block: hold ->invalidate_lock in blkdev_fallocate
When running ->fallocate(), blkdev_fallocate() should hold
mapping->invalidate_lock to prevent page cache from being accessed,
otherwise stale data may be read in page cache.
Without this patch, blktests block/009 fails sometimes. With this patch,
block/009 can pass always.
Also as Jan pointed out, no pages can be created in the discarded area
while you are holding the invalidate_lock, so remove the 2nd
truncate_bdev_range().
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210923023751.1441091-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/fops.c b/block/fops.c
index ffce6f6..1e970c2 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -14,6 +14,7 @@
#include <linux/task_io_accounting_ops.h>
#include <linux/falloc.h>
#include <linux/suspend.h>
+#include <linux/fs.h>
#include "blk.h"
static struct inode *bdev_file_inode(struct file *file)
@@ -553,7 +554,8 @@
static long blkdev_fallocate(struct file *file, int mode, loff_t start,
loff_t len)
{
- struct block_device *bdev = I_BDEV(bdev_file_inode(file));
+ struct inode *inode = bdev_file_inode(file);
+ struct block_device *bdev = I_BDEV(inode);
loff_t end = start + len - 1;
loff_t isize;
int error;
@@ -580,10 +582,12 @@
if ((start | len) & (bdev_logical_block_size(bdev) - 1))
return -EINVAL;
+ filemap_invalidate_lock(inode->i_mapping);
+
/* Invalidate the page cache, including dirty pages. */
error = truncate_bdev_range(bdev, file->f_mode, start, end);
if (error)
- return error;
+ goto fail;
switch (mode) {
case FALLOC_FL_ZERO_RANGE:
@@ -600,17 +604,12 @@
GFP_KERNEL, 0);
break;
default:
- return -EOPNOTSUPP;
+ error = -EOPNOTSUPP;
}
- if (error)
- return error;
- /*
- * Invalidate the page cache again; if someone wandered in and dirtied
- * a page, we just discard it - userspace has no way of knowing whether
- * the write happened before or after discard completing...
- */
- return truncate_bdev_range(bdev, file->f_mode, start, end);
+ fail:
+ filemap_invalidate_unlock(inode->i_mapping);
+ return error;
}
const struct file_operations def_blk_fops = {
