Re: [PATCH] f2fs: fix i_size when pinned fallocate partially fails

[Chao Yu <chao@kernel.org>]

On 8/17/26 10:27, Zhan Xusheng wrote:
> From: Zhan Xusheng <zhanxusheng1024@gmail.com>
> 
> From: Zhan Xusheng <zhanxusheng@xiaomi.com>
> 
> Commit 4275b59673eb ("f2fs: fix to round down start offset of fallocate
> for pin file") moved the allocation loop's start down to a section
> boundary, but the error path still converts @expanded against @pg_start,
> which holds the unrounded start.
> 
> @pg_start exists for that conversion: commit 88f2cfc5fa90 ("f2fs: fix to
> update last i_size if fallocate partially succeeds") added it as an
> immutable base because map.m_lblk moves every round.  Each round now maps
> exactly sec_blks blocks starting from rounddown(pg_start, sec_blks), so
> pg_start + expanded overshoots the last allocated block by
> pg_start % sec_blks, and a partial failure leaves i_size covering a tail
> that was never allocated.  Nothing corrects that afterwards either, since
> file_dont_truncate() has already cleared FADVISE_TRUNC_BIT.
> 
> Keep @pg_start pointing at where allocation actually begins.

Hi Xuesheng,

Can you please provide a reproducer?

Thanks,

> 
> Fixes: 4275b59673eb ("f2fs: fix to round down start offset of fallocate for pin file")
> Cc: stable@vger.kernel.org
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
> ---
>   fs/f2fs/file.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 4b52c56d71f0..cc0d2b8c4684 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1919,8 +1919,9 @@ static int f2fs_expand_inode_data(struct inode *inode, loff_t offset,
>   		block_t sec_len;
>   
>   		if (map.m_lblk % sec_blks) {
> -			map.m_lblk = rounddown(map.m_lblk, sec_blks);
> -			map.m_len = pg_end - map.m_lblk;
> +			pg_start = rounddown(map.m_lblk, sec_blks);
> +			map.m_lblk = pg_start;
> +			map.m_len = pg_end - pg_start;
>   			if (off_end)
>   				map.m_len++;
>   		}