linux-ext4 - [Bug 15906] serious performance regression in "umount" on ext4 over LVM

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Date:	Wed, 5 May 2010 07:28:17 GMT
From:	bugzilla-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 15906] serious performance regression in "umount" on ext4 over
 LVM

https://bugzilla.kernel.org/show_bug.cgi?id=15906


Dmitry Monakhov <dmonakhov@...nvz.org> changed:

           What    |Removed                     |Added
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                 CC|                            |dmonakhov@...nvz.org




--- Comment #13 from Dmitry Monakhov <dmonakhov@...nvz.org>  2010-05-05 07:28:10 ---
Yep. i've already know that issue. In fact it was broken by followng commit

>From 03ba3782e8dcc5b0e1efe440d33084f066e38cae Mon Sep 17 00:00:00 2001          
From: Jens Axboe <jens.axboe@...cle.com>                                        
Date: Wed, 9 Sep 2009 09:08:54 +0200                                            
Subject: [PATCH] writeback: switch to per-bdi threads for flushing data

The problem with __sync_filesystem(0) is no longer works on umount
because sb can not be pined s_mount sem is downed for write and s_root is NULL.

And in fact ext3 is also broken in case of "-obarrier=1"
The patch attached fix the original regression, but there is one more issue
left

A delalloc option. In fact dirty inode is still dirty even after first
call of writeback_single_inode which is called from __sync_filesystem(0)
due to delalloc allocation happen during inode write. So it takes second
__sync_filesystem call to clear dirty flags. Currently i'm working on that
issue. I hope i'll post a solution today.

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