From: David Sterba <dsterba@suse.cz>
To: David Howells <dhowells@redhat.com>
Cc: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>,
WenRuo Qu <wqu@suse.com>,
linux-btrfs@vger.kernel.org, nborisov@suse.com
Subject: Re: fs/btrfs/volumes.c:6114 suspicious rcu_dereference_check() usage!
Date: Thu, 23 Aug 2018 17:59:55 +0200 [thread overview]
Message-ID: <20180823155955.GO24025@suse.cz> (raw)
In-Reply-To: <22614.1535039351@warthog.procyon.org.uk>
On Thu, Aug 23, 2018 at 04:49:11PM +0100, David Howells wrote:
> I'm seeing the attached message generated from this line:
>
> btrfs_debug_in_rcu(fs_info,
> "btrfs_map_bio: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
> bio_op(bio), bio->bi_opf, (u64)bio->bi_iter.bi_sector,
> (u_long)dev->bdev->bd_dev, rcu_str_deref(dev->name), dev->devid,
> bio->bi_iter.bi_size);
>
> in submit_stripe_bio(). I'm not sure exactly why, but I suspect
> rcu_str_deref() is the point from where it is generated.
Yes, the macro is rcu_dereference in disguise.
The code previously had explicit rcu_lock/unlock, now it uses the
btrfs_debug_in_rcu helper which is supposed to provide that. It's
possible that the helper is missing it due to some #ifdef mess, but I
don't see it.
next prev parent reply other threads:[~2018-08-23 19:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 15:49 fs/btrfs/volumes.c:6114 suspicious rcu_dereference_check() usage! David Howells
2018-08-23 15:59 ` David Sterba [this message]
2018-08-23 16:08 ` David Howells
2018-08-24 2:07 ` Misono Tomohiro
2018-08-24 2:35 ` [PATCH] btrfs: ctree.h: Fix suspicious rcu usage warning in btrfs_debug_in_rcu() Misono Tomohiro
2018-08-24 11:46 ` David Sterba
2018-08-24 12:08 ` David Howells
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