linux-ext4 - Re: System hang with EXT4

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Message-id: <873a3ick2q.fsf@openvz.org>
Date:	Fri, 11 Dec 2009 05:37:17 +0300
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Justin Maggard <jmaggard10@...il.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: System hang with EXT4

Justin Maggard <jmaggard10@...il.com> writes:

> On Thu, Dec 10, 2009 at 5:29 PM, Dmitry Monakhov <dmonakhov@...nvz.org> wrote:
>> Justin Maggard <jmaggard10@...il.com> writes:
>>> I have a little more information to add.  After noticing the recent
>>> "Fix potential quota deadlock" patch on the mailing list, I figured it
>>> would be worth a shot to try it without quotas enabled.  This also
>>> avoids the system hang.  I tried applying that patch, but still had
>>> the same symptoms using that kernel.  So I'm seeing a consistent
>>> system hang with ext4 when delalloc and quotas are enabled on an SMP
>>> system.  With either quotas or delalloc disabled, it doesn't hang.
>>> Both enabled on a single processor system also doesn't hang.
>> You also may try another patch
>> "[PATCH] ext4: fix sleep inside spinlock issue aka #14739 V2"
>
> Yes, that patch looks like it did the trick.  Thanks!
Ohhh.. in fact i've to apologies my patch is wrong a little bit
after i_block_reservation_lock was reacquired second time
i_reserved_meta_blocks block's may be changed so we have to
use add instead of assign
 
-       EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;
+       EXT4_I(inode)->i_reserved_meta_blocks += md_needed;
As result quota leak is possible on heavy SMP stress test.
I've already send correct version.
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