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

Mike Snitzer
2023-04-20T16:21:21Z

On Wed, Apr 19 2023 at 9:47P -0400,
Sarthak Kukreti <sarthakkukreti@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: stable@vger.kernel.org
Reported-by: Darrick J. Wong <djwong@kernel.org>

> Signed-off-by: Sarthak Kukreti <sarthakkukreti@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.