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SubjectRe: [PATCH] nilfs2: fix very long mount time issue
>On Sun, 13 Jan 2013 16:07:23 +0900 (JST)
>Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:
>
>> On Sat, 12 Jan 2013 19:34:48 +0400, Vyacheslav Dubeyko wrote:
>> > From: Vyacheslav Dubeyko <slava@dubeyko.com>
>> > Subject: [PATCH] nilfs2: fix very long mount time issue
>> >
>> > DESCRIPTION:
>> > It exists situation when GC can work in background alone without any other filesystem activity during significant
time. The nilfs_clean_segments() method calls nilfs_segctor_construct() that updates superblocks in the case of
NILFS_SC_SUPER_ROOT and THE_NILFS_DISCONTINUED flags are set. But when GC is working alone the nilfs_clean_segments() is
called with unset THE_NILFS_DISCONTINUED flag. As a result, the update of superblocks doesn't occurred all this time and
in the case of SPOR superblocks keep very old values of last super root placement.
>> >
>> > SYMPTOMS:
>> > Trying to mount a NILFS2 volume after SPOR in such environment ends with very long mounting time (it can achieve
about several hours in some cases).
>> >
>> > REPRODUCING PATH:
>> > 1. It needs to use external USB HDD, disable automount and doesn't make any additional filesystem activity on the
NILFS2 volume.
>> > 2. Generate temporary file with size about 100 - 500 GB (for example, dd if=/dev/zero of=<file_name> bs=1073741824
count=200). The size of file defines duration of GC working.
>> > 3. Then it needs to delete file.
>> > 4. Start GC manually by means of command "nilfs-clean -p 0". When you start GC by means of such way then, at the end,
superblocks is updated by once. So, for simulation of SPOR, it needs to wait sometime (15 - 40 minutes) and simply switch
off USB HDD manually.
>> > 5. Switch on USB HDD again and try to mount NILFS2 volume. As a result, NILFS2 volume will mount during very long
time.
>> >
>> > REPRODUCIBILITY: 100%
>> >
>> > FIX:
>> > This patch adds checking that superblocks need to update and set THE_NILFS_DISCONTINUED flag before
nilfs_clean_segments() call.
>> >
>> > Reported-by: Sergey Alexandrov <splavgm@gmail.com>
>> > Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
>> > Tested-by: Vyacheslav Dubeyko <slava@dubeyko.com>
>>
>> Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
>>
>> Thanks, Vyacheslav. I confirmed the issue and could reproduce it.
>> Your patch fixed it.
>>
>> Andrew, please apply.
>
>I added a Cc:stable so the fix will be backported into earlier kernels.
>40 minutes mount time is pretty bad!

Yup, I agree.

Thanks.

Ryusuke Konishi



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