linux-ext4 - Re: warning in ext4_journal_start

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Date:	Mon, 24 Feb 2014 10:55:25 +0100
From:	Jan Kara <jack@...e.cz>
To:	Matthew Rahtz <mrahtz@...itasystems.com>
Cc:	Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org,
	linux-nfs@...r.kernel.org, "J. Bruce Fields" <bfields@...ldses.org>
Subject: Re: warning in ext4_journal_start_sb on filesystem freeze

On Sat 22-02-14 09:50:06, Matthew Rahtz wrote:
> Thanks for your help Jan,
> 
> A few months later, we've noticed the issue is actually still there.
> Using 3.11.0-17-generic on Ubuntu 12.04, we’re seeing this in the kernel
> logs:
> 
> [29243.606215] WARNING: CPU: 0 PID: 1785 at
> /build/buildd/linux-lts-saucy-3.11.0/fs/ext4/ext4_jbd2.c:48
> ext4_journal_check_start+0x83/0x90()
> 
> Having a look at the Ubuntu source package for that version, it
> definitely does include commit 03d95eb2f2578083a3f6286262e1cb5d88a00c02,
> and the line generating the warning is still:
> 
> WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE);
> 
> Are there any other obvious possibilities for what may be causing this?
> There seem to be some users of Oracle Linux experiencing similar problems
> at https://community.oracle.com/thread/2617418, which was apparently
> fixed in Oracle's kernel version '3.8.13-26.el6uek'. Any word on when
> this might be integrated into the official kernel?
> 
> Full call trace included below.
  Looking at the trace below, now the problem seems to be in the NFS server
code. NFS should get protection against the filesystem being frozen (or
remounted read-only for that matter) via mnt_want_write() before calling
into notify_change() (actually before calling fh_lock() because of lock
ordering).  Similarly to what we do e.g. in fchownat(). Bruce?

								Honza

> [29243.606212] ------------[ cut here ]------------
> [29243.606215] WARNING: CPU: 0 PID: 1785 at /build/buildd/linux-lts-saucy-3.11.0/fs/ext4/ext4_jbd2.c:48 ext4_journal_check_start+0x83/0x90()
> [29243.606216] Modules linked in: parport_pc ppdev nfsd nfs_acl auth_rpcgss nfs fscache lockd sunrpc ext2 cirrus ttm drm_kms_helper drm sysimgblt psmouse i2c_piix4 virtio_balloon sysfillrect mac_hid serio_raw syscopyarea virtio_console lp parport floppy
> [29243.606227] CPU: 0 PID: 1785 Comm: nfsd Tainted: G        W    3.11.0-17-generic #31~precise1-Ubuntu
> [29243.606228] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
> [29243.606228]  0000000000000030 ffff8801162f3b08 ffffffff8173c72d 0000000000000007
> [29243.606230]  0000000000000000 ffff8801162f3b48 ffffffff8106540c 0000000000000000
> [29243.606232]  ffff880114892800 0000000000000007 0000000000000068 0000000000000000
> [29243.606235] Call Trace:
> [29243.606237]  [<ffffffff8173c72d>] dump_stack+0x46/0x58
> [29243.606239]  [<ffffffff8106540c>] warn_slowpath_common+0x8c/0xc0
> [29243.606241]  [<ffffffff8106545a>] warn_slowpath_null+0x1a/0x20
> [29243.606244]  [<ffffffff8127ebb3>] ext4_journal_check_start+0x83/0x90
> [29243.606246]  [<ffffffff8127ec35>] __ext4_journal_start_sb+0x45/0x100
> [29243.606249]  [<ffffffff81258a03>] ? ext4_dirty_inode+0x33/0x70
> [29243.606251]  [<ffffffff81258a03>] ext4_dirty_inode+0x33/0x70
> [29243.606254]  [<ffffffff811de348>] __mark_inode_dirty+0x48/0x350
> [29243.606256]  [<ffffffff81256b53>] ext4_setattr+0x1b3/0x5b0
> [29243.606259]  [<ffffffff811d0903>] notify_change+0x1d3/0x390
> [29243.606263]  [<ffffffffa01c7fe2>] nfsd_setattr+0x232/0x2a0 [nfsd]
> [29243.606267]  [<ffffffffa01d00f6>] nfsd3_proc_setattr+0x76/0xc0 [nfsd]
> [29243.606271]  [<ffffffffa01c0d85>] nfsd_dispatch+0xe5/0x230 [nfsd]
> [29243.606283]  [<ffffffffa0128465>] svc_process_common+0x345/0x680 [sunrpc]
> [29243.606289]  [<ffffffffa0128af3>] svc_process+0x103/0x160 [sunrpc]
> [29243.606293]  [<ffffffffa01c08df>] nfsd+0xbf/0x130 [nfsd]
> [29243.606297]  [<ffffffffa01c0820>] ? nfsd_destroy+0x80/0x80 [nfsd]
> [29243.606299]  [<ffffffff81089170>] kthread+0xc0/0xd0
> [29243.606302]  [<ffffffff810890b0>] ? flush_kthread_worker+0xb0/0xb0
> [29243.606304]  [<ffffffff8175122c>] ret_from_fork+0x7c/0xb0
> [29243.606307]  [<ffffffff810890b0>] ? flush_kthread_worker+0xb0/0xb0
> [29243.606308] ---[ end trace e9d4726f92c62d43 ]---
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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