Merge tag 'md-3.7' of git://neil.brown.name/md

Pull md updates from NeilBrown:
 - "discard" support, some dm-raid improvements and other assorted bits
   and pieces.

* tag 'md-3.7' of git://neil.brown.name/md: (29 commits)
  md: refine reporting of resync/reshape delays.
  md/raid5: be careful not to resize_stripes too big.
  md: make sure manual changes to recovery checkpoint are saved.
  md/raid10: use correct limit variable
  md: writing to sync_action should clear the read-auto state.
  Subject: [PATCH] md:change resync_mismatches to atomic64_t to avoid races
  md/raid5: make sure to_read and to_write never go negative.
  md: When RAID5 is dirty, force reconstruct-write instead of read-modify-write.
  md/raid5: protect debug message against NULL derefernce.
  md/raid5: add some missing locking in handle_failed_stripe.
  MD: raid5 avoid unnecessary zero page for trim
  MD: raid5 trim support
  md/bitmap:Don't use IS_ERR to judge alloc_page().
  md/raid1: Don't release reference to device while handling read error.
  raid: replace list_for_each_continue_rcu with new interface
  add further __init annotations to crypto/xor.c
  DM RAID: Fix for "sync" directive ineffectiveness
  DM RAID: Fix comparison of index and quantity for "rebuild" parameter
  DM RAID: Add rebuild capability for RAID10
  DM RAID: Move 'rebuild' checking code to its own function
  ...

11 files changed, 567 insertions, 127 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 94e7f6ba2e11..7155945f8eb8 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -163,20 +163,17 @@ static struct md_rdev *next_active_rdev(struct md_rdev *rdev, struct mddev *mdde
          * As devices are only added or removed when raid_disk is < 0 and
          * nr_pending is 0 and In_sync is clear, the entries we return will
          * still be in the same position on the list when we re-enter
-         * list_for_each_continue_rcu.
+         * list_for_each_entry_continue_rcu.
          */
-        struct list_head *pos;
         rcu_read_lock();
         if (rdev == NULL)
                 /* start at the beginning */
-                pos = &mddev->disks;
+                rdev = list_entry_rcu(&mddev->disks, struct md_rdev, same_set);
         else {
                 /* release the previous rdev and start from there. */
                 rdev_dec_pending(rdev, mddev);
-                pos = &rdev->same_set;
         }
-        list_for_each_continue_rcu(pos, &mddev->disks) {
-                rdev = list_entry(pos, struct md_rdev, same_set);
+        list_for_each_entry_continue_rcu(rdev, &mddev->disks, same_set) {
                 if (rdev->raid_disk >= 0 &&
                     !test_bit(Faulty, &rdev->flags)) {
                         /* this is a usable devices */
@@ -473,14 +470,10 @@ static int bitmap_new_disk_sb(struct bitmap *bitmap)
 {
         bitmap_super_t *sb;
         unsigned long chunksize, daemon_sleep, write_behind;
-        int err = -EINVAL;
 
         bitmap->storage.sb_page = alloc_page(GFP_KERNEL);
-        if (IS_ERR(bitmap->storage.sb_page)) {
-                err = PTR_ERR(bitmap->storage.sb_page);
-                bitmap->storage.sb_page = NULL;
-                return err;
-        }
+        if (bitmap->storage.sb_page == NULL)
+                return -ENOMEM;
         bitmap->storage.sb_page->index = 0;
 
         sb = kmap_atomic(bitmap->storage.sb_page);
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 982e3e390c45..45d94a7e7f6d 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -338,6 +338,84 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
 }
 
 /*
+ * validate_rebuild_devices
+ * @rs
+ *
+ * Determine if the devices specified for rebuild can result in a valid
+ * usable array that is capable of rebuilding the given devices.
+ *
+ * Returns: 0 on success, -EINVAL on failure.
+ */
+static int validate_rebuild_devices(struct raid_set *rs)
+{
+        unsigned i, rebuild_cnt = 0;
+        unsigned rebuilds_per_group, copies, d;
+
+        if (!(rs->print_flags & DMPF_REBUILD))
+                return 0;
+
+        for (i = 0; i < rs->md.raid_disks; i++)
+                if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
+                        rebuild_cnt++;
+
+        switch (rs->raid_type->level) {
+        case 1:
+                if (rebuild_cnt >= rs->md.raid_disks)
+                        goto too_many;
+                break;
+        case 4:
+        case 5:
+        case 6:
+                if (rebuild_cnt > rs->raid_type->parity_devs)
+                        goto too_many;
+                break;
+        case 10:
+                copies = raid10_md_layout_to_copies(rs->md.layout);
+                if (rebuild_cnt < copies)
+                        break;
+
+                /*
+                 * It is possible to have a higher rebuild count for RAID10,
+                 * as long as the failed devices occur in different mirror
+                 * groups (i.e. different stripes).
+                 *
+                 * Right now, we only allow for "near" copies.  When other
+                 * formats are added, we will have to check those too.
+                 *
+                 * When checking "near" format, make sure no adjacent devices
+                 * have failed beyond what can be handled.  In addition to the
+                 * simple case where the number of devices is a multiple of the
+                 * number of copies, we must also handle cases where the number
+                 * of devices is not a multiple of the number of copies.
+                 * E.g.    dev1 dev2 dev3 dev4 dev5
+                 *          A    A    B    B    C
+                 *          C    D    D    E    E
+                 */
+                rebuilds_per_group = 0;
+                for (i = 0; i < rs->md.raid_disks * copies; i++) {
+                        d = i % rs->md.raid_disks;
+                        if (!test_bit(In_sync, &rs->dev[d].rdev.flags) &&
+                            (++rebuilds_per_group >= copies))
+                                goto too_many;
+                        if (!((i + 1) % copies))
+                                rebuilds_per_group = 0;
+                }
+                break;
+        default:
+                DMERR("The rebuild parameter is not supported for %s",
+                      rs->raid_type->name);
+                rs->ti->error = "Rebuild not supported for this RAID type";
+                return -EINVAL;
+        }
+
+        return 0;
+
+too_many:
+        rs->ti->error = "Too many rebuild devices specified";
+        return -EINVAL;
+}
+
+/*
  * Possible arguments are...
  *      <chunk_size> [optional_args]
  *
@@ -365,7 +443,7 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
 {
         char *raid10_format = "near";
         unsigned raid10_copies = 2;
-        unsigned i, rebuild_cnt = 0;
+        unsigned i;
         unsigned long value, region_size = 0;
         sector_t sectors_per_dev = rs->ti->len;
         sector_t max_io_len;
@@ -461,31 +539,7 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
 
                 /* Parameters that take a numeric value are checked here */
                 if (!strcasecmp(key, "rebuild")) {
-                        rebuild_cnt++;
-
-                        switch (rs->raid_type->level) {
-                        case 1:
-                                if (rebuild_cnt >= rs->md.raid_disks) {
-                                        rs->ti->error = "Too many rebuild devices specified";
-                                        return -EINVAL;
-                                }
-                                break;
-                        case 4:
-                        case 5:
-                        case 6:
-                                if (rebuild_cnt > rs->raid_type->parity_devs) {
-                                        rs->ti->error = "Too many rebuild devices specified for given RAID type";
-                                        return -EINVAL;
-                                }
-                                break;
-                        case 10:
-                        default:
-                                DMERR("The rebuild parameter is not supported for %s", rs->raid_type->name);
-                                rs->ti->error = "Rebuild not supported for this RAID type";
-                                return -EINVAL;
-                        }
-
-                        if (value > rs->md.raid_disks) {
+                        if (value >= rs->md.raid_disks) {
                                 rs->ti->error = "Invalid rebuild index given";
                                 return -EINVAL;
                         }
@@ -608,6 +662,9 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
         }
         rs->md.dev_sectors = sectors_per_dev;
 
+        if (validate_rebuild_devices(rs))
+                return -EINVAL;
+
         /* Assume there are no metadata devices until the drives are parsed */
         rs->md.persistent = 0;
         rs->md.external = 1;
@@ -960,6 +1017,19 @@ static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
 
         freshest = NULL;
         rdev_for_each_safe(rdev, tmp, mddev) {
+                /*
+                 * Skipping super_load due to DMPF_SYNC will cause
+                 * the array to undergo initialization again as
+                 * though it were new.  This is the intended effect
+                 * of the "sync" directive.
+                 *
+                 * When reshaping capability is added, we must ensure
+                 * that the "sync" directive is disallowed during the
+                 * reshape.
+                 */
+                if (rs->print_flags & DMPF_SYNC)
+                        continue;
+
                 if (!rdev->meta_bdev)
                         continue;
 
@@ -1360,7 +1430,7 @@ static void raid_resume(struct dm_target *ti)
 
 static struct target_type raid_target = {
         .name = "raid",
-        .version = {1, 3, 0},
+        .version = {1, 3, 1},
         .module = THIS_MODULE,
         .ctr = raid_ctr,
         .dtr = raid_dtr,
diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index fa211d80fc0a..21014836bdbf 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -138,6 +138,7 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
         struct linear_conf *conf;
         struct md_rdev *rdev;
         int i, cnt;
+        bool discard_supported = false;
 
         conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(struct dev_info),
                         GFP_KERNEL);
@@ -171,6 +172,8 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
                 conf->array_sectors += rdev->sectors;
                 cnt++;
 
+                if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+                        discard_supported = true;
         }
         if (cnt != raid_disks) {
                 printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
@@ -178,6 +181,11 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
                 goto out;
         }
 
+        if (!discard_supported)
+                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+        else
+                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
         /*
          * Here we calculate the device offsets.
          */
@@ -244,7 +252,9 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
         if (!newconf)
                 return -ENOMEM;
 
-        oldconf = rcu_dereference(mddev->private);
+        oldconf = rcu_dereference_protected(mddev->private,
+                                            lockdep_is_held(
+                                                    &mddev->reconfig_mutex));
         mddev->raid_disks++;
         rcu_assign_pointer(mddev->private, newconf);
         md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
@@ -256,7 +266,10 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
 
 static int linear_stop (struct mddev *mddev)
 {
-        struct linear_conf *conf = mddev->private;
+        struct linear_conf *conf =
+                rcu_dereference_protected(mddev->private,
+                                          lockdep_is_held(
+                                                  &mddev->reconfig_mutex));
 
         /*
          * We do not require rcu protection here since
@@ -326,6 +339,14 @@ static void linear_make_request(struct mddev *mddev, struct bio *bio)
         bio->bi_sector = bio->bi_sector - start_sector
                 + tmp_dev->rdev->data_offset;
         rcu_read_unlock();
+
+        if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+                     !blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
+                /* Just ignore it */
+                bio_endio(bio, 0);
+                return;
+        }
+
         generic_make_request(bio);
 }
 
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 95c88012a3b9..9ab768acfb62 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -674,7 +674,18 @@ static struct md_rdev * find_rdev_nr(struct mddev *mddev, int nr)
         return NULL;
 }
 
-static struct md_rdev * find_rdev(struct mddev * mddev, dev_t dev)
+static struct md_rdev *find_rdev_nr_rcu(struct mddev *mddev, int nr)
+{
+        struct md_rdev *rdev;
+
+        rdev_for_each_rcu(rdev, mddev)
+                if (rdev->desc_nr == nr)
+                        return rdev;
+
+        return NULL;
+}
+
+static struct md_rdev *find_rdev(struct mddev *mddev, dev_t dev)
 {
         struct md_rdev *rdev;
 
@@ -685,6 +696,17 @@ static struct md_rdev * find_rdev(struct mddev * mddev, dev_t dev)
         return NULL;
 }
 
+static struct md_rdev *find_rdev_rcu(struct mddev *mddev, dev_t dev)
+{
+        struct md_rdev *rdev;
+
+        rdev_for_each_rcu(rdev, mddev)
+                if (rdev->bdev->bd_dev == dev)
+                        return rdev;
+
+        return NULL;
+}
+
 static struct md_personality *find_pers(int level, char *clevel)
 {
         struct md_personality *pers;
@@ -2022,8 +2044,14 @@ EXPORT_SYMBOL(md_integrity_register);
 /* Disable data integrity if non-capable/non-matching disk is being added */
 void md_integrity_add_rdev(struct md_rdev *rdev, struct mddev *mddev)
 {
-        struct blk_integrity *bi_rdev = bdev_get_integrity(rdev->bdev);
-        struct blk_integrity *bi_mddev = blk_get_integrity(mddev->gendisk);
+        struct blk_integrity *bi_rdev;
+        struct blk_integrity *bi_mddev;
+
+        if (!mddev->gendisk)
+                return;
+
+        bi_rdev = bdev_get_integrity(rdev->bdev);
+        bi_mddev = blk_get_integrity(mddev->gendisk);
 
         if (!bi_mddev) /* nothing to do */
                 return;
@@ -3754,6 +3782,8 @@ resync_start_store(struct mddev *mddev, const char *buf, size_t len)
                 return -EINVAL;
 
         mddev->recovery_cp = n;
+        if (mddev->pers)
+                set_bit(MD_CHANGE_CLEAN, &mddev->flags);
         return len;
 }
 static struct md_sysfs_entry md_resync_start =
@@ -4231,6 +4261,13 @@ action_store(struct mddev *mddev, const char *page, size_t len)
                 set_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
                 set_bit(MD_RECOVERY_SYNC, &mddev->recovery);
         }
+        if (mddev->ro == 2) {
+                /* A write to sync_action is enough to justify
+                 * canceling read-auto mode
+                 */
+                mddev->ro = 0;
+                md_wakeup_thread(mddev->sync_thread);
+        }
         set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
         md_wakeup_thread(mddev->thread);
         sysfs_notify_dirent_safe(mddev->sysfs_action);
@@ -4241,7 +4278,8 @@ static ssize_t
 mismatch_cnt_show(struct mddev *mddev, char *page)
 {
         return sprintf(page, "%llu\n",
-                       (unsigned long long) mddev->resync_mismatches);
+                       (unsigned long long)
+                       atomic64_read(&mddev->resync_mismatches));
 }
 
 static struct md_sysfs_entry md_scan_mode =
@@ -4362,6 +4400,10 @@ sync_completed_show(struct mddev *mddev, char *page)
         if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
                 return sprintf(page, "none\n");
 
+        if (mddev->curr_resync == 1 ||
+            mddev->curr_resync == 2)
+                return sprintf(page, "delayed\n");
+
         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
             test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
                 max_sectors = mddev->resync_max_sectors;
@@ -5207,7 +5249,7 @@ static void md_clean(struct mddev *mddev)
         mddev->new_layout = 0;
         mddev->new_chunk_sectors = 0;
         mddev->curr_resync = 0;
-        mddev->resync_mismatches = 0;
+        atomic64_set(&mddev->resync_mismatches, 0);
         mddev->suspend_lo = mddev->suspend_hi = 0;
         mddev->sync_speed_min = mddev->sync_speed_max = 0;
         mddev->recovery = 0;
@@ -5509,8 +5551,9 @@ static int get_array_info(struct mddev * mddev, void __user * arg)
         int nr,working,insync,failed,spare;
         struct md_rdev *rdev;
 
-        nr=working=insync=failed=spare=0;
-        rdev_for_each(rdev, mddev) {
+        nr = working = insync = failed = spare = 0;
+        rcu_read_lock();
+        rdev_for_each_rcu(rdev, mddev) {
                 nr++;
                 if (test_bit(Faulty, &rdev->flags))
                         failed++;
@@ -5522,6 +5565,7 @@ static int get_array_info(struct mddev * mddev, void __user * arg)
                                 spare++;
                 }
         }
+        rcu_read_unlock();
 
         info.major_version = mddev->major_version;
         info.minor_version = mddev->minor_version;
@@ -5605,7 +5649,8 @@ static int get_disk_info(struct mddev * mddev, void __user * arg)
         if (copy_from_user(&info, arg, sizeof(info)))
                 return -EFAULT;
 
-        rdev = find_rdev_nr(mddev, info.number);
+        rcu_read_lock();
+        rdev = find_rdev_nr_rcu(mddev, info.number);
         if (rdev) {
                 info.major = MAJOR(rdev->bdev->bd_dev);
                 info.minor = MINOR(rdev->bdev->bd_dev);
@@ -5624,6 +5669,7 @@ static int get_disk_info(struct mddev * mddev, void __user * arg)
                 info.raid_disk = -1;
                 info.state = (1<<MD_DISK_REMOVED);
         }
+        rcu_read_unlock();
 
         if (copy_to_user(arg, &info, sizeof(info)))
                 return -EFAULT;
@@ -6232,18 +6278,22 @@ static int update_array_info(struct mddev *mddev, mdu_array_info_t *info)
 static int set_disk_faulty(struct mddev *mddev, dev_t dev)
 {
         struct md_rdev *rdev;
+        int err = 0;
 
         if (mddev->pers == NULL)
                 return -ENODEV;
 
-        rdev = find_rdev(mddev, dev);
+        rcu_read_lock();
+        rdev = find_rdev_rcu(mddev, dev);
         if (!rdev)
-                return -ENODEV;
-
-        md_error(mddev, rdev);
-        if (!test_bit(Faulty, &rdev->flags))
-                return -EBUSY;
-        return 0;
+                err =  -ENODEV;
+        else {
+                md_error(mddev, rdev);
+                if (!test_bit(Faulty, &rdev->flags))
+                        err = -EBUSY;
+        }
+        rcu_read_unlock();
+        return err;
 }
 
 /*
@@ -6315,6 +6365,27 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
                 goto abort;
         }
 
+        /* Some actions do not requires the mutex */
+        switch (cmd) {
+        case GET_ARRAY_INFO:
+                if (!mddev->raid_disks && !mddev->external)
+                        err = -ENODEV;
+                else
+                        err = get_array_info(mddev, argp);
+                goto abort;
+
+        case GET_DISK_INFO:
+                if (!mddev->raid_disks && !mddev->external)
+                        err = -ENODEV;
+                else
+                        err = get_disk_info(mddev, argp);
+                goto abort;
+
+        case SET_DISK_FAULTY:
+                err = set_disk_faulty(mddev, new_decode_dev(arg));
+                goto abort;
+        }
+
         err = mddev_lock(mddev);
         if (err) {
                 printk(KERN_INFO 
@@ -6387,18 +6458,10 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
          */
         switch (cmd)
         {
-                case GET_ARRAY_INFO:
-                        err = get_array_info(mddev, argp);
-                        goto done_unlock;
-
                 case GET_BITMAP_FILE:
                         err = get_bitmap_file(mddev, argp);
                         goto done_unlock;
 
-                case GET_DISK_INFO:
-                        err = get_disk_info(mddev, argp);
-                        goto done_unlock;
-
                 case RESTART_ARRAY_RW:
                         err = restart_array(mddev);
                         goto done_unlock;
@@ -6480,10 +6543,6 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
                         err = hot_add_disk(mddev, new_decode_dev(arg));
                         goto done_unlock;
 
-                case SET_DISK_FAULTY:
-                        err = set_disk_faulty(mddev, new_decode_dev(arg));
-                        goto done_unlock;
-
                 case RUN_ARRAY:
                         err = do_md_run(mddev);
                         goto done_unlock;
@@ -6641,7 +6700,7 @@ static int md_thread(void * arg)
 
                 clear_bit(THREAD_WAKEUP, &thread->flags);
                 if (!kthread_should_stop())
-                        thread->run(thread->mddev);
+                        thread->run(thread);
         }
 
         return 0;
@@ -6656,8 +6715,8 @@ void md_wakeup_thread(struct md_thread *thread)
         }
 }
 
-struct md_thread *md_register_thread(void (*run) (struct mddev *), struct mddev *mddev,
-                                 const char *name)
+struct md_thread *md_register_thread(void (*run) (struct md_thread *),
+                struct mddev *mddev, const char *name)
 {
         struct md_thread *thread;
 
@@ -6752,7 +6811,11 @@ static void status_resync(struct seq_file *seq, struct mddev * mddev)
         int scale;
         unsigned int per_milli;
 
-        resync = mddev->curr_resync - atomic_read(&mddev->recovery_active);
+        if (mddev->curr_resync <= 3)
+                resync = 0;
+        else
+                resync = mddev->curr_resync
+                        - atomic_read(&mddev->recovery_active);
 
         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
             test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
@@ -6978,7 +7041,7 @@ static int md_seq_show(struct seq_file *seq, void *v)
                                 if (mddev->curr_resync > 2) {
                                         status_resync(seq, mddev);
                                         seq_printf(seq, "\n      ");
-                                } else if (mddev->curr_resync == 1 || mddev->curr_resync == 2)
+                                } else if (mddev->curr_resync >= 1)
                                         seq_printf(seq, "\tresync=DELAYED\n      ");
                                 else if (mddev->recovery_cp < MaxSector)
                                         seq_printf(seq, "\tresync=PENDING\n      ");
@@ -7206,8 +7269,9 @@ EXPORT_SYMBOL_GPL(md_allow_write);
 
 #define SYNC_MARKS      10
 #define SYNC_MARK_STEP  (3*HZ)
-void md_do_sync(struct mddev *mddev)
+void md_do_sync(struct md_thread *thread)
 {
+        struct mddev *mddev = thread->mddev;
         struct mddev *mddev2;
         unsigned int currspeed = 0,
                  window;
@@ -7311,7 +7375,7 @@ void md_do_sync(struct mddev *mddev)
                  * which defaults to physical size, but can be virtual size
                  */
                 max_sectors = mddev->resync_max_sectors;
-                mddev->resync_mismatches = 0;
+                atomic64_set(&mddev->resync_mismatches, 0);
                 /* we don't use the checkpoint if there's a bitmap */
                 if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
                         j = mddev->resync_min;
@@ -7367,8 +7431,11 @@ void md_do_sync(struct mddev *mddev)
                        "md: resuming %s of %s from checkpoint.\n",
                        desc, mdname(mddev));
                 mddev->curr_resync = j;
-        }
+        } else
+                mddev->curr_resync = 3; /* no longer delayed */
         mddev->curr_resync_completed = j;
+        sysfs_notify(&mddev->kobj, NULL, "sync_completed");
+        md_new_event(mddev);
 
         blk_start_plug(&plug);
         while (j < max_sectors) {
@@ -7421,7 +7488,8 @@ void md_do_sync(struct mddev *mddev)
                         break;
 
                 j += sectors;
-                if (j>1) mddev->curr_resync = j;
+                if (j > 2)
+                        mddev->curr_resync = j;
                 mddev->curr_mark_cnt = io_sectors;
                 if (last_check == 0)
                         /* this is the earliest that rebuild will be
@@ -7543,8 +7611,6 @@ static int remove_and_add_spares(struct mddev *mddev)
         int spares = 0;
         int removed = 0;
 
-        mddev->curr_resync_completed = 0;
-
         rdev_for_each(rdev, mddev)
                 if (rdev->raid_disk >= 0 &&
                     !test_bit(Blocked, &rdev->flags) &&
@@ -7739,6 +7805,7 @@ void md_check_recovery(struct mddev *mddev)
                 /* Set RUNNING before clearing NEEDED to avoid
                  * any transients in the value of "sync_action".
                  */
+                mddev->curr_resync_completed = 0;
                 set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
                 /* Clear some bits that don't mean anything, but
                  * might be left set
@@ -7752,7 +7819,7 @@ void md_check_recovery(struct mddev *mddev)
                 /* no recovery is running.
                  * remove any failed drives, then
                  * add spares if possible.
-                 * Spare are also removed and re-added, to allow
+                 * Spares are also removed and re-added, to allow
                  * the personality to fail the re-add.
                  */
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index f385b038589d..af443ab868db 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -282,7 +282,7 @@ struct mddev {
 
         sector_t                        resync_max_sectors; /* may be set by personality */
 
-        sector_t                        resync_mismatches; /* count of sectors where
+        atomic64_t                      resync_mismatches; /* count of sectors where
                                                             * parity/replica mismatch found
                                                             */
 
@@ -540,12 +540,13 @@ static inline void sysfs_unlink_rdev(struct mddev *mddev, struct md_rdev *rdev)
         list_for_each_entry_rcu(rdev, &((mddev)->disks), same_set)
 
 struct md_thread {
-        void                    (*run) (struct mddev *mddev);
+        void                    (*run) (struct md_thread *thread);
         struct mddev            *mddev;
         wait_queue_head_t       wqueue;
         unsigned long           flags;
         struct task_struct      *tsk;
         unsigned long           timeout;
+        void                    *private;
 };
 
 #define THREAD_WAKEUP  0
@@ -584,7 +585,7 @@ static inline void safe_put_page(struct page *p)
 extern int register_md_personality(struct md_personality *p);
 extern int unregister_md_personality(struct md_personality *p);
 extern struct md_thread *md_register_thread(
-        void (*run)(struct mddev *mddev),
+        void (*run)(struct md_thread *thread),
         struct mddev *mddev,
         const char *name);
 extern void md_unregister_thread(struct md_thread **threadp);
@@ -603,7 +604,7 @@ extern void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
 extern void md_super_wait(struct mddev *mddev);
 extern int sync_page_io(struct md_rdev *rdev, sector_t sector, int size, 
                         struct page *page, int rw, bool metadata_op);
-extern void md_do_sync(struct mddev *mddev);
+extern void md_do_sync(struct md_thread *thread);
 extern void md_new_event(struct mddev *mddev);
 extern int md_allow_write(struct mddev *mddev);
 extern void md_wait_for_blocked_rdev(struct md_rdev *rdev, struct mddev *mddev);
diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c
index 61a1833ebaf3..1642eae75a33 100644
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -335,8 +335,9 @@ abort:
  *      3.      Performs writes following reads for array syncronising.
  */
 
-static void multipathd (struct mddev *mddev)
+static void multipathd(struct md_thread *thread)
 {
+        struct mddev *mddev = thread->mddev;
         struct multipath_bh *mp_bh;
         struct bio *bio;
         unsigned long flags;
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index a9e4fa95dfaa..24b359717a7e 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -88,6 +88,7 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
         char b[BDEVNAME_SIZE];
         char b2[BDEVNAME_SIZE];
         struct r0conf *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
+        bool discard_supported = false;
 
         if (!conf)
                 return -ENOMEM;
@@ -195,6 +196,9 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
                 if (!smallest || (rdev1->sectors < smallest->sectors))
                         smallest = rdev1;
                 cnt++;
+
+                if (blk_queue_discard(bdev_get_queue(rdev1->bdev)))
+                        discard_supported = true;
         }
         if (cnt != mddev->raid_disks) {
                 printk(KERN_ERR "md/raid0:%s: too few disks (%d of %d) - "
@@ -272,6 +276,11 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
         blk_queue_io_opt(mddev->queue,
                          (mddev->chunk_sectors << 9) * mddev->raid_disks);
 
+        if (!discard_supported)
+                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+        else
+                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
         pr_debug("md/raid0:%s: done.\n", mdname(mddev));
         *private_conf = conf;
 
@@ -423,6 +432,7 @@ static int raid0_run(struct mddev *mddev)
                 return -EINVAL;
         blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
         blk_queue_max_write_same_sectors(mddev->queue, mddev->chunk_sectors);
+        blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
 
         /* if private is not null, we are here after takeover */
         if (mddev->private == NULL) {
@@ -510,7 +520,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
                 sector_t sector = bio->bi_sector;
                 struct bio_pair *bp;
                 /* Sanity check -- queue functions should prevent this happening */
-                if (bio->bi_vcnt != 1 ||
+                if ((bio->bi_vcnt != 1 && bio->bi_vcnt != 0) ||
                     bio->bi_idx != 0)
                         goto bad_map;
                 /* This is a one page bio that upper layers
@@ -536,6 +546,13 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
         bio->bi_sector = sector_offset + zone->dev_start +
                 tmp_dev->data_offset;
 
+        if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+                     !blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
+                /* Just ignore it */
+                bio_endio(bio, 0);
+                return;
+        }
+
         generic_make_request(bio);
         return;
 
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 611b5f797618..8034fbd6190c 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -333,9 +333,10 @@ static void raid1_end_read_request(struct bio *bio, int error)
                 spin_unlock_irqrestore(&conf->device_lock, flags);
         }
 
-        if (uptodate)
+        if (uptodate) {
                 raid_end_bio_io(r1_bio);
-        else {
+                rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
+        } else {
                 /*
                  * oops, read error:
                  */
@@ -349,9 +350,8 @@ static void raid1_end_read_request(struct bio *bio, int error)
                         (unsigned long long)r1_bio->sector);
                 set_bit(R1BIO_ReadError, &r1_bio->state);
                 reschedule_retry(r1_bio);
+                /* don't drop the reference on read_disk yet */
         }
-
-        rdev_dec_pending(conf->mirrors[mirror].rdev, conf->mddev);
 }
 
 static void close_write(struct r1bio *r1_bio)
@@ -781,7 +781,12 @@ static void flush_pending_writes(struct r1conf *conf)
                 while (bio) { /* submit pending writes */
                         struct bio *next = bio->bi_next;
                         bio->bi_next = NULL;
-                        generic_make_request(bio);
+                        if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+                            !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+                                /* Just ignore it */
+                                bio_endio(bio, 0);
+                        else
+                                generic_make_request(bio);
                         bio = next;
                 }
         } else
@@ -994,6 +999,8 @@ static void make_request(struct mddev *mddev, struct bio * bio)
         const int rw = bio_data_dir(bio);
         const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
         const unsigned long do_flush_fua = (bio->bi_rw & (REQ_FLUSH | REQ_FUA));
+        const unsigned long do_discard = (bio->bi_rw
+                                          & (REQ_DISCARD | REQ_SECURE));
         struct md_rdev *blocked_rdev;
         struct blk_plug_cb *cb;
         struct raid1_plug_cb *plug = NULL;
@@ -1295,7 +1302,7 @@ read_again:
                                    conf->mirrors[i].rdev->data_offset);
                 mbio->bi_bdev = conf->mirrors[i].rdev->bdev;
                 mbio->bi_end_io = raid1_end_write_request;
-                mbio->bi_rw = WRITE | do_flush_fua | do_sync;
+                mbio->bi_rw = WRITE | do_flush_fua | do_sync | do_discard;
                 mbio->bi_private = r1_bio;
 
                 atomic_inc(&r1_bio->remaining);
@@ -1549,6 +1556,8 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
                 clear_bit(Unmerged, &rdev->flags);
         }
         md_integrity_add_rdev(rdev, mddev);
+        if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
         print_conf(conf);
         return err;
 }
@@ -1867,7 +1876,7 @@ static int process_checks(struct r1bio *r1_bio)
                 } else
                         j = 0;
                 if (j >= 0)
-                        mddev->resync_mismatches += r1_bio->sectors;
+                        atomic64_add(r1_bio->sectors, &mddev->resync_mismatches);
                 if (j < 0 || (test_bit(MD_RECOVERY_CHECK, &mddev->recovery)
                               && test_bit(BIO_UPTODATE, &sbio->bi_flags))) {
                         /* No need to write to this device. */
@@ -2220,6 +2229,7 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
                 unfreeze_array(conf);
         } else
                 md_error(mddev, conf->mirrors[r1_bio->read_disk].rdev);
+        rdev_dec_pending(conf->mirrors[r1_bio->read_disk].rdev, conf->mddev);
 
         bio = r1_bio->bios[r1_bio->read_disk];
         bdevname(bio->bi_bdev, b);
@@ -2285,8 +2295,9 @@ read_more:
         }
 }
 
-static void raid1d(struct mddev *mddev)
+static void raid1d(struct md_thread *thread)
 {
+        struct mddev *mddev = thread->mddev;
         struct r1bio *r1_bio;
         unsigned long flags;
         struct r1conf *conf = mddev->private;
@@ -2783,6 +2794,7 @@ static int run(struct mddev *mddev)
         int i;
         struct md_rdev *rdev;
         int ret;
+        bool discard_supported = false;
 
         if (mddev->level != 1) {
                 printk(KERN_ERR "md/raid1:%s: raid level not set to mirroring (%d)\n",
@@ -2812,6 +2824,8 @@ static int run(struct mddev *mddev)
                         continue;
                 disk_stack_limits(mddev->gendisk, rdev->bdev,
                                   rdev->data_offset << 9);
+                if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+                        discard_supported = true;
         }
 
         mddev->degraded = 0;
@@ -2846,6 +2860,13 @@ static int run(struct mddev *mddev)
                 mddev->queue->backing_dev_info.congested_fn = raid1_congested;
                 mddev->queue->backing_dev_info.congested_data = mddev;
                 blk_queue_merge_bvec(mddev->queue, raid1_mergeable_bvec);
+
+                if (discard_supported)
+                        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
+                                                mddev->queue);
+                else
+                        queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD,
+                                                  mddev->queue);
         }
 
         ret =  md_integrity_register(mddev);
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0138a727c1f3..906ccbd0f7dc 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -911,7 +911,12 @@ static void flush_pending_writes(struct r10conf *conf)
                 while (bio) { /* submit pending writes */
                         struct bio *next = bio->bi_next;
                         bio->bi_next = NULL;
-                        generic_make_request(bio);
+                        if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+                            !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+                                /* Just ignore it */
+                                bio_endio(bio, 0);
+                        else
+                                generic_make_request(bio);
                         bio = next;
                 }
         } else
@@ -1050,6 +1055,44 @@ static sector_t choose_data_offset(struct r10bio *r10_bio,
                 return rdev->new_data_offset;
 }
 
+struct raid10_plug_cb {
+        struct blk_plug_cb      cb;
+        struct bio_list         pending;
+        int                     pending_cnt;
+};
+
+static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
+{
+        struct raid10_plug_cb *plug = container_of(cb, struct raid10_plug_cb,
+                                                   cb);
+        struct mddev *mddev = plug->cb.data;
+        struct r10conf *conf = mddev->private;
+        struct bio *bio;
+
+        if (from_schedule) {
+                spin_lock_irq(&conf->device_lock);
+                bio_list_merge(&conf->pending_bio_list, &plug->pending);
+                conf->pending_count += plug->pending_cnt;
+                spin_unlock_irq(&conf->device_lock);
+                md_wakeup_thread(mddev->thread);
+                kfree(plug);
+                return;
+        }
+
+        /* we aren't scheduling, so we can do the write-out directly. */
+        bio = bio_list_get(&plug->pending);
+        bitmap_unplug(mddev->bitmap);
+        wake_up(&conf->wait_barrier);
+
+        while (bio) { /* submit pending writes */
+                struct bio *next = bio->bi_next;
+                bio->bi_next = NULL;
+                generic_make_request(bio);
+                bio = next;
+        }
+        kfree(plug);
+}
+
 static void make_request(struct mddev *mddev, struct bio * bio)
 {
         struct r10conf *conf = mddev->private;
@@ -1061,8 +1104,12 @@ static void make_request(struct mddev *mddev, struct bio * bio)
         const int rw = bio_data_dir(bio);
         const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
         const unsigned long do_fua = (bio->bi_rw & REQ_FUA);
+        const unsigned long do_discard = (bio->bi_rw
+                                          & (REQ_DISCARD | REQ_SECURE));
         unsigned long flags;
         struct md_rdev *blocked_rdev;
+        struct blk_plug_cb *cb;
+        struct raid10_plug_cb *plug = NULL;
         int sectors_handled;
         int max_sectors;
         int sectors;
@@ -1081,7 +1128,7 @@ static void make_request(struct mddev *mddev, struct bio * bio)
                          || conf->prev.near_copies < conf->prev.raid_disks))) {
                 struct bio_pair *bp;
                 /* Sanity check -- queue functions should prevent this happening */
-                if (bio->bi_vcnt != 1 ||
+                if ((bio->bi_vcnt != 1 && bio->bi_vcnt != 0) ||
                     bio->bi_idx != 0)
                         goto bad_map;
                 /* This is a one page bio that upper layers
@@ -1410,15 +1457,26 @@ retry_write:
                                                       conf->mirrors[d].rdev));
                 mbio->bi_bdev = conf->mirrors[d].rdev->bdev;
                 mbio->bi_end_io = raid10_end_write_request;
-                mbio->bi_rw = WRITE | do_sync | do_fua;
+                mbio->bi_rw = WRITE | do_sync | do_fua | do_discard;
                 mbio->bi_private = r10_bio;
 
                 atomic_inc(&r10_bio->remaining);
+
+                cb = blk_check_plugged(raid10_unplug, mddev, sizeof(*plug));
+                if (cb)
+                        plug = container_of(cb, struct raid10_plug_cb, cb);
+                else
+                        plug = NULL;
                 spin_lock_irqsave(&conf->device_lock, flags);
-                bio_list_add(&conf->pending_bio_list, mbio);
-                conf->pending_count++;
+                if (plug) {
+                        bio_list_add(&plug->pending, mbio);
+                        plug->pending_cnt++;
+                } else {
+                        bio_list_add(&conf->pending_bio_list, mbio);
+                        conf->pending_count++;
+                }
                 spin_unlock_irqrestore(&conf->device_lock, flags);
-                if (!mddev_check_plugged(mddev))
+                if (!plug)
                         md_wakeup_thread(mddev->thread);
 
                 if (!r10_bio->devs[i].repl_bio)
@@ -1439,7 +1497,7 @@ retry_write:
                                            conf->mirrors[d].replacement));
                 mbio->bi_bdev = conf->mirrors[d].replacement->bdev;
                 mbio->bi_end_io = raid10_end_write_request;
-                mbio->bi_rw = WRITE | do_sync | do_fua;
+                mbio->bi_rw = WRITE | do_sync | do_fua | do_discard;
                 mbio->bi_private = r10_bio;
 
                 atomic_inc(&r10_bio->remaining);
@@ -1638,7 +1696,7 @@ static int raid10_spare_active(struct mddev *mddev)
                            && !test_bit(Faulty, &tmp->rdev->flags)
                            && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
                         count++;
-                        sysfs_notify_dirent(tmp->rdev->sysfs_state);
+                        sysfs_notify_dirent_safe(tmp->rdev->sysfs_state);
                 }
         }
         spin_lock_irqsave(&conf->device_lock, flags);
@@ -1725,6 +1783,9 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
                 clear_bit(Unmerged, &rdev->flags);
         }
         md_integrity_add_rdev(rdev, mddev);
+        if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
         print_conf(conf);
         return err;
 }
@@ -1952,7 +2013,7 @@ static void sync_request_write(struct mddev *mddev, struct r10bio *r10_bio)
                                         break;
                         if (j == vcnt)
                                 continue;
-                        mddev->resync_mismatches += r10_bio->sectors;
+                        atomic64_add(r10_bio->sectors, &mddev->resync_mismatches);
                         if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
                                 /* Don't fix anything. */
                                 continue;
@@ -2673,8 +2734,9 @@ static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)
         }
 }
 
-static void raid10d(struct mddev *mddev)
+static void raid10d(struct md_thread *thread)
 {
+        struct mddev *mddev = thread->mddev;
         struct r10bio *r10_bio;
         unsigned long flags;
         struct r10conf *conf = mddev->private;
@@ -3158,7 +3220,7 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr,
                                 else {
                                         bad_sectors -= (sector - first_bad);
                                         if (max_sync > bad_sectors)
-                                                max_sync = max_sync;
+                                                max_sync = bad_sectors;
                                         continue;
                                 }
                         }
@@ -3482,6 +3544,7 @@ static int run(struct mddev *mddev)
         sector_t size;
         sector_t min_offset_diff = 0;
         int first = 1;
+        bool discard_supported = false;
 
         if (mddev->private == NULL) {
                 conf = setup_conf(mddev);
@@ -3498,6 +3561,8 @@ static int run(struct mddev *mddev)
 
         chunk_size = mddev->chunk_sectors << 9;
         if (mddev->queue) {
+                blk_queue_max_discard_sectors(mddev->queue,
+                                              mddev->chunk_sectors);
                 blk_queue_io_min(mddev->queue, chunk_size);
                 if (conf->geo.raid_disks % conf->geo.near_copies)
                         blk_queue_io_opt(mddev->queue, chunk_size * conf->geo.raid_disks);
@@ -3543,8 +3608,16 @@ static int run(struct mddev *mddev)
                                           rdev->data_offset << 9);
 
                 disk->head_position = 0;
+
+                if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+                        discard_supported = true;
         }
 
+        if (discard_supported)
+                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+        else
+                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
         /* need to check that every block has at least one working mirror */
         if (!enough(conf, -1)) {
                 printk(KERN_ERR "md/raid10:%s: not enough operational mirrors.\n",
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 0689173fd9f5..c5439dce0295 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -551,6 +551,8 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
                                 rw = WRITE_FUA;
                         else
                                 rw = WRITE;
+                        if (test_bit(R5_Discard, &sh->dev[i].flags))
+                                rw |= REQ_DISCARD;
                 } else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
                         rw = READ;
                 else if (test_and_clear_bit(R5_WantReplace,
@@ -1174,8 +1176,11 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
                                         set_bit(R5_WantFUA, &dev->flags);
                                 if (wbi->bi_rw & REQ_SYNC)
                                         set_bit(R5_SyncIO, &dev->flags);
-                                tx = async_copy_data(1, wbi, dev->page,
-                                        dev->sector, tx);
+                                if (wbi->bi_rw & REQ_DISCARD)
+                                        set_bit(R5_Discard, &dev->flags);
+                                else
+                                        tx = async_copy_data(1, wbi, dev->page,
+                                                dev->sector, tx);
                                 wbi = r5_next_bio(wbi, dev->sector);
                         }
                 }
@@ -1191,7 +1196,7 @@ static void ops_complete_reconstruct(void *stripe_head_ref)
         int pd_idx = sh->pd_idx;
         int qd_idx = sh->qd_idx;
         int i;
-        bool fua = false, sync = false;
+        bool fua = false, sync = false, discard = false;
 
         pr_debug("%s: stripe %llu\n", __func__,
                 (unsigned long long)sh->sector);
@@ -1199,13 +1204,15 @@ static void ops_complete_reconstruct(void *stripe_head_ref)
         for (i = disks; i--; ) {
                 fua |= test_bit(R5_WantFUA, &sh->dev[i].flags);
                 sync |= test_bit(R5_SyncIO, &sh->dev[i].flags);
+                discard |= test_bit(R5_Discard, &sh->dev[i].flags);
         }
 
         for (i = disks; i--; ) {
                 struct r5dev *dev = &sh->dev[i];
 
                 if (dev->written || i == pd_idx || i == qd_idx) {
-                        set_bit(R5_UPTODATE, &dev->flags);
+                        if (!discard)
+                                set_bit(R5_UPTODATE, &dev->flags);
                         if (fua)
                                 set_bit(R5_WantFUA, &dev->flags);
                         if (sync)
@@ -1241,6 +1248,18 @@ ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
         pr_debug("%s: stripe %llu\n", __func__,
                 (unsigned long long)sh->sector);
 
+        for (i = 0; i < sh->disks; i++) {
+                if (pd_idx == i)
+                        continue;
+                if (!test_bit(R5_Discard, &sh->dev[i].flags))
+                        break;
+        }
+        if (i >= sh->disks) {
+                atomic_inc(&sh->count);
+                set_bit(R5_Discard, &sh->dev[pd_idx].flags);
+                ops_complete_reconstruct(sh);
+                return;
+        }
         /* check if prexor is active which means only process blocks
          * that are part of a read-modify-write (written)
          */
@@ -1285,10 +1304,24 @@ ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
 {
         struct async_submit_ctl submit;
         struct page **blocks = percpu->scribble;
-        int count;
+        int count, i;
 
         pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
 
+        for (i = 0; i < sh->disks; i++) {
+                if (sh->pd_idx == i || sh->qd_idx == i)
+                        continue;
+                if (!test_bit(R5_Discard, &sh->dev[i].flags))
+                        break;
+        }
+        if (i >= sh->disks) {
+                atomic_inc(&sh->count);
+                set_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
+                set_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
+                ops_complete_reconstruct(sh);
+                return;
+        }
+
         count = set_syndrome_sources(blocks, sh);
 
         atomic_inc(&sh->count);
@@ -2408,11 +2441,11 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
                 if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
                         set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
         }
-        spin_unlock_irq(&sh->stripe_lock);
 
         pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
                 (unsigned long long)(*bip)->bi_sector,
                 (unsigned long long)sh->sector, dd_idx);
+        spin_unlock_irq(&sh->stripe_lock);
 
         if (conf->mddev->bitmap && firstwrite) {
                 bitmap_startwrite(conf->mddev->bitmap, sh->sector,
@@ -2479,10 +2512,8 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
                 bi = sh->dev[i].towrite;
                 sh->dev[i].towrite = NULL;
                 spin_unlock_irq(&sh->stripe_lock);
-                if (bi) {
-                        s->to_write--;
+                if (bi)
                         bitmap_end = 1;
-                }
 
                 if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
                         wake_up(&conf->wait_for_overlap);
@@ -2524,11 +2555,12 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
                 if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
                     (!test_bit(R5_Insync, &sh->dev[i].flags) ||
                       test_bit(R5_ReadError, &sh->dev[i].flags))) {
+                        spin_lock_irq(&sh->stripe_lock);
                         bi = sh->dev[i].toread;
                         sh->dev[i].toread = NULL;
+                        spin_unlock_irq(&sh->stripe_lock);
                         if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
                                 wake_up(&conf->wait_for_overlap);
-                        if (bi) s->to_read--;
                         while (bi && bi->bi_sector <
                                sh->dev[i].sector + STRIPE_SECTORS) {
                                 struct bio *nextbi =
@@ -2741,7 +2773,8 @@ static void handle_stripe_clean_event(struct r5conf *conf,
                 if (sh->dev[i].written) {
                         dev = &sh->dev[i];
                         if (!test_bit(R5_LOCKED, &dev->flags) &&
-                                test_bit(R5_UPTODATE, &dev->flags)) {
+                            (test_bit(R5_UPTODATE, &dev->flags) ||
+                             test_and_clear_bit(R5_Discard, &dev->flags))) {
                                 /* We can return any write requests */
                                 struct bio *wbi, *wbi2;
                                 pr_debug("Return write for disc %d\n", i);
@@ -2775,12 +2808,25 @@ static void handle_stripe_dirtying(struct r5conf *conf,
                                    int disks)
 {
         int rmw = 0, rcw = 0, i;
-        if (conf->max_degraded == 2) {
-                /* RAID6 requires 'rcw' in current implementation
-                 * Calculate the real rcw later - for now fake it
+        sector_t recovery_cp = conf->mddev->recovery_cp;
+
+        /* RAID6 requires 'rcw' in current implementation.
+         * Otherwise, check whether resync is now happening or should start.
+         * If yes, then the array is dirty (after unclean shutdown or
+         * initial creation), so parity in some stripes might be inconsistent.
+         * In this case, we need to always do reconstruct-write, to ensure
+         * that in case of drive failure or read-error correction, we
+         * generate correct data from the parity.
+         */
+        if (conf->max_degraded == 2 ||
+            (recovery_cp < MaxSector && sh->sector >= recovery_cp)) {
+                /* Calculate the real rcw later - for now make it
                  * look like rcw is cheaper
                  */
                 rcw = 1; rmw = 2;
+                pr_debug("force RCW max_degraded=%u, recovery_cp=%llu sh->sector=%llu\n",
+                         conf->max_degraded, (unsigned long long)recovery_cp,
+                         (unsigned long long)sh->sector);
         } else for (i = disks; i--; ) {
                 /* would I have to read this buffer for read_modify_write */
                 struct r5dev *dev = &sh->dev[i];
@@ -2932,7 +2978,7 @@ static void handle_parity_checks5(struct r5conf *conf, struct stripe_head *sh,
                          */
                         set_bit(STRIPE_INSYNC, &sh->state);
                 else {
-                        conf->mddev->resync_mismatches += STRIPE_SECTORS;
+                        atomic64_add(STRIPE_SECTORS, &conf->mddev->resync_mismatches);
                         if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
                                 /* don't try to repair!! */
                                 set_bit(STRIPE_INSYNC, &sh->state);
@@ -3084,7 +3130,7 @@ static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
                                  */
                         }
                 } else {
-                        conf->mddev->resync_mismatches += STRIPE_SECTORS;
+                        atomic64_add(STRIPE_SECTORS, &conf->mddev->resync_mismatches);
                         if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
                                 /* don't try to repair!! */
                                 set_bit(STRIPE_INSYNC, &sh->state);
@@ -3459,10 +3505,12 @@ static void handle_stripe(struct stripe_head *sh)
         if (s.written &&
             (s.p_failed || ((test_bit(R5_Insync, &pdev->flags)
                              && !test_bit(R5_LOCKED, &pdev->flags)
-                             && test_bit(R5_UPTODATE, &pdev->flags)))) &&
+                             && (test_bit(R5_UPTODATE, &pdev->flags) ||
+                                 test_bit(R5_Discard, &pdev->flags))))) &&
             (s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
                              && !test_bit(R5_LOCKED, &qdev->flags)
-                             && test_bit(R5_UPTODATE, &qdev->flags)))))
+                             && (test_bit(R5_UPTODATE, &qdev->flags) ||
+                                 test_bit(R5_Discard, &qdev->flags))))))
                 handle_stripe_clean_event(conf, sh, disks, &s.return_bi);
 
         /* Now we might consider reading some blocks, either to check/generate
@@ -3489,9 +3537,11 @@ static void handle_stripe(struct stripe_head *sh)
                 /* All the 'written' buffers and the parity block are ready to
                  * be written back to disk
                  */
-                BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
+                BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags) &&
+                       !test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags));
                 BUG_ON(sh->qd_idx >= 0 &&
-                       !test_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags));
+                       !test_bit(R5_UPTODATE, &sh->dev[sh->qd_idx].flags) &&
+                       !test_bit(R5_Discard, &sh->dev[sh->qd_idx].flags));
                 for (i = disks; i--; ) {
                         struct r5dev *dev = &sh->dev[i];
                         if (test_bit(R5_LOCKED, &dev->flags) &&
@@ -4072,6 +4122,88 @@ static void release_stripe_plug(struct mddev *mddev,
                 release_stripe(sh);
 }
 
+static void make_discard_request(struct mddev *mddev, struct bio *bi)
+{
+        struct r5conf *conf = mddev->private;
+        sector_t logical_sector, last_sector;
+        struct stripe_head *sh;
+        int remaining;
+        int stripe_sectors;
+
+        if (mddev->reshape_position != MaxSector)
+                /* Skip discard while reshape is happening */
+                return;
+
+        logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
+        last_sector = bi->bi_sector + (bi->bi_size>>9);
+
+        bi->bi_next = NULL;
+        bi->bi_phys_segments = 1; /* over-loaded to count active stripes */
+
+        stripe_sectors = conf->chunk_sectors *
+                (conf->raid_disks - conf->max_degraded);
+        logical_sector = DIV_ROUND_UP_SECTOR_T(logical_sector,
+                                               stripe_sectors);
+        sector_div(last_sector, stripe_sectors);
+
+        logical_sector *= conf->chunk_sectors;
+        last_sector *= conf->chunk_sectors;
+
+        for (; logical_sector < last_sector;
+             logical_sector += STRIPE_SECTORS) {
+                DEFINE_WAIT(w);
+                int d;
+        again:
+                sh = get_active_stripe(conf, logical_sector, 0, 0, 0);
+                prepare_to_wait(&conf->wait_for_overlap, &w,
+                                TASK_UNINTERRUPTIBLE);
+                spin_lock_irq(&sh->stripe_lock);
+                for (d = 0; d < conf->raid_disks; d++) {
+                        if (d == sh->pd_idx || d == sh->qd_idx)
+                                continue;
+                        if (sh->dev[d].towrite || sh->dev[d].toread) {
+                                set_bit(R5_Overlap, &sh->dev[d].flags);
+                                spin_unlock_irq(&sh->stripe_lock);
+                                release_stripe(sh);
+                                schedule();
+                                goto again;
+                        }
+                }
+                finish_wait(&conf->wait_for_overlap, &w);
+                for (d = 0; d < conf->raid_disks; d++) {
+                        if (d == sh->pd_idx || d == sh->qd_idx)
+                                continue;
+                        sh->dev[d].towrite = bi;
+                        set_bit(R5_OVERWRITE, &sh->dev[d].flags);
+                        raid5_inc_bi_active_stripes(bi);
+                }
+                spin_unlock_irq(&sh->stripe_lock);
+                if (conf->mddev->bitmap) {
+                        for (d = 0;
+                             d < conf->raid_disks - conf->max_degraded;
+                             d++)
+                                bitmap_startwrite(mddev->bitmap,
+                                                  sh->sector,
+                                                  STRIPE_SECTORS,
+                                                  0);
+                        sh->bm_seq = conf->seq_flush + 1;
+                        set_bit(STRIPE_BIT_DELAY, &sh->state);
+                }
+
+                set_bit(STRIPE_HANDLE, &sh->state);
+                clear_bit(STRIPE_DELAYED, &sh->state);
+                if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+                        atomic_inc(&conf->preread_active_stripes);
+                release_stripe_plug(mddev, sh);
+        }
+
+        remaining = raid5_dec_bi_active_stripes(bi);
+        if (remaining == 0) {
+                md_write_end(mddev);
+                bio_endio(bi, 0);
+        }
+}
+
 static void make_request(struct mddev *mddev, struct bio * bi)
 {
         struct r5conf *conf = mddev->private;
@@ -4094,6 +4226,11 @@ static void make_request(struct mddev *mddev, struct bio * bi)
              chunk_aligned_read(mddev,bi))
                 return;
 
+        if (unlikely(bi->bi_rw & REQ_DISCARD)) {
+                make_discard_request(mddev, bi);
+                return;
+        }
+
         logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
         last_sector = bi->bi_sector + (bi->bi_size>>9);
         bi->bi_next = NULL;
@@ -4630,8 +4767,9 @@ static int handle_active_stripes(struct r5conf *conf)
  * During the scan, completed stripes are saved for us by the interrupt
  * handler, so that they will not have to wait for our next wakeup.
  */
-static void raid5d(struct mddev *mddev)
+static void raid5d(struct md_thread *thread)
 {
+        struct mddev *mddev = thread->mddev;
         struct r5conf *conf = mddev->private;
         int handled;
         struct blk_plug plug;
@@ -5366,6 +5504,7 @@ static int run(struct mddev *mddev)
 
         if (mddev->queue) {
                 int chunk_size;
+                bool discard_supported = true;
                 /* read-ahead size must cover two whole stripes, which
                  * is 2 * (datadisks) * chunksize where 'n' is the
                  * number of raid devices
@@ -5385,13 +5524,48 @@ static int run(struct mddev *mddev)
                 blk_queue_io_min(mddev->queue, chunk_size);
                 blk_queue_io_opt(mddev->queue, chunk_size *
                                  (conf->raid_disks - conf->max_degraded));
+                /*
+                 * We can only discard a whole stripe. It doesn't make sense to
+                 * discard data disk but write parity disk
+                 */
+                stripe = stripe * PAGE_SIZE;
+                mddev->queue->limits.discard_alignment = stripe;
+                mddev->queue->limits.discard_granularity = stripe;
+                /*
+                 * unaligned part of discard request will be ignored, so can't
+                 * guarantee discard_zerors_data
+                 */
+                mddev->queue->limits.discard_zeroes_data = 0;
 
                 rdev_for_each(rdev, mddev) {
                         disk_stack_limits(mddev->gendisk, rdev->bdev,
                                           rdev->data_offset << 9);
                         disk_stack_limits(mddev->gendisk, rdev->bdev,
                                           rdev->new_data_offset << 9);
+                        /*
+                         * discard_zeroes_data is required, otherwise data
+                         * could be lost. Consider a scenario: discard a stripe
+                         * (the stripe could be inconsistent if
+                         * discard_zeroes_data is 0); write one disk of the
+                         * stripe (the stripe could be inconsistent again
+                         * depending on which disks are used to calculate
+                         * parity); the disk is broken; The stripe data of this
+                         * disk is lost.
+                         */
+                        if (!blk_queue_discard(bdev_get_queue(rdev->bdev)) ||
+                            !bdev_get_queue(rdev->bdev)->
+                                                limits.discard_zeroes_data)
+                                discard_supported = false;
                 }
+
+                if (discard_supported &&
+                   mddev->queue->limits.max_discard_sectors >= stripe &&
+                   mddev->queue->limits.discard_granularity >= stripe)
+                        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
+                                                mddev->queue);
+                else
+                        queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD,
+                                                mddev->queue);
         }
 
         return 0;
@@ -5702,7 +5876,8 @@ static int check_reshape(struct mddev *mddev)
         if (!check_stripe_cache(mddev))
                 return -ENOSPC;
 
-        return resize_stripes(conf, conf->raid_disks + mddev->delta_disks);
+        return resize_stripes(conf, (conf->previous_raid_disks
+                                     + mddev->delta_disks));
 }
 
 static int raid5_start_reshape(struct mddev *mddev)
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index a9fc24901eda..18b2c4a8a1fd 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -298,6 +298,7 @@ enum r5dev_flags {
         R5_WantReplace, /* We need to update the replacement, we have read
                          * data in, and now is a good time to write it out.
                          */
+        R5_Discard,     /* Discard the stripe */
 };
 
 /*