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

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 9/9/26 09:12, Zhiguo Niu wrote:
> Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>
> 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@kernel.org
>> Fixes: 608514deba38 ("f2fs: set fsync mark only for the last dnode")
>> Signed-off-by: Chao Yu <chao@kernel.org>
>> ---
>>  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"

Hi Zhiguo,

Ah, seems we need to revert ("f2fs: introduce is_{meta,node}_folio") which
introduce this bug? IIUC.

Thanks,

> 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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