Re: [PATCH v5 1/5] block: Don't invalidate pagecache for invalid falloc modes

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Apr 19, 2023 at 05:48:46PM -0700, Sarthak Kukreti wrote:
> Only call truncate_bdev_range() if the fallocate mode is
> supported. This fixes a bug where data in the pagecache
> could be invalidated if the fallocate() was called on the
> block device with an invalid mode.
> 
> Fixes: 25f4c41415e5 ("block: implement (some of) fallocate for block devices")
> Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
> ---
>  block/fops.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/block/fops.c b/block/fops.c
> index d2e6be4e3d1c..2fd7e8b9ab48 100644
> --- a/block/fops.c
> +++ b/block/fops.c
> @@ -648,25 +648,27 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
>  
>  	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)
> -		goto fail;
> -
> +	/*
> +	 * Invalidate the page cache, including dirty pages, for valid
> +	 * de-allocate mode calls to fallocate().
> +	 */
>  	switch (mode) {
>  	case FALLOC_FL_ZERO_RANGE:
>  	case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:
> -		error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
> +		error = truncate_bdev_range(bdev, file->f_mode, start, end) ||
> +			blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,

I'm pretty sure we're supposed to preserve the error codes returned by
both functions.

	error = truncate_bdev_range(...);
	if (!error)
		error = blkdev_issue_zeroout(...);

--D

>  					     len >> SECTOR_SHIFT, GFP_KERNEL,
>  					     BLKDEV_ZERO_NOUNMAP);
>  		break;
>  	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
> -		error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
> +		error = truncate_bdev_range(bdev, file->f_mode, start, end) ||
> +			blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
>  					     len >> SECTOR_SHIFT, GFP_KERNEL,
>  					     BLKDEV_ZERO_NOFALLBACK);
>  		break;
>  	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
> -		error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
> +		error = truncate_bdev_range(bdev, file->f_mode, start, end) ||
> +			blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
>  					     len >> SECTOR_SHIFT, GFP_KERNEL);
>  		break;
>  	default:
> -- 
> 2.40.0.634.g4ca3ef3211-goog
>