Re: 3.7.10+: BUG Dentry still in use [unmount of cifs cifs]

[Jeff Layton]

On Tue, 05 Mar 2013 11:42:46 -0800
Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote:

> On 03/05/2013 11:22 AM, Jeff Layton wrote:
> > On Tue, 5 Mar 2013 14:08:49 -0500
> > Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> >
> >> On Tue, 05 Mar 2013 10:54:56 -0800
> >> Ben Greear <greearb@xxxxxxxxxxxxxxx> wrote:
> >>
> >>> In doing some CIFS testing (utilizing it's feature to bind to local
> >>> address..but not sure that matters), we saw this error when trying
> >>> to un-mount.
> >>>
> >>> Our kernel is patched (nfs, some networking related patches), but there
> >>> are no out-of-kernel patches to CIFS, so I don't *think* this is anything
> >>> we could have caused.
> >>>
> >>> This problem appears to be easily reproducible, so we will be happy
> >>> to test patches if anyone has any suggestions.
> >>>
> >>> BUG: Dentry ffff8800c07e43c0{i=45762,n=cifs2-01.7.lf-data} still in use (1) [unmount of cifs cifs]
> >>> ------------[ cut here ]------------
> >>> kernel BUG at /home/greearb/git/linux-3.7.dev.y/fs/dcache.c:967!
> >>> invalid opcode: 0000 [#1] PREEMPT SMP
> >>> Modules linked in: nls_utf8 cifs 8021q garp stp llc iptable_raw xt_CT veth nf_nat_ipv4 nf_nat fuse macvlan wanlink(O) pktgen nfsv3 nfs_acl nfsv4 auth_rpcgss nfs
> >>> fscache lockd sunrpc be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i cxgb3 mdio libcxgbi ib_iser rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core
> >>> w83793 iscsi_tcp w83627hf libiscsi_tcp hwmon_vid libiscsi scsi_transport_iscsi coretemp mperf kvm_intel kvm i5k_amb uinput i5000_edac gpio_ich edac_core
> >>> iTCO_wdt e1000e iTCO_vendor_support lpc_ich i2c_i801 pcspkr ioatdma dca microcode shpchp ipv6 floppy radeon i2c_algo_bit hwmon drm_kms_helper ttm drm i2c_core
> >>> [last unloaded: iptable_nat]
> >>> CPU 6
> >>> Pid: 6610, comm: umount Tainted: G         C O 3.7.10+ #74 Supermicro X7DBU/X7DBU
> >>> RIP: 0010:[<ffffffff811591c9>]  [<ffffffff811591c9>] shrink_dcache_for_umount_subtree+0x84/0x194
> >>> RSP: 0018:ffff8800c0085dc8  EFLAGS: 00010296
> >>> RAX: 0000000000000062 RBX: ffff8800c07e43c0 RCX: 0000000000000059
> >>> RDX: ffffffff81bc25a8 RSI: 0000000000000046 RDI: 0000000000000246
> >>> RBP: ffff8800c0085de8 R08: 0000000000000001 R09: ffff8800c0085cc8
> >>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff8800c050e9c0
> >>> R13: ffff880128ee8000 R14: 0000000000000000 R15: ffff8800c0085f28
> >>> FS:  00007f6084847840(0000) GS:ffff88012fd80000(0000) knlGS:0000000000000000
> >>> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> >>> CR2: 00007f608442c3a0 CR3: 00000000c7c2d000 CR4: 00000000000007e0
> >>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> >>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> >>> Process umount (pid: 6610, threadinfo ffff8800c0084000, task ffff88012a6a0000)
> >>> Stack:
> >>>    ffff880128ee8310 00000000000128c0 ffff880128ee8000 ffffffffa06b96b0
> >>>    ffff8800c0085e08 ffffffff81159310 ffff8800c0084000 ffff880128ee8000
> >>>    ffff8800c0085e38 ffffffff81149afe ffff8800c0085e38 0000000000000021
> >>> Call Trace:
> >>>    [<ffffffff81159310>] shrink_dcache_for_umount+0x37/0x49
> >>>    [<ffffffff81149afe>] generic_shutdown_super+0x20/0xd2
> >>>    [<ffffffff81149c25>] kill_anon_super+0x11/0x1c
> >>>    [<ffffffffa068b1ea>] cifs_kill_sb+0x15/0x21 [cifs]
> >>>    [<ffffffff81149e48>] deactivate_locked_super+0x32/0x5e
> >>>    [<ffffffff8114a942>] deactivate_super+0x40/0x46
> >>>    [<ffffffff8115fdb3>] mntput_no_expire+0x12d/0x136
> >>>    [<ffffffff81160b59>] sys_umount+0x321/0x34c
> >>>    [<ffffffff8114f846>] ? path_put+0x1d/0x21
> >>>    [<ffffffff81525229>] system_call_fastpath+0x16/0x1b
> >>> Code: 50 28 4c 8b 0a 31 d2 48 85 f6 74 04 48 8b 56 40 48 05 10 03 00 00 48 89 de 48 c7 c7 9d d0 7b 81 48 89 04 24 31 c0 e8 b9 4e 3c 00 <0f> 0b eb fe 4c 8b 63 18
> >>> 4c 39 e3 75 3c 48 8b 93 90 00 00 00 48
> >>> RIP  [<ffffffff811591c9>] shrink_dcache_for_umount_subtree+0x84/0x194
> >>>    RSP <ffff8800c0085dc8>
> >>> ---[ end trace 9b2978a89532c292 ]---
> >>
> >> Hmmm...dentry leak. Are there any jobs queued to the cifsiod workqueue
> >> when the box oopses?
> >>
> >
> > In fact...
> >
> > It's just a guess, but does this patch help at all? Note that it builds
> > but is otherwise untested ;). If it works we might want to go with
> > something a bit less invasive but this may tell us if we're on the
> > right track.
> 
> This does not fix the problem, though possibly it is still
> a correct fix for some other bug.  Some more details on this test case:
> 
> We create 8 writer processes (which do one mount per thread), write some files.
> 
> Then, stop those, and un-mount.
> 
> Then, start 8 reader processes, which will create 8 mounts and then start
> reading data.
> 
> Finally, stop these readers, which will stop the read IO calls and immediately
> try to un-mount the the 8 mounts.  These unmount attempts cause the bug.
> 
> Thanks,
> Ben
> 
> 

Ok, thanks...it was worth a shot. I guess we'll have to track this down
the hard way then and try to figure out where the dentry leak is coming
from.

My guess would be that it's coming from the async read code path
somewhere. When you stop the processes doing the reading, how do you do
it? Are they sent a signal?

-- 
Jeff Layton <jlayton@xxxxxxxxxx>
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