Merge branch 'for-3.10/drivers' of git://git.kernel.dk/linux-block

Pull block driver updates from Jens Axboe:
 "It might look big in volume, but when categorized, not a lot of
  drivers are touched.  The pull request contains:

   - mtip32xx fixes from Micron.

   - A slew of drbd updates, this time in a nicer series.

   - bcache, a flash/ssd caching framework from Kent.

   - Fixes for cciss"

* 'for-3.10/drivers' of git://git.kernel.dk/linux-block: (66 commits)
  bcache: Use bd_link_disk_holder()
  bcache: Allocator cleanup/fixes
  cciss: bug fix to prevent cciss from loading in kdump crash kernel
  cciss: add cciss_allow_hpsa module parameter
  drivers/block/mg_disk.c: add CONFIG_PM_SLEEP to suspend/resume functions
  mtip32xx: Workaround for unaligned writes
  bcache: Make sure blocksize isn't smaller than device blocksize
  bcache: Fix merge_bvec_fn usage for when it modifies the bvm
  bcache: Correctly check against BIO_MAX_PAGES
  bcache: Hack around stuff that clones up to bi_max_vecs
  bcache: Set ra_pages based on backing device's ra_pages
  bcache: Take data offset from the bdev superblock.
  mtip32xx: mtip32xx: Disable TRIM support
  mtip32xx: fix a smatch warning
  bcache: Disable broken btree fuzz tester
  bcache: Fix a format string overflow
  bcache: Fix a minor memory leak on device teardown
  bcache: Documentation updates
  bcache: Use WARN_ONCE() instead of __WARN()
  bcache: Add missing #include <linux/prefetch.h>
  ...

46 files changed, 16713 insertions, 350 deletions

diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index 5efed089a702..fc803ecbbce4 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -920,16 +920,14 @@ bio_pagedec(struct bio *bio)
 static void
 bufinit(struct buf *buf, struct request *rq, struct bio *bio)
 {
-	struct bio_vec *bv;
-
 	memset(buf, 0, sizeof(*buf));
 	buf->rq = rq;
 	buf->bio = bio;
 	buf->resid = bio->bi_size;
 	buf->sector = bio->bi_sector;
 	bio_pageinc(bio);
-	buf->bv = bv = bio_iovec(bio);
-	buf->bv_resid = bv->bv_len;
+	buf->bv = bio_iovec(bio);
+	buf->bv_resid = buf->bv->bv_len;
 	WARN_ON(buf->bv_resid == 0);
 }
 
diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 94b51c5e0678..6374dc103521 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -75,6 +75,12 @@ module_param(cciss_simple_mode, int, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(cciss_simple_mode,
 	"Use 'simple mode' rather than 'performant mode'");
 
+static int cciss_allow_hpsa;
+module_param(cciss_allow_hpsa, int, S_IRUGO|S_IWUSR);
+MODULE_PARM_DESC(cciss_allow_hpsa,
+	"Prevent cciss driver from accessing hardware known to be "
+	" supported by the hpsa driver");
+
 static DEFINE_MUTEX(cciss_mutex);
 static struct proc_dir_entry *proc_cciss;
 
@@ -4115,9 +4121,13 @@ static int cciss_lookup_board_id(struct pci_dev *pdev, u32 *board_id)
 	*board_id = ((subsystem_device_id << 16) & 0xffff0000) |
 			subsystem_vendor_id;
 
-	for (i = 0; i < ARRAY_SIZE(products); i++)
+	for (i = 0; i < ARRAY_SIZE(products); i++) {
+		/* Stand aside for hpsa driver on request */
+		if (cciss_allow_hpsa)
+			return -ENODEV;
 		if (*board_id == products[i].board_id)
 			return i;
+	}
 	dev_warn(&pdev->dev, "unrecognized board ID: 0x%08x, ignoring.\n",
 		*board_id);
 	return -ENODEV;
@@ -4959,6 +4969,16 @@ static int cciss_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	ctlr_info_t *h;
 	unsigned long flags;
 
+	/*
+	 * By default the cciss driver is used for all older HP Smart Array
+	 * controllers. There are module paramaters that allow a user to
+	 * override this behavior and instead use the hpsa SCSI driver. If
+	 * this is the case cciss may be loaded first from the kdump initrd
+	 * image and cause a kernel panic. So if reset_devices is true and
+	 * cciss_allow_hpsa is set just bail.
+	 */
+	if ((reset_devices) && (cciss_allow_hpsa == 1))
+		return -ENODEV;
 	rc = cciss_init_reset_devices(pdev);
 	if (rc) {
 		if (rc != -ENOTSUPP)
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 92510f8ad013..6608076dc39e 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -104,7 +104,6 @@ struct update_al_work {
 	int err;
 };
 
-static int al_write_transaction(struct drbd_conf *mdev);
 
 void *drbd_md_get_buffer(struct drbd_conf *mdev)
 {
@@ -168,7 +167,11 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
 	bio->bi_end_io = drbd_md_io_complete;
 	bio->bi_rw = rw;
 
-	if (!get_ldev_if_state(mdev, D_ATTACHING)) {  /* Corresponding put_ldev in drbd_md_io_complete() */
+	if (!(rw & WRITE) && mdev->state.disk == D_DISKLESS && mdev->ldev == NULL)
+		/* special case, drbd_md_read() during drbd_adm_attach(): no get_ldev */
+		;
+	else if (!get_ldev_if_state(mdev, D_ATTACHING)) {
+		/* Corresponding put_ldev in drbd_md_io_complete() */
 		dev_err(DEV, "ASSERT FAILED: get_ldev_if_state() == 1 in _drbd_md_sync_page_io()\n");
 		err = -ENODEV;
 		goto out;
@@ -199,9 +202,10 @@ int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
 
 	BUG_ON(!bdev->md_bdev);
 
-	dev_dbg(DEV, "meta_data io: %s [%d]:%s(,%llus,%s)\n",
+	dev_dbg(DEV, "meta_data io: %s [%d]:%s(,%llus,%s) %pS\n",
 	     current->comm, current->pid, __func__,
-	     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
+	     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ",
+	     (void*)_RET_IP_ );
 
 	if (sector < drbd_md_first_sector(bdev) ||
 	    sector + 7 > drbd_md_last_sector(bdev))
@@ -209,7 +213,8 @@ int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
 		     current->comm, current->pid, __func__,
 		     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
 
-	err = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, MD_BLOCK_SIZE);
+	/* we do all our meta data IO in aligned 4k blocks. */
+	err = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, 4096);
 	if (err) {
 		dev_err(DEV, "drbd_md_sync_page_io(,%llus,%s) failed with error %d\n",
 		    (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ", err);
@@ -217,44 +222,99 @@ int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
 	return err;
 }
 
-static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr)
+static struct bm_extent *find_active_resync_extent(struct drbd_conf *mdev, unsigned int enr)
 {
-	struct lc_element *al_ext;
 	struct lc_element *tmp;
-	int wake;
-
-	spin_lock_irq(&mdev->al_lock);
 	tmp = lc_find(mdev->resync, enr/AL_EXT_PER_BM_SECT);
 	if (unlikely(tmp != NULL)) {
 		struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
-		if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
-			wake = !test_and_set_bit(BME_PRIORITY, &bm_ext->flags);
-			spin_unlock_irq(&mdev->al_lock);
-			if (wake)
-				wake_up(&mdev->al_wait);
-			return NULL;
-		}
+		if (test_bit(BME_NO_WRITES, &bm_ext->flags))
+			return bm_ext;
+	}
+	return NULL;
+}
+
+static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr, bool nonblock)
+{
+	struct lc_element *al_ext;
+	struct bm_extent *bm_ext;
+	int wake;
+
+	spin_lock_irq(&mdev->al_lock);
+	bm_ext = find_active_resync_extent(mdev, enr);
+	if (bm_ext) {
+		wake = !test_and_set_bit(BME_PRIORITY, &bm_ext->flags);
+		spin_unlock_irq(&mdev->al_lock);
+		if (wake)
+			wake_up(&mdev->al_wait);
+		return NULL;
 	}
-	al_ext = lc_get(mdev->act_log, enr);
+	if (nonblock)
+		al_ext = lc_try_get(mdev->act_log, enr);
+	else
+		al_ext = lc_get(mdev->act_log, enr);
 	spin_unlock_irq(&mdev->al_lock);
 	return al_ext;
 }
 
-void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
+bool drbd_al_begin_io_fastpath(struct drbd_conf *mdev, struct drbd_interval *i)
 {
 	/* for bios crossing activity log extent boundaries,
 	 * we may need to activate two extents in one go */
 	unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
 	unsigned last = i->size == 0 ? first : (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);
-	unsigned enr;
-	bool locked = false;
 
+	D_ASSERT((unsigned)(last - first) <= 1);
+	D_ASSERT(atomic_read(&mdev->local_cnt) > 0);
+
+	/* FIXME figure out a fast path for bios crossing AL extent boundaries */
+	if (first != last)
+		return false;
+
+	return _al_get(mdev, first, true);
+}
+
+bool drbd_al_begin_io_prepare(struct drbd_conf *mdev, struct drbd_interval *i)
+{
+	/* for bios crossing activity log extent boundaries,
+	 * we may need to activate two extents in one go */
+	unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
+	unsigned last = i->size == 0 ? first : (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);
+	unsigned enr;
+	bool need_transaction = false;
 
 	D_ASSERT(first <= last);
 	D_ASSERT(atomic_read(&mdev->local_cnt) > 0);
 
-	for (enr = first; enr <= last; enr++)
-		wait_event(mdev->al_wait, _al_get(mdev, enr) != NULL);
+	for (enr = first; enr <= last; enr++) {
+		struct lc_element *al_ext;
+		wait_event(mdev->al_wait,
+				(al_ext = _al_get(mdev, enr, false)) != NULL);
+		if (al_ext->lc_number != enr)
+			need_transaction = true;
+	}
+	return need_transaction;
+}
+
+static int al_write_transaction(struct drbd_conf *mdev, bool delegate);
+
+/* When called through generic_make_request(), we must delegate
+ * activity log I/O to the worker thread: a further request
+ * submitted via generic_make_request() within the same task
+ * would be queued on current->bio_list, and would only start
+ * after this function returns (see generic_make_request()).
+ *
+ * However, if we *are* the worker, we must not delegate to ourselves.
+ */
+
+/*
+ * @delegate:   delegate activity log I/O to the worker thread
+ */
+void drbd_al_begin_io_commit(struct drbd_conf *mdev, bool delegate)
+{
+	bool locked = false;
+
+	BUG_ON(delegate && current == mdev->tconn->worker.task);
 
 	/* Serialize multiple transactions.
 	 * This uses test_and_set_bit, memory barrier is implicit.
@@ -264,13 +324,6 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
 			(locked = lc_try_lock_for_transaction(mdev->act_log)));
 
 	if (locked) {
-		/* drbd_al_write_transaction(mdev,al_ext,enr);
-		 * recurses into generic_make_request(), which
-		 * disallows recursion, bios being serialized on the
-		 * current->bio_tail list now.
-		 * we have to delegate updates to the activity log
-		 * to the worker thread. */
-
 		/* Double check: it may have been committed by someone else,
 		 * while we have been waiting for the lock. */
 		if (mdev->act_log->pending_changes) {
@@ -280,11 +333,8 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
 			write_al_updates = rcu_dereference(mdev->ldev->disk_conf)->al_updates;
 			rcu_read_unlock();
 
-			if (write_al_updates) {
-				al_write_transaction(mdev);
-				mdev->al_writ_cnt++;
-			}
-
+			if (write_al_updates)
+				al_write_transaction(mdev, delegate);
 			spin_lock_irq(&mdev->al_lock);
 			/* FIXME
 			if (err)
@@ -298,6 +348,66 @@ void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i)
 	}
 }
 
+/*
+ * @delegate:   delegate activity log I/O to the worker thread
+ */
+void drbd_al_begin_io(struct drbd_conf *mdev, struct drbd_interval *i, bool delegate)
+{
+	BUG_ON(delegate && current == mdev->tconn->worker.task);
+
+	if (drbd_al_begin_io_prepare(mdev, i))
+		drbd_al_begin_io_commit(mdev, delegate);
+}
+
+int drbd_al_begin_io_nonblock(struct drbd_conf *mdev, struct drbd_interval *i)
+{
+	struct lru_cache *al = mdev->act_log;
+	/* for bios crossing activity log extent boundaries,
+	 * we may need to activate two extents in one go */
+	unsigned first = i->sector >> (AL_EXTENT_SHIFT-9);
+	unsigned last = i->size == 0 ? first : (i->sector + (i->size >> 9) - 1) >> (AL_EXTENT_SHIFT-9);
+	unsigned nr_al_extents;
+	unsigned available_update_slots;
+	unsigned enr;
+
+	D_ASSERT(first <= last);
+
+	nr_al_extents = 1 + last - first; /* worst case: all touched extends are cold. */
+	available_update_slots = min(al->nr_elements - al->used,
+				al->max_pending_changes - al->pending_changes);
+
+	/* We want all necessary updates for a given request within the same transaction
+	 * We could first check how many updates are *actually* needed,
+	 * and use that instead of the worst-case nr_al_extents */
+	if (available_update_slots < nr_al_extents)
+		return -EWOULDBLOCK;
+
+	/* Is resync active in this area? */
+	for (enr = first; enr <= last; enr++) {
+		struct lc_element *tmp;
+		tmp = lc_find(mdev->resync, enr/AL_EXT_PER_BM_SECT);
+		if (unlikely(tmp != NULL)) {
+			struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
+			if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
+				if (!test_and_set_bit(BME_PRIORITY, &bm_ext->flags))
+					return -EBUSY;
+				return -EWOULDBLOCK;
+			}
+		}
+	}
+
+	/* Checkout the refcounts.
+	 * Given that we checked for available elements and update slots above,
+	 * this has to be successful. */
+	for (enr = first; enr <= last; enr++) {
+		struct lc_element *al_ext;
+		al_ext = lc_get_cumulative(mdev->act_log, enr);
+		if (!al_ext)
+			dev_info(DEV, "LOGIC BUG for enr=%u\n", enr);
+	}
+	return 0;
+}
+
 void drbd_al_complete_io(struct drbd_conf *mdev, struct drbd_interval *i)
 {
 	/* for bios crossing activity log extent boundaries,
@@ -350,6 +460,24 @@ static unsigned int rs_extent_to_bm_page(unsigned int rs_enr)
 		 (BM_EXT_SHIFT - BM_BLOCK_SHIFT));
 }
 
+static sector_t al_tr_number_to_on_disk_sector(struct drbd_conf *mdev)
+{
+	const unsigned int stripes = mdev->ldev->md.al_stripes;
+	const unsigned int stripe_size_4kB = mdev->ldev->md.al_stripe_size_4k;
+
+	/* transaction number, modulo on-disk ring buffer wrap around */
+	unsigned int t = mdev->al_tr_number % (mdev->ldev->md.al_size_4k);
+
+	/* ... to aligned 4k on disk block */
+	t = ((t % stripes) * stripe_size_4kB) + t/stripes;
+
+	/* ... to 512 byte sector in activity log */
+	t *= 8;
+
+	/* ... plus offset to the on disk position */
+	return mdev->ldev->md.md_offset + mdev->ldev->md.al_offset + t;
+}
+
 static int
 _al_write_transaction(struct drbd_conf *mdev)
 {
@@ -432,23 +560,27 @@ _al_write_transaction(struct drbd_conf *mdev)
 	if (mdev->al_tr_cycle >= mdev->act_log->nr_elements)
 		mdev->al_tr_cycle = 0;
 
-	sector =  mdev->ldev->md.md_offset
-		+ mdev->ldev->md.al_offset
-		+ mdev->al_tr_pos * (MD_BLOCK_SIZE>>9);
+	sector = al_tr_number_to_on_disk_sector(mdev);
 
 	crc = crc32c(0, buffer, 4096);
 	buffer->crc32c = cpu_to_be32(crc);
 
 	if (drbd_bm_write_hinted(mdev))
 		err = -EIO;
-		/* drbd_chk_io_error done already */
-	else if (drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
-		err = -EIO;
-		drbd_chk_io_error(mdev, 1, DRBD_META_IO_ERROR);
-	} else {
-		/* advance ringbuffer position and transaction counter */
-		mdev->al_tr_pos = (mdev->al_tr_pos + 1) % (MD_AL_SECTORS*512/MD_BLOCK_SIZE);
-		mdev->al_tr_number++;
+	else {
+		bool write_al_updates;
+		rcu_read_lock();
+		write_al_updates = rcu_dereference(mdev->ldev->disk_conf)->al_updates;
+		rcu_read_unlock();
+		if (write_al_updates) {
+			if (drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
+				err = -EIO;
+				drbd_chk_io_error(mdev, 1, DRBD_META_IO_ERROR);
+			} else {
+				mdev->al_tr_number++;
+				mdev->al_writ_cnt++;
+			}
+		}
 	}
 
 	drbd_md_put_buffer(mdev);
@@ -474,20 +606,18 @@ static int w_al_write_transaction(struct drbd_work *w, int unused)
 /* Calls from worker context (see w_restart_disk_io()) need to write the
    transaction directly. Others came through generic_make_request(),
    those need to delegate it to the worker. */
-static int al_write_transaction(struct drbd_conf *mdev)
+static int al_write_transaction(struct drbd_conf *mdev, bool delegate)
 {
-	struct update_al_work al_work;
-
-	if (current == mdev->tconn->worker.task)
+	if (delegate) {
+		struct update_al_work al_work;
+		init_completion(&al_work.event);
+		al_work.w.cb = w_al_write_transaction;
+		al_work.w.mdev = mdev;
+		drbd_queue_work_front(&mdev->tconn->sender_work, &al_work.w);
+		wait_for_completion(&al_work.event);
+		return al_work.err;
+	} else
 		return _al_write_transaction(mdev);
-
-	init_completion(&al_work.event);
-	al_work.w.cb = w_al_write_transaction;
-	al_work.w.mdev = mdev;
-	drbd_queue_work_front(&mdev->tconn->sender_work, &al_work.w);
-	wait_for_completion(&al_work.event);
-
-	return al_work.err;
 }
 
 static int _try_lc_del(struct drbd_conf *mdev, struct lc_element *al_ext)
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 8dc29502dc08..64fbb8385cdc 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -612,6 +612,17 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
 	}
 }
 
+/* For the layout, see comment above drbd_md_set_sector_offsets(). */
+static u64 drbd_md_on_disk_bits(struct drbd_backing_dev *ldev)
+{
+	u64 bitmap_sectors;
+	if (ldev->md.al_offset == 8)
+		bitmap_sectors = ldev->md.md_size_sect - ldev->md.bm_offset;
+	else
+		bitmap_sectors = ldev->md.al_offset - ldev->md.bm_offset;
+	return bitmap_sectors << (9 + 3);
+}
+
 /*
  * make sure the bitmap has enough room for the attached storage,
  * if necessary, resize.
@@ -668,7 +679,7 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 	words = ALIGN(bits, 64) >> LN2_BPL;
 
 	if (get_ldev(mdev)) {
-		u64 bits_on_disk = ((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12;
+		u64 bits_on_disk = drbd_md_on_disk_bits(mdev->ldev);
 		put_ldev(mdev);
 		if (bits > bits_on_disk) {
 			dev_info(DEV, "bits = %lu\n", bits);
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 6b51afa1aae1..f943aacfdad8 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -753,13 +753,16 @@ struct drbd_md {
 	u32 flags;
 	u32 md_size_sect;
 
-	s32 al_offset;	/* signed relative sector offset to al area */
+	s32 al_offset;	/* signed relative sector offset to activity log */
 	s32 bm_offset;	/* signed relative sector offset to bitmap */
 
-	/* u32 al_nr_extents;	   important for restoring the AL
-	 * is stored into  ldev->dc.al_extents, which in turn
-	 * gets applied to act_log->nr_elements
-	 */
+	/* cached value of bdev->disk_conf->meta_dev_idx (see below) */
+	s32 meta_dev_idx;
+
+	/* see al_tr_number_to_on_disk_sector() */
+	u32 al_stripes;
+	u32 al_stripe_size_4k;
+	u32 al_size_4k; /* cached product of the above */
 };
 
 struct drbd_backing_dev {
@@ -891,6 +894,14 @@ struct drbd_tconn {			/* is a resource from the config file */
 	} send;
 };
 
+struct submit_worker {
+	struct workqueue_struct *wq;
+	struct work_struct worker;
+
+	spinlock_t lock;
+	struct list_head writes;
+};
+
 struct drbd_conf {
 	struct drbd_tconn *tconn;
 	int vnr;			/* volume number within the connection */
@@ -1009,7 +1020,6 @@ struct drbd_conf {
 	struct lru_cache *act_log;	/* activity log */
 	unsigned int al_tr_number;
 	int al_tr_cycle;
-	int al_tr_pos;   /* position of the next transaction in the journal */
 	wait_queue_head_t seq_wait;
 	atomic_t packet_seq;
 	unsigned int peer_seq;
@@ -1032,6 +1042,10 @@ struct drbd_conf {
 	atomic_t ap_in_flight; /* App sectors in flight (waiting for ack) */
 	unsigned int peer_max_bio_size;
 	unsigned int local_max_bio_size;
+
+	/* any requests that would block in drbd_make_request()
+	 * are deferred to this single-threaded work queue */
+	struct submit_worker submit;
 };
 
 static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
@@ -1148,25 +1162,44 @@ extern int drbd_bitmap_io_from_worker(struct drbd_conf *mdev,
 		char *why, enum bm_flag flags);
 extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
 extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
-extern void drbd_go_diskless(struct drbd_conf *mdev);
 extern void drbd_ldev_destroy(struct drbd_conf *mdev);
 
 /* Meta data layout
-   We reserve a 128MB Block (4k aligned)
-   * either at the end of the backing device
-   * or on a separate meta data device. */
+ *
+ * We currently have two possible layouts.
+ * Offsets in (512 byte) sectors.
+ * external:
+ *   |----------- md_size_sect ------------------|
+ *   [ 4k superblock ][ activity log ][  Bitmap  ]
+ *   | al_offset == 8 |
+ *   | bm_offset = al_offset + X      |
+ *  ==> bitmap sectors = md_size_sect - bm_offset
+ *
+ *  Variants:
+ *     old, indexed fixed size meta data:
+ *
+ * internal:
+ *            |----------- md_size_sect ------------------|
+ * [data.....][  Bitmap  ][ activity log ][ 4k superblock ][padding*]
+ *                        | al_offset < 0 |
+ *            | bm_offset = al_offset - Y |
+ *  ==> bitmap sectors = Y = al_offset - bm_offset
+ *
+ *  [padding*] are zero or up to 7 unused 512 Byte sectors to the
+ *  end of the device, so that the [4k superblock] will be 4k aligned.
+ *
+ *  The activity log consists of 4k transaction blocks,
+ *  which are written in a ring-buffer, or striped ring-buffer like fashion,
+ *  which are writtensize used to be fixed 32kB,
+ *  but is about to become configurable.
+ */
 
-/* The following numbers are sectors */
-/* Allows up to about 3.8TB, so if you want more,
+/* Our old fixed size meta data layout
+ * allows up to about 3.8TB, so if you want more,
  * you need to use the "flexible" meta data format. */
-#define MD_RESERVED_SECT (128LU << 11)  /* 128 MB, unit sectors */
-#define MD_AL_OFFSET	8    /* 8 Sectors after start of meta area */
-#define MD_AL_SECTORS	64   /* = 32 kB on disk activity log ring buffer */
-#define MD_BM_OFFSET (MD_AL_OFFSET + MD_AL_SECTORS)
-
-/* we do all meta data IO in 4k blocks */
-#define MD_BLOCK_SHIFT	12
-#define MD_BLOCK_SIZE	(1<<MD_BLOCK_SHIFT)
+#define MD_128MB_SECT (128LLU << 11)  /* 128 MB, unit sectors */
+#define MD_4kB_SECT	 8
+#define MD_32kB_SECT	64
 
 /* One activity log extent represents 4M of storage */
 #define AL_EXTENT_SHIFT 22
@@ -1256,7 +1289,6 @@ struct bm_extent {
 
 /* in one sector of the bitmap, we have this many activity_log extents. */
 #define AL_EXT_PER_BM_SECT  (1 << (BM_EXT_SHIFT - AL_EXTENT_SHIFT))
-#define BM_WORDS_PER_AL_EXT (1 << (AL_EXTENT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
 
 #define BM_BLOCKS_PER_BM_EXT_B (BM_EXT_SHIFT - BM_BLOCK_SHIFT)
 #define BM_BLOCKS_PER_BM_EXT_MASK  ((1<<BM_BLOCKS_PER_BM_EXT_B) - 1)
@@ -1276,16 +1308,18 @@ struct bm_extent {
  */
 
 #define DRBD_MAX_SECTORS_32 (0xffffffffLU)
-#define DRBD_MAX_SECTORS_BM \
-	  ((MD_RESERVED_SECT - MD_BM_OFFSET) * (1LL<<(BM_EXT_SHIFT-9)))
-#if DRBD_MAX_SECTORS_BM < DRBD_MAX_SECTORS_32
-#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
-#define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_BM
-#elif !defined(CONFIG_LBDAF) && BITS_PER_LONG == 32
+/* we have a certain meta data variant that has a fixed on-disk size of 128
+ * MiB, of which 4k are our "superblock", and 32k are the fixed size activity
+ * log, leaving this many sectors for the bitmap.
+ */
+
+#define DRBD_MAX_SECTORS_FIXED_BM \
+	  ((MD_128MB_SECT - MD_32kB_SECT - MD_4kB_SECT) * (1LL<<(BM_EXT_SHIFT-9)))
+#if !defined(CONFIG_LBDAF) && BITS_PER_LONG == 32
 #define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_32
 #define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_32
 #else
-#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
+#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_FIXED_BM
 /* 16 TB in units of sectors */
 #if BITS_PER_LONG == 32
 /* adjust by one page worth of bitmap,
@@ -1418,6 +1452,7 @@ extern void conn_free_crypto(struct drbd_tconn *tconn);
 extern int proc_details;
 
 /* drbd_req */
+extern void do_submit(struct work_struct *ws);
 extern void __drbd_make_request(struct drbd_conf *, struct bio *, unsigned long);
 extern void drbd_make_request(struct request_queue *q, struct bio *bio);
 extern int drbd_read_remote(struct drbd_conf *mdev, struct drbd_request *req);
@@ -1576,7 +1611,10 @@ extern const char *drbd_conn_str(enum drbd_conns s);
 extern const char