From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + loop-use-worker-per-cgroup-instead-of-kworker-fix-2.patch added to -mm tree Date: Sat, 29 Feb 2020 18:11:56 -0800 Message-ID: <20200301021156.TU2JedzPA%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:35916 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727228AbgCACL7 (ORCPT ); Sat, 29 Feb 2020 21:11:59 -0500 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: axboe@kernel.dk, chris@chrisdown.name, guro@fb.com, hannes@cmpxchg.org, hughd@google.com, lizefan@huawei.com, mhocko@kernel.org, mm-commits@vger.kernel.org, schatzberg.dan@gmail.com, shakeelb@google.com, tglx@linutronix.de, tj@kernel.org, vdavydov.dev@gmail.com, yang.shi@linux.alibaba.com The patch titled Subject: loop: fix irq lock ordering bug has been added to the -mm tree. Its filename is loop-use-worker-per-cgroup-instead-of-kworker-fix-2.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/loop-use-worker-per-cgroup-instead-of-kworker-fix-2.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/loop-use-worker-per-cgroup-instead-of-kworker-fix-2.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Dan Schatzberg Subject: loop: fix irq lock ordering bug "loop: Use worker per cgroup instead of kworker" in patch series "Charge loop device i/o to issuing cgroup", v3. introduced a lock ordering bug. The previously existing lo->lo_lock was always acquired as spin_lock_irq but never actually used in irq context. The above patch started to use this lock in irq context which triggered a lockdep warning on sysfs reading. Fix this by executing file_path outside of the lock. Link: http://lkml.kernel.org/r/20200228161847.28107-1-schatzberg.dan@gmail.com Signed-off-by: Dan Schatzberg Cc: Johannes Weiner Cc: Jens Axboe Cc: Tejun Heo Cc: Li Zefan Cc: Michal Hocko Cc: Vladimir Davydov Cc: Hugh Dickins Cc: Roman Gushchin Cc: Shakeel Butt Cc: Chris Down Cc: Yang Shi Cc: Thomas Gleixner , Signed-off-by: Andrew Morton --- drivers/block/loop.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/drivers/block/loop.c~loop-use-worker-per-cgroup-instead-of-kworker-fix-2 +++ a/drivers/block/loop.c @@ -776,12 +776,18 @@ static ssize_t loop_attr_backing_file_sh { ssize_t ret; char *p = NULL; + struct file *filp = NULL; spin_lock_irq(&lo->lo_lock); if (lo->lo_backing_file) - p = file_path(lo->lo_backing_file, buf, PAGE_SIZE - 1); + filp = get_file(lo->lo_backing_file); spin_unlock_irq(&lo->lo_lock); + if (filp) { + p = file_path(filp, buf, PAGE_SIZE - 1); + fput(filp); + } + if (IS_ERR_OR_NULL(p)) ret = PTR_ERR(p); else { _ Patches currently in -mm which might be from schatzberg.dan@gmail.com are loop-use-worker-per-cgroup-instead-of-kworker.patch loop-use-worker-per-cgroup-instead-of-kworker-fix-2.patch mm-charge-active-memcg-when-no-mm-is-set.patch loop-charge-i-o-to-mem-and-blk-cg.patch