Re: [PATCH v2] f2fs: fsverity: Truncate cache pages if set verity failed

[Eric Biggers <ebiggers@kernel.org>]

On Mon, Mar 01, 2021 at 10:15:06PM +0800, Yunlei He wrote:
> If file enable verity failed, should truncate anything wrote
> past i_size, including cache pages.

The commit message and title need to be updated to properly describe the change.
They were okay for v1, but v2 makes additional changes.

> 
> Fixes: 95ae251fe828 ("f2fs: add fs-verity support")
> Cc: <stable@vger.kernel.org> # v5.4+
> Signed-off-by: Yunlei He <heyunlei@hihonor.com>
> ---
>  fs/f2fs/verity.c | 47 +++++++++++++++++++++++++----------------------
>  1 file changed, 25 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/f2fs/verity.c b/fs/f2fs/verity.c
> index 054ec852b5ea..3aa851affc46 100644
> --- a/fs/f2fs/verity.c
> +++ b/fs/f2fs/verity.c
> @@ -158,33 +158,36 @@ static int f2fs_end_enable_verity(struct file *filp, const void *desc,
>  		.size = cpu_to_le32(desc_size),
>  		.pos = cpu_to_le64(desc_pos),
>  	};
> -	int err = 0;
> +	int err;
>  
> -	if (desc != NULL) {
> -		/* Succeeded; write the verity descriptor. */
> -		err = pagecache_write(inode, desc, desc_size, desc_pos);
> +	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
> +	if (!desc)
> +		return 0;

This isn't correct.  If desc == NULL (indicating that enabling verity failed),
it's still necessary to truncate the stuff past i_size.

>  
> -		/* Write all pages before clearing FI_VERITY_IN_PROGRESS. */
> -		if (!err)
> -			err = filemap_write_and_wait(inode->i_mapping);

As the comment above (which you deleted) says, all pages need to be written
before clearing FI_VERITY_IN_PROGRESS.

- Eric