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Date: Mon, 2 Sep 2013 01:09:55 -0400
From: ycbzzjlby@...il.com
To: neilb@...e.de
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
Bian Yu <bianyu@...acom.com>
Subject: [PATCH v2] md/raid5: avoid deadlock when raid5 array has unack badblocks during md_stop_writes.
From: Bian Yu <bianyu@...acom.com>
When raid5 hit a fresh badblock, this badblock will flagged as unack
badblock until md_update_sb is called.
But md_stop/reboot/md_set_readonly will avoid raid5d call md_update_sb
in md_check_recovery, the badblock will always be unack, so raid5d
thread enter a infinite loop and never can unregister sync_thread
that cause deadlock.
To solve this, before md_stop_writes call md_unregister_thread, set
MD_STOPPING_WRITES on mddev->flags. In raid5.c analyse_stripe judge
MD_STOPPING_WRITES bit on mddev->flags, if setted don't block rdev
to wait md_update_sb. so raid5d thread can be stopped.
I can reproduce it by using follow way:
When raid5 array is recovering and hit a fresh badblock, then shutdown array at once.
[ 480.850203] Not tainted 3.11.0-next-20130906+ #4
[ 480.852344] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 480.854380] [<ffffffff8153b324>] md_do_sync+0x7e4/0xe60
[ 480.854386] [<ffffffff81747fcb>] ? _raw_spin_unlock_irq+0x2b/0x40
[ 480.854395] [<ffffffff81536fa0>] ? md_unregister_thread+0x90/0x90
[ 480.854400] [<ffffffff810a716d>] ? trace_hardirqs_on+0xd/0x10
[ 480.854405] [<ffffffff815370bf>] md_thread+0x11f/0x170
[ 480.854410] [<ffffffff81536fa0>] ? md_unregister_thread+0x90/0x90
[ 480.854415] [<ffffffff8106d956>] kthread+0xd6/0xe0
[ 480.854423] [<ffffffff8106d880>] ? __init_kthread_worker+0x70/0x70
[ 480.854428] [<ffffffff8174ff2c>] ret_from_fork+0x7c/0xb0
[ 480.854432] [<ffffffff8106d880>] ? __init_kthread_worker+0x70/0x70
[ 480.854435] no locks held by md0_resync/3246.
[ 480.854437] INFO: task mdadm:3257 blocked for more than 120 seconds.
[ 480.854438] Not tainted 3.11.0-next-20130906+ #4
[ 480.854439] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 480.854442] mdadm D 0000000000000000 5024 3257 3209 0x00000080
[ 480.854445] ffff880138c37b18 0000000000000046 00000000ffffffff ffff880037d3b120
[ 480.854447] ffff88013a038720 ffff88013a038000 0000000000013500 ffff880138c37fd8
[ 480.854449] ffff880138c36010 0000000000013500 0000000000013500 ffff880138c37fd8
[ 480.854449] Call Trace:
[ 480.854452] [<ffffffff81745fa4>] schedule+0x24/0x70
[ 480.854453] [<ffffffff81742725>] schedule_timeout+0x175/0x200
[ 480.854455] [<ffffffff810a6d30>] ? mark_held_locks+0x80/0x130
[ 480.854457] [<ffffffff81747fcb>] ? _raw_spin_unlock_irq+0x2b/0x40
[ 480.854459] [<ffffffff810a709d>] ? trace_hardirqs_on_caller+0xfd/0x1c0
[ 480.854461] [<ffffffff810a716d>] ? trace_hardirqs_on+0xd/0x10
[ 480.854463] [<ffffffff81746600>] wait_for_completion+0xa0/0x110
[ 480.854465] [<ffffffff8107d160>] ? try_to_wake_up+0x300/0x300
[ 480.854467] [<ffffffff8106ddbc>] kthread_stop+0x4c/0xe0
[ 480.854468] [<ffffffff81536f5e>] md_unregister_thread+0x4e/0x90
[ 480.854470] [<ffffffff8153965d>] md_reap_sync_thread+0x1d/0x140
[ 480.854472] [<ffffffff815397ab>] __md_stop_writes+0x2b/0x80
[ 480.854473] [<ffffffff8153c911>] do_md_stop+0x91/0x4d0
[ 480.854475] [<ffffffff8153e8a7>] ? md_ioctl+0xf7/0x15c0
[ 480.854477] [<ffffffff810a716d>] ? trace_hardirqs_on+0xd/0x10
[ 480.854479] [<ffffffff8153f6a9>] md_ioctl+0xef9/0x15c0
[ 480.854481] [<ffffffff8113145d>] ? handle_mm_fault+0x17d/0x920
Signed-off-by: Bian Yu <bianyu@...acom.com>
---
drivers/md/md.c | 2 ++
drivers/md/md.h | 4 ++++
drivers/md/raid5.c | 3 ++-
3 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index adf4d7e..54ef71f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5278,6 +5278,7 @@ static void md_clean(struct mddev *mddev)
static void __md_stop_writes(struct mddev *mddev)
{
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+ set_bit(MD_STOPPING_WRITES, &mddev->flags);
if (mddev->sync_thread) {
set_bit(MD_RECOVERY_INTR, &mddev->recovery);
md_reap_sync_thread(mddev);
@@ -5294,6 +5295,7 @@ static void __md_stop_writes(struct mddev *mddev)
mddev->in_sync = 1;
md_update_sb(mddev, 1);
}
+ clear_bit(MD_STOPPING_WRITES, &mddev->flags);
}
void md_stop_writes(struct mddev *mddev)
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 608050c..a24ae1d 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -214,6 +214,10 @@ struct mddev {
#define MD_STILL_CLOSED 4 /* If set, then array has not been opened since
* md_ioctl checked on it.
*/
+#define MD_STOPPING_WRITES 5 /* If set, raid5 shouldn't set unacknowledged
+ * badblock blocked in analyse_stripe to avoid
+ * infinite loop.
+ */
int suspended;
atomic_t active_io;
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f9972e2..ff1aecf 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3446,7 +3446,8 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
if (rdev) {
is_bad = is_badblock(rdev, sh->sector, STRIPE_SECTORS,
&first_bad, &bad_sectors);
- if (s->blocked_rdev == NULL
+ if (!test_bit(MD_STOPPING_WRITES, &conf->mddev->flags)
+ && s->blocked_rdev == NULL
&& (test_bit(Blocked, &rdev->flags)
|| is_bad < 0)) {
if (is_bad < 0)
--
1.7.1
--
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