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From: Qingfang Deng <dqfext@gmail.com>
Date: Fri, 15 Mar 2024 20:19:30 +0800
Message-ID: <CALW65jbKBUDN8ybE1oqrNW5VK1QGpZ1RmnFCCzxjQCo4obaA4A@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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Hi Zhihao,

On Fri, Mar 15, 2024 at 7:19=E2=80=AFPM Zhihao Cheng <chengzhihao1@huawei.c=
om> 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.