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From: Qingfang Deng <dqfext@gmail.com>
Date: Tue, 19 Mar 2024 14:41:59 +0800
Message-ID: <CALW65jbQCvkpeoOv275jgQAHf+Tk3QBR0HdwdGhK3s7gF+HVeg@mail.gmail.com>
Subject: Re: [RFC PATCH] jffs2: fix recursive fs_reclaim deadlock
To: Zhihao Cheng <chengzhihao1@huawei.com>
Cc: David Woodhouse <dwmw2@infradead.org>, Richard Weinberger <richard@nod.at>, linux-mtd@lists.infradead.org, 
	linux-kernel@vger.kernel.org
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On Fri, Mar 15, 2024 at 9:00=E2=80=AFPM Zhihao Cheng <chengzhihao1@huawei.c=
om> wrote:
>
> =E5=9C=A8 2024/3/15 20:19, Qingfang Deng =E5=86=99=E9=81=93:
> > Hi Zhihao,
> >
> > On Fri, Mar 15, 2024 at 7:19=E2=80=AFPM Zhihao Cheng <chengzhihao1@huaw=
ei.com> wrote:
> >> I think it's a false positive warning. Jffs2 is trying to get root ino=
de
> >> 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?