Merge tag 'md/4.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md

Pull MD fixes from Shaohua Li:
 "A few bug fixes for MD:

   - Guoqing fixed a bug compiling md-cluster in kernel

   - I fixed a potential deadlock in raid5-cache superblock write, a
     hang in raid5 reshape resume and a race condition introduced in
     rc4"

* tag 'md/4.8-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md:
  raid5: fix a small race condition
  md-cluster: make md-cluster also can work when compiled into kernel
  raid5: guarantee enough stripes to avoid reshape hang
  raid5-cache: fix a deadlock in superblock write

3 files changed, 31 insertions, 41 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 67642bacd597..915e84d631a2 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7610,16 +7610,12 @@ EXPORT_SYMBOL(unregister_md_cluster_operations);
 
 int md_setup_cluster(struct mddev *mddev, int nodes)
 {
-        int err;
-
-        err = request_module("md-cluster");
-        if (err) {
-                pr_err("md-cluster module not found.\n");
-                return -ENOENT;
-        }
-
+        if (!md_cluster_ops)
+                request_module("md-cluster");
         spin_lock(&pers_lock);
+        /* ensure module won't be unloaded */
         if (!md_cluster_ops || !try_module_get(md_cluster_mod)) {
+                pr_err("can't find md-cluster module or get it's reference.\n");
                 spin_unlock(&pers_lock);
                 return -ENOENT;
         }
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);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index da583bb43c84..ee7fc3701700 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2423,10 +2423,10 @@ static void raid5_end_read_request(struct bio * bi)
                 }
         }
         rdev_dec_pending(rdev, conf->mddev);
+        bio_reset(bi);
         clear_bit(R5_LOCKED, &sh->dev[i].flags);
         set_bit(STRIPE_HANDLE, &sh->state);
         raid5_release_stripe(sh);
-        bio_reset(bi);
 }
 
 static void raid5_end_write_request(struct bio *bi)
@@ -2498,6 +2498,7 @@ static void raid5_end_write_request(struct bio *bi)
         if (sh->batch_head && bi->bi_error && !replacement)
                 set_bit(STRIPE_BATCH_ERR, &sh->batch_head->state);
 
+        bio_reset(bi);
         if (!test_and_clear_bit(R5_DOUBLE_LOCKED, &sh->dev[i].flags))
                 clear_bit(R5_LOCKED, &sh->dev[i].flags);
         set_bit(STRIPE_HANDLE, &sh->state);
@@ -2505,7 +2506,6 @@ static void raid5_end_write_request(struct bio *bi)
 
         if (sh->batch_head && sh != sh->batch_head)
                 raid5_release_stripe(sh->batch_head);
-        bio_reset(bi);
 }
 
 static void raid5_build_block(struct stripe_head *sh, int i, int previous)
@@ -6639,6 +6639,16 @@ static struct r5conf *setup_conf(struct mddev *mddev)
         }
 
         conf->min_nr_stripes = NR_STRIPES;
+        if (mddev->reshape_position != MaxSector) {
+                int stripes = max_t(int,
+                        ((mddev->chunk_sectors << 9) / STRIPE_SIZE) * 4,
+                        ((mddev->new_chunk_sectors << 9) / STRIPE_SIZE) * 4);
+                conf->min_nr_stripes = max(NR_STRIPES, stripes);
+                if (conf->min_nr_stripes != NR_STRIPES)
+                        printk(KERN_INFO
+                                "md/raid:%s: force stripe size %d for reshape\n",
+                                mdname(mddev), conf->min_nr_stripes);
+        }
         memory = conf->min_nr_stripes * (sizeof(struct stripe_head) +
                  max_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
         atomic_set(&conf->empty_inactive_list_nr, NR_STRIPE_HASH_LOCKS);