[RFC PATCH] jffs2: fix recursive fs_reclaim deadlock

[Qingfang Deng]

On Fri, Mar 15, 2024 at 9:00 PM Zhihao Cheng <chengzhihao1 at huawei.com> wrote:
>
> 在 2024/3/15 20:19, Qingfang Deng 写道:
> > Hi Zhihao,
> >
> > On Fri, Mar 15, 2024 at 7:19 PM Zhihao Cheng <chengzhihao1 at huawei.com> wrote:
> >> I think it's a false positive warning. Jffs2 is trying to get root inode
> >> in process '#1', which means that the filesystem is not mounted
> >> yet(Because d_make_root is after jffs2_iget(sb,1), there is no way to
> >> access other inodes.), so it is impossible that jffs2 inode is being
> >> evicted in '#0'.
> >>
> >
> > You're right that process '#1' is getting the root inode. However,
> > lockdep only records the stack of the first unique lock ordering (see
> > https://docs.kernel.org/locking/lockdep-design.html#performance ), and
> > there are many occasions where GFP_KERNEL is used inside a
> > jffs2_inode_info::sem 's critical section.
> > .
> >
> Allocating memory without GFP_NOFS flags under sleeping lock is a normal
> thing. The vfs_write is an example(eg. ext4), page is allocated with
> FGP_WRITEBEGIN flag(no FGP_NOFS) when holding inode lock.

If this is a false positive, is there a way to suppress the warning?