From f6eca2d43ed694ab8124dd24c88277f7eca93b7d Mon Sep 17 00:00:00 2001
From: Nate Dailey <nate.dailey@stratus.com>
Date: Tue, 17 Oct 2017 08:17:03 -0400
Subject: [PATCH] raid1: prevent freeze_array/wait_all_barriers deadlock
Git-commit: f6eca2d43ed694ab8124dd24c88277f7eca93b7d
Patch-mainline: v4.15-rc1
References: bsc#1093023
If freeze_array is attempted in the middle of close_sync/
wait_all_barriers, deadlock can occur.
freeze_array will wait for nr_pending and nr_queued to line up.
wait_all_barriers increments nr_pending for each barrier bucket, one
at a time, but doesn't actually issue IO that could be counted in
nr_queued. So freeze_array is blocked until wait_all_barriers
completes and allow_all_barriers runs. At the same time, when
_wait_barrier sees array_frozen == 1, it stops and waits for
freeze_array to complete.
Prevent the deadlock by making close_sync call _wait_barrier and
_allow_barrier for one bucket at a time, instead of deferring the
_allow_barrier calls until after all _wait_barriers are complete.
Signed-off-by: Nate Dailey <nate.dailey@stratus.com>
Fix: fd76863e37fe(RAID1: a new I/O barrier implementation to remove resync window)
Reviewed-by: Coly Li <colyli@suse.de>
Cc: stable@vger.kernel.org (v4.11)
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Coly Li <colyli@suse.de>
---
drivers/md/raid1.c | 24 ++++++------------------
1 file changed, 6 insertions(+), 18 deletions(-)
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 1f36473c79dc..038f5eb299ce 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -989,14 +989,6 @@ static void wait_barrier(struct r1conf *conf, sector_t sector_nr)
_wait_barrier(conf, idx);
}
-static void wait_all_barriers(struct r1conf *conf)
-{
- int idx;
-
- for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++)
- _wait_barrier(conf, idx);
-}
-
static void _allow_barrier(struct r1conf *conf, int idx)
{
atomic_dec(&conf->nr_pending[idx]);
@@ -1010,14 +1002,6 @@ static void allow_barrier(struct r1conf *conf, sector_t sector_nr)
_allow_barrier(conf, idx);
}
-static void allow_all_barriers(struct r1conf *conf)
-{
- int idx;
-
- for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++)
- _allow_barrier(conf, idx);
-}
-
/* conf->resync_lock should be held */
static int get_unqueued_pending(struct r1conf *conf)
{
@@ -1645,8 +1629,12 @@ static void print_conf(struct r1conf *conf)
static void close_sync(struct r1conf *conf)
{
- wait_all_barriers(conf);
- allow_all_barriers(conf);
+ int idx;
+
+ for (idx = 0; idx < BARRIER_BUCKETS_NR; idx++) {
+ _wait_barrier(conf, idx);
+ _allow_barrier(conf, idx);
+ }
mempool_destroy(conf->r1buf_pool);
conf->r1buf_pool = NULL;
--
2.16.3