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Date:   Wed, 2 Sep 2020 19:45:49 +0200
From:   David Sterba <dsterba@suse.cz>
To:     Anand Jain <anand.jain@oracle.com>
Cc:     Josef Bacik <josef@toxicpanda.com>, linux-btrfs@vger.kernel.org,
        kernel-team@fb.com
Subject: Re: [PATCH 2/4] btrfs: init sysfs for devices outside of the
 chunk_mutex
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On Wed, Sep 02, 2020 at 02:21:31PM +0800, Anand Jain wrote:
> > @@ -2609,6 +2606,10 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
> >   	btrfs_clear_space_info_full(fs_info);
> >   
> >   	mutex_unlock(&fs_info->chunk_mutex);
> > +
> > +	/* add sysfs device entry */
> > +	btrfs_sysfs_add_devices_dir(fs_devices, device);
> > +
> >   	mutex_unlock(&fs_devices->device_list_mutex);
> >   
> >   	if (seeding_dev) {
> > 
> 
> Strange we should get this splat when btrfs_sysfs_add_devices_dir()
> already has implicit GFP_NOFS allocation scope right? What did I
> miss?

The problem is the sysfs' kernfs_mutex, all sysfs allocations are
GFP_KERNEL thus it can grab fs_reclaim at some point.