Re: [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadloop in f2fs_fsync_node_pages()

[Zhiguo Niu]

Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx>
于2026年8月24日周一 21:19写道：
>
> There is potential deadloop in race condition:
>
> Thread A                                Thread B
> - fsync
>  - f2fs_do_sync_file
>   - f2fs_fsync_node_pages
>    - last_fsync_dnode
>     - folio_get(last_folio)
>                                         - f2fs_setattr
>                                          - f2fs_truncate
>                                           - f2fs_truncate_blocks
>                                            - f2fs_do_truncate_blocks
>                                             - f2fs_truncate_inode_blocks
>                                              - truncate_dnode
>                                               - truncate_node
>                                                - invalidate_mapping_pages
>                                                 - folio->mapping = NULL
>    - is_node_folio alwasy return false
>    - atomic && !marked is always true,
>      then goto retry
>
> Cc: stable@xxxxxxxxxx
> Fixes: 608514deba38 ("f2fs: set fsync mark only for the last dnode")
> Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
> ---
>  fs/f2fs/node.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 968e5ed38816..86c2e67e43b6 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -2016,6 +2016,11 @@ int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
>                 f2fs_debug(sbi, "Retry to write fsync mark: ino=%u, idx=%lx",
>                            ino, last_folio->index);
>                 folio_lock(last_folio);
> +               if (unlikely(!is_node_folio(last_folio))) {
Hi Chao,
is_node_folio->NODE_MAPPING(F2FS_F_SB(folio))->F2FS_M_SB(folio->mappping)->F2FS_I_SB(mapping->host)
if mapping==NULL, panic will occur here?
just like  commit msg in  mai: "f2fs: parameterize node helpers and macros"
thanks！

> +                       f2fs_folio_put(last_folio, true);
> +                       ret = -EAGAIN;
> +                       goto out;
> +               }
>                 f2fs_folio_wait_writeback(last_folio, NODE, true, true);
>                 folio_mark_dirty(last_folio);
>                 folio_unlock(last_folio);
> --
> 2.49.0
>
>
>
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