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>
---
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 f3f3e40dc9d8..e4e8f9e565b7 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -990,14 +990,6 @@ 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]);
@@ -1011,14 +1003,6 @@ 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)
{
@@ -1654,8 +1638,12 @@ 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;
--
2.11.0
--
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