| Changes since 2.5.0: | |
| --- | |
| [recommended] | |
| New helpers: sb_bread(), sb_getblk(), sb_find_get_block(), set_bh(), | |
| sb_set_blocksize() and sb_min_blocksize(). | |
| Use them. | |
| (sb_find_get_block() replaces 2.4's get_hash_table()) | |
| --- | |
| [recommended] | |
| New methods: ->alloc_inode() and ->destroy_inode(). | |
| Remove inode->u.foo_inode_i | |
| Declare | |
| struct foo_inode_info { | |
| /* fs-private stuff */ | |
| struct inode vfs_inode; | |
| }; | |
| static inline struct foo_inode_info *FOO_I(struct inode *inode) | |
| { | |
| return list_entry(inode, struct foo_inode_info, vfs_inode); | |
| } | |
| Use FOO_I(inode) instead of &inode->u.foo_inode_i; | |
| Add foo_alloc_inode() and foo_destory_inode() - the former should allocate | |
| foo_inode_info and return the address of ->vfs_inode, the latter should free | |
| FOO_I(inode) (see in-tree filesystems for examples). | |
| Make them ->alloc_inode and ->destroy_inode in your super_operations. | |
| Keep in mind that now you need explicit initialization of private data - | |
| typically in ->read_inode() and after getting an inode from new_inode(). | |
| At some point that will become mandatory. | |
| --- | |
| [mandatory] | |
| Change of file_system_type method (->read_super to ->get_sb) | |
| ->read_super() is no more. Ditto for DECLARE_FSTYPE and DECLARE_FSTYPE_DEV. | |
| Turn your foo_read_super() into a function that would return 0 in case of | |
| success and negative number in case of error (-EINVAL unless you have more | |
| informative error value to report). Call it foo_fill_super(). Now declare | |
| int foo_get_sb(struct file_system_type *fs_type, | |
| int flags, const char *dev_name, void *data, struct vfsmount *mnt) | |
| { | |
| return get_sb_bdev(fs_type, flags, dev_name, data, foo_fill_super, | |
| mnt); | |
| } | |
| (or similar with s/bdev/nodev/ or s/bdev/single/, depending on the kind of | |
| filesystem). | |
| Replace DECLARE_FSTYPE... with explicit initializer and have ->get_sb set as | |
| foo_get_sb. | |
| --- | |
| [mandatory] | |
| Locking change: ->s_vfs_rename_sem is taken only by cross-directory renames. | |
| Most likely there is no need to change anything, but if you relied on | |
| global exclusion between renames for some internal purpose - you need to | |
| change your internal locking. Otherwise exclusion warranties remain the | |
| same (i.e. parents and victim are locked, etc.). | |
| --- | |
| [informational] | |
| Now we have the exclusion between ->lookup() and directory removal (by | |
| ->rmdir() and ->rename()). If you used to need that exclusion and do | |
| it by internal locking (most of filesystems couldn't care less) - you | |
| can relax your locking. | |
| --- | |
| [mandatory] | |
| ->lookup(), ->truncate(), ->create(), ->unlink(), ->mknod(), ->mkdir(), | |
| ->rmdir(), ->link(), ->lseek(), ->symlink(), ->rename() | |
| and ->readdir() are called without BKL now. Grab it on entry, drop upon return | |
| - that will guarantee the same locking you used to have. If your method or its | |
| parts do not need BKL - better yet, now you can shift lock_kernel() and | |
| unlock_kernel() so that they would protect exactly what needs to be | |
| protected. | |
| --- | |
| [mandatory] | |
| BKL is also moved from around sb operations. ->write_super() Is now called | |
| without BKL held. BKL should have been shifted into individual fs sb_op | |
| functions. If you don't need it, remove it. | |
| --- | |
| [informational] | |
| check for ->link() target not being a directory is done by callers. Feel | |
| free to drop it... | |
| --- | |
| [informational] | |
| ->link() callers hold ->i_mutex on the object we are linking to. Some of your | |
| problems might be over... | |
| --- | |
| [mandatory] | |
| new file_system_type method - kill_sb(superblock). If you are converting | |
| an existing filesystem, set it according to ->fs_flags: | |
| FS_REQUIRES_DEV - kill_block_super | |
| FS_LITTER - kill_litter_super | |
| neither - kill_anon_super | |
| FS_LITTER is gone - just remove it from fs_flags. | |
| --- | |
| [mandatory] | |
| FS_SINGLE is gone (actually, that had happened back when ->get_sb() | |
| went in - and hadn't been documented ;-/). Just remove it from fs_flags | |
| (and see ->get_sb() entry for other actions). | |
| --- | |
| [mandatory] | |
| ->setattr() is called without BKL now. Caller _always_ holds ->i_mutex, so | |
| watch for ->i_mutex-grabbing code that might be used by your ->setattr(). | |
| Callers of notify_change() need ->i_mutex now. | |
| --- | |
| [recommended] | |
| New super_block field "struct export_operations *s_export_op" for | |
| explicit support for exporting, e.g. via NFS. The structure is fully | |
| documented at its declaration in include/linux/fs.h, and in | |
| Documentation/filesystems/Exporting. | |
| Briefly it allows for the definition of decode_fh and encode_fh operations | |
| to encode and decode filehandles, and allows the filesystem to use | |
| a standard helper function for decode_fh, and provide file-system specific | |
| support for this helper, particularly get_parent. | |
| It is planned that this will be required for exporting once the code | |
| settles down a bit. | |
| [mandatory] | |
| s_export_op is now required for exporting a filesystem. | |
| isofs, ext2, ext3, resierfs, fat | |
| can be used as examples of very different filesystems. | |
| --- | |
| [mandatory] | |
| iget4() and the read_inode2 callback have been superseded by iget5_locked() | |
| which has the following prototype, | |
| struct inode *iget5_locked(struct super_block *sb, unsigned long ino, | |
| int (*test)(struct inode *, void *), | |
| int (*set)(struct inode *, void *), | |
| void *data); | |
| 'test' is an additional function that can be used when the inode | |
| number is not sufficient to identify the actual file object. 'set' | |
| should be a non-blocking function that initializes those parts of a | |
| newly created inode to allow the test function to succeed. 'data' is | |
| passed as an opaque value to both test and set functions. | |
| When the inode has been created by iget5_locked(), it will be returned with | |
| the I_NEW flag set and will still be locked. read_inode has not been | |
| called so the file system still has to finalize the initialization. Once | |
| the inode is initialized it must be unlocked by calling unlock_new_inode(). | |
| The filesystem is responsible for setting (and possibly testing) i_ino | |
| when appropriate. There is also a simpler iget_locked function that | |
| just takes the superblock and inode number as arguments and does the | |
| test and set for you. | |
| e.g. | |
| inode = iget_locked(sb, ino); | |
| if (inode->i_state & I_NEW) { | |
| read_inode_from_disk(inode); | |
| unlock_new_inode(inode); | |
| } | |
| --- | |
| [recommended] | |
| ->getattr() finally getting used. See instances in nfs, minix, etc. | |
| --- | |
| [mandatory] | |
| ->revalidate() is gone. If your filesystem had it - provide ->getattr() | |
| and let it call whatever you had as ->revlidate() + (for symlinks that | |
| had ->revalidate()) add calls in ->follow_link()/->readlink(). | |
| --- | |
| [mandatory] | |
| ->d_parent changes are not protected by BKL anymore. Read access is safe | |
| if at least one of the following is true: | |
| * filesystem has no cross-directory rename() | |
| * dcache_lock is held | |
| * we know that parent had been locked (e.g. we are looking at | |
| ->d_parent of ->lookup() argument). | |
| * we are called from ->rename(). | |
| * the child's ->d_lock is held | |
| Audit your code and add locking if needed. Notice that any place that is | |
| not protected by the conditions above is risky even in the old tree - you | |
| had been relying on BKL and that's prone to screwups. Old tree had quite | |
| a few holes of that kind - unprotected access to ->d_parent leading to | |
| anything from oops to silent memory corruption. | |
| --- | |
| [mandatory] | |
| FS_NOMOUNT is gone. If you use it - just set MS_NOUSER in flags | |
| (see rootfs for one kind of solution and bdev/socket/pipe for another). | |
| --- | |
| [recommended] | |
| Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter | |
| is still alive, but only because of the mess in drivers/s390/block/dasd.c. | |
| As soon as it gets fixed is_read_only() will die. | |
| --- | |
| [mandatory] | |
| ->permission() is called without BKL now. Grab it on entry, drop upon | |
| return - that will guarantee the same locking you used to have. If | |
| your method or its parts do not need BKL - better yet, now you can | |
| shift lock_kernel() and unlock_kernel() so that they would protect | |
| exactly what needs to be protected. | |
| --- | |
| [mandatory] | |
| ->statfs() is now called without BKL held. BKL should have been | |
| shifted into individual fs sb_op functions where it's not clear that | |
| it's safe to remove it. If you don't need it, remove it. | |
| --- | |
| [mandatory] | |
| is_read_only() is gone; use bdev_read_only() instead. | |
| --- | |
| [mandatory] | |
| destroy_buffers() is gone; use invalidate_bdev(). | |
| --- | |
| [mandatory] | |
| fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is | |
| deliberate; as soon as struct block_device * is propagated in a reasonable | |
| way by that code fixing will become trivial; until then nothing can be | |
| done. |