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

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Message-ID: <bug-15906-13602@https.bugzilla.kernel.org/>
Date:	Tue, 4 May 2010 20:36:59 GMT
From:	bugzilla-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 15906] New: serious performance regression in "umount" on ext4
 over LVM

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

           Summary: serious performance regression in "umount" on ext4
                    over LVM
           Product: File System
           Version: 2.5
    Kernel Version: 2.6.33
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
        AssignedTo: fs_ext4@...nel-bugs.osdl.org
        ReportedBy: kees@...flux.net
        Regression: Yes


As root, if /tmp is on an LV (or possibly even without this):

cd /tmp
dd if=/dev/zero of=test.ext4 bs=1 count=1 seek=1G
mkfs.ext4 -F test.ext4
mkdir -p /mnt/test
mount -o loop test.ext4 /mnt/test
echo $(seq 65536) | (cd /mnt/test; xargs touch)
time umount /mnt/test

Prior to 2.6.32, this took a second or so.  Now it takes over a minute.

Reproduced in both Ubuntu 10.04 (2.6.32) and Fedora 12 (2.6.33).
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617

The current Ubuntu work-around is only useful on an otherwise idle system.

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