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block: hold ->invalidate_lock in blkdev_fallocate

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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>
This commit is contained in:
Ming Lei 2021-09-23 10:37:51 +08:00 committed by Jens Axboe
parent 5afedf670c
commit f278eb3d81
1 changed files with 10 additions and 11 deletions
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21
block/fops.c
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@ -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 ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
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 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
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 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
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 = {