Re: [PATCH 1/2] block: Hold invalidate_lock in BLKDISCARD ioctl

[Jan Kara <jack@suse.cz>]

On Tue 09-11-21 19:47:22, Shin'ichiro Kawasaki wrote:
> When BLKDISCARD ioctl and data read race, the data read leaves stale
> page cache. To avoid the stale page cache, hold invalidate_lock of the
> block device file mapping. The stale page cache is observed when
> blktests test case block/009 is repeated hundreds of times.
> 
> This patch can be applied back to the stable kernel version v5.15.y
> with slight patch edit. Rework is required for older stable kernels.
> 
> Fixes: 351499a172c0 ("block: Invalidate cache on discard v2")
> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> Cc: stable@vger.kernel.org # v5.15

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  block/ioctl.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/block/ioctl.c b/block/ioctl.c
> index d6af0ac97e57..9fa87f64f703 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -113,6 +113,7 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
>  	uint64_t range[2];
>  	uint64_t start, len;
>  	struct request_queue *q = bdev_get_queue(bdev);
> +	struct inode *inode = bdev->bd_inode;
>  	int err;
>  
>  	if (!(mode & FMODE_WRITE))
> @@ -135,12 +136,17 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
>  	if (start + len > bdev_nr_bytes(bdev))
>  		return -EINVAL;
>  
> +	filemap_invalidate_lock(inode->i_mapping);
>  	err = truncate_bdev_range(bdev, mode, start, start + len - 1);
>  	if (err)
> -		return err;
> +		goto fail;
> +
> +	err = blkdev_issue_discard(bdev, start >> 9, len >> 9,
> +				   GFP_KERNEL, flags);
>  
> -	return blkdev_issue_discard(bdev, start >> 9, len >> 9,
> -				    GFP_KERNEL, flags);
> +fail:
> +	filemap_invalidate_unlock(inode->i_mapping);
> +	return err;
>  }
>  
>  static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode,
> -- 
> 2.33.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR