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On 2010-05-04T20:41:39+00:00 Kees wrote:

Description of problem: umount on ext4 has seriously regressed, stalling for 
over a minute (or more):
https://bugzilla.kernel.org/show_bug.cgi?id=15906

Version-Release number of selected component (if applicable): 2.6.33


How reproducible: always


Steps to Reproduce:
1. install a Fedora 13, accepted defaults.
2. Run the following as root:

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

  
Actual results: over a minute to perform umount.


Expected results: a few seconds.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/21

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On 2010-05-04T21:00:36+00:00 Eric wrote:

Looks barrier related, if you change the mount -o loop to mount -o
loop,nobarrier, it's speedy.

commit 68db1961bbf4e16c220ccec4a780e966bc1fece3
Author: Nikanth Karthikesan <[email protected]>
Date:   Tue Mar 24 12:29:54 2009 +0100

    loop: support barrier writes
    
    Honour barrier requests in the loop back block device driver.
    In case of barrier bios, flush the backing file once before processing the
    barrier and once after to guarantee ordering. In case of filesystems that
    does not support fsync, barrier bios would be failed with -EOPNOTSUPP.
    
    Signed-off-by: Nikanth Karthikesan <[email protected]>
    Signed-off-by: Jens Axboe <[email protected]>


So you're fsyncing the loop file 2x for each barrier, and those fsyncs in turn 
cause cache flushes on your underlying device; once upon a time lvm didn't do 
anything there, but now it does ... I think you're just getting bitten by the 
new and improved barrier support at every level.

-Eric

Reply at:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/23

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On 2010-05-04T21:28:05+00:00 Eric wrote:

Since this really seems to be an upstream-relevant bug motivated by an
ubuntu bug that ubuntu seemed unable to solve, I'm going to close this
as UPSTREAM and worry about it there, rather than working the ubuntu bug
through the fedora bugzilla.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/24

------------------------------------------------------------------------
On 2010-05-04T21:32:29+00:00 Eric wrote:

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/21

Reply at:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/25

------------------------------------------------------------------------
On 2010-05-11T04:37:37+00:00 Michael wrote:

The mad skillz that did the new colour schemes for a new release of an
os (Ubuntu 10.04) should be just as capable at being able to overcome
the limitation of journal transaction and barrier blocks between every
single inode update by breakfast.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/27

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On 2010-05-17T05:39:39+00:00 Fedora wrote:

kernel-2.6.33.4-95.fc13 has been submitted as an update for Fedora 13.
http://admin.fedoraproject.org/updates/kernel-2.6.33.4-95.fc13

Reply at:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/28

------------------------------------------------------------------------
On 2010-05-19T19:17:52+00:00 Fedora wrote:

kernel-2.6.33.4-95.fc13 has been pushed to the Fedora 13 stable
repository.  If problems still persist, please make note of it in this
bug report.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/543617/comments/29


** Changed in: linux (Fedora)
       Status: Unknown => Won't Fix

** Changed in: linux (Fedora)
   Importance: Unknown => Medium

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https://bugs.launchpad.net/bugs/543617

Title:
  Unmount of an fs with dirty cache buffers causes pathological slowdown

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