Re: [PATCH] bcache: Make gc wakeup sane, remove set_task_state()

[Greg KH <greg@kroah.com>]

On Mon, Jan 23, 2017 at 03:54:07PM +0100, Greg KH wrote:
> On Mon, Jan 23, 2017 at 10:45:47PM +0800, Coly Li wrote:
> > On 2017/1/23 下午10:16, Greg KH wrote:
> > > On Mon, Jan 23, 2017 at 09:20:12PM +0800, colyli@suse.de wrote:
> > >> Hi stable maintainers,
> > >>
> > >> This patch is from Kent, upstream commit ID is be628be09563.
> > >> Olav Reinert <seroton10@gmail.com> reports a kerenl crash from
> > >> bcache (boo#1021260) and Oliver Nuekum points out this patch fixes the problem. 
> > > 
> > > "boo"?
> > > 
> > 
> > Hi Greg,
> > 
> > 
> > "boo" is abbreviation of bugzilla.opensuse.org, I paste the original bug
> > report here,
> > ==== start of bug report ==========
> > I have starting seeing errors like the one quoted below in the system
> > log. It occurs infrequently, but quite regularly, about 1-3 times a
> > week, on a server running 24x7.
> > 
> > Around the time it began, I started running a beta version of Leap 42.2,
> > upgraded from 42.1. Also, I enabled the "discard" option (SSD TRIM) on
> > the bcache cache about 3-6 months ago. I believe one of those two events
> > caused the bug to appear.
> > 
> > Not sure what other info is useful, please ask for whatever you need.
> > 
> > 
> > Oct 10 00:00:02 blackbox kernel: ------------[ cut here ]------------
> > Oct 10 00:00:02 blackbox kernel: WARNING: CPU: 4 PID: 1269 at
> > ../kernel/sched/core.c:7891 __might_sleep+0x76/0x80()
> > Oct 10 00:00:02 blackbox kernel: do not call blocking ops when
> > !TASK_RUNNING; state=1 set at [<ffffffffa09e2325>]
> > bch_gc_thread+0x25/0x100 [
> > Oct 10 00:00:02 blackbox kernel: Modules linked in: vhost_net vhost
> > macvtap macvlan fuse ebt_arp ebt_ip ebtable_nat ebtable_filter ebtables
> > Oct 10 00:00:02 blackbox kernel:  mxm_wmi
> > Oct 10 00:00:02 blackbox kernel:  bcache aesni_intel raid1
> > snd_hda_codec_realtek aes_x86_64 lrw snd_hda_codec_generic gf128mul
> > md_mod glue_h
> > Oct 10 00:00:02 blackbox kernel:
> > Oct 10 00:00:02 blackbox kernel: CPU: 4 PID: 1269 Comm: bcache_gc Not
> > tainted 4.4.21-2-default #1
> > Oct 10 00:00:02 blackbox kernel: Hardware name: To be filled by O.E.M.
> > To be filled by O.E.M./M5A99X EVO R2.0, BIOS 2301 01/06/2014
> > Oct 10 00:00:02 blackbox kernel:  0000000000000000 ffffffff81326967
> > ffff8800b605be10 ffffffff81a5e431
> > Oct 10 00:00:02 blackbox kernel:  ffffffff8107e7d1 ffffffff81a5f54f
> > ffff8800b605be60 0000000000000061
> > Oct 10 00:00:02 blackbox kernel:  0000000000000000
> > Oct 10 00:00:02 blackbox kernel:  0000000000000000 ffffffff8107e84c
> > ffffffff81a4ef88
> > Oct 10 00:00:02 blackbox kernel: Call Trace:
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff81019e69>] dump_trace+0x59/0x320
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff8101a22a>]
> > show_stack_log_lvl+0xfa/0x180
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff8101afd1>] show_stack+0x21/0x40
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff81326967>] dump_stack+0x5c/0x85
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff8107e7d1>]
> > warn_slowpath_common+0x81/0xb0
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff8107e84c>]
> > warn_slowpath_fmt+0x4c/0x50
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff810a3026>]
> > __might_sleep+0x76/0x80
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff81605cac>] mutex_lock+0x1c/0x38
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffffa09e2365>]
> > bch_gc_thread+0x65/0x100 [bcache]
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff8109d268>] kthread+0xc8/0xe0
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff8160828f>]
> > ret_from_fork+0x3f/0x70
> > Oct 10 00:00:02 blackbox kernel: DWARF2 unwinder stuck at
> > ret_from_fork+0x3f/0x70
> > Oct 10 00:00:02 blackbox kernel:
> > Oct 10 00:00:02 blackbox kernel: Leftover inexact backtrace:
> > Oct 10 00:00:02 blackbox kernel:  [<ffffffff8109d1a0>] ?
> > kthread_park+0x50/0x50
> > Oct 10 00:00:02 blackbox kernel: ---[ end trace c63abcb6c473e79b ]---
> > ==== end of bug report ==========
> > 
> > 
> > # journalctl|grep "blocking ops"
> > Oct 10 00:00:02 blackbox kernel: do not call blocking ops when
> > !TASK_RUNNING; state=1 set at [<ffffffffa09e2325>]
> > bch_gc_thread+0x25/0x100 [bcache]
> > [snip repeated lines]
> > 
> > 
> > 
> > >> I send this patch to stable@kernel.vger.org, hope this patch can be taken care
> > >> in stable kernels.
> > >>
> > >> Thanks in advance.
> > >>
> > >> Coly Li
> > >>
> > >> Here I attach the original patch, just FYI.
> > >> ---
> > >> From: Kent Overstreet <kent.overstreet@gmail.com>
> > >> Date: Wed, 26 Oct 2016 20:31:17 -0700
> > >> Subject: [PATCH] bcache: Make gc wakeup sane, remove set_task_state()
> > >>
> > >> Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
> > > 
> > > No changelog text?  Worst short changelog description ever?
> > 
> > There is no change log from original patch, I am not the author, and it
> > is in upstream already. So I think I am not the right person to change
> > its commit log.
> 
> Oh, I didn't mean to complain to you, my complain was to Kent.
> 
> Kent, please go read the section, "The canonical patch format" in the
> Documentation/SubmittingPatches file for how to do this properly.
> 
> > This is the first time I encounter this situation, that send a patch to
> > stable which is not from me. I guess Kent does not notice that this
> > patch indeed fixes a kernel oops. But it does fix a bug report for Leap
> > 42.2 and SLE12-SP2.
> > > 
> > > This gives me no context of what is going on here.  Why does this fix a
> > > bug?  What kernel(s) should it be backported to?
> > > 
> > 
> > The bug is reported on Linux 4.4 based kernel, so at least all kernels
> > since Linux 4.4 should have the fix. Maybe Kent can provide more
> > accurate suggestion.
> 
> Kent, any hints?

Without a response from the maintainer, I can't apply this...

greg k-h