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Diffstat (limited to 'drivers/md/raid5-cache.c')
-rw-r--r--drivers/md/raid5-cache.c46
1 files changed, 15 insertions, 31 deletions
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 51f76ddbe265..1b1ab4a1d132 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -96,7 +96,6 @@ struct r5l_log {
spinlock_t no_space_stripes_lock;
bool need_cache_flush;
- bool in_teardown;
};
/*
@@ -704,31 +703,22 @@ static void r5l_write_super_and_discard_space(struct r5l_log *log,
mddev = log->rdev->mddev;
/*
- * This is to avoid a deadlock. r5l_quiesce holds reconfig_mutex and
- * wait for this thread to finish. This thread waits for
- * MD_CHANGE_PENDING clear, which is supposed to be done in
- * md_check_recovery(). md_check_recovery() tries to get
- * reconfig_mutex. Since r5l_quiesce already holds the mutex,
- * md_check_recovery() fails, so the PENDING never get cleared. The
- * in_teardown check workaround this issue.
+ * Discard could zero data, so before discard we must make sure
+ * superblock is updated to new log tail. Updating superblock (either
+ * directly call md_update_sb() or depend on md thread) must hold
+ * reconfig mutex. On the other hand, raid5_quiesce is called with
+ * reconfig_mutex hold. The first step of raid5_quiesce() is waitting
+ * for all IO finish, hence waitting for reclaim thread, while reclaim
+ * thread is calling this function and waitting for reconfig mutex. So
+ * there is a deadlock. We workaround this issue with a trylock.
+ * FIXME: we could miss discard if we can't take reconfig mutex
*/
- if (!log->in_teardown) {
- set_mask_bits(&mddev->flags, 0,
- BIT(MD_CHANGE_DEVS) | BIT(MD_CHANGE_PENDING));
- md_wakeup_thread(mddev->thread);
- wait_event(mddev->sb_wait,
- !test_bit(MD_CHANGE_PENDING, &mddev->flags) ||
- log->in_teardown);
- /*
- * r5l_quiesce could run after in_teardown check and hold
- * mutex first. Superblock might get updated twice.
- */
- if (log->in_teardown)
- md_update_sb(mddev, 1);
- } else {
- WARN_ON(!mddev_is_locked(mddev));
- md_update_sb(mddev, 1);
- }
+ set_mask_bits(&mddev->flags, 0,
+ BIT(MD_CHANGE_DEVS) | BIT(MD_CHANGE_PENDING));
+ if (!mddev_trylock(mddev))
+ return;
+ md_update_sb(mddev, 1);
+ mddev_unlock(mddev);
/* discard IO error really doesn't matter, ignore it */
if (log->last_checkpoint < end) {
@@ -827,7 +817,6 @@ void r5l_quiesce(struct r5l_log *log, int state)
if (!log || state == 2)
return;
if (state == 0) {
- log->in_teardown = 0;
/*
* This is a special case for hotadd. In suspend, the array has
* no journal. In resume, journal is initialized as well as the
@@ -838,11 +827,6 @@ void r5l_quiesce(struct r5l_log *log, int state)
log->reclaim_thread = md_register_thread(r5l_reclaim_thread,
log->rdev->mddev, "reclaim");
} else if (state == 1) {
- /*
- * at this point all stripes are finished, so io_unit is at
- * least in STRIPE_END state
- */
- log->in_teardown = 1;
/* make sure r5l_write_super_and_discard_space exits */
mddev = log->rdev->mddev;
wake_up(&mddev->sb_wait);