linux-kernel - Re: BUG: enabling psacct breaks fsfreeze

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Message-ID: <20121101225053.GB31937@quack.suse.cz>
Date:	Thu, 1 Nov 2012 23:50:53 +0100
From:	Jan Kara <jack@...e.cz>
To:	Nikola Ciprich <nikola.ciprich@...uxbox.cz>
Cc:	Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: BUG: enabling psacct breaks fsfreeze

On Thu 01-11-12 15:23:25, Nikola Ciprich wrote:
> Nov  1 14:23:25 vmnci22 [ 1075.178123] SysRq : Show Blocked State
> Nov  1 14:23:25 vmnci22 [ 1075.180555]   task                        PC stack   pid father
> Nov  1 14:23:25 vmnci22 [ 1075.180592] fsfreeze      D 0000000000000000     0  4215   4195 0x00000000
> Nov  1 14:23:25 vmnci22 [ 1075.180599]  ffff8800090b9b28 0000000000000046 0000000000000000 ffffffff00000000
> Nov  1 14:23:25 vmnci22 [ 1075.180606]  0000000000013780 ffff8800090b9fd8 ffff88000f716170 ffff88000f715e80
> Nov  1 14:23:25 vmnci22 [ 1075.180612]  ffff88000f715dc0 ffffffff81566080 ffff88000f716170 000000010002f405
> Nov  1 14:23:25 vmnci22 [ 1075.180619] Call Trace:
> Nov  1 14:23:25 vmnci22 [ 1075.180693]  [<ffffffff810e2dbb>] __generic_file_aio_write+0xbb/0x420
> Nov  1 14:23:25 vmnci22 [ 1075.180729]  [<ffffffff81079290>] ? autoremove_wake_function+0x0/0x40
> Nov  1 14:23:25 vmnci22 [ 1075.180736]  [<ffffffff810e317f>] generic_file_aio_write+0x5f/0xc0
  Thanks. So the system isn't really deadlocked. It's just that fsfreeze
command hangs, isn't it? OK, I understand that it's kind of incovenient
situation because every command will hang like this when the filesystem is
frozen.

Now I only have to come up with a way to improve this... It isn't quite
simple - to properly protect against freezing be have to communicate down
into generic_file_aio_write() that we want to bail out if filesystem is
frozen instead of waiting.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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