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Date:	Tue, 02 Aug 2011 18:14:18 +0900
From:	Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
To:	Jan Kara <jack@...e.cz>
CC:	akpm@...ux-foundation.org, adilger.kernel@...ger.ca,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext3: fix message in ext3_remount for rw-remount case

Hi.

(2011/08/01 18:57), Jan Kara wrote:
> On Mon 01-08-11 18:45:58, Toshiyuki Okajima wrote:
>> (2011/08/01 17:45), Jan Kara wrote:
>>> On Mon 01-08-11 13:54:51, Toshiyuki Okajima wrote:
>>>> If there are some inodes in orphan list while a filesystem is being
>>>> read-only mounted, we should recommend that pepole umount and then
>>>> mount it when they try to remount with read-write. But the current
>>>> message/comment recommends that they umount and then remount it.
>>>>
>>>> ext3_remount:
>>>> 	/*
>>>> 	 * If we have an unprocessed orphan list hanging
>>>> 	 * around from a previously readonly bdev mount,
>>>> 	 * require a full umount/remount for now.
>>>>                            ^^^^^^^^^^^^^^
>>>> 	 */
>>>> 	if (es->s_last_orphan) {
>>>> 		printk(KERN_WARNING "EXT3-fs: %s: couldn't "
>>>> 			"remount RDWR because of unprocessed "
>>>> 			"orphan inode list.  Please "
>>>> 			"umount/remount instead.\n",
>>>>                           ^^^^^^^^^^^^^^
>>>> 			sb->s_id);
>>
>>>    OK, so how about using "umount&   mount"? The '/' is what would confuse me
>> OK. I modify it like your comment.
>>
>>   umount/mount =>  umount&  mount
>    Thanks.
>

>>> the most... BTW, I guess you didn't really see this message in practice, did
>>> you?
>> No.
>> I have seen this message in practice while quotacheck command was repeatedly
>> executed per an hour.
>    Interesting. Are you able to reproduce this? Quotacheck does remount
> read-only + remount read-write but you cannot really remount the filesystem
> read-only when it has orphan inodes and so you should not see those when
> you remount read-write again. Possibly there's race between remounting and
> unlinking...
Yes. I can reproduce it. However, it is not frequently reproduced
by using the original procedure (qutacheck per an hour). So, I made a
reproducer.

It is:
[go.sh]
#!/bin/sh

dd if=/dev/zero of=./img bs=1k count=1 seek=100k > /dev/null 2>&1
/sbin/mkfs.ext3 -Fq ./img
/sbin/tune2fs -c 0 ./img
mkdir -p mnt
LOOP=10000
for ((i=0; i<LOOP; i++));
do
         mount -o loop ./img ./mnt
         sh ./writer.sh ./mnt &
         PID=$!
	j=0
         while [ 1 ];
         do
                 sleep 1
# remount
                 if ((j%2 == 0));
                 then
                         mount -o loop,remount,ro ./mnt
                 else
                         mount -o loop,remount,rw ./mnt
                 fi
                 tail -n 1 /var/log/messages| grep "remount RDWR"
                 if [ $? -eq 0 ];
                 then
                         break
                 fi
                 j=$((j+1))
         done
         kill -9 $PID
         umount ./mnt
         /sbin/e2fsck -pf ./img
done
exit

[writer.sh]
#!/bin/sh

i=0
path=$1
num=0
stride=64
while [ 1 ];
do
         for ((j=0;j<stride;j++));
         do
                 num=$((i*stride + j))
                 dd if=/dev/zero of=${path}/file${num} bs=8k count=1 > /dev/null 2>&1 &
         done
         for ((j=0;j<stride;j++));
         do
                 num=$((i*stride + j))
                 rm -f ${path}/file${num} &
         done
         wait
         i=$((i+1))
done

# vi go.sh
# vi writer.sh
# sh go.sh
(It might be reproduced after a while...)

Thanks,
Toshiyuki Okajima

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