Re: [f2fs-dev][PATCH] f2fs: fsverity: modify truncation for verity enable failed

[Eric Biggers <ebiggers@kernel.org>]

Hi Yunlei,

On Tue, Mar 02, 2021 at 07:38:50PM +0800, Yunlei He wrote:
> If file enable verity failed, should truncate anything wrote
> past i_size, including cache pages. Move the truncation to
> the end of function, in case of f2fs set xattr failed.
> 
> 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 | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/f2fs/verity.c b/fs/f2fs/verity.c
> index 054ec852b5ea..610f2a9b4928 100644
> --- a/fs/f2fs/verity.c
> +++ b/fs/f2fs/verity.c
> @@ -169,10 +169,6 @@ static int f2fs_end_enable_verity(struct file *filp, const void *desc,
>  			err = filemap_write_and_wait(inode->i_mapping);
>  	}
>  
> -	/* If we failed, truncate anything we wrote past i_size. */
> -	if (desc == NULL || err)
> -		f2fs_truncate(inode);
> -
>  	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
>  
>  	if (desc != NULL && !err) {
> @@ -185,6 +181,13 @@ static int f2fs_end_enable_verity(struct file *filp, const void *desc,
>  			f2fs_mark_inode_dirty_sync(inode, true);
>  		}
>  	}
> +
> +	/* If we failed, truncate anything we wrote past i_size. */
> +	if (desc == NULL || err) {
> +		truncate_inode_pages(inode->i_mapping, inode->i_size);
> +		f2fs_truncate(inode);
> +	}
> +
>  	return err;

This is better, but we really should properly separate the success path from the
error paths in this function; otherwise it's too hard to understand.  Also, the
same bugs need to be fixed in ext4 too, and the commit message could be better.
I went ahead and sent out a new patchset which addresses all this
(https://lkml.kernel.org/linux-f2fs-devel/20210302200420.137977-1-ebiggers@kernel.org/T/#u);
can you take a look at that instead?  Thanks!

- Eric