Re: [f2fs-dev] [PATCH] f2fs: convert inline quota files when turning quota on

[Chao Yu <chao@kernel.org>]

On 10/5/26 01:04, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@google.com>
> 
> With a block size larger than 4KB, the inline data area is large enough
> to hold a freshly created quota file (quotacheck writes 6KB), so
> aquota.user/aquota.group stay inline after quotaon. f2fs does not
> expect quota files to be inline, and this causes two problems:
> 
> 1. Quota file corruption. f2fs_write_single_data_page() sends quota
>    inodes straight to f2fs_do_write_data_page(), which sees NULL_ADDR
>    for index 0, treats the folio as truncated and drops it. Updates to
>    the quota file are lost once the folio is reclaimed, so the quota
>    tree reads stale data: chown/chgrp fail with EIO and quota entries
>    of users disappear. For example, the kernel log shows:
> 
>      find_free_dqentry: Data block full but it shouldn't
>      qtree_write_dquot: Error -5 occurred while creating quota
> 
> 2. Deadlock. Writing a quota file past MAX_INLINE_DATA converts it from
>    f2fs_write_begin() under f2fs_lock_op(). dquot_transfer() is called
>    from f2fs_setattr() with f2fs_lock_op() already held, so chown/chgrp
>    take cp_rwsem for read twice and hang, together with the checkpoint
>    and every other writer, once a checkpoint waits for cp_rwsem in
>    between (seen with generic/232).
> 
> Quota files only grow and there are at most MAXQUOTAS of them, so there
> is no point in keeping them inline. Convert them in f2fs_quota_on() and
> after dquot_quota_on_mount(), which keeps every block size on the same
> path as 4KB blocks, where quota files never fit inline. Quota sysfiles
> are created by mkfs with real blocks and are not affected.
> 

Cc: stable@kernel.org

> Fixes: d7e9a9037de2 ("f2fs: Support Block Size == Page Size")
> Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,