This is a note to let you know that I've just added the patch titled
raid1: prevent freeze_array/wait_all_barriers deadlock
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
raid1-prevent-freeze_array-wait_all_barriers-deadlock.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f6eca2d43ed694ab8124dd24c88277f7eca93b7d Mon Sep 17 00:00:00 2001
From: Nate Dailey <nate.dailey@xxxxxxxxxxx>
Date: Tue, 17 Oct 2017 08:17:03 -0400
Subject: raid1: prevent freeze_array/wait_all_barriers deadlock
From: Nate Dailey <nate.dailey@xxxxxxxxxxx>
commit f6eca2d43ed694ab8124dd24c88277f7eca93b7d upstream.
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@xxxxxxxxxxx>
Fix: fd76863e37fe(RAID1: a new I/O barrier implementation to remove resync window)
Reviewed-by: Coly Li <colyli@xxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/raid1.c | 24 ++++++------------------
1 file changed, 6 insertions(+), 18 deletions(-)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -990,14 +990,6 @@ static void wait_barrier(struct r1conf *
_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]);
@@ -1011,14 +1003,6 @@ static void allow_barrier(struct r1conf
_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)
{
@@ -1654,8 +1638,12 @@ static void print_conf(struct r1conf *co
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;
Patches currently in stable-queue which might be from nate.dailey@xxxxxxxxxxx are
queue-4.14/raid1-prevent-freeze_array-wait_all_barriers-deadlock.patch