Merge tag 'md-3.10' of git://neil.brown.name/md

Pull md fixes from NeilBrown:
 "A mixed bag of little fixes.  No real new functionality here.  Several
  patches are tagged for -stable."

* tag 'md-3.10' of git://neil.brown.name/md:
  MD: ignore discard request for hard disks of hybid raid1/raid10 array
  md: bad block list should default to disabled.
  md: raid1/raid10 md devices leak memory when stopping
  DM RAID: Add message/status support for changing sync action
  MD: Export 'md_reap_sync_thread' function
  md: don't update metadata when stopping a read-only array.
  md: Allow devices to be re-added to a read-only array.
  md/raid10: Allow skipping recovery when clean arrays are assembled
  MD: Fix typos in MD documentation
  md/raid5: avoid an extra write when writing to a known-bad-block.
  md/raid5: Change or of some order to improve efficiency.
  md: use set_bit_le and clear_bit_le
  md: HOT_DISK_REMOVE shouldn't make a read-auto device active.
  md: use common code for all calls to ->hot_remove_disk()
  md: never update metadata when array is read-only.

9 files changed, 368 insertions, 131 deletions

diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index b428556197c9..e9192283e5a5 100644
--- a/Documentation/device-mapper/dm-raid.txt
+++ b/Documentation/device-mapper/dm-raid.txt
@@ -1,10 +1,13 @@
 dm-raid
--------
+=======
 
 The device-mapper RAID (dm-raid) target provides a bridge from DM to MD.
 It allows the MD RAID drivers to be accessed using a device-mapper
 interface.
 
+
+Mapping Table Interface
+-----------------------
 The target is named "raid" and it accepts the following parameters:
 
   <raid_type> <#raid_params> <raid_params> \
@@ -47,7 +50,7 @@ The target is named "raid" and it accepts the following parameters:
     followed by optional parameters (in any order):
 	[sync|nosync]   Force or prevent RAID initialization.
 
-	[rebuild <idx>]	Rebuild drive number idx (first drive is 0).
+	[rebuild <idx>]	Rebuild drive number 'idx' (first drive is 0).
 
 	[daemon_sleep <ms>]
 		Interval between runs of the bitmap daemon that
@@ -56,9 +59,9 @@ The target is named "raid" and it accepts the following parameters:
 
 	[min_recovery_rate <kB/sec/disk>]  Throttle RAID initialization
 	[max_recovery_rate <kB/sec/disk>]  Throttle RAID initialization
-	[write_mostly <idx>]		   Drive index is write-mostly
-	[max_write_behind <sectors>]       See '-write-behind=' (man mdadm)
-	[stripe_cache <sectors>]           Stripe cache size (higher RAIDs only)
+	[write_mostly <idx>]		   Mark drive index 'idx' write-mostly.
+	[max_write_behind <sectors>]       See '--write-behind=' (man mdadm)
+	[stripe_cache <sectors>]           Stripe cache size (RAID 4/5/6 only)
 	[region_size <sectors>]
 		The region_size multiplied by the number of regions is the
 		logical size of the array.  The bitmap records the device
@@ -122,7 +125,7 @@ The target is named "raid" and it accepts the following parameters:
 	given for both the metadata and data drives for a given position.
 
 
-Example tables
+Example Tables
 --------------
 # RAID4 - 4 data drives, 1 parity (no metadata devices)
 # No metadata devices specified to hold superblock/bitmap info
@@ -141,26 +144,70 @@ Example tables
         raid4 4 2048 sync min_recovery_rate 20 \
         5 8:17 8:18 8:33 8:34 8:49 8:50 8:65 8:66 8:81 8:82
 
+
+Status Output
+-------------
 'dmsetup table' displays the table used to construct the mapping.
 The optional parameters are always printed in the order listed
 above with "sync" or "nosync" always output ahead of the other
 arguments, regardless of the order used when originally loading the table.
 Arguments that can be repeated are ordered by value.
 
-'dmsetup status' yields information on the state and health of the
-array.
-The output is as follows:
+
+'dmsetup status' yields information on the state and health of the array.
+The output is as follows (normally a single line, but expanded here for
+clarity):
 1: <s> <l> raid \
-2:      <raid_type> <#devices> <1 health char for each dev> <resync_ratio>
+2:      <raid_type> <#devices> <health_chars> \
+3:      <sync_ratio> <sync_action> <mismatch_cnt>
 
 Line 1 is the standard output produced by device-mapper.
-Line 2 is produced by the raid target, and best explained by example:
-        0 1960893648 raid raid4 5 AAAAA 2/490221568
+Line 2 & 3 are produced by the raid target and are best explained by example:
+        0 1960893648 raid raid4 5 AAAAA 2/490221568 init 0
 Here we can see the RAID type is raid4, there are 5 devices - all of
-which are 'A'live, and the array is 2/490221568 complete with recovery.
-Faulty or missing devices are marked 'D'.  Devices that are out-of-sync
-are marked 'a'.
-
+which are 'A'live, and the array is 2/490221568 complete with its initial
+recovery.  Here is a fuller description of the individual fields:
+	<raid_type>     Same as the <raid_type> used to create the array.
+	<health_chars>  One char for each device, indicating: 'A' = alive and
+			in-sync, 'a' = alive but not in-sync, 'D' = dead/failed.
+	<sync_ratio>    The ratio indicating how much of the array has undergone
+			the process described by 'sync_action'.  If the
+			'sync_action' is "check" or "repair", then the process
+			of "resync" or "recover" can be considered complete.
+	<sync_action>   One of the following possible states:
+			idle    - No synchronization action is being performed.
+			frozen  - The current action has been halted.
+			resync  - Array is undergoing its initial synchronization
+				  or is resynchronizing after an unclean shutdown
+				  (possibly aided by a bitmap).
+			recover - A device in the array is being rebuilt or
+				  replaced.
+			check   - A user-initiated full check of the array is
+				  being performed.  All blocks are read and
+				  checked for consistency.  The number of
+				  discrepancies found are recorded in
+				  <mismatch_cnt>.  No changes are made to the
+				  array by this action.
+			repair  - The same as "check", but discrepancies are
+				  corrected.
+			reshape - The array is undergoing a reshape.
+	<mismatch_cnt>  The number of discrepancies found between mirror copies
+			in RAID1/10 or wrong parity values found in RAID4/5/6.
+			This value is valid only after a "check" of the array
+			is performed.  A healthy array has a 'mismatch_cnt' of 0.
+
+Message Interface
+-----------------
+The dm-raid target will accept certain actions through the 'message' interface.
+('man dmsetup' for more information on the message interface.)  These actions
+include:
+	"idle"   - Halt the current sync action.
+	"frozen" - Freeze the current sync action.
+	"resync" - Initiate/continue a resync.
+	"recover"- Initiate/continue a recover process.
+	"check"  - Initiate a check (i.e. a "scrub") of the array.
+	"repair" - Initiate a repair of the array.
+	"reshape"- Currently unsupported (-EINVAL).
 
 Version History
 ---------------
@@ -171,4 +218,7 @@ Version History
 1.3.1	Allow device replacement/rebuild for RAID 10
 1.3.2   Fix/improve redundancy checking for RAID10
 1.4.0	Non-functional change.  Removes arg from mapping function.
-1.4.1   Add RAID10 "far" and "offset" algorithm support.
+1.4.1   RAID10 fix redundancy validation checks (commit 55ebbb5).
+1.4.2   Add RAID10 "far" and "offset" algorithm support.
+1.5.0   Add message interface to allow manipulation of the sync_action.
+	New status (STATUSTYPE_INFO) fields: sync_action and mismatch_cnt.
diff --git a/Documentation/md.txt b/Documentation/md.txt
index 993fba37b7d1..e0ddd327632d 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -119,7 +119,7 @@ device to add.
 The array is started with the RUN_ARRAY ioctl.
 
 Once started, new devices can be added.  They should have an
-appropriate superblock written to them, and then passed be in with
+appropriate superblock written to them, and then be passed in with
 ADD_NEW_DISK.
 
 Devices that have failed or are not yet active can be detached from an
@@ -131,7 +131,7 @@ Specific Rules that apply to format-0 super block arrays, and
 -------------------------------------------------------------
 
 An array can be 'created' by describing the array (level, chunksize
-etc) in a SET_ARRAY_INFO ioctl.  This must has major_version==0 and
+etc) in a SET_ARRAY_INFO ioctl.  This must have major_version==0 and
 raid_disks != 0.
 
 Then uninitialized devices can be added with ADD_NEW_DISK.  The
@@ -426,7 +426,7 @@ Each directory contains:
       offset
         This gives the location in the device (in sectors from the
         start) where data from the array will be stored.  Any part of
-        the device before this offset us not touched, unless it is
+        the device before this offset is not touched, unless it is
         used for storing metadata (Formats 1.1 and 1.2).
 
       size
@@ -440,7 +440,7 @@ Each directory contains:
         When the device is not 'in_sync', this records the number of
 	sectors from the start of the device which are known to be
 	correct.  This is normally zero, but during a recovery
-	operation is will steadily increase, and if the recovery is
+	operation it will steadily increase, and if the recovery is
 	interrupted, restoring this value can cause recovery to
 	avoid repeating the earlier blocks.  With v1.x metadata, this
 	value is saved and restored automatically.
@@ -468,7 +468,7 @@ Each directory contains:
 
 
 
-An active md device will also contain and entry for each active device
+An active md device will also contain an entry for each active device
 in the array.  These are named
 
     rdNN
@@ -482,7 +482,7 @@ will show 'in_sync' on every line.
 
 
 
-Active md devices for levels that support data redundancy (1,4,5,6)
+Active md devices for levels that support data redundancy (1,4,5,6,10)
 also have
 
    sync_action
@@ -494,7 +494,7 @@ also have
                        failed/missing device
        idle          - nothing is happening
        check         - A full check of redundancy was requested and is
-                       happening.  This reads all block and checks
+                       happening.  This reads all blocks and checks
                        them. A repair may also happen for some raid
                        levels.
        repair        - A full check and repair is happening.  This is
@@ -522,7 +522,7 @@ also have
 
    degraded
       This contains a count of the number of devices by which the
-      arrays is degraded.  So an optimal array with show '0'.  A
+      arrays is degraded.  So an optimal array will show '0'.  A
       single failed/missing drive will show '1', etc.
       This file responds to select/poll, any increase or decrease
       in the count of missing devices will trigger an event.
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 4fd9d6aeff6a..5a2c75499824 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -846,7 +846,7 @@ static void bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
 	if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
 		set_bit(bit, kaddr);
 	else
-		test_and_set_bit_le(bit, kaddr);
+		set_bit_le(bit, kaddr);
 	kunmap_atomic(kaddr);
 	pr_debug("set file bit %lu page %lu\n", bit, page->index);
 	/* record page number so it gets flushed to disk when unplug occurs */
@@ -868,7 +868,7 @@ static void bitmap_file_clear_bit(struct bitmap *bitmap, sector_t block)
 	if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
 		clear_bit(bit, paddr);
 	else
-		test_and_clear_bit_le(bit, paddr);
+		clear_bit_le(bit, paddr);
 	kunmap_atomic(paddr);
 	if (!test_page_attr(bitmap, page->index, BITMAP_PAGE_NEEDWRITE)) {
 		set_page_attr(bitmap, page->index, BITMAP_PAGE_PENDING);
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 311e3d35b272..1d3fe1a40a9b 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -1279,6 +1279,31 @@ static int raid_map(struct dm_target *ti, struct bio *bio)
 	return DM_MAPIO_SUBMITTED;
 }
 
+static const char *decipher_sync_action(struct mddev *mddev)
+{
+	if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
+		return "frozen";
+
+	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
+	    (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) {
+		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+			return "reshape";
+
+		if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
+			if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+				return "resync";
+			else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
+				return "check";
+			return "repair";
+		}
+
+		if (test_bit(MD_RECOVERY_RECOVER, &mddev->recovery))
+			return "recover";
+	}
+
+	return "idle";
+}
+
 static void raid_status(struct dm_target *ti, status_type_t type,
 			unsigned status_flags, char *result, unsigned maxlen)
 {
@@ -1298,8 +1323,18 @@ static void raid_status(struct dm_target *ti, status_type_t type,
 			sync = rs->md.recovery_cp;
 
 		if (sync >= rs->md.resync_max_sectors) {
+			/*
+			 * Sync complete.
+			 */
 			array_in_sync = 1;
 			sync = rs->md.resync_max_sectors;
+		} else if (test_bit(MD_RECOVERY_REQUESTED, &rs->md.recovery)) {
+			/*
+			 * If "check" or "repair" is occurring, the array has
+			 * undergone and initial sync and the health characters
+			 * should not be 'a' anymore.
+			 */
+			array_in_sync = 1;
 		} else {
 			/*
 			 * The array may be doing an initial sync, or it may
@@ -1311,6 +1346,7 @@ static void raid_status(struct dm_target *ti, status_type_t type,
 				if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
 					array_in_sync = 1;
 		}
+
 		/*
 		 * Status characters:
 		 *  'D' = Dead/Failed device
@@ -1339,6 +1375,21 @@ static void raid_status(struct dm_target *ti, status_type_t type,
 		       (unsigned long long) sync,
 		       (unsigned long long) rs->md.resync_max_sectors);
 
+		/*
+		 * Sync action:
+		 *   See Documentation/device-mapper/dm-raid.c for
+		 *   information on each of these states.
+		 */
+		DMEMIT(" %s", decipher_sync_action(&rs->md));
+
+		/*
+		 * resync_mismatches/mismatch_cnt
+		 *   This field shows the number of discrepancies found when
+		 *   performing a "check" of the array.
+		 */
+		DMEMIT(" %llu",
+		       (unsigned long long)
+		       atomic64_read(&rs->md.resync_mismatches));
 		break;
 	case STATUSTYPE_TABLE:
 		/* The string you would use to construct this array */
@@ -1425,7 +1476,62 @@ static void raid_status(struct dm_target *ti, status_type_t type,
 	}
 }
 
-static int raid_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
+static int raid_message(struct dm_target *ti, unsigned argc, char **argv)
+{
+	struct raid_set *rs = ti->private;
+	struct mddev *mddev = &rs->md;
+
+	if (!strcasecmp(argv[0], "reshape")) {
+		DMERR("Reshape not supported.");
+		return -EINVAL;
+	}
+
+	if (!mddev->pers || !mddev->pers->sync_request)
+		return -EINVAL;
+
+	if (!strcasecmp(argv[0], "frozen"))
+		set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+	else
+		clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+
+	if (!strcasecmp(argv[0], "idle") || !strcasecmp(argv[0], "frozen")) {
+		if (mddev->sync_thread) {
+			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+			md_reap_sync_thread(mddev);
+		}
+	} else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
+		   test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
+		return -EBUSY;
+	else if (!strcasecmp(argv[0], "resync"))
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	else if (!strcasecmp(argv[0], "recover")) {
+		set_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
+		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	} else {
+		if (!strcasecmp(argv[0], "check"))
+			set_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+		else if (!!strcasecmp(argv[0], "repair"))
+			return -EINVAL;
+		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;
+		if (!mddev->suspended)
+			md_wakeup_thread(mddev->sync_thread);
+	}
+	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	if (!mddev->suspended)
+		md_wakeup_thread(mddev->thread);
+
+	return 0;
+}
+
+static int raid_iterate_devices(struct dm_target *ti,
+				iterate_devices_callout_fn fn, void *data)
 {
 	struct raid_set *rs = ti->private;
 	unsigned i;
@@ -1482,12 +1588,13 @@ static void raid_resume(struct dm_target *ti)
 
 static struct target_type raid_target = {
 	.name = "raid",
-	.version = {1, 4, 2},
+	.version = {1, 5, 0},
 	.module = THIS_MODULE,
 	.ctr = raid_ctr,
 	.dtr = raid_dtr,
 	.map = raid_map,
 	.status = raid_status,
+	.message = raid_message,
 	.iterate_devices = raid_iterate_devices,
 	.io_hints = raid_io_hints,
 	.presuspend = raid_presuspend,
diff --git a/drivers/md/md.c b/drivers/md/md.c
index aeceedfc530b..4c74424c78b0 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -72,6 +72,9 @@ static DECLARE_WAIT_QUEUE_HEAD(resync_wait);
 static struct workqueue_struct *md_wq;
 static struct workqueue_struct *md_misc_wq;
 
+static int remove_and_add_spares(struct mddev *mddev,
+				 struct md_rdev *this);
+
 #define MD_BUG(x...) { printk("md: bug in file %s, line %d\n", __FILE__, __LINE__); md_print_devices(); }
 
 /*
@@ -1564,8 +1567,8 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
 					     sector, count, 1) == 0)
 				return -EINVAL;
 		}
-	} else if (sb->bblog_offset == 0)
-		rdev->badblocks.shift = -1;
+	} else if (sb->bblog_offset != 0)
+		rdev->badblocks.shift = 0;
 
 	if (!refdev) {
 		ret = 1;
@@ -2411,6 +2414,11 @@ static void md_update_sb(struct mddev * mddev, int force_change)
 	int nospares = 0;
 	int any_badblocks_changed = 0;
 
+	if (mddev->ro) {
+		if (force_change)
+			set_bit(MD_CHANGE_DEVS, &mddev->flags);
+		return;
+	}
 repeat:
 	/* First make sure individual recovery_offsets are correct */
 	rdev_for_each(rdev, mddev) {
@@ -2800,12 +2808,10 @@ slot_store(struct md_rdev *rdev, const char *buf, size_t len)
 		/* personality does all needed checks */
 		if (rdev->mddev->pers->hot_remove_disk == NULL)
 			return -EINVAL;
-		err = rdev->mddev->pers->
-			hot_remove_disk(rdev->mddev, rdev);
-		if (err)
-			return err;
-		sysfs_unlink_rdev(rdev->mddev, rdev);
-		rdev->raid_disk = -1;
+		clear_bit(Blocked, &rdev->flags);
+		remove_and_add_spares(rdev->mddev, rdev);
+		if (rdev->raid_disk >= 0)
+			return -EBUSY;
 		set_bit(MD_RECOVERY_NEEDED, &rdev->mddev->recovery);
 		md_wakeup_thread(rdev->mddev->thread);
 	} else if (rdev->mddev->pers) {
@@ -3221,7 +3227,7 @@ int md_rdev_init(struct md_rdev *rdev)
 	 * be used - I wonder if that matters
 	 */
 	rdev->badblocks.count = 0;
-	rdev->badblocks.shift = 0;
+	rdev->badblocks.shift = -1; /* disabled until explicitly enabled */
 	rdev->badblocks.page = kmalloc(PAGE_SIZE, GFP_KERNEL);
 	seqlock_init(&rdev->badblocks.lock);
 	if (rdev->badblocks.page == NULL)
@@ -3293,9 +3299,6 @@ static struct md_rdev *md_import_device(dev_t newdev, int super_format, int supe
 			goto abort_free;
 		}
 	}
-	if (super_format == -1)
-		/* hot-add for 0.90, or non-persistent: so no badblocks */
-		rdev->badblocks.shift = -1;
 
 	return rdev;
 
@@ -4225,8 +4228,6 @@ action_show(struct mddev *mddev, char *page)
 	return sprintf(page, "%s\n", type);
 }
 
-static void reap_sync_thread(struct mddev *mddev);
-
 static ssize_t
 action_store(struct mddev *mddev, const char *page, size_t len)
 {
@@ -4241,7 +4242,7 @@ action_store(struct mddev *mddev, const char *page, size_t len)
 	if (cmd_match(page, "idle") || cmd_match(page, "frozen")) {
 		if (mddev->sync_thread) {
 			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
-			reap_sync_thread(mddev);
+			md_reap_sync_thread(mddev);
 		}
 	} else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
 		   test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))
@@ -5279,7 +5280,7 @@ static void __md_stop_writes(struct mddev *mddev)
 	if (mddev->sync_thread) {
 		set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
 		set_bit(MD_RECOVERY_INTR, &mddev->recovery);
-		reap_sync_thread(mddev);
+		md_reap_sync_thread(mddev);
 	}
 
 	del_timer_sync(&mddev->safemode_timer);
@@ -5287,7 +5288,8 @@ static void __md_stop_writes(struct mddev *mddev)
 	bitmap_flush(mddev);
 	md_super_wait(mddev);
 
-	if (!mddev->in_sync || mddev->flags) {
+	if (mddev->ro == 0 &&
+	    (!mddev->in_sync || mddev->flags)) {
 		/* mark array as shutdown cleanly */
 		mddev->in_sync = 1;
 		md_update_sb(mddev, 1);
@@ -5810,7 +5812,7 @@ static int add_new_disk(struct mddev * mddev, mdu_disk_info_t *info)
 		else
 			sysfs_notify_dirent_safe(rdev->sysfs_state);
 
-		md_update_sb(mddev, 1);
+		set_bit(MD_CHANGE_DEVS, &mddev->flags);
 		if (mddev->degraded)
 			set_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
 		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
@@ -5877,6 +5879,9 @@ static int hot_remove_disk(struct mddev * mddev, dev_t dev)
 	if (!rdev)
 		return -ENXIO;
 
+	clear_bit(Blocked, &rdev->flags);
+	remove_and_add_spares(mddev, rdev);
+
 	if (rdev->raid_disk >= 0)
 		goto busy;
 
@@ -6490,6 +6495,28 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 		err = md_set_readonly(mddev, bdev);
 		goto done_unlock;
 
+	case HOT_REMOVE_DISK:
+		err = hot_remove_disk(mddev, new_decode_dev(arg));
+		goto done_unlock;
+
+	case ADD_NEW_DISK:
+		/* We can support ADD_NEW_DISK on read-only arrays
+		 * on if we are re-adding a preexisting device.
+		 * So require mddev->pers and MD_DISK_SYNC.
+		 */
+		if (mddev->pers) {
+			mdu_disk_info_t info;
+			if (copy_from_user(&info, argp, sizeof(info)))
+				err = -EFAULT;
+			else if (!(info.state & (1<<MD_DISK_SYNC)))
+				/* Need to clear read-only for this */
+				break;
+			else
+				err = add_new_disk(mddev, &info);
+			goto done_unlock;
+		}
+		break;
+
 	case BLKROSET:
 		if (get_user(ro, (int __user *)(arg))) {
 			err = -EFAULT;
@@ -6560,10 +6587,6 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 		goto done_unlock;
 	}
 
-	case HOT_REMOVE_DISK:
-		err = hot_remove_disk(mddev, new_decode_dev(arg));
-		goto done_unlock;
-
 	case HOT_ADD_DISK:
 		err = hot_add_disk(mddev, new_decode_dev(arg));
 		goto done_unlock;
@@ -7644,14 +7667,16 @@ void md_do_sync(struct md_thread *thread)
 }
 EXPORT_SYMBOL_GPL(md_do_sync);
 
-static int remove_and_add_spares(struct mddev *mddev)
+static int remove_and_add_spares(struct mddev *mddev,
+				 struct md_rdev *this)
 {
 	struct md_rdev *rdev;
 	int spares = 0;
 	int removed = 0;
 
 	rdev_for_each(rdev, mddev)
-		if (rdev->raid_disk >= 0 &&
+		if ((this == NULL || rdev == this) &&
+		    rdev->raid_disk >= 0 &&
 		    !test_bit(Blocked, &rdev->flags) &&
 		    (test_bit(Faulty, &rdev->flags) ||
 		     ! test_bit(In_sync, &rdev->flags)) &&
@@ -7666,74 +7691,52 @@ static int remove_and_add_spares(struct mddev *mddev)
 	if (removed && mddev->kobj.sd)
 		sysfs_notify(&mddev->kobj, NULL, "degraded");
 
+	if (this)
+		goto no_add;
+
 	rdev_for_each(rdev, mddev) {
 		if (rdev->raid_disk >= 0 &&
 		    !test_bit(In_sync, &rdev->flags) &&
 		    !test_bit(Faulty, &rdev->flags))
 			spares++;
-		if (rdev->raid_disk < 0
-		    && !test_bit(Faulty, &rdev->flags)) {
-			rdev->recovery_offset = 0;
-			if (mddev->pers->
-			    hot_add_disk(mddev, rdev) == 0) {
-				if (sysfs_link_rdev(mddev, rdev))
-					/* failure here is OK */;
-				spares++;
-				md_new_event(mddev);
-				set_bit(MD_CHANGE_DEVS, &mddev->flags);
-			}
+		if (rdev->raid_disk >= 0)
+			continue;
+		if (test_bit(Faulty, &rdev->flags))
+			continue;
+		if (mddev->ro &&
+		    rdev->saved_raid_disk < 0)
+			continue;
+
+		rdev->recovery_offset = 0;
+		if (rdev->saved_raid_disk >= 0 && mddev->in_sync) {
+			spin_lock_irq(&mddev->write_lock);
+			if (mddev->in_sync)
+				/* OK, this device, which is in_sync,
+				 * will definitely be noticed before
+				 * the next write, so recovery isn't
+				 * needed.
+				 */
+				rdev->recovery_offset = mddev->recovery_cp;
+			spin_unlock_irq(&mddev->write_lock);
+		}
+		if (mddev->ro && rdev->recovery_offset != MaxSector)
+			/* not safe to add this disk now */
+			continue;
+		if (mddev->pers->
+		    hot_add_disk(mddev, rdev) == 0) {
+			if (sysfs_link_rdev(mddev, rdev))
+				/* failure here is OK */;
+			spares++;
+			md_new_event(mddev);
+			set_bit(MD_CHANGE_DEVS, &mddev->flags);
 		}
 	}
+no_add:
 	if (removed)
 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
 	return spares;
 }
 
-static void reap_sync_thread(struct mddev *mddev)
-{
-	struct md_rdev *rdev;
-
-	/* resync has finished, collect result */
-	md_unregister_thread(&mddev->sync_thread);
-	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
-	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
-		/* success...*/
-		/* activate any spares */
-		if (mddev->pers->spare_active(mddev)) {
-			sysfs_notify(&mddev->kobj, NULL,
-				     "degraded");
-			set_bit(MD_CHANGE_DEVS, &mddev->flags);
-		}
-	}
-	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
-	    mddev->pers->finish_reshape)
-		mddev->pers->finish_reshape(mddev);
-
-	/* If array is no-longer degraded, then any saved_raid_disk
-	 * information must be scrapped.  Also if any device is now
-	 * In_sync we must scrape the saved_raid_disk for that device
-	 * do the superblock for an incrementally recovered device
-	 * written out.
-	 */
-	rdev_for_each(rdev, mddev)
-		if (!mddev->degraded ||
-		    test_bit(In_sync, &rdev->flags))
-			rdev->saved_raid_disk = -1;
-
-	md_update_sb(mddev, 1);
-	clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
-	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
-	clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
-	clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
-	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
-	/* flag recovery needed just to double check */
-	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
-	sysfs_notify_dirent_safe(mddev->sysfs_action);
-	md_new_event(mddev);
-	if (mddev->event_work.func)
-		queue_work(md_misc_wq, &mddev->event_work);
-}
-
 /*
  * This routine is regularly called by all per-raid-array threads to
  * deal with generic issues like resync and super-block update.
@@ -7789,22 +7792,16 @@ void md_check_recovery(struct mddev *mddev)
 		int spares = 0;
 
 		if (mddev->ro) {
-			/* Only thing we do on a ro array is remove
-			 * failed devices.
+			/* On a read-only array we can:
+			 * - remove failed devices
+			 * - add already-in_sync devices if the array itself
+			 *   is in-sync.
+			 * As we only add devices that are already in-sync,
+			 * we can activate the spares immediately.
 			 */
-			struct md_rdev *rdev;
-			rdev_for_each(rdev, mddev)
-				if (rdev->raid_disk >= 0 &&
-				    !test_bit(Blocked, &rdev->flags) &&
-				    test_bit(Faulty, &rdev->flags) &&
-				    atomic_read(&rdev->nr_pending)==0) {
-					if (mddev->pers->hot_remove_disk(
-						    mddev, rdev) == 0) {
-						sysfs_unlink_rdev(mddev, rdev);
-						rdev->raid_disk = -1;
-					}
-				}
 			clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+			remove_and_add_spares(mddev, NULL);
+			mddev->pers->spare_active(mddev);
 			goto unlock;
 		}
 
@@ -7836,7 +7833,7 @@ void md_check_recovery(struct mddev *mddev)
 			goto unlock;
 		}
 		if (mddev->sync_thread) {
-			reap_sync_thread(mddev);
+			md_reap_sync_thread(mddev);
 			goto unlock;
 		}
 		/* Set RUNNING before clearing NEEDED to avoid
@@ -7867,7 +7864,7 @@ void md_check_recovery(struct mddev *mddev)
 				goto unlock;
 			set_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
 			clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
-		} else if ((spares = remove_and_add_spares(mddev))) {
+		} else if ((spares = remove_and_add_spares(mddev, NULL))) {
 			clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
 			clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
 			clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
@@ -7917,6 +7914,51 @@ void md_check_recovery(struct mddev *mddev)
 	}
 }
 
+void md_reap_sync_thread(struct mddev *mddev)
+{
+	struct md_rdev *rdev;
+
+	/* resync has finished, collect result */
+	md_unregister_thread(&mddev->sync_thread);
+	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
+	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
+		/* success...*/
+		/* activate any spares */
+		if (mddev->pers->spare_active(mddev)) {
+			sysfs_notify(&mddev->kobj, NULL,
+				     "degraded");
+			set_bit(MD_CHANGE_DEVS, &mddev->flags);
+		}
+	}
+	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
+	    mddev->pers->finish_reshape)
+		mddev->pers->finish_reshape(mddev);
+
+	/* If array is no-longer degraded, then any saved_raid_disk
+	 * information must be scrapped.  Also if any device is now
+	 * In_sync we must scrape the saved_raid_disk for that device
+	 * do the superblock for an incrementally recovered device
+	 * written out.
+	 */
+	rdev_for_each(rdev, mddev)
+		if (!mddev->degraded ||
+		    test_bit(In_sync, &rdev->flags))
+			rdev->saved_raid_disk = -1;
+
+	md_update_sb(mddev, 1);
+	clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
+	clear_bit(MD_RECOVERY_SYNC, &mddev->recovery);
+	clear_bit(MD_RECOVERY_RESHAPE, &mddev->recovery);
+	clear_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);
+	clear_bit(MD_RECOVERY_CHECK, &mddev->recovery);
+	/* flag recovery needed just to double check */
+	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	sysfs_notify_dirent_safe(mddev->sysfs_action);
+	md_new_event(mddev);
+	if (mddev->event_work.func)
+		queue_work(md_misc_wq, &mddev->event_work);
+}
+
 void md_wait_for_blocked_rdev(struct md_rdev *rdev, struct mddev *mddev)
 {
 	sysfs_notify_dirent_safe(rdev->sysfs_state);
@@ -8642,6 +8684,7 @@ EXPORT_SYMBOL(md_register_thread);
 EXPORT_SYMBOL(md_unregister_thread);
 EXPORT_SYMBOL(md_wakeup_thread);
 EXPORT_SYMBOL(md_check_recovery);
+EXPORT_SYMBOL(md_reap_sync_thread);
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("MD RAID framework");
 MODULE_ALIAS("md");
diff --git a/drivers/md/md.h b/drivers/md/md.h
index d90fb1a879e1..653f992b687a 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -567,6 +567,7 @@ extern struct md_thread *md_register_thread(
 extern void md_unregister_thread(struct md_thread **threadp);
 extern void md_wakeup_thread(struct md_thread *thread);
 extern void md_check_recovery(struct mddev *mddev);
+extern void md_reap_sync_thread(struct mddev *mddev);
 extern void md_write_start(struct mddev *mddev, struct bio *bi);
 extern void md_write_end(struct mddev *mddev);
 extern void md_done_sync(struct mddev *mddev, int blocks, int ok);
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index fd86b372692d..851023e2ba5d 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -981,7 +981,12 @@ static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule)
 	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;
 	}
 	kfree(plug);
@@ -2901,6 +2906,7 @@ static int stop(struct mddev *mddev)
 	if (conf->r1bio_pool)
 		mempool_destroy(conf->r1bio_pool);
 	kfree(conf->mirrors);
+	safe_put_page(conf->tmppage);
 	kfree(conf->poolinfo);
 	kfree(conf);
 	mddev->private = NULL;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 77b562d18a90..018741ba9310 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1133,7 +1133,12 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
 	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;
 	}
 	kfree(plug);
@@ -2913,6 +2918,22 @@ static sector_t sync_request(struct mddev *mddev, sector_t sector_nr,
 		if (init_resync(conf))
 			return 0;
 
+	/*
+	 * Allow skipping a full rebuild for incremental assembly
+	 * of a clean array, like RAID1 does.
+	 */
+	if (mddev->bitmap == NULL &&
+	    mddev->recovery_cp == MaxSector &&
+	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
+	    conf->fullsync == 0) {
+		*skipped = 1;
+		max_sector = mddev->dev_sectors;
+		if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
+		    test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+			max_sector = mddev->resync_max_sectors;
+		return max_sector - sector_nr;
+	}
+
  skipped:
 	max_sector = mddev->dev_sectors;
 	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
@@ -3810,6 +3831,7 @@ static int stop(struct mddev *mddev)
 
 	if (conf->r10bio_pool)
 		mempool_destroy(conf->r10bio_pool);
+	safe_put_page(conf->tmppage);
 	kfree(conf->mirrors);
 	kfree(conf);
 	mddev->private = NULL;
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f4e87bfc7567..4a7be455d6d8 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1887,8 +1887,15 @@ static void raid5_end_write_request(struct bio *bi, int error)
 					&rdev->mddev->recovery);
 		} else if (is_badblock(rdev, sh->sector,
 				       STRIPE_SECTORS,
-				       &first_bad, &bad_sectors))
+				       &first_bad, &bad_sectors)) {
 			set_bit(R5_MadeGood, &sh->dev[i].flags);
+			if (test_bit(R5_ReadError, &sh->dev[i].flags))
+				/* That was a successful write so make
+				 * sure it looks like we already did
+				 * a re-write.
+				 */
+				set_bit(R5_ReWrite, &sh->dev[i].flags);
+		}
 	}
 	rdev_dec_pending(rdev, conf->mddev);
 
@@ -4672,9 +4679,10 @@ static inline sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int
 		*skipped = 1;
 		return rv;
 	}
-	if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
-	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
-	    !conf->fullsync && sync_blocks >= STRIPE_SECTORS) {
+	if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
+	    !conf->fullsync &&
+	    !bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
+	    sync_blocks >= STRIPE_SECTORS) {
 		/* we can skip this block, and probably more */
 		sync_blocks /= STRIPE_SECTORS;
 		*skipped = 1;