page on the dirty page list. |
| * |
| * We use private_lock to lock against try_to_free_buffers while using the |
| * page's buffer list. Also use this to protect against clean buffers being |
| * added to the page after it was set dirty. |
| * |
| * FIXME: may need to call ->reservepage here as well. That's rather up to the |
| * address_space though. |
| */ |
| int __set_page_dirty_buffers(struct page *page) |
| { |
| int newly_dirty; |
| struct address_space *mapping = page_mapping(page); |
| |
| if (unlikely(!mapping)) |
| return !TestSetPageDirty(page); |
| |
| spin_lock(&mapping->private_lock); |
| if (page_has_buffers(page)) { |
| struct buffer_head *head = page_buffers(page); |
| struct buffer_head *bh = head; |
| |
| do { |
| set_buffer_dirty(bh); |
| bh = bh->b_this_page; |
| } while (bh != head); |
| } |
| newly_dirty = !TestSetPageDirty(page); |
| spin_unlock(&mapping->private_lock); |
| |
| if (newly_dirty) |
| __set_page_dirty(page, mapping, 1); |
| return newly_dirty; |
| } |
| EXPORT_SYMBOL(__set_page_dirty_buffers); |
| |
| /* |
| * Write out and wait upon a list of buffers. |
| * |
| * We have conflicting pressures: we want to make sure that all |
| * initially dirty buffers get waited on, but that any subsequently |
| * dirtied buffers don't. After all, we don't want fsync to last |
| * forever if somebody is actively writing to the file. |
| * |
| * Do this in two main stages: first we copy dirty buffers to a |
| * temporary inode list, queueing the writes as we go. Then we clean |
| * up, waiting for those writes to complete. |
| * |
| * During this second stage, any subsequent updates to the file may end |
| * up refiling the buffer on the original inode's dirty list again, so |
| * there is a chance we will end up with a buffer queued for write but |
| * not yet completed on that list. So, as a final cleanup we go through |
| * the osync code to catch these locked, dirty buffers without requeuing |
| * any newly dirty buffers for write. |
| */ |
| static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) |
| { |
| struct buffer_head *bh; |
| struct list_head tmp; |
| struct address_space *mapping; |
| int err = 0, err2; |
| struct blk_plug plug; |
| |
| INIT_LIST_HEAD(&tmp); |
| blk_start_plug(&plug); |
| |
| spin_lock(lock); |
| while (!list_empty(list)) { |
| bh = BH_ENTRY(list->next); |
| mapping = bh->b_assoc_map; |
| __remove_assoc_queue(bh); |
| /* Avoid race with mark_buffer_dirty_inode() which does |
| * a lockless check and we rely on seeing the dirty bit */ |
| smp_mb(); |
| if (buffer_dirty(bh) || buffer_locked(bh)) { |
| list_add(&bh->b_assoc_buffers, &tmp); |
| bh->b_assoc_map = mapping; |
| if (buffer_dirty(bh)) { |
| get_bh(bh); |
| spin_unlock(lock); |
| /* |
| * Ensure any pending I/O completes so that |
| * write_dirty_buffer() actually writes the |
| * current contents - it is a noop if I/O is |
| * still in flight on potentially older |
| * contents. |
| */ |
| write_dirty_buffer(bh, WRITE_SYNC); |
| |
| /* |
| * Kick off IO for the previous mapping. Note |
| * that we will not run the very last mapping, |
| * wait_on_buffer() will do that for us |
| * through sync_buffer(). |
| */ |
| brelse(bh); |
| spin_lock(lock); |
| } |
| } |
| } |
| |
| spin_unlock(lock); |
| blk_finish_plug(&plug); |
| spin_lock(lock); |
| |
| while (!list_empty(&tmp)) { |
| bh = BH_ENTRY(tmp.prev); |
| get_bh(bh); |
| mapping = bh->b_assoc_map; |
| __remove_assoc_queue(bh); |
| /* Avoid race with mark_buffer_dirty_inode() which does |
| * a lockless check and we rely on seeing the dirty bit */ |
| smp_mb(); |
| if (buffer_dirty(bh)) { |
| list_add(&bh->b_assoc_buffers, |
| &mapping->private_list); |
| bh->b_assoc_map = mapping; |
| } |
| spin_unlock(lock); |
| wait_on_buffer(bh); |
| if (!buffer_uptodate(bh)) |
| err = -EIO; |
| brelse(bh); |
| spin_lock(lock); |
| } |
| |
| spin_unlock(lock); |
| err2 = osync_buffers_list(lock, list); |
| if (err) |
| return err; |
| else |
| return err2; |
| } |
| |
| /* |
| * Invalidate any and all dirty buffers on a given inode. We are |
| * probably unmounting the fs, but that doesn't mean we have already |
| * done a sync(). Just drop the buffers from the inode list. |
| * |
| * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
| * assumes that all the buffers are against the blockdev. Not true |
| * for reiserfs. |
| */ |
| void invalidate_inode_buffers(struct inode *inode) |
| { |
| if (inode_has_buffers(inode)) { |
| struct address_space *mapping = &inode->i_data; |
| struct list_head *list = &mapping->private_list; |
| struct address_space *buffer_mapping = mapping->assoc_mapping; |
| |
| spin_lock(&buffer_mapping->private_lock); |
| while (!list_empty(list)) |
| __remove_assoc_queue(BH_ENTRY(list->next)); |
| spin_unlock(&buffer_mapping->private_lock); |
| } |
| } |
| EXPORT_SYMBOL(invalidate_inode_buffers); |
| |
| /* |
| * Remove any clean buffers from the inode's buffer list. This is called |
| * when we're trying to free the inode itself. Those buffers can pin it. |
| * |
| * Returns true if all buffers were removed. |
| */ |
| int remove_inode_buffers(struct inode *inode) |
| { |
| int ret = 1; |
| |
| if (inode_has_buffers(inode)) { |
| struct address_space *mapping = &inode->i_data; |
| struct list_head *list = &mapping->private_list; |
| struct address_space *buffer_mapping = mapping->assoc_mapping; |
| |
| spin_lock(&buffer_mapping->private_lock); |
| while (!list_empty(list)) { |
| struct buffer_head *bh = BH_ENTRY(list->next); |
| if (buffer_dirty(bh)) { |
| ret = 0; |
| break; |
| } |
| __remove_assoc_queue(bh); |
| } |
| spin_unlock(&buffer_mapping->private_lock); |
| } |
| return ret; |
| } |
| |
| /* |
| * Create the appropriate buffers when given a page for data area and |
| * the size of each buffer.. Use the bh->b_this_page linked list to |
| * follow the buffers created. Return NULL if unable to create more |
| * buffers. |
| * |
| * The retry flag is used to differentiate async IO (paging, swapping) |
| * which may not fail from ordinary buffer allocations. |
| */ |
| struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
| int retry) |
| { |
| struct buffer_head *bh, *head; |
| long offset; |
| |
| try_again: |
| head = NULL; |
| offset = PAGE_SIZE; |
| while ((offset -= size) >= 0) { |
| bh = alloc_buffer_head(GFP_NOFS); |
| if (!bh) |
| goto no_grow; |
| |
| bh->b_bdev = NULL; |
| bh->b_this_page = head; |
| bh->b_blocknr = -1; |
| head = bh; |
| |
| bh->b_state = 0; |
| atomic_set(&bh->b_count, 0); |
| bh->b_size = size; |
| |
| /* Link the buffer to its page */ |
| set_bh_page(bh, page, offset); |
| |
| init_buffer(bh, NULL, NULL); |
| } |
| return head; |
| /* |
| * In case anything failed, we just free everything we got. |
| */ |
| no_grow: |
| if (head) { |
| do { |
| bh = head; |
| head = head->b_this_page; |
| free_buffer_head(bh); |
| } while (head); |
| } |
| |
| /* |
| * Return failure for non-async IO requests. Async IO requests |
| * are not allowed to fail, so we have to wait until buffer heads |
| * become available. But we don't want tasks sleeping with |
| * partially complete buffers, so all were released above. |
| */ |
| if (!retry) |
| return NULL; |
| |
| /* We're _really_ low on memory. Now we just |
| * wait for old buffer heads to become free due to |
| * finishing IO. Since this is an async request and |
| * the reserve list is empty, we're sure there are |
| * async buffer heads in use. |
| */ |
| free_more_memory(); |
| goto try_again; |
| } |
| EXPORT_SYMBOL_GPL(alloc_page_buffers); |
| |
| static inline void |
| link_dev_buffers(struct page *page, struct buffer_head *head) |
| { |
| struct buffer_head *bh, *tail; |
| |
| bh = head; |
| do { |
| tail = bh; |
| bh = bh->b_this_page; |
| } while (bh); |
| tail->b_this_page = head; |
| attach_page_buffers(page, head); |
| } |
| |
| /* |
| * Initialise the state of a blockdev page's buffers. |
| */ |
| static void |
| init_page_buffers(struct page *page, struct block_device *bdev, |
| sector_t block, int size) |
| { |
| struct buffer_head *head = page_buffers(page); |
| struct buffer_head *bh = head; |
| int uptodate = PageUptodate(page); |
| sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode)); |
| |
| do { |
| if (!buffer_mapped(bh)) { |
| init_buffer(bh, NULL, NULL); |
| bh->b_bdev = bdev; |
| bh->b_blocknr = block; |
| if (uptodate) |
| set_buffer_uptodate(bh); |
| if (block < end_block) |
| set_buffer_mapped(bh); |
| } |
| block++; |
| bh = bh->b_this_page; |
| } while (bh != head); |
| } |
| |
| /* |
| * Create the page-cache page that contains the requested block. |
| * |
| * This is user purely for blockdev mappings. |
| */ |
| static struct page * |
| grow_dev_page(struct block_device *bdev, sector_t block, |
| pgoff_t index, int size) |
| { |
| struct inode *inode = bdev->bd_inode; |
| struct page *page; |
| struct buffer_head *bh; |
| |
| page = find_or_create_page(inode->i_mapping, index, |
| (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); |
| if (!page) |
| return NULL; |
| |
| BUG_ON(!PageLocked(page)); |
| |
| if (page_has_buffers(page)) { |
| bh = page_buffers(page); |
| if (bh->b_size == size) { |
| init_page_buffers(page, bdev, block, size); |
| return page; |
| } |
| if (!try_to_free_buffers(page)) |
| goto failed; |
| } |
| |
| /* |
| * Allocate some buffers for this page |
| */ |
| bh = alloc_page_buffers(page, size, 0); |
| if (!bh) |
| goto failed; |
| |
| /* |
| * Link the page to the buffers and initialise them. Take the |
| * lock to be atomic wrt __find_get_block(), which does not |
| * run under the page lock. |
| */ |
| spin_lock(&inode->i_mapping->private_lock); |
| link_dev_buffers(page, bh); |
| init_page_buffers(page, bdev, block, size); |
| spin_unlock(&inode->i_mapping->private_lock); |
| return page; |
| |
| failed: |
| unlock_page(page); |
| page_cache_release(page); |
| return NULL; |
| } |
| |
| /* |
| * Create buffers for the specified block device block's page. If |
| * that page was dirty, the buffers are set dirty also. |
| */ |
| static int |
| grow_buffers(struct block_device *bdev, sector_t block, int size) |
| { |
| struct page *page; |
| pgoff_t index; |
| int sizebits; |
| |
| sizebits = -1; |
| do { |
| sizebits++; |
| } while ((size << sizebits) < PAGE_SIZE); |
| |
| index = block >> sizebits; |
| |
| /* |
| * Check for a block which wants to lie outside our maximum possible |
| * pagecache index. (this comparison is done using sector_t types). |
| */ |
| if (unlikely(index != block >> sizebits)) { |
| char b[BDEVNAME_SIZE]; |
| |
| printk(KERN_ERR "%s: requested out-of-range block %llu for " |
| "device %s\n", |
| __func__, (unsigned long long)block, |
| bdevname(bdev, b)); |
| return -EIO; |
| } |
| block = index << sizebits; |
| /* Create a page with the proper size buffers.. */ |
| page = grow_dev_page(bdev, block, index, size); |
| if (!page) |
| return 0; |
| unlock_page(page); |
| page_cache_release(page); |
| return 1; |
| } |
| |
| static struct buffer_head * |
| __getblk_slow(struct block_device *bdev, sector_t block, int size) |
| { |
| int ret; |
| struct buffer_head *bh; |
| |
| /* Size must be multiple of hard sectorsize */ |
| if (unlikely(size & (bdev_logical_block_size(bdev)-1) || |
| (size < 512 || size > PAGE_SIZE))) { |
| printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
| size); |
| printk(KERN_ERR "logical block size: %d\n", |
| bdev_logical_block_size(bdev)); |
| |
| dump_stack(); |
| return NULL; |
| } |
| |
| retry: |
| bh = __find_get_block(bdev, block, size); |
| if (bh) |
| return bh; |
| |
| ret = grow_buffers(bdev, block, size); |
| if (ret == 0) { |
| free_more_memory(); |
| goto retry; |
| } else if (ret > 0) { |
| bh = __find_get_block(bdev, block, size); |
| if (bh) |
| return bh; |
| } |
| return NULL; |
| } |
| |
| /* |
| * The relationship between dirty buffers and dirty pages: |
| * |
| * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
| * the page is tagged dirty in its radix tree. |
| * |
| * At all times, the dirtiness of the buffers represents the dirtiness of |
| * subsections of the page. If the page has buffers, the page dirty bit is |
| * merely a hint about the true dirty state. |
| * |
| * When a page is set dirty in its entirety, all its buffers are marked dirty |
| * (if the page has buffers). |
| * |
| * When a buffer is marked dirty, its page is dirtied, but the page's other |
| * buffers are not. |
| * |
| * Also. When blockdev buffers are explicitly read with bread(), they |
| * individually become uptodate. But their backing page remains not |
| * uptodate - even if all of its buffers are uptodate. A subsequent |
| * block_read_full_page() against that page will discover all the uptodate |
| * buffers, will set the page uptodate and will perform no I/O. |
| */ |
| |
| /** |
| * mark_buffer_dirty - mark a buffer_head as needing writeout |
| * @bh: the buffer_head to mark dirty |
| * |
| * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
| * backing page dirty, then tag the page as dirty in its address_space's radix |
| * tree and then attach the address_space's inode to its superblock's dirty |
| * inode list. |
| * |
| * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
| * mapping->tree_lock and mapping->host->i_lock. |
| */ |
| void mark_buffer_dirty(struct buffer_head *bh) |
| { |
| WARN_ON_ONCE(!buffer_uptodate(bh)); |
| |
| /* |
| * Very *carefully* optimize the it-is-already-dirty case. |
| * |
| * Don't let the final "is it dirty" escape to before we |
| * perhaps modified the buffer. |
| */ |
| if (buffer_dirty(bh)) { |
| smp_mb(); |
| if (buffer_dirty(bh)) |
| return; |
| } |
| |
| if (!test_set_buffer_dirty(bh)) { |
| struct page *page = bh->b_page; |
| if (!TestSetPageDirty(page)) { |
| struct address_space *mapping = page_mapping(page); |
| if (mapping) |
| __set_page_dirty(page, mapping, 0); |
| } |
| } |
| } |
| EXPORT_SYMBOL(mark_buffer_dirty); |
| |
| /* |
| * Decrement a buffer_head's reference count. If all buffers against a page |
| * have zero reference count, are clean and unlocked, and if the page is clean |
| * and unlocked then try_to_free_buffers() may strip the buffers from the page |
| * in preparation for freeing it (sometimes, rarely, buffers are removed from |
| * a page but it ends up not being freed, and buffers may later be reattached). |
| */ |
| void __brelse(struct buffer_head * buf) |
| { |
| if (atomic_read(&buf->b_count)) { |
| put_bh(buf); |
| return; |
| } |
| WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
| } |
| EXPORT_SYMBOL(__brelse); |
| |
| /* |
| * bforget() is like brelse(), except it discards any |
| * potentially dirty data. |
| */ |
| void __bforget(struct buffer_head *bh) |
| { |
| clear_buffer_dirty(bh); |
| if (bh->b_assoc_map) { |
| struct address_space *buffer_mapping = bh->b_page->mapping; |
| |
| spin_lock(&buffer_mapping->private_lock); |
| list_del_init(&bh->b_assoc_buffers); |
| bh->b_assoc_map = NULL; |
| spin_unlock(&buffer_mapping->private_lock); |
| } |
| __brelse(bh); |
| } |
| EXPORT_SYMBOL(__bforget); |
| |
| static struct buffer_head *__bread_slow(struct buffer_head *bh) |
| { |
| lock_buffer(bh); |
| if (buffer_uptodate(bh)) { |
| unlock_buffer(bh); |
| return bh; |
| } else { |
| get_bh(bh); |
| bh->b_end_io = end_buffer_read_sync; |
| submit_bh(READ, bh); |
| wait_on_buffer(bh); |
| if (buffer_uptodate(bh)) |
| return bh; |
| } |
| brelse(bh); |
| return NULL; |
| } |
| |
| /* |
| * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
| * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
| * refcount elevated by one when they're in an LRU. A buffer can only appear |
| * once in a particular CPU's LRU. A single buffer can be present in multiple |
| * CPU's LRUs at the same time. |
| * |
| * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
| * sb_find_get_block(). |
| * |
| * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
| * a local interrupt disable for that. |
| */ |
| |
| #define BH_LRU_SIZE 8 |
| |
| struct bh_lru { |
| struct buffer_head *bhs[BH_LRU_SIZE]; |
| }; |
| |
| static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
| |
| #ifdef CONFIG_SMP |
| #define bh_lru_lock() local_irq_disable() |
| #define bh_lru_unlock() local_irq_enable() |
| #else |
| #define bh_lru_lock() preempt_disable() |
| #define bh_lru_unlock() preempt_enable() |
| #endif |
| |
| static inline void check_irqs_on(void) |
| { |
| #ifdef irqs_disabled |
| BUG_ON(irqs_disabled()); |
| #endif |
| } |
| |
| /* |
| * The LRU management algorithm is dopey-but-simple. Sorry. |
| */ |
| static void bh_lru_install(struct buffer_head *bh) |
| { |
| struct buffer_head *evictee = NULL; |
| |
| check_irqs_on(); |
| bh_lru_lock(); |
| if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { |
| struct buffer_head *bhs[BH_LRU_SIZE]; |
| int in; |
| int out = 0; |
| |
| get_bh(bh); |
| bhs[out++] = bh; |
| for (in = 0; in < BH_LRU_SIZE; in++) { |
| struct buffer_head *bh2 = |
| __this_cpu_read(bh_lrus.bhs[in]); |
| |
| if (bh2 == bh) { |
| __brelse(bh2); |
| } else { |
| if (out >= BH_LRU_SIZE) { |
| BUG_ON(evictee != NULL); |
| evictee = bh2; |
| } else { |
| bhs[out++] = bh2; |
| } |
| } |
| } |
| while (out < BH_LRU_SIZE) |
| bhs[out++] = NULL; |
| memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); |
| } |
| bh_lru_unlock(); |
| |
| if (evictee) |
| __brelse(evictee); |
| } |
| |
| /* |
| * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
| */ |
| static struct buffer_head * |
| lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) |
| { |
| struct buffer_head *ret = NULL; |
| unsigned int i; |
| |
| check_irqs_on(); |
| bh_lru_lock(); |
| for (i = 0; i < BH_LRU_SIZE; i++) { |
| struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); |
| |
| if (bh && bh->b_bdev == bdev && |
| bh->b_blocknr == block && bh->b_size == size) { |
| if (i) { |
| while (i) { |
| __this_cpu_write(bh_lrus.bhs[i], |
| __this_cpu_read(bh_lrus.bhs[i - 1])); |
| i--; |
| } |
| __this_cpu_write(bh_lrus.bhs[0], bh); |
| } |
| get_bh(bh); |
| ret = bh; |
| break; |
| } |
| } |
| bh_lru_unlock(); |
| return ret; |
| } |
| |
| /* |
| * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
| * it in the LRU and mark it as accessed. If it is not present then return |
| * NULL |
| */ |
| struct buffer_head * |
| __find_get_block(struct block_device *bdev, sector_t block, unsigned size) |
| { |
| struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
| |
| if (bh == NULL) { |
| bh = __find_get_block_slow(bdev, block); |
| if (bh) |
| bh_lru_install(bh); |
| } |
| if (bh) |
| touch_buffer(bh); |
| return bh; |
| } |
| EXPORT_SYMBOL(__find_get_block); |
| |
| /* |
| * __getblk will locate (and, if necessary, create) the buffer_head |
| * which corresponds to the passed block_device, block and size. The |
| * returned buffer has its reference count incremented. |
| * |
| * __getblk() cannot fail - it just keeps trying. If you pass it an |
| * illegal block number, __getblk() will happily return a buffer_head |
| * which represents the non-existent block. Very weird. |
| * |
| * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() |
| * attempt is failing. FIXME, perhaps? |
| */ |
| struct buffer_head * |
| __getblk(struct block_device *bdev, sector_t block, unsigned size) |
| { |
| struct buffer_head *bh = __find_get_block(bdev, block, size); |
| |
| might_sleep(); |
| if (bh == NULL) |
| bh = __getblk_slow(bdev, block, size); |
| return bh; |
| } |
| EXPORT_SYMBOL(__getblk); |
| |
| /* |
| * Do async read-ahead on a buffer.. |
| */ |
| void __breadahead(struct block_device *bdev, sector_t block, unsigned size) |
| { |
| struct buffer_head *bh = __getblk(bdev, block, size); |
| if (likely(bh)) { |
| ll_rw_block(READA, 1, &bh); |
| brelse(bh); |
| } |
| } |
| EXPORT_SYMBOL(__breadahead); |
| |
| /** |
| * __bread() - reads a specified block and returns the bh |
| * @bdev: the block_device to read from |
| * @block: number of block |
| * @size: size (in bytes) to read |
| * |
| * Reads a specified block, and returns buffer head that contains it. |
| * It returns NULL if the block was unreadable. |
| */ |
| struct buffer_head * |
| __bread(struct block_device *bdev, sector_t block, unsigned size) |
| { |
| struct buffer_head *bh = __getblk(bdev, block, size); |
| |
| if (likely(bh) && !buffer_uptodate(bh)) |
| bh = __bread_slow(bh); |
| return bh; |
| } |
| EXPORT_SYMBOL(__bread); |
| |
| /* |
| * invalidate_bh_lrus() is called rarely - but not only at unmount. |
| * This doesn't race because it runs in each cpu either in irq |
| * or with preempt disabled. |
| */ |
| static void invalidate_bh_lru(void *arg) |
| { |
| struct bh_lru *b = &get_cpu_var(bh_lrus); |
| int i; |
| |
| for (i = 0; i < BH_LRU_SIZE; i++) { |
| brelse(b->bhs[i]); |
| b->bhs[i] = NULL; |
| } |
| put_cpu_var(bh_lrus); |
| } |
| |
| static bool has_bh_in_lru(int cpu, void *dummy) |
| { |
| struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); |
| int i; |
| |
| for (i = 0; i < BH_LRU_SIZE; i++) { |
| if (b->bhs[i]) |
| return 1; |
| } |
| |
| return 0; |
| } |
| |
| void invalidate_bh_lrus(void) |
| { |
| on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL); |
| } |
| EXPORT_SYMBOL_GPL(invalidate_bh_lrus); |
| |
| void set_bh_page(struct buffer_head *bh, |
| struct page *page, unsigned long offset) |
| { |
| bh->b_page = page; |
| BUG_ON(offset >= PAGE_SIZE); |
| if (PageHighMem(page)) |
| /* |
| * This catches illegal uses and preserves the offset: |
| */ |
| bh->b_data = (char *)(0 + offset); |
| else |
| bh->b_data = page_address(page) + offset; |
| } |
| EXPORT_SYMBOL(set_bh_page); |
| |
| /* |
| * Called when truncating a buffer on a page completely. |
| */ |
| static void discard_buffer(struct buffer_head * bh) |
| { |
| lock_buffer(bh); |
| clear_buffer_dirty(bh); |
| bh->b_bdev = NULL; |
| clear_buffer_mapped(bh); |
| clear_buffer_req(bh); |
| clear_buffer_new(bh); |
| clear_buffer_delay(bh); |
| clear_buffer_unwritten(bh); |
| unlock_buffer(bh); |
| } |
| |
| /** |
| * block_invalidatepage - invalidate part or all of a buffer-backed page |
| * |
| * @page: the page which is affected |
| * @offset: the index of the truncation point |
| * |
| * block_invalidatepage() is called when all or part of the page has become |
| * invalidated by a truncate operation. |
| * |
| * block_invalidatepage() does not have to release all buffers, but it must |
| * ensure that no dirty buffer is left outside @offset and that no I/O |
| * is underway against any of the blocks which are outside the truncation |
| * point. Because the caller is about to free (and possibly reuse) those |
| * blocks on-disk. |
| */ |
| void block_invalidatepage(struct page *page, unsigned long offset) |
| { |
| struct buffer_head *head, *bh, *next; |
| unsigned int curr_off = 0; |
| |
| BUG_ON(!PageLocked(page)); |
| if (!page_has_buffers(page)) |
| goto out; |
| |
| head = page_buffers(page); |
| bh = head; |
| do { |
| unsigned int next_off = curr_off + bh->b_size; |
| next = bh->b_this_page; |
| |
| /* |
| * is this block fully invalidated? |
| */ |
| if (offset <= curr_off) |
| discard_buffer(bh); |
| curr_off = next_off; |
| bh = next; |
| } while (bh != head); |
| |
| /* |
| * We release buffers only if the entire page is being invalidated. |
| * The get_block cached value has been unconditionally invalidated, |
| * so real IO is not possible anymore. |
| */ |
| if (offset == 0) |
| try_to_release_page(page, 0); |
| out: |
| return; |
| } |
| EXPORT_SYMBOL(block_invalidatepage); |
| |
| /* |
| * We attach and possibly dirty the buffers atomically wrt |
| * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
| * is already excluded via the page lock. |
| */ |
| void create_empty_buffers(struct page *page, |
| unsigned long blocksize, unsigned long b_state) |
| { |
| struct buffer_head *bh, *head, *tail; |
| |
| head = alloc_page_buffers(page, blocksize, 1); |
| bh = head; |
| do { |
| bh->b_state |= b_state; |
| tail = bh; |
| bh = bh->b_this_page; |
| } while (bh); |
| tail->b_this_page = head; |
| |
| spin_lock(&page->mapping->private_lock); |
| if (PageUptodate(page) || PageDirty(page)) { |
| bh = head; |
| do { |
| if (PageDirty(page)) |
| set_buffer_dirty(bh); |
| if (PageUptodate(page)) |
| set_buffer_uptodate(bh); |
| bh = bh->b_this_page; |
| } while (bh != head); |
| } |
| attach_page_buffers(page, head); |
| spin_unlock(&page->mapping->private_lock); |
| } |
| EXPORT_SYMBOL(create_empty_buffers); |
| |
| /* |
| * We are taking a block for data and we don't want any output from any |
| * buffer-cache aliases starting from return from that function and |
| * until the moment when something will explicitly mark the buffer |
| * dirty (hopefully that will not happen until we will free that block ;-) |
| * We don't even need to mark it not-uptodate - nobody can expect |
| * anything from a newly allocated buffer anyway. We used to used |
| * unmap_buffer() for such invalidation, but that was wrong. We definitely |
| * don't want to mark the alias unmapped, for example - it would confuse |
| * anyone who might pick it with bread() afterwards... |
| * |
| * Also.. Note that bforget() doesn't lock the buffer. So there can |
| * be writeout I/O going on against recently-freed buffers. We don't |
| * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
| * only if we really need to. That happens here. |
| */ |
| void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
| { |
| struct buffer_head *old_bh; |
| |
| might_sleep(); |
| |
| old_bh = __find_get_block_slow(bdev, block); |
| if (old_bh) { |
| clear_buffer_dirty(old_bh); |
| wait_on_buffer(old_bh); |
| clear_buffer_req(old_bh); |
| __brelse(old_bh); |
| } |
| } |
| EXPORT_SYMBOL(unmap_underlying_metadata); |
| |
| /* |
| * NOTE! All mapped/uptodate combinations are valid: |
| * |
| * Mapped Uptodate Meaning |
| * |
| * No No "unknown" - must do get_block() |
| * No Yes "hole" - zero-filled |
| * Yes No "allocated" - allocated on disk, not read in |
| * Yes Yes "valid" - allocated and up-to-date in memory. |
| * |
| * "Dirty" is valid only with the last case (mapped+uptodate). |
| */ |
| |
| /* |
| * While block_write_full_page is writing back the dirty buffers under |
| * the page lock, whoever dirtied the buffers may decide to clean them |
| * again at any time. We handle that by only looking at the buffer |
| * state inside lock_buffer(). |
| * |
| * If block_write_full_page() is called for regular writeback |
| * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
| * locked buffer. This only can happen if someone has written the buffer |
| * directly, with submit_bh(). At the address_space level PageWriteback |
| * prevents this contention from occurring. |
| * |
| * If block_write_full_page() is called with wbc->sync_mode == |
| * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this |
| * causes the writes to be flagged as synchronous writes. |
| */ |
| static int __block_write_full_page(struct inode *inode, struct page *page, |
| get_block_t *get_block, struct writeback_control *wbc, |
| bh_end_io_t *handler) |
| { |
| int err; |
| sector_t block; |
| sector_t last_block; |
| struct buffer_head *bh, *head; |
| const unsigned blocksize = 1 << inode->i_blkbits; |
| int nr_underway = 0; |
| int write_op = (wbc->sync_mode == WB_SYNC_ALL ? |
| WRITE_SYNC : WRITE); |
| |
| BUG_ON(!PageLocked(page)); |
| |
| last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; |
| |
| if (!page_has_buffers(page)) { |
| create_empty_buffers(page, blocksize, |
| (1 << BH_Dirty)|(1 << BH_Uptodate)); |
| } |
| |
| /* |
| * Be very careful. We have no exclusion from __set_page_dirty_buffers |
| * here, and the (potentially unmapped) buffers may become dirty at |
| * any time. If a buffer becomes dirty here after we've inspected it |
| * then we just miss that fact, and the page stays dirty. |
| * |
| * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
| * handle that here by just cleaning them. |
| */ |
| |
| block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| head = page_buffers(page); |
| bh = head; |
| |
| /* |
| * Get all the dirty buffers mapped to disk addresses and |
| * handle any aliases from the underlying blockdev's mapping. |
| */ |
| do { |
| if (block > last_block) { |
| /* |
| * mapped buffers outside i_size will occur, because |
| * this page can be outside i_size when there is a |
| * truncate in progress. |
| */ |
| /* |
| * The buffer was zeroed by block_write_full_page() |
| */ |
| clear_buffer_dirty(bh); |
| set_buffer_uptodate(bh); |
| } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && |
| buffer_dirty(bh)) { |
| WARN_ON(bh->b_size != blocksize); |
| err = get_block(inode, block, bh, 1); |
| if (err) |
| goto recover; |
| clear_buffer_delay(bh); |
| if (buffer_new(bh)) { |
| /* blockdev mappings never come here */ |
| clear_buffer_new(bh); |
| unmap_underlying_metadata(bh->b_bdev, |
| bh->b_blocknr); |
| } |
| } |
| bh = bh->b_this_page; |
| block++; |
| } while (bh != head); |
| |
| do { |
| if (!buffer_mapped(bh)) |
| continue; |
| /* |
| * If it's a fully non-blocking write attempt and we cannot |
| * lock the buffer then redirty the page. Note that this can |
| * potentially cause a busy-wait loop from writeback threads |
| * and kswapd activity, but those code paths have their own |
| * higher-level throttling. |
| */ |
| if (wbc->sync_mode != WB_SYNC_NONE) { |
| lock_buffer(bh); |
| } else if (!trylock_buffer(bh)) { |
| redirty_page_for_writepage(wbc, page); |
| continue; |
| } |
| if (test_clear_buffer_dirty(bh)) { |
| mark_buffer_async_write_endio(bh, handler); |
| } else { |
| unlock_buffer(bh); |
| } |
| } while ((bh = bh->b_this_page) != head); |
| |
| /* |
| * The page and its buffers are protected by PageWriteback(), so we can |
| * drop the bh refcounts early. |
| */ |
| BUG_ON(PageWriteback(page)); |
| set_page_writeback(page); |
| |
| do { |
| struct buffer_head *next = bh->b_this_page; |
| if (buffer_async_write(bh)) { |
| submit_bh(write_op, bh); |
| nr_underway++; |
| } |
| bh = next; |
| } while (bh != head); |
| unlock_page(page); |
| |
| err = 0; |
| done: |
| if (nr_underway == 0) { |
| /* |
| * The page was marked dirty, but the buffers were |
| * clean. Someone wrote them back by hand with |
| * ll_rw_block/submit_bh. A rare case. |
| */ |
| end_page_writeback(page); |
| |
| /* |
| * The page and buffer_heads can be released at any time from |
| * here on. |
| */ |
| } |
| return err; |
| |
| recover: |
| /* |
| * ENOSPC, or some other error. We may already have added some |
| * blocks to the file, so we need to write these out to avoid |
| * exposing stale data. |
| * The page is currently locked and not marked for writeback |
| */ |
| bh = head; |
| /* Recovery: lock and submit the mapped buffers */ |
| do { |
| if (buffer_mapped(bh) && buffer_dirty(bh) && |
| !buffer_delay(bh)) { |
| lock_buffer(bh); |
| mark_buffer_async_write_endio(bh, handler); |
| } else { |
| /* |
| * The buffer may have been set dirty during |
| * attachment to a dirty page. |
| */ |
| clear_buffer_dirty(bh); |
| } |
| } while ((bh = bh->b_this_page) != head); |
| SetPageError(page); |
| BUG_ON(PageWriteback(page)); |
| mapping_set_error(page->mapping, err); |
| set_page_writeback(page); |
| do { |
| struct buffer_head *next = bh->b_this_page; |
| if (buffer_async_write(bh)) { |
| clear_buffer_dirty(bh); |
| submit_bh(write_op, bh); |
| nr_underway++; |
| } |
| bh = next; |
| } while (bh != head); |
| unlock_page(page); |
| goto done; |
| } |
| |
| /* |
| * If a page has any new buffers, zero them out here, and mark them uptodate |
| * and dirty so they'll be written out (in order to prevent uninitialised |
| * block data from leaking). And clear the new bit. |
| */ |
| void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) |
| { |
| unsigned int block_start, block_end; |
| struct buffer_head *head, *bh; |
| |
| BUG_ON(!PageLocked(page)); |
| if (!page_has_buffers(page)) |
| return; |
| |
| bh = head = page_buffers(page); |
| block_start = 0; |
| do { |
| block_end = block_start + bh->b_size; |
| |
| if (buffer_new(bh)) { |
| if (block_end > from && block_start < to) { |
| if (!PageUptodate(page)) { |
| unsigned start, size; |
| |
| start = max(from, block_start); |
| size = min(to, block_end) - start; |
| |
| zero_user(page, start, size); |
| set_buffer_uptodate(bh); |
| } |
| |
| clear_buffer_new(bh); |
| mark_buffer_dirty(bh); |
| } |
| } |
| |
| block_start = block_end; |
| bh = bh->b_this_page; |
| } while (bh != head); |
| } |
| EXPORT_SYMBOL(page_zero_new_buffers); |
| |
| int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
| get_block_t *get_block) |
| { |
| unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
| unsigned to = from + len; |
| struct inode *inode = page->mapping->host; |
| unsigned block_start, block_end; |
| sector_t block; |
| int err = 0; |
| unsigned blocksize, bbits; |
| struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
| |
| BUG_ON(!PageLocked(page)); |
| BUG_ON(from > PAGE_CACHE_SIZE); |
| BUG_ON(to > PAGE_CACHE_SIZE); |
| BUG_ON(from > to); |
| |
| blocksize = 1 << inode->i_blkbits; |
| if (!page_has_buffers(page)) |
| create_empty_buffers(page, blocksize, 0); |
| head = page_buffers(page); |
| |
| bbits = inode->i_blkbits; |
| block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
| |
| for(bh = head, block_start = 0; bh != head || !block_start; |
| block++, block_start=block_end, bh = bh->b_this_page) { |
| block_end = block_start + blocksize; |
| if (block_end <= from || block_start >= to) { |
| if (PageUptodate(page)) { |
| if (!buffer_uptodate(bh)) |
| set_buffer_uptodate(bh); |
| } |
| continue; |
| } |
| if (buffer_new(bh)) |
| clear_buffer_new(bh); |
| if (!buffer_mapped(bh)) { |
| WARN_ON(bh->b_size != blocksize); |
| err = get_block(inode, block, bh, 1); |
| if (err) |
| break; |
| if (buffer_new(bh)) { |
| unmap_underlying_metadata(bh->b_bdev, |
| bh->b_blocknr); |
| if (PageUptodate(page)) { |
| clear_buffer_new(bh); |
| set_buffer_uptodate(bh); |
| mark_buffer_dirty(bh); |
| continue; |
| } |
| if (block_end > to || block_start < from) |
| zero_user_segments(page, |
| to, block_end, |
| block_start, from); |
| continue; |
| } |
| } |
| if (PageUptodate(page)) { |
| if (!buffer_uptodate(bh)) |
| set_buffer_uptodate(bh); |
| continue; |
| } |
| if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
| !buffer_unwritten(bh) && |
| (block_start < from || block_end > to)) { |
| ll_rw_block(READ, 1, &bh); |
| *wait_bh++=bh; |
| } |
| } |
| /* |
| * If we issued read requests - let them complete. |
| */ |
| while(wait_bh > wait) { |
| wait_on_buffer(*--wait_bh); |
| if (!buffer_uptodate(*wait_bh)) |
| err = -EIO; |
| } |
| if (unlikely(err)) |
| page_zero_new_buffers(page, from, to); |
| return err; |
| } |
| EXPORT_SYMBOL(__block_write_begin); |
| |
| static int __block_commit_write(struct inode *inode, struct page *page, |
| unsigned from, unsigned to) |
| { |
| unsigned block_start, block_end; |
| int partial = 0; |
| unsigned blocksize; |
| struct buffer_head *bh, *head; |
| |
| blocksize = 1 << inode->i_blkbits; |
| |
| for(bh = head = page_buffers(page), block_start = 0; |
| bh != head || !block_start; |
| block_start=block_end, bh = bh->b_this_page) { |
| block_end = block_start + blocksize; |
| if (block_end <= from || block_start >= to) { |
| if (!buffer_uptodate(bh)) |
| partial = 1; |
| } else { |
| set_buffer_uptodate(bh); |
| mark_buffer_dirty(bh); |
| } |
| clear_buffer_new(bh); |
| } |
| |
| /* |
| * If this is a partial write which happened to make all buffers |
| * uptodate then we can optimize away a bogus readpage() for |
| * the next read(). Here we 'discover' whether the page went |
| * uptodate as a result of this (potentially partial) write. |
| */ |
| if (!partial) |
| SetPageUptodate(page); |
| return 0; |
| } |
| |
| /* |
| * block_write_begin takes care of the basic task of block allocation and |
| * bringing partial write blocks uptodate first. |
| * |
| * The filesystem needs to handle block truncation upon failure. |
| */ |
| int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
| unsigned flags, struct page **pagep, get_block_t *get_block) |
| { |
| pgoff_t index = pos >> PAGE_CACHE_SHIFT; |
| struct page *page; |
| int status; |
| |
| page = grab_cache_page_write_begin(mapping, index, flags); |
| if (!page) |
| return -ENOMEM; |
| |
| status = __block_write_begin(page, pos, len, get_block); |
| if (unlikely(status)) { |
| unlock_page(page); |
| page_cache_release(page); |
| page = NULL; |
| } |
| |
| *pagep = page; |
| return status; |
| } |
| EXPORT_SYMBOL(block_write_begin); |
| |
| int block_write_end(struct file *file, struct address_space *mapping, |
| loff_t pos, unsigned len, unsigned copied, |
| struct page *page, void *fsdata) |
| { |
| struct inode *inode = mapping->host; |
| unsigned start; |
| |
| start = pos & (PAGE_CACHE_SIZE - 1); |
| |
| if (unlikely(copied < len)) { |
| /* |
| * The buffers that were written will now be uptodate, so we |
| * don't have to worry about a readpage reading them and |
| * overwriting a partial write. However if we have encountered |
| * a short write and only partially written into a buffer, it |
| * will not be marked uptodate, so a readpage might come in and |
| * destroy our partial write. |
| * |
| * Do the simplest thing, and just treat any short write to a |
| * non uptodate page as a zero-length write, and force the |
| * caller to redo the whole thing. |
| */ |
| if (!PageUptodate(page)) |
| copied = 0; |
| |
| page_zero_new_buffers(page, start+copied, start+len); |
| } |
| flush_dcache_page(page); |
| |
| /* This could be a short (even 0-length) commit */ |
| __block_commit_write(inode, page, start, start+copied); |
| |
| return copied; |
| } |
| EXPORT_SYMBOL(block_write_end); |
| |
| int generic_write_end(struct file *file, struct address_space *mapping, |
| loff_t pos, unsigned len, unsigned copied, |
| struct page *page, void *fsdata) |
| { |
| struct inode *inode = mapping->host; |
| int i_size_changed = 0; |
| |
| copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); |
| |
| /* |
| * No need to use i_size_read() here, the i_size |
| * cannot change under us because we hold i_mutex. |
| * |
| * But it's important to update i_size while still holding page lock: |
| * page writeout could otherwise come in and zero beyond i_size. |
| */ |
| if (pos+copied > inode->i_size) { |
| i_size_write(inode, pos+copied); |
| i_size_changed = 1; |
| } |
| |
| unlock_page(page); |
| page_cache_release(page); |
| |
| /* |
| * Don't mark the inode dirty under page lock. First, it unnecessarily |
| * makes the holding time of page lock longer. Second, it forces lock |
| * ordering of page lock and transaction start for journaling |
| * filesystems. |
| */ |
| if (i_size_changed) |
| mark_inode_dirty(inode); |
| |
| return copied; |
| } |
| EXPORT_SYMBOL(generic_write_end); |
| |
| /* |
| * block_is_partially_uptodate checks whether buffers within a page are |
| * uptodate or not. |
| * |
| * Returns true if all buffers which correspond to a file portion |
| * we want to read are uptodate. |
| */ |
| int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, |
| unsigned long from) |
| { |
| struct inode *inode = page->mapping->host; |
| unsigned block_start, block_end, blocksize; |
| unsigned to; |
| struct buffer_head *bh, *head; |
| int ret = 1; |
| |
| if (!page_has_buffers(page)) |
| return 0; |
| |
| blocksize = 1 << inode->i_blkbits; |
| to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count); |
| to = from + to; |
| if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) |
| return 0; |
| |
| head = page_buffers(page); |
| bh = head; |
| block_start = 0; |
| do { |
| block_end = block_start + blocksize; |
| if (block_end > from && block_start < to) { |
| if (!buffer_uptodate(bh)) { |
| ret = 0; |
| break; |
| } |
| if (block_end >= to) |
| break; |
| } |
| block_start = block_end; |
| bh = bh->b_this_page; |
| } while (bh != head); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(block_is_partially_uptodate); |
| |
| /* |
| * Generic "read page" function for block devices that have the normal |
| * get_block functionality. This is most of the block device filesystems. |
| * Reads the page asynchronously --- the unlock_buffer() and |
| * set/clear_buffer_uptodate() functions propagate buffer state into the |
| * page struct once IO has completed. |
| */ |
| int block_read_full_page(struct page *page, get_block_t *get_block) |
| { |
| struct inode *inode = page->mapping->host; |
| sector_t iblock, lblock; |
| struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; |
| unsigned int blocksize; |
| int nr, i; |
| int fully_mapped = 1; |
| |
| BUG_ON(!PageLocked(page)); |
| blocksize = 1 << inode->i_blkbits; |
| if (!page_has_buffers(page)) |
| create_empty_buffers(page, blocksize, 0); |
| head = page_buffers(page); |
| |
| iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; |
| bh = head; |
| nr = 0; |
| i = 0; |
| |
| do { |
| if (buffer_uptodate(bh)) |
| continue; |
| |
| if (!buffer_mapped(bh)) { |
| int err = 0; |
| |
| fully_mapped = 0; |
| if (iblock < lblock) { |
| WARN_ON(bh->b_size != blocksize); |
| err = get_block(inode, iblock, bh, 0); |
| if (err) |
| SetPageError(page); |
| } |
| if (!buffer_mapped(bh)) { |
| zero_user(page, i * blocksize, blocksize); |
| if (!err) |
| set_buffer_uptodate(bh); |
| continue; |
| } |
| /* |
| * get_block() might have updated the buffer |
| * synchronously |
| */ |
| if (buffer_uptodate(bh)) |
| continue; |
| } |
| arr[nr++] = bh; |
| } while (i++, iblock++, (bh = bh->b_this_page) != head); |
| |
| if (fully_mapped) |
| SetPageMappedToDisk(page); |
| |
| if (!nr) { |
| /* |
| * All buffers are uptodate - we can set the page uptodate |
| * as well. But not if get_block() returned an error. |
| */ |
| if (!PageError(page)) |
| SetPageUptodate(page); |
| unlock_page(page); |
| return 0; |
| } |
| |
| /* Stage two: lock the buffers */ |
| for (i = 0; i < nr; i++) { |
| bh = arr[i]; |
| lock_buffer(bh); |
| mark_buffer_async_read(bh); |
| } |
| |
| /* |
| * Stage 3: start the IO. Check for uptodateness |
| * inside the buffer lock in case another process reading |
| * the underlying blockdev brought it uptodate (the sct fix). |
| */ |
| for (i = 0; i < nr; i++) { |
| bh = arr[i]; |
| if (buffer_uptodate(bh)) |
| end_buffer_async_read(bh, 1); |
| else |
| submit_bh(READ, bh); |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL(block_read_full_page); |
| |
| /* utility function for filesystems that need to do work on expanding |
| * truncates. Uses filesystem pagecache writes to allow the filesystem to |
| * deal with the hole. |
| */ |
| int generic_cont_expand_simple(struct inode *inode, loff_t size) |
| { |
| struct address_space *mapping = inode->i_mapping; |
| struct page *page; |
| void *fsdata; |
| int err; |
| |
| err = inode_newsize_ok(inode, size); |
| if (err) |
| goto out; |
| |
| err = pagecache_write_begin(NULL, mapping, size, 0, |
| AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, |
| &page, &fsdata); |
| if (err) |
| goto out; |
| |
| err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); |
| BUG_ON(err > 0); |
| |
| out: |
| return err; |
| } |
| EXPORT_SYMBOL(generic_cont_expand_simple); |
| |
| static int cont_expand_zero(struct file *file, struct address_space *mapping, |
| loff_t pos, loff_t *bytes) |
| { |
| struct inode *inode = mapping->host; |
| unsigned blocksize = 1 << inode->i_blkbits; |
| struct page *page; |
| void *fsdata; |
| pgoff_t index, curidx; |
| loff_t curpos; |
| unsigned zerofrom, offset, len; |
| int err = 0; |
| |
| index = pos >> PAGE_CACHE_SHIFT; |
| offset = pos & ~PAGE_CACHE_MASK; |
| |
| while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { |
| zerofrom = curpos & ~PAGE_CACHE_MASK; |
| if (zerofrom & (blocksize-1)) { |
| *bytes |= (blocksize-1); |
| (*bytes)++; |
| } |
| len = PAGE_CACHE_SIZE - zerofrom; |
| |
| err = pagecache_write_begin(file, mapping, curpos, len, |
| AOP_FLAG_UNINTERRUPTIBLE, |
| &page, &fsdata); |
| if (err) |
| goto out; |
| zero_user(page, zerofrom, len); |
| err = pagecache_write_end(file, mapping, curpos, len, len, |
| page, fsdata); |
| if (err < 0) |
| goto out; |
| BUG_ON(err != len); |
| err = 0; |
| |
| balance_dirty_pages_ratelimited(mapping); |
| } |
| |
| /* page covers the boundary, find the boundary offset */ |
| if (index == curidx) { |
| zerofrom = curpos & ~PAGE_CACHE_MASK; |
| /* if we will expand the thing last block will be filled */ |
| if (offset <= zerofrom) { |
| goto out; |
| } |
| if (zerofrom & (blocksize-1)) { |
| *bytes |= (blocksize-1); |
| (*bytes)++; |
| } |
| len = offset - zerofrom; |
| |
| err = pagecache_write_begin(file, mapping, curpos, len, |
| AOP_FLAG_UNINTERRUPTIBLE, |
| &page, &fsdata); |
| if (err) |
| goto out; |
| zero_user(page, zerofrom, len); |
| err = pagecache_write_end(file, mapping, curpos, len, len, |
| page, fsdata); |
| if (err < 0) |
| goto out; |
| BUG_ON(err != len); |
| err = 0; |
| } |
| out: |
| return err; |
| } |
| |
| /* |
| * For moronic filesystems that do not allow holes in file. |
| * We may have to extend the file. |
| */ |
| int cont_write_begin(struct file *file, struct address_space *mapping, |
| loff_t pos, unsigned len, unsigned flags, |
| struct page **pagep, void **fsdata, |
| get_block_t *get_block, loff_t *bytes) |
| { |
| struct inode *inode = mapping->host; |
| unsigned blocksize = 1 << inode->i_blkbits; |
| unsigned zerofrom; |
| int err; |
| |
| err = cont_expand_zero(file, mapping, pos, bytes); |
| if (err) |
| return err; |
| |
| zerofrom = *bytes & ~PAGE_CACHE_MASK; |
| if (pos+len > *bytes && zerofrom & (blocksize-1)) { |
| *bytes |= (blocksize-1); |
| (*bytes)++; |
| } |
| |
| return block_write_begin(mapping, pos, len, flags, pagep, get_block); |
| } |
| EXPORT_SYMBOL(cont_write_begin); |
| |
| int block_commit_write(struct page *page, unsigned from, unsigned to) |
| { |
| struct inode *inode = page->mapping->host; |
| __block_commit_write(inode,page,from,to); |
| return 0; |
| } |
| EXPORT_SYMBOL(block_commit_write); |
| |
| /* |
| * block_page_mkwrite() is not allowed to change the file size as it gets |
| * called from a page fault handler when a page is first dirtied. Hence we must |
| * be careful to check for EOF conditions here. We set the page up correctly |
| * for a written page which means we get ENOSPC checking when writing into |
| * holes and correct delalloc and unwritten extent mapping on filesystems that |
| * support these features. |
| * |
| * We are not allowed to take the i_mutex here so we have to play games to |
| * protect against truncate races as the page could now be beyond EOF. Because |
| * truncate writes the inode size before removing pages, once we have the |
| * page lock we can determine safely if the page is beyond EOF. If it is not |
| * beyond EOF, then the page is guaranteed safe against truncation until we |
| * unlock the page. |
| * |
| * Direct callers of this function should protect against filesystem freezing |
| * using sb_start_write() - sb_end_write() functions. |
| */ |
| int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
| get_block_t get_block) |
| { |
| struct page *page = vmf->page; |
| struct inode *inode = vma->vm_file->f_path.dentry->d_inode; |
| unsigned long end; |
| loff_t size; |
| int ret; |
| |
| /* |
| * Update file times before taking page lock. We may end up failing the |
| * fault so this update may be superfluous but who really cares... |
| */ |
| file_update_time(vma->vm_file); |
| |
| lock_page(page); |
| size = i_size_read(inode); |
| if ((page->mapping != inode->i_mapping) || |
| (page_offset(page) > size)) { |
| /* We overload EFAULT to mean page got truncated */ |
| ret = -EFAULT; |
| goto out_unlock; |
| } |
| |
| /* page is wholly or partially inside EOF */ |
| if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) |
| end = size & ~PAGE_CACHE_MASK; |
| else |
| end = PAGE_CACHE_SIZE; |
| |
| ret = __block_write_begin(page, 0, end, get_block); |
| if (!ret) |
| ret = block_commit_write(page, 0, end); |
| |
| if (unlikely(ret < 0)) |
| goto out_unlock; |
| set_page_dirty(page); |
| wait_on_page_writeback(page); |
| return 0; |
| out_unlock: |
| unlock_page(page); |
| return ret; |
| } |
| EXPORT_SYMBOL(__block_page_mkwrite); |
| |
| int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
| get_block_t get_block) |
| { |
| int ret; |
| struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb; |
| |
| sb_start_pagefault(sb); |
| ret = __block_page_mkwrite(vma, vmf, get_block); |
| sb_end_pagefault(sb); |
| return block_page_mkwrite_return(ret); |
| } |
| EXPORT_SYMBOL(block_page_mkwrite); |
| |
| /* |
| * nobh_write_begin()'s prereads are special: the buffer_heads are freed |
| * immediately, while under the page lock. So it needs a special end_io |
| * handler which does not touch the bh after unlocking it. |
| */ |
| static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
| { |
| __end_buffer_read_notouch(bh, uptodate); |
| } |
| |
| /* |
| * Attach the singly-linked list of buffers created by nobh_write_begin, to |
| * the page (converting it to circular linked list and taking care of page |
| * dirty races). |
| */ |
| static void attach_nobh_buffers(struct page *page, struct buffer_head *head) |
| { |
| struct buffer_head *bh; |
| |
| BUG_ON(!PageLocked(page)); |
| |
| spin_lock(&page->mapping->private_lock); |
| bh = head; |
| do { |
| if (PageDirty(page)) |
| set_buffer_dirty(bh); |
| if (!bh->b_this_page) |
| bh->b_this_page = head; |
| bh = bh->b_this_page; |
| } while (bh != head); |
| attach_page_buffers(page, head); |
| spin_unlock(&page->mapping->private_lock); |
| } |
| |
| /* |
| * On entry, the page is fully not uptodate. |
| * On exit the page is fully uptodate in the areas outside (from,to) |
| * The filesystem needs to handle block truncation upon failure. |
| */ |
| int nobh_write_begin(struct address_space *mapping, |
| loff_t pos, unsigned len, unsigned flags, |
| struct page **pagep, void **fsdata, |
| get_block_t *get_block) |
| { |
| struct inode *inode = mapping->host; |
| const unsigned blkbits = inode->i_blkbits; |
| const unsigned blocksize = 1 << blkbits; |
| struct buffer_head *head, *bh; |
| struct page *page; |
| pgoff_t index; |
| unsigned from, to; |
| unsigned block_in_page; |
| unsigned block_start, block_end; |
| sector_t block_in_file; |
| int nr_reads = 0; |
| int ret = 0; |
| int is_mapped_to_disk = 1; |
| |
| index = pos >> PAGE_CACHE_SHIFT; |
| from = pos & (PAGE_CACHE_SIZE - 1); |
| to = from + len; |
| |
| page = grab_cache_page_write_begin(mapping, index, flags); |
| if (!page) |
| return -ENOMEM; |
| *pagep = page; |
| *fsdata = NULL; |
| |
| if (page_has_buffers(page)) { |
| ret = __block_write_begin(page, pos, len, get_block); |
| if (unlikely(ret)) |
| goto out_release; |
| return ret; |
| } |
| |
| if (PageMappedToDisk(page)) |
| return 0; |
| |
| /* |
| * Allocate buffers so that we can keep track of state, and potentially |
| * attach them to the page if an error occurs. In the common case of |
| * no error, they will just be freed again without ever being attached |
| * to the page (which is all OK, because we're under the page lock). |
| * |
| * Be careful: the buffer linked list is a NULL terminated one, rather |
| * than the circular one we're used to. |
| */ |
| head = alloc_page_buffers(page, blocksize, 0); |
| if (!head) { |
| ret = -ENOMEM; |
| goto out_release; |
| } |
| |
| block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
| |
| /* |
| * We loop across all blocks in the page, whether or not they are |
| * part of the affected region. This is so we can discover if the |
| * page is fully mapped-to-disk. |
| */ |
| for (block_start = 0, block_in_page = 0, bh = head; |
| block_start < PAGE_CACHE_SIZE; |
| block_in_page++, block_start += blocksize, bh = bh->b_this_page) { |
| int create; |
| |
| block_end = block_start + blocksize; |
| bh->b_state = 0; |
| create = 1; |
| if (block_start >= to) |
| create = 0; |
| ret = get_block(inode, block_in_file + block_in_page, |
| bh, create); |
| if (ret) |
| goto failed; |
| if (!buffer_mapped(bh)) |
| is_mapped_to_disk = 0; |
| if (buffer_new(bh)) |
| unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); |
| if (PageUptodate(page)) { |
| set_buffer_uptodate(bh); |
| continue; |
| } |
| if (buffer_new(bh) || !buffer_mapped(bh)) { |
| zero_user_segments(page, block_start, from, |
| to, block_end); |
| continue; |
| } |
| if (buffer_uptodate(bh)) |
| continue; /* reiserfs does this */ |
| if (block_start < from || block_end > to) { |
| lock_buffer(bh); |
| bh->b_end_io = end_buffer_read_nobh; |
| submit_bh(READ, bh); |
| nr_reads++; |
| } |
| } |
| |
| if (nr_reads) { |
| /* |
| * The page is locked, so these buffers are protected from |
| * any VM or truncate activity. Hence we don't need to care |
| * for the buffer_head refcounts. |
| */ |
| for (bh = head; bh; bh = bh->b_this_page) { |
| wait_on_buffer(bh); |
| if (!buffer_uptodate(bh)) |
| ret = -EIO; |
| } |
| if (ret) |
| goto failed; |
| } |
| |
| if (is_mapped_to_disk) |
| SetPageMappedToDisk(page); |
| |
| *fsdata = head; /* to be released by nobh_write_end */ |
| |
| return 0; |
| |
| failed: |
| BUG_ON(!ret); |
| /* |
| * Error recovery is a bit difficult. We need to zero out blocks that |
| * were newly allocated, and dirty them to ensure they get written out. |
| * Buffers need to be attached to the page at this point, otherwise |
| * the handling of potential IO errors during writeout would be hard |
| * (could try doing synchronous writeout, but what if that fails too?) |
| */ |
| attach_nobh_buffers(page, head); |
| page_zero_new_buffers(page, from, to); |
| |
| out_release: |
| unlock_page(page); |
| page_cache_release(page); |
| *pagep = NULL; |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(nobh_write_begin); |
| |
| int nobh_write_end(struct file *file, struct address_space *mapping, |
| loff_t pos, unsigned len, unsigned copied, |
| struct page *page, void *fsdata) |
| { |
| struct inode *inode = page->mapping->host; |
| struct buffer_head *head = fsdata; |
| struct buffer_head *bh; |
| BUG_ON(fsdata != NULL && page_has_buffers(page)); |
| |
| if (unlikely(copied < len) && head) |
| attach_nobh_buffers(page, head); |
| if (page_has_buffers(page)) |
| return generic_write_end(file, mapping, pos, len, |
| copied, page, fsdata); |
| |
| SetPageUptodate(page); |
| set_page_dirty(page); |
| if (pos+copied > inode->i_size) { |
| i_size_write(inode, pos+copied); |
| mark_inode_dirty(inode); |
| } |
| |
| unlock_page(page); |
| page_cache_release(page); |
| |
| while (head) { |
| bh = head; |
| head = head->b_this_page; |
| free_buffer_head(bh); |
| } |
| |
| return copied; |
| } |
| EXPORT_SYMBOL(nobh_write_end); |
| |
| /* |
| * nobh_writepage() - based on block_full_write_page() except |
| * that it tries to operate without attaching bufferheads to |
| * the page. |
| */ |
| int nobh_writepage(struct page *page, get_block_t *get_block, |
| struct writeback_control *wbc) |
| { |
| struct inode * const inode = page->mapping->host; |
| loff_t i_size = i_size_read(inode); |
| const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
| unsigned offset; |
| int ret; |
| |
| /* Is the page fully inside i_size? */ |
| if (page->index < end_index) |
| goto out; |
| |
| /* Is the page fully outside i_size? (truncate in progress) */ |
| offset = i_size & (PAGE_CACHE_SIZE-1); |
| if (page->index >= end_index+1 || !offset) { |
| /* |
| * The page may have dirty, unmapped buffers. For example, |
| * they may have been added in ext3_writepage(). Make them |
| * freeable here, so the page does not leak. |
| */ |
| #if 0 |
| /* Not really sure about this - do we need this ? */ |
| if (page->mapping->a_ops->invalidatepage) |
| page->mapping->a_ops->invalidatepage(page, offset); |
| #endif |
| unlock_page(page); |
| return 0; /* don't care */ |
| } |
| |
| /* |
| * The page straddles i_size. It must be zeroed out on each and every |
| * writepage invocation because it may be mmapped. "A file is mapped |
| * in multiples of the page size. For a file that is not a multiple of |
| * the page size, the remaining memory is zeroed when mapped, and |
| * writes to that region are not written out to the file." |
| */ |
| zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
| out: |
| ret = mpage_writepage(page, get_block, wbc); |
| if (ret == -EAGAIN) |
| ret = __block_write_full_page(inode, page, get_block, wbc, |
| end_buffer_async_write); |
| return ret; |
| } |
| EXPORT_SYMBOL(nobh_writepage); |
| |
| int nobh_truncate_page(struct address_space *mapping, |
| loff_t from, get_block_t *get_block) |
| { |
| pgoff_t index = from >> PAGE_CACHE_SHIFT; |
| unsigned offset = from & (PAGE_CACHE_SIZE-1); |
| unsigned blocksize; |
| sector_t iblock; |
| unsigned length, pos; |
| struct inode *inode = mapping->host; |
| struct page *page; |
| struct buffer_head map_bh; |
| int err; |
| |
| blocksize = 1 << inode->i_blkbits; |
| length = offset & (blocksize - 1); |
| |
| /* Block boundary? Nothing to do */ |
| if (!length) |
| return 0; |
| |
| length = blocksize - length; |
| iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| |
| page = grab_cache_page(mapping, index); |
| err = -ENOMEM; |
| if (!page) |
| goto out; |
| |
| if (page_has_buffers(page)) { |
| has_buffers: |
| unlock_page(page); |
| page_cache_release(page); |
| return block_truncate_page(mapping, from, get_block); |
| } |
| |
| /* Find the buffer that contains "offset" */ |
| pos = blocksize; |
| while (offset >= pos) { |
| iblock++; |
| pos += blocksize; |
| } |
| |
| map_bh.b_size = blocksize; |
| map_bh.b_state = 0; |
| err = get_block(inode, iblock, &map_bh, 0); |
| if (err) |
| goto unlock; |
| /* unmapped? It's a hole - nothing to do */ |
| if (!buffer_mapped(&map_bh)) |
| goto unlock; |
| |
| /* Ok, it's mapped. Make sure it's up-to-date */ |
| if (!PageUptodate(page)) { |
| err = mapping->a_ops->readpage(NULL, page); |
| if (err) { |
| page_cache_release(page); |
| goto out; |
| } |
| lock_page(page); |
| if (!PageUptodate(page)) { |
| err = -EIO; |
| goto unlock; |
| } |
| if (page_has_buffers(page)) |
| goto has_buffers; |
| } |
| zero_user(page, offset, length); |
| set_page_dirty(page); |
| err = 0; |
| |
| unlock: |
| unlock_page(page); |
| page_cache_release(page); |
| out: |
| return err; |
| } |
| EXPORT_SYMBOL(nobh_truncate_page); |
| |
| int block_truncate_page(struct address_space *mapping, |
| loff_t from, get_block_t *get_block) |
| { |
| pgoff_t index = from >> PAGE_CACHE_SHIFT; |
| unsigned offset = from & (PAGE_CACHE_SIZE-1); |
| unsigned blocksize; |
| sector_t iblock; |
| unsigned length, pos; |
| struct inode *inode = mapping->host; |
| struct page *page; |
| struct buffer_head *bh; |
| int err; |
| |
| blocksize = 1 << inode->i_blkbits; |
| length = offset & (blocksize - 1); |
| |
| /* Block boundary? Nothing to do */ |
| if (!length) |
| return 0; |
| |
| length = blocksize - length; |
| iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
| |
| page = grab_cache_page(mapping, index); |
| err = -ENOMEM; |
| if (!page) |
| goto out; |
| |
| if (!page_has_buffers(page)) |
| create_empty_buffers(page, blocksize, 0); |
| |
| /* Find the buffer that contains "offset" */ |
| bh = page_buffers(page); |
| pos = blocksize; |
| while (offset >= pos) { |
| bh = bh->b_this_page; |
| iblock++; |
| pos += blocksize; |
| } |
| |
| err = 0; |
| if (!buffer_mapped(bh)) { |
| WARN_ON(bh->b_size != blocksize); |
| err = get_block(inode, iblock, bh, 0); |
| if (err) |
| goto unlock; |
| /* unmapped? It's a hole - nothing to do */ |
| if (!buffer_mapped(bh)) |
| goto unlock; |
| } |
| |
| /* Ok, it's mapped. Make sure it's up-to-date */ |
| if (PageUptodate(page)) |
| set_buffer_uptodate(bh); |
| |
| if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { |
| err = -EIO; |
| ll_rw_block(READ, 1, &bh); |
| wait_on_buffer(bh); |
| /* Uhhuh. Read error. Complain and punt. */ |
| if (!buffer_uptodate(bh)) |
| goto unlock; |
| } |
| |
| zero_user(page, offset, length); |
| mark_buffer_dirty(bh); |
| err = 0; |
| |
| unlock: |
| unlock_page(page); |
| page_cache_release(page); |
| out: |
| return err; |
| } |
| EXPORT_SYMBOL(block_truncate_page); |
| |
| /* |
| * The generic ->writepage function for buffer-backed address_spaces |
| * this form passes in the end_io handler used to finish the IO. |
| */ |
| int block_write_full_page_endio(struct page *page, get_block_t *get_block, |
| struct writeback_control *wbc, bh_end_io_t *handler) |
| { |
| struct inode * const inode = page->mapping->host; |
| loff_t i_size = i_size_read(inode); |
| const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
| unsigned offset; |
| |
| /* Is the page fully inside i_size? */ |
| if (page->index < end_index) |
| return __block_write_full_page(inode, page, get_block, wbc, |
| handler); |
| |
| /* Is the page fully outside i_size? (truncate in progress) */ |
| offset = i_size & (PAGE_CACHE_SIZE-1); |
| if (page->index >= end_index+1 || !offset) { |
| /* |
| * The page may have dirty, unmapped buffers. For example, |
| * they may have been added in ext3_writepage(). Make them |
| * freeable here, so the page does not leak. |
| */ |
| do_invalidatepage(page, 0); |
| unlock_page(page); |
| return 0; /* don't care */ |
| } |
| |
| /* |
| * The page straddles i_size. It must be zeroed out on each and every |
| * writepage invocation because it may be mmapped. "A file is mapped |
| * in multiples of the page size. For a file that is not a multiple of |
| * the page size, the remaining memory is zeroed when mapped, and |
| * writes to that region are not written out to the file." |
| */ |
| zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
| return __block_write_full_page(inode, page, get_block, wbc, handler); |
| } |
| EXPORT_SYMBOL(block_write_full_page_endio); |
| |
| /* |
| * The generic ->writepage function for buffer-backed address_spaces |
| */ |
| int block_write_full_page(struct page *page, get_block_t *get_block, |
| struct writeback_control *wbc) |
| { |
| return block_write_full_page_endio(page, get_block, wbc, |
| end_buffer_async_write); |
| } |
| EXPORT_SYMBOL(block_write_full_page); |
| |
| sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
| get_block_t *get_block) |
| { |
| struct buffer_head tmp; |
| struct inode *inode = mapping->host; |
| tmp.b_state = 0; |
| tmp.b_blocknr = 0; |
| tmp.b_size = 1 << inode->i_blkbits; |
| get_block(inode, block, &tmp, 0); |
| return tmp.b_blocknr; |
| } |
| EXPORT_SYMBOL(generic_block_bmap); |
| |
| static void end_bio_bh_io_sync(struct bio *bio, int err) |
| { |
| struct buffer_head *bh = bio->bi_private; |
| |
| if (err == -EOPNOTSUPP) { |
| set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
| } |
| |
| if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) |
| set_bit(BH_Quiet, &bh->b_state); |
| |
| bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
| bio_put(bio); |
| } |
| |
| int submit_bh(int rw, struct buffer_head * bh) |
| { |
| struct bio *bio; |
| int ret = 0; |
| |
| BUG_ON(!buffer_locked(bh)); |
| BUG_ON(!buffer_mapped(bh)); |
| BUG_ON(!bh->b_end_io); |
| BUG_ON(buffer_delay(bh)); |
| BUG_ON(buffer_unwritten(bh)); |
| |
| /* |
| * Only clear out a write error when rewriting |
| */ |
| if (test_set_buffer_req(bh) && (rw & WRITE)) |
| clear_buffer_write_io_error(bh); |
| |
| /* |
| * from here on down, it's all bio -- do the initial mapping, |
| * submit_bio -> generic_make_request may further map this bio around |
| */ |
| bio = bio_alloc(GFP_NOIO, 1); |
| |
| bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
| bio->bi_bdev = bh->b_bdev; |
| bio->bi_io_vec[0].bv_page = bh->b_page; |
| bio->bi_io_vec[0].bv_len = bh->b_size; |
| bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
| |
| bio->bi_vcnt = 1; |
| bio->bi_idx = 0; |
| bio->bi_size = bh->b_size; |
| |
| bio->bi_end_io = end_bio_bh_io_sync; |
| bio->bi_private = bh; |
| |
| bio_get(bio); |
| submit_bio(rw, bio); |
| |
| if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
| ret = -EOPNOTSUPP; |
| |
| bio_put(bio); |
| return ret; |
| } |
| EXPORT_SYMBOL(submit_bh); |
| |
| /** |
| * ll_rw_block: low-level access to block devices (DEPRECATED) |
| * @rw: whether to %READ or %WRITE or maybe %READA (readahead) |
| * @nr: number of &struct buffer_heads in the array |
| * @bhs: array of pointers to &struct buffer_head |
| * |
| * ll_rw_block() takes an array of pointers to &struct buffer_heads, and |
| * requests an I/O operation on them, either a %READ or a %WRITE. The third |
| * %READA option is described in the documentation for generic_make_request() |
| * which ll_rw_block() calls. |
| * |
| * This function drops any buffer that it cannot get a lock on (with the |
| * BH_Lock state bit), any buffer that appears to be clean when doing a write |
| * request, and any buffer that appears to be up-to-date when doing read |
| * request. Further it marks as clean buffers that are processed for |
| * writing (the buffer cache won't assume that they are actually clean |
| * until the buffer gets unlocked). |
| * |
| * ll_rw_block sets b_end_io to simple completion handler that marks |
| * the buffer up-to-date (if approriate), unlocks the buffer and wakes |
| * any waiters. |
| * |
| * All of the buffers must be for the same device, and must also be a |
| * multiple of the current approved size for the device. |
| */ |
| void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
| { |
| int i; |
| |
| for (i = 0; i < nr; i++) { |
| struct buffer_head *bh = bhs[i]; |
| |
| if (!trylock_buffer(bh)) |
| continue; |
| if (rw == WRITE) { |
| if (test_clear_buffer_dirty(bh)) { |
| bh->b_end_io = end_buffer_write_sync; |
| get_bh(bh); |
| submit_bh(WRITE, bh); |
| continue; |
| } |
| } else { |
| if (!buffer_uptodate(bh)) { |
| bh->b_end_io = end_buffer_read_sync; |
| get_bh(bh); |
| submit_bh(rw, bh); |
| continue; |
| } |
| } |
| unlock_buffer(bh); |
| } |
| } |
| EXPORT_SYMBOL(ll_rw_block); |
| |
| void write_dirty_buffer(struct buffer_head *bh, int rw) |
| { |
| lock_buffer(bh); |
| if (!test_clear_buffer_dirty(bh)) { |
| unlock_buffer(bh); |
| return; |
| } |
| bh->b_end_io = end_buffer_write_sync; |
| get_bh(bh); |
| submit_bh(rw, bh); |
| } |
| EXPORT_SYMBOL(write_dirty_buffer); |
| |
| /* |
| * For a data-integrity writeout, we need to wait upon any in-progress I/O |
| * and then start new I/O and then wait upon it. The caller must have a ref on |
| * the buffer_head. |
| */ |
| int __sync_dirty_buffer(struct buffer_head *bh, int rw) |
| { |
| int ret = 0; |
| |
| WARN_ON(atomic_read(&bh->b_count) < 1); |
| lock_buffer(bh); |
| if (test_clear_buffer_dirty(bh)) { |
| get_bh(bh); |
| bh->b_end_io = end_buffer_write_sync; |
| ret = submit_bh(rw, bh); |
| wait_on_buffer(bh); |
| if (!ret && !buffer_uptodate(bh)) |
| ret = -EIO; |
| } else { |
| unlock_buffer(bh); |
| } |
| return ret; |
| } |
| EXPORT_SYMBOL(__sync_dirty_buffer); |
| |
| int sync_dirty_buffer(struct buffer_head *bh) |
| { |
| return __sync_dirty_buffer(bh, WRITE_SYNC); |
| } |
| EXPORT_SYMBOL(sync_dirty_buffer); |
| |
| /* |
| * try_to_free_buffers() checks if all the buffers on this particular page |
| * are unused, and releases them if so. |
| * |
| * Exclusion against try_to_free_buffers may be obtained by either |
| * locking the page or by holding its mapping's private_lock. |
| * |
| * If the page is dirty but all the buffers are clean then we need to |
| * be sure to mark the page clean as well. This is because the page |
| * may be against a block device, and a later reattachment of buffers |
| * to a dirty page will set *all* buffers dirty. Which would corrupt |
| * filesystem data on the same device. |
| * |
| * The same applies to regular filesystem pages: if all the buffers are |
| * clean then we set the page clean and proceed. To do that, we require |
| * total exclusion from __set_page_dirty_buffers(). That is obtained with |
| * private_lock. |
| * |
| * try_to_free_buffers() is non-blocking. |
| */ |
| static inline int buffer_busy(struct buffer_head *bh) |
| { |
| return atomic_read(&bh->b_count) | |
| (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
| } |
| |
| static int |
| drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
| { |
| struct buffer_head *head = page_buffers(page); |
| struct buffer_head *bh; |
| |
| bh = head; |
| do { |
| if (buffer_write_io_error(bh) && page->mapping) |
| set_bit(AS_EIO, &page->mapping->flags); |
| if (buffer_busy(bh)) |
| goto failed; |
| bh = bh->b_this_page; |
| } while (bh != head); |
| |
| do { |
| struct buffer_head *next = bh->b_this_page; |
| |
| if (bh->b_assoc_map) |
| __remove_assoc_queue(bh); |
| bh = next; |
| } while (bh != head); |
| *buffers_to_free = head; |
| __clear_page_buffers(page); |
| return 1; |
| failed: |
| return 0; |
| } |
| |
| int try_to_free_buffers(struct page *page) |
| { |
| struct address_space * const mapping = page->mapping; |
| struct buffer_head *buffers_to_free = NULL; |
| int ret = 0; |
| |
| BUG_ON(!PageLocked(page)); |
| if (PageWriteback(page)) |
| return 0; |
| |
| if (mapping == NULL) { /* can this still happen? */ |
| ret = drop_buffers(page, &buffers_to_free); |
| goto out; |
| } |
| |
| spin_lock(&mapping->private_lock); |
| ret = drop_buffers(page, &buffers_to_free); |
| |
| /* |
| * If the filesystem writes its buffers by hand (eg ext3) |
| * then we can have clean buffers against a dirty page. We |
| * clean the page here; otherwise the VM will never notice |
| * that the filesystem did any IO at all. |
| * |
| * Also, during truncate, discard_buffer will have marked all |
| * the page's buffers clean. We discover that here and clean |
| * the page also. |
| * |
| * private_lock must be held over this entire operation in order |
| * to synchronise against __set_page_dirty_buffers and prevent the |
| * dirty bit from being lost. |
| */ |
| if (ret) |
| cancel_dirty_page(page, PAGE_CACHE_SIZE); |
| spin_unlock(&mapping->private_lock); |
| out: |
| if (buffers_to_free) { |
| struct buffer_head *bh = buffers_to_free; |
| |
| do { |
| struct buffer_head *next = bh->b_this_page; |
| free_buffer_head(bh); |
| bh = next; |
| } while (bh != buffers_to_free); |
| } |
| return ret; |
| } |
| EXPORT_SYMBOL(try_to_free_buffers); |
| |
| /* |
| * There are no bdflush tunables left. But distributions are |
| * still running obsolete flush daemons, so we terminate them here. |
| * |
| * Use of bdflush() is deprecated and will be removed in a future kernel. |
| * The `flush-X' kernel threads fully replace bdflush daemons and this call. |
| */ |
| SYSCALL_DEFINE2(bdflush, int, func, long, data) |
| { |
| static int msg_count; |
| |
| if (!capable(CAP_SYS_ADMIN)) |
| return -EPERM; |
| |
| if (msg_count < 5) { |
| msg_count++; |
| printk(KERN_INFO |
| "warning: process `%s' used the obsolete bdflush" |
| " system call\n", current->comm); |
| printk(KERN_INFO "Fix your initscripts?\n"); |
| } |
| |
| if (func == 1) |
| do_exit(0); |
| return 0; |
| } |
| |
| /* |
| * Buffer-head allocation |
| */ |
| static struct kmem_cache *bh_cachep __read_mostly; |
| |
| /* |
| * Once the number of bh's in the machine exceeds this level, we start |
| * stripping them in writeback. |
| */ |
| static int max_buffer_heads; |
| |
| int buffer_heads_over_limit; |
| |
| struct bh_accounting { |
| int nr; /* Number of live bh's */ |
| int ratelimit; /* Limit cacheline bouncing */ |
| }; |
| |
| static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
| |
| static void recalc_bh_state(void) |
| { |
| int i; |
| int tot = 0; |
| |
| if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) |
| return; |
| __this_cpu_write(bh_accounting.ratelimit, 0); |
| for_each_online_cpu(i) |
| tot += per_cpu(bh_accounting, i).nr; |
| buffer_heads_over_limit = (tot > max_buffer_heads); |
| } |
| |
| struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) |
| { |
| struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); |
| if (ret) { |
| INIT_LIST_HEAD(&ret->b_assoc_buffers); |
| preempt_disable(); |
| __this_cpu_inc(bh_accounting.nr); |
| recalc_bh_state(); |
| preempt_enable(); |
| } |
| return ret; |
| } |
| EXPORT_SYMBOL(alloc_buffer_head); |
| |
| void free_buffer_head(struct buffer_head *bh) |
| { |
| BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
| kmem_cache_free(bh_cachep, bh); |
| preempt_disable(); |
| __this_cpu_dec(bh_accounting.nr); |
| recalc_bh_state(); |
| preempt_enable(); |
| } |
| EXPORT_SYMBOL(free_buffer_head); |
| |
| static void buffer_exit_cpu(int cpu) |
| { |
| int i; |
| struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
| |
| for (i = 0; i < BH_LRU_SIZE; i++) { |
| brelse(b->bhs[i]); |
| b->bhs[i] = NULL; |
| } |
| this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); |
| per_cpu(bh_accounting, cpu).nr = 0; |
| } |
| |
| static int buffer_cpu_notify(struct notifier_block *self, |
| unsigned long action, void *hcpu) |
| { |
| if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) |
| buffer_exit_cpu((unsigned long)hcpu); |
| return NOTIFY_OK; |
| } |
| |
| /** |
| * bh_uptodate_or_lock - Test whether the buffer is uptodate |
| * @bh: struct buffer_head |
| * |
| * Return true if the buffer is up-to-date and false, |
| * with the buffer locked, if not. |
| */ |
| int bh_uptodate_or_lock(struct buffer_head *bh) |
| { |
| if (!buffer_uptodate(bh)) { |
| lock_buffer(bh); |
| if (!buffer_uptodate(bh)) |
| return 0; |
| unlock_buffer(bh); |
| } |
| return 1; |
| } |
| EXPORT_SYMBOL(bh_uptodate_or_lock); |
| |
| /** |
| * bh_submit_read - Submit a locked buffer for reading |
| * @bh: struct buffer_head |
| * |
| * Returns zero on success and -EIO on error. |
| */ |
| int bh_submit_read(struct buffer_head *bh) |
| { |
| BUG_ON(!buffer_locked(bh)); |
| |
| if (buffer_uptodate(bh)) { |
| unlock_buffer(bh); |
| return 0; |
| } |
| |
| get_bh(bh); |
| bh->b_end_io = end_buffer_read_sync; |
| submit_bh(READ, bh); |
| wait_on_buffer(bh); |
| if (buffer_uptodate(bh)) |
| return 0; |
| return -EIO; |
|