On Wed, Apr 19 2023 at  9:47P -0400,
Sarthak Kukreti <sarthakkukr...@chromium.org> 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")

You should add:

Cc: sta...@vger.kernel.org
Reported-by: Darrick J. Wong <djw...@kernel.org>

> Signed-off-by: Sarthak Kukreti <sarthakkukr...@chromium.org>
> ---
>  block/fops.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/block/fops.c b/block/fops.c
> index d2e6be4e3d1c..d359254c645d 100644
> --- a/block/fops.c
> +++ b/block/fops.c
> @@ -648,26 +648,37 @@ 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;
> -

You remove the only user of the 'fail' label.  But I think it'd be
cleaner to keep using it below (reduces indentation churn too).

> +     /*
> +      * 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,
> -                                          len >> SECTOR_SHIFT, GFP_KERNEL,
> -                                          BLKDEV_ZERO_NOUNMAP);
> +             error = truncate_bdev_range(bdev, file->f_mode, start, end);
> +             if (!error)
> +                     error = blkdev_issue_zeroout(bdev,
> +                                                  start >> SECTOR_SHIFT,
> +                                                  len >> SECTOR_SHIFT,
> +                                                  GFP_KERNEL,
> +                                                  BLKDEV_ZERO_NOUNMAP);
>               break;


So:

                error = truncate_bdev_range(bdev, file->f_mode, start, end);
                if (error)
                        goto fail;
                ...


>       case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
> -             error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
> -                                          len >> SECTOR_SHIFT, GFP_KERNEL,
> -                                          BLKDEV_ZERO_NOFALLBACK);
> +             error = truncate_bdev_range(bdev, file->f_mode, start, end);
> +             if (!error)
> +                     error = blkdev_issue_zeroout(bdev,
> +                                                  start >> SECTOR_SHIFT,
> +                                                  len >> SECTOR_SHIFT,
> +                                                  GFP_KERNEL,
> +                                                  BLKDEV_ZERO_NOFALLBACK);
>               break;

Same.

>       case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | 
> FALLOC_FL_NO_HIDE_STALE:
> -             error = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT,
> -                                          len >> SECTOR_SHIFT, GFP_KERNEL);
> +             error = truncate_bdev_range(bdev, file->f_mode, start, end);
> +             if (!error)
> +                     error = blkdev_issue_discard(bdev,
> +                                                  start >> SECTOR_SHIFT,
> +                                                  len >> SECTOR_SHIFT,
> +                                                  GFP_KERNEL);
>               break;

Same.

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