From: Jeff Layton Subject: Re: regression: oops due to recent nfsd4_lockt patch Date: Fri, 16 Jan 2009 15:57:42 -0500 Message-ID: <20090116155742.36f4dea4@tleilax.poochiereds.net> References: <1230856611-32574-1-git-send-email-bfields@citi.umich.edu> <1230856611-32574-2-git-send-email-bfields@citi.umich.edu> <1230856611-32574-3-git-send-email-bfields@citi.umich.edu> <20090116145832.0f93014a@tleilax.poochiereds.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: linux-nfs@vger.kernel.org, Marc Eshel To: "J. Bruce Fields" Return-path: Received: from mx2.redhat.com ([66.187.237.31]:50264 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937455AbZAPU7p (ORCPT ); Fri, 16 Jan 2009 15:59:45 -0500 In-Reply-To: <20090116145832.0f93014a-RtJpwOs3+0O+kQycOl6kW4xkIHaj4LzF@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, 16 Jan 2009 14:58:32 -0500 Jeff Layton wrote: > On Thu, 1 Jan 2009 19:36:51 -0500 > "J. Bruce Fields" wrote: > > > I've got a slight fear that the problem Marc tripped across won't be the > > last that's caused by this hack of faking up a struct file with only > > some fields initialized. We may as well just do an open, just as we do > > with reads and writes in the v2/v3 case, and get a proper struct file. > > > > Signed-off-by: J. Bruce Fields > > --- > > I was working on backporting this patch, but it seems to be causing a > reliable oops: > > ----------------[snip]------------------ > > BUG: unable to handle kernel NULL pointer dereference at (null) > IP: [] kref_get+0xc/0x2f > PGD 1685f067 PUD 16860067 PMD 0 > Oops: 0000 [#1] SMP DEBUG_PAGEALLOC > last sysfs file: /sys/fs/gfs2/jtltest:v1/lock_module/recover_status > CPU 0 > Modules linked in: nfsd lockd nfs_acl exportfs ipt_MASQUERADE iptable_nat nf_nat bridge stp llc lock_dlm gfs2 dlm configfs autofs4 rpcsec_gss_krb5 auth_rpcgss des_generic sunrpc ipv6 dm_multipath uinput i2c_piix4 8139cp pcspkr i2c_core 8139too mii ata_generic pata_acpi [last unloaded: freq_table] > Pid: 4088, comm: nfsd Tainted: G W 2.6.29-0.35.rc1.git4.fc11.x86_64 #1 > RIP: 0010:[] [] kref_get+0xc/0x2f > RSP: 0018:ffff88000dadfc40 EFLAGS: 00010282 > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000009 > RDX: 0000000000000000 RSI: ffff88000fec42e0 RDI: 0000000000000000 > RBP: ffff88000dadfc50 R08: ffff8800154b03d8 R09: ffffffff810dfc9f > R10: ffff88000f496d80 R11: ffff88000dadfc20 R12: ffff88000fec42e0 > R13: ffff88000dadfcc0 R14: ffff88000dadfcc0 R15: ffffffffa04938d0 > FS: 0000000000000000(0000) GS:ffffffff81934000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b > CR2: 0000000000000000 CR3: 000000001685e000 CR4: 00000000000006e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process nfsd (pid: 4088, threadinfo ffff88000dade000, task ffff88000dad2350) > Stack: > ffff88000fec42a8 0000000000000000 ffff88000dadfc80 ffffffffa04628c3 > ffff88000dadfc70 0000000000000000 ffff88000fec42a8 000000001a270000 > ffff88000dadfde0 ffffffffa0464db0 0000000000000004 ffff88000f58b360 > Call Trace: > [] nfs4_set_lock_denied+0x2c/0xa9 [nfsd] > [] nfsd4_lockt+0x323/0x38d [nfsd] > [] nfsd4_proc_compound+0x1d0/0x30c [nfsd] > [] nfsd_dispatch+0xe9/0x1ca [nfsd] > [] svc_process+0x3fc/0x63f [sunrpc] > [] ? down_read+0x77/0x7f > [] nfsd+0x149/0x1a9 [nfsd] > [] ? nfsd+0x0/0x1a9 [nfsd] > [] ? nfsd+0x0/0x1a9 [nfsd] > [] kthread+0x49/0x76 > [] child_rip+0xa/0x20 > [] ? _spin_unlock_irq+0x2b/0x37 > [] ? restore_args+0x0/0x30 > [] ? kthreadd+0x176/0x19b > [] ? kthread+0x0/0x76 > [] ? child_rip+0x0/0x20 > Code: ff f0 ff 0b 0f 94 c0 31 d2 84 c0 74 0b 48 89 df 41 ff d4 ba 01 00 00 00 5b 89 d0 41 5c c9 c3 55 48 89 e5 53 48 89 fb 48 83 ec 08 <8b> 07 85 c0 75 13 31 d2 be 2b 00 00 00 48 c7 c7 a9 5d 4c 81 e8 > RIP [] kref_get+0xc/0x2f > RSP > CR2: 0000000000000000 > ---[ end trace 4eaa2a86a8e2da24 ]--- > > ----------------[snip]------------------ > > Basically I have a GFS2 filesystem and have one process on the server > taking a lock on a file. When a NFSv4 client tries to do a GETLK > against the same file I get the above stack trace. > > The problem is that nfsd4_lockt does this: > > lockt->lt_stateowner = find_lockstateowner_str(inode, > &lockt->lt_clientid, &lockt->lt_owner); > if (lockt->lt_stateowner) > file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner; > > ...but it's not finding anything in the lockowner hash since no NFSv4 > client is holding a lock. So fl_owner ends up being NULL, but fl_type > is F_UNLCK. We then call into nfs4_set_lock_denied(), which does this: > > if (fl->fl_lmops == &nfsd_posix_mng_ops) { > sop = (struct nfs4_stateowner *) fl->fl_owner; > hval = lockownerid_hashval(sop->so_id); > kref_get(&sop->so_ref); > > ...and that then oops when dereferencing sop->so_ref. > > So in any case, I see the cause here but the fix is not immediately > clear to me. Does nfs4_set_lock_denied() need to take into account the > possibility of a NULL fl_owner, or should we be allocating a new > lockstateowner in this case? > A little bit more info (and this is a little strange). Both with and without the patch, nfsd4_lockt does this: file_lock.fl_lmops = &nfsd_posix_mng_ops; ...but pre-patch, the fl_lmops ends up getting nulled out before calling into nfs4_set_lock_denied(), but after the patch it remains set to nfsd_posix_mng_ops. This accounts for why we didn't see this before the patch was applied. -- Jeff Layton