Re: [f2fs-dev] [PATCH] f2fs: fix to prevent clearing immutable for large folio supported inode

[Nanzhe Zhao <nzzhao@126.com>]

Hi all:

在 2026/1/9 16:44, Chao Yu via Linux-f2fs-devel 写道:

> w/ above locks, it seems there is still a race condition as below:
> 
> f2fs_fileattr_set                read
>   - f2fs_setflags_common
>    - truncate_pagecache
>                          - f2fs_read_data_large_folio
>                          : read large folios
>    - mapping_set_folio_order_range
> 
> Thanks,

I noticed that the comment for `mapping_set_folio_order_range()` says:

> "Context: This should not be called while the inode is active as it is non-atomic."

I'm not sure whether cases like f2fs_fileattr_set falls into the inode 
active case.

>>
>>
>> If clearing immutable is indeed rare, we may leave this as is, since
>> writes are not supported until the page cache is fully dropped.
>> Eventually, we will support large folios on non-immutable files.
>>
>> Thanks
>> Barry

Also, I couldn’t find any API in `include/linux/pagemap.h` that can 
atomically set the
folio order range. However, I think dynamically setting large folio 
order while an inode
is active is a reasonable requirement. In my non immutable file large 
folio write work, I need to enable large folio support for a file when 
it is converted from an inline file to a non-inline file. The lack of an 
atomic API seems to be a blocker for moving large folio write forward.
Any idea on that?

Thanks,
Nanzhe Zhao