[PATCH] mempool.c: Replace io_schedule_timeout with io_schedule

[PATCH] mempool.c: Replace io_schedule_timeout with io_schedule

[Timofey Titovets]

io_schedule_timeout(5*HZ);
Introduced for avoidance dm bug:
http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-08/msg04869.html
According to description must be replaced with io_schedule()

I replace it and recompile kernel, tested it by following script:
---
dev=""
block_dev=zram #loop
if [ "$block_dev" == "loop" ]; then
        f1=$RANDOM
        f2=${f1}_2
        truncate -s 256G ./$f1
        truncate -s 256G ./$f2
        dev="$(losetup -f --show ./$f1) $(losetup -f --show ./$f2)"
        rm ./$f1 ./$f2
else
        modprobe zram num_devices=8
        # needed ~1g free ram for test
        echo 128G > /sys/block/zram7/disksize
        echo 128G > /sys/block/zram6/disksize
        dev="/dev/zram7 /dev/zram6"
fi

md=/dev/md$[$RANDOM%8]
echo "y\n" | mdadm --create $md --chunk=4 --level=1 --raid-devices=2 $(echo $dev)
[ "$block_dev" == "loop" ] && losetup -d $(echo $dev) &

mkfs.xfs -f $md
mount $md /mnt

cat /dev/zero > /mnt/$RANDOM &
cat /dev/zero > /mnt/$RANDOM &
wait
umount -l /mnt
mdadm --stop $md

if [ "$block_dev" == "zram" ]; then
        echo 1 > /sys/block/zram7/reset
        echo 1 > /sys/block/zram6/reset
fi
---

i.e. i can't get this error for fast test with zram and slow test with loop devices

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
---
 mm/mempool.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/mm/mempool.c b/mm/mempool.c
index e209c98..ae230c9 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -253,11 +253,7 @@ repeat_alloc:
 
 	spin_unlock_irqrestore(&pool->lock, flags);
 
-	/*
-	 * FIXME: this should be io_schedule().  The timeout is there as a
-	 * workaround for some DM problems in 2.6.18.
-	 */
-	io_schedule_timeout(5*HZ);
+	io_schedule();
 
 	finish_wait(&pool->wait, &wait);
 	goto repeat_alloc;
-- 
2.1.3

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Re: [PATCH] mempool.c: Replace io_schedule_timeout with io_schedule

[Andrew Morton]

On Sun, 14 Dec 2014 15:34:46 +0300 Timofey Titovets <nefelim4ag@gmail.com> wrote:

> io_schedule_timeout(5*HZ);
> Introduced for avoidance dm bug:
> http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-08/msg04869.html
> According to description must be replaced with io_schedule()
> 
> I replace it and recompile kernel, tested it by following script:

How do we know DM doesn't still depend on the io_schedule_timeout()?

It would require input from the DM developers and quite a lot of
stress-testing of many kernel subsystems before we could make this
change.

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Re: [PATCH] mempool.c: Replace io_schedule_timeout with io_schedule

[Timofey Titovets]

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2014-12-18 2:06 GMT+03:00 Andrew Morton <akpm@linux-foundation.org>:
>
> On Sun, 14 Dec 2014 15:34:46 +0300 Timofey Titovets <nefelim4ag@gmail.com>
> wrote:
>
> > io_schedule_timeout(5*HZ);
> > Introduced for avoidance dm bug:
> > http://linux.derkeiler.com/Mailing-Lists/Kernel/2006-08/msg04869.html
> > According to description must be replaced with io_schedule()
> >
> > I replace it and recompile kernel, tested it by following script:
>
> How do we know DM doesn't still depend on the io_schedule_timeout()?
>
> It would require input from the DM developers and quite a lot of
> stress-testing of many kernel subsystems before we could make this
> change.
>

Okay, sorry for noise, will talking with dm devels, and after, if all be
good, will resend it.

-- 
Have a nice day,
Timofey.

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