Commit f278eb3d authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

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: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210923023751.1441091-1-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5afedf67

block/fops.c

+10 −11
Original line number Diff line number Diff line
@@ -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 = {