linux-kernel - Re: [PATCH 2/4] ceph: fix buffer free while holding i_ceph_lock in __ceph

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Message-ID: <20190719232307.GA17978@ZenIV.linux.org.uk>
Date:   Sat, 20 Jul 2019 00:23:08 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Luis Henriques <lhenriques@...e.com>,
        Ilya Dryomov <idryomov@...il.com>, Sage Weil <sage@...hat.com>,
        ceph-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] ceph: fix buffer free while holding i_ceph_lock in
 __ceph_setxattr()

On Fri, Jul 19, 2019 at 07:07:49PM -0400, Jeff Layton wrote:

> Al pointed out on IRC that vfree should be callable under spinlock.

Al had been near-terminally low on caffeine at the time, posted
a retraction a few minutes later and went to grab some coffee...

> It
> only sleeps if !in_interrupt(), and I think that should return true if
> we're holding a spinlock.

It can be used from RCU callbacks and all such; it *can't* be used from
under spinlock - on non-preempt builds there's no way to recognize that.