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Date:   Tue, 17 Sep 2019 13:01:17 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     "zhengbin (A)" <zhengbin13@huawei.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        kernel test robot <lkp@intel.com>, Jan Kara <jack@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        "zhangyi (F)" <yi.zhang@huawei.com>, renxudong1@huawei.com,
        Hou Tao <houtao1@huawei.com>, LKP <lkp@01.org>
Subject: Re: 266a9a8b41: WARNING:possible_recursive_locking_detected
Message-ID: <20190917120117.GG1131@ZenIV.linux.org.uk>
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On Tue, Sep 17, 2019 at 03:03:33PM +0800, zhengbin (A) wrote:
> 
> On 2019/9/17 1:16, Al Viro wrote:
> > On Sun, Sep 15, 2019 at 08:44:05PM -0700, Linus Torvalds wrote:
> >> On Sun, Sep 15, 2019 at 8:04 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >>> Perhaps lockref_get_nested(struct lockref *lockref, unsigned int subclass)?
> >>> With s/spin_lock/spin_lock_nested/ in the body...
> >> Sure. Under the usual CONFIG_DEBUG_LOCK_ALLOC, with the non-debug case
> >> just turning into a regular lockref_get().
> >>
> >> Sounds fine to me.
> > Done and force-pushed into vfs.git#fixes
> + if (file->f_pos > 2) {
> + p = scan_positives(cursor, &dentry->d_subdirs,
> + file->f_pos - 2, &to);
> + spin_lock(&dentry->d_lock);
> + list_move(&cursor->d_child, p);
> + spin_unlock(&dentry->d_lock);
> + } else {
> + spin_lock(&dentry->d_lock);
> + list_del_init(&cursor->d_child);
> + spin_unlock(&dentry->d_lock);
> }
> +
> + dput(to);
> dput(to) should be in if if (file->f_pos > 2)? cause we dget(to) in scan_positives

dput(NULL) is a no-op