Merge branch 'for-2.6.35' of git://git.kernel.dk/linux-2.6-block

* 'for-2.6.35' of git://git.kernel.dk/linux-2.6-block: (86 commits)
  pipe: set lower and upper limit on max pages in the pipe page array
  pipe: add support for shrinking and growing pipes
  drbd: This is now equivalent to drbd release 8.3.8rc1
  drbd: Do not free p_uuid early, this is done in the exit code of the receiver
  drbd: Null pointer deref fix to the large "multi bio rewrite"
  drbd: Fix: Do not detach, if a bio with a barrier fails
  drbd: Ensure to not trigger late-new-UUID creation multiple times
  drbd: Do not Oops when C_STANDALONE when uuid gets generated
  writeback: fix mixed up arguments to bdi_start_writeback()
  writeback: fix problem with !CONFIG_BLOCK compilation
  block: improve automatic native capacity unlocking
  block: use struct parsed_partitions *state universally in partition check code
  block,ide: simplify bdops->set_capacity() to ->unlock_native_capacity()
  block: restart partition scan after resizing a device
  buffer: make invalidate_bdev() drain all percpu LRU add caches
  block: remove all rcu head initializations
  writeback: fixups for !dirty_writeback_centisecs
  writeback: bdi_writeback_task() must set task state before calling schedule()
  writeback: ensure that WB_SYNC_NONE writeback with sb pinned is sync
  drivers/block/drbd: Use kzalloc
  ...

13 files changed, 934 insertions, 470 deletions

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 77bfce52e9ca..de277689da61 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -76,6 +76,17 @@ config BLK_DEV_XD
 
 	  It's pretty unlikely that you have one of these: say N.
 
+config GDROM
+	tristate "SEGA Dreamcast GD-ROM drive"
+	depends on SH_DREAMCAST
+	help
+	  A standard SEGA Dreamcast comes with a modified CD ROM drive called a
+	  "GD-ROM" by SEGA to signify it is capable of reading special disks
+	  with up to 1 GB of data. This drive will also read standard CD ROM
+	  disks. Select this option to access any disks in your GD ROM drive.
+	  Most users will want to say "Y" here.
+	  You can also build this as a module which will be called gdrom.
+
 config PARIDE
 	tristate "Parallel port IDE device support"
 	depends on PARPORT_PC
@@ -103,17 +114,6 @@ config PARIDE
 	  "MicroSolutions backpack protocol", "DataStor Commuter protocol"
 	  etc.).
 
-config GDROM
-	tristate "SEGA Dreamcast GD-ROM drive"
-	depends on SH_DREAMCAST
-	help
-	  A standard SEGA Dreamcast comes with a modified CD ROM drive called a
-	  "GD-ROM" by SEGA to signify it is capable of reading special disks
-	  with up to 1 GB of data. This drive will also read standard CD ROM
-	  disks. Select this option to access any disks in your GD ROM drive.
-	  Most users will want to say "Y" here.
-	  You can also build this as a module which will be called gdrom.
-
 source "drivers/block/paride/Kconfig"
 
 config BLK_CPQ_DA
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 3390716898d5..e3f88d6e1412 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -84,6 +84,9 @@ struct drbd_bitmap {
 #define BM_MD_IO_ERROR  1
 #define BM_P_VMALLOCED  2
 
+static int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+			       unsigned long e, int val, const enum km_type km);
+
 static int bm_is_locked(struct drbd_bitmap *b)
 {
 	return test_bit(BM_LOCKED, &b->bm_flags);
@@ -441,7 +444,7 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
  * In case this is actually a resize, we copy the old bitmap into the new one.
  * Otherwise, the bitmap is initialized to all bits set.
  */
-int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity)
+int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
 {
 	struct drbd_bitmap *b = mdev->bitmap;
 	unsigned long bits, words, owords, obits, *p_addr, *bm;
@@ -516,7 +519,7 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity)
 	obits  = b->bm_bits;
 
 	growing = bits > obits;
-	if (opages)
+	if (opages && growing && set_new_bits)
 		bm_set_surplus(b);
 
 	b->bm_pages = npages;
@@ -526,8 +529,12 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity)
 	b->bm_dev_capacity = capacity;
 
 	if (growing) {
-		bm_memset(b, owords, 0xff, words-owords);
-		b->bm_set += bits - obits;
+		if (set_new_bits) {
+			bm_memset(b, owords, 0xff, words-owords);
+			b->bm_set += bits - obits;
+		} else
+			bm_memset(b, owords, 0x00, words-owords);
+
 	}
 
 	if (want < have) {
@@ -773,7 +780,7 @@ static void bm_page_io_async(struct drbd_conf *mdev, struct drbd_bitmap *b, int
 	/* nothing to do, on disk == in memory */
 # define bm_cpu_to_lel(x) ((void)0)
 # else
-void bm_cpu_to_lel(struct drbd_bitmap *b)
+static void bm_cpu_to_lel(struct drbd_bitmap *b)
 {
 	/* need to cpu_to_lel all the pages ...
 	 * this may be optimized by using
@@ -1015,7 +1022,7 @@ unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_f
  * wants bitnr, not sector.
  * expected to be called for only a few bits (e - s about BITS_PER_LONG).
  * Must hold bitmap lock already. */
-int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+static int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
 	unsigned long e, int val, const enum km_type km)
 {
 	struct drbd_bitmap *b = mdev->bitmap;
@@ -1053,7 +1060,7 @@ int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
  * for val != 0, we change 0 -> 1, return code positive
  * for val == 0, we change 1 -> 0, return code negative
  * wants bitnr, not sector */
-int bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+static int bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
 	const unsigned long e, int val)
 {
 	unsigned long flags;
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index e5e86a781820..e9654c8d5b62 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -132,6 +132,7 @@ enum {
 	DRBD_FAULT_DT_RA = 6,	/* data read ahead */
 	DRBD_FAULT_BM_ALLOC = 7,	/* bitmap allocation */
 	DRBD_FAULT_AL_EE = 8,	/* alloc ee */
+	DRBD_FAULT_RECEIVE = 9, /* Changes some bytes upon receiving a [rs]data block */
 
 	DRBD_FAULT_MAX,
 };
@@ -208,8 +209,11 @@ enum drbd_packets {
 	P_RS_IS_IN_SYNC	      = 0x22, /* meta socket */
 	P_SYNC_PARAM89	      = 0x23, /* data socket, protocol version 89 replacement for P_SYNC_PARAM */
 	P_COMPRESSED_BITMAP   = 0x24, /* compressed or otherwise encoded bitmap transfer */
+	/* P_CKPT_FENCE_REQ      = 0x25, * currently reserved for protocol D */
+	/* P_CKPT_DISABLE_REQ    = 0x26, * currently reserved for protocol D */
+	P_DELAY_PROBE         = 0x27, /* is used on BOTH sockets */
 
-	P_MAX_CMD	      = 0x25,
+	P_MAX_CMD	      = 0x28,
 	P_MAY_IGNORE	      = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
 	P_MAX_OPT_CMD	      = 0x101,
 
@@ -264,6 +268,7 @@ static inline const char *cmdname(enum drbd_packets cmd)
 		[P_CSUM_RS_REQUEST]     = "CsumRSRequest",
 		[P_RS_IS_IN_SYNC]	= "CsumRSIsInSync",
 		[P_COMPRESSED_BITMAP]   = "CBitmap",
+		[P_DELAY_PROBE]         = "DelayProbe",
 		[P_MAX_CMD]	        = NULL,
 	};
 
@@ -481,7 +486,8 @@ struct p_sizes {
 	u64	    u_size;  /* user requested size */
 	u64	    c_size;  /* current exported size */
 	u32	    max_segment_size;  /* Maximal size of a BIO */
-	u32	    queue_order_type;
+	u16	    queue_order_type;  /* not yet implemented in DRBD*/
+	u16	    dds_flags; /* use enum dds_flags here. */
 } __packed;
 
 struct p_state {
@@ -538,6 +544,18 @@ struct p_compressed_bm {
 	u8 code[0];
 } __packed;
 
+struct p_delay_probe {
+	struct p_header head;
+	u32	seq_num; /* sequence number to match the two probe packets */
+	u32	offset;	 /* usecs the probe got sent after the reference time point */
+} __packed;
+
+struct delay_probe {
+	struct list_head list;
+	unsigned int seq_num;
+	struct timeval time;
+};
+
 /* DCBP: Drbd Compressed Bitmap Packet ... */
 static inline enum drbd_bitmap_code
 DCBP_get_code(struct p_compressed_bm *p)
@@ -722,22 +740,6 @@ enum epoch_event {
 	EV_CLEANUP = 32, /* used as flag */
 };
 
-struct drbd_epoch_entry {
-	struct drbd_work    w;
-	struct drbd_conf *mdev;
-	struct bio *private_bio;
-	struct hlist_node colision;
-	sector_t sector;
-	unsigned int size;
-	struct drbd_epoch *epoch;
-
-	/* up to here, the struct layout is identical to drbd_request;
-	 * we might be able to use that to our advantage...  */
-
-	unsigned int flags;
-	u64    block_id;
-};
-
 struct drbd_wq_barrier {
 	struct drbd_work w;
 	struct completion done;
@@ -748,17 +750,49 @@ struct digest_info {
 	void *digest;
 };
 
-/* ee flag bits */
+struct drbd_epoch_entry {
+	struct drbd_work w;
+	struct hlist_node colision;
+	struct drbd_epoch *epoch;
+	struct drbd_conf *mdev;
+	struct page *pages;
+	atomic_t pending_bios;
+	unsigned int size;
+	/* see comments on ee flag bits below */
+	unsigned long flags;
+	sector_t sector;
+	u64 block_id;
+};
+
+/* ee flag bits.
+ * While corresponding bios are in flight, the only modification will be
+ * set_bit WAS_ERROR, which has to be atomic.
+ * If no bios are in flight yet, or all have been completed,
+ * non-atomic modification to ee->flags is ok.
+ */
 enum {
 	__EE_CALL_AL_COMPLETE_IO,
-	__EE_CONFLICT_PENDING,
 	__EE_MAY_SET_IN_SYNC,
+
+	/* This epoch entry closes an epoch using a barrier.
+	 * On sucessful completion, the epoch is released,
+	 * and the P_BARRIER_ACK send. */
 	__EE_IS_BARRIER,
+
+	/* In case a barrier failed,
+	 * we need to resubmit without the barrier flag. */
+	__EE_RESUBMITTED,
+
+	/* we may have several bios per epoch entry.
+	 * if any of those fail, we set this flag atomically
+	 * from the endio callback */
+	__EE_WAS_ERROR,
 };
 #define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
-#define EE_CONFLICT_PENDING    (1<<__EE_CONFLICT_PENDING)
 #define EE_MAY_SET_IN_SYNC     (1<<__EE_MAY_SET_IN_SYNC)
 #define EE_IS_BARRIER          (1<<__EE_IS_BARRIER)
+#define	EE_RESUBMITTED         (1<<__EE_RESUBMITTED)
+#define EE_WAS_ERROR           (1<<__EE_WAS_ERROR)
 
 /* global flag bits */
 enum {
@@ -908,9 +942,12 @@ struct drbd_conf {
 	unsigned int ko_count;
 	struct drbd_work  resync_work,
 			  unplug_work,
-			  md_sync_work;
+			  md_sync_work,
+			  delay_probe_work,
+			  uuid_work;
 	struct timer_list resync_timer;
 	struct timer_list md_sync_timer;
+	struct timer_list delay_probe_timer;
 
 	/* Used after attach while negotiating new disk state. */
 	union drbd_state new_state_tmp;
@@ -1026,6 +1063,13 @@ struct drbd_conf {
 	u64 ed_uuid; /* UUID of the exposed data */
 	struct mutex state_mutex;
 	char congestion_reason;  /* Why we where congested... */
+	struct list_head delay_probes; /* protected by peer_seq_lock */
+	int data_delay;   /* Delay of packets on the data-sock behind meta-sock */
+	unsigned int delay_seq; /* To generate sequence numbers of delay probes */
+	struct timeval dps_time; /* delay-probes-start-time */
+	unsigned int dp_volume_last;  /* send_cnt of last delay probe */
+	int c_sync_rate; /* current resync rate after delay_probe magic */
+	atomic_t new_c_uuid;
 };
 
 static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
@@ -1081,6 +1125,11 @@ enum chg_state_flags {
 	CS_ORDERED      = CS_WAIT_COMPLETE + CS_SERIALIZE,
 };
 
+enum dds_flags {
+	DDSF_FORCED    = 1,
+	DDSF_NO_RESYNC = 2, /* Do not run a resync for the new space */
+};
+
 extern void drbd_init_set_defaults(struct drbd_conf *mdev);
 extern int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
 			union drbd_state mask, union drbd_state val);
@@ -1113,7 +1162,7 @@ extern int drbd_send_protocol(struct drbd_conf *mdev);
 extern int drbd_send_uuids(struct drbd_conf *mdev);
 extern int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev);
 extern int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val);
-extern int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply);
+extern int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags flags);
 extern int _drbd_send_state(struct drbd_conf *mdev);
 extern int drbd_send_state(struct drbd_conf *mdev);
 extern int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
@@ -1311,7 +1360,7 @@ struct bm_extent {
 #define APP_R_HSIZE 15
 
 extern int  drbd_bm_init(struct drbd_conf *mdev);
-extern int  drbd_bm_resize(struct drbd_conf *mdev, sector_t sectors);
+extern int  drbd_bm_resize(struct drbd_conf *mdev, sector_t sectors, int set_new_bits);
 extern void drbd_bm_cleanup(struct drbd_conf *mdev);
 extern void drbd_bm_set_all(struct drbd_conf *mdev);
 extern void drbd_bm_clear_all(struct drbd_conf *mdev);
@@ -1383,7 +1432,7 @@ extern void drbd_resume_io(struct drbd_conf *mdev);
 extern char *ppsize(char *buf, unsigned long long size);
 extern sector_t drbd_new_dev_size(struct drbd_conf *, struct drbd_backing_dev *, int);
 enum determine_dev_size { dev_size_error = -1, unchanged = 0, shrunk = 1, grew = 2 };
-extern enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *, int force) __must_hold(local);
+extern enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *, enum dds_flags) __must_hold(local);
 extern void resync_after_online_grow(struct drbd_conf *);
 extern void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int) __must_hold(local);
 extern int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role,
@@ -1414,7 +1463,8 @@ static inline void ov_oos_print(struct drbd_conf *mdev)
 }
 
 
-extern void drbd_csum(struct drbd_conf *, struct crypto_hash *, struct bio *, void *);
+extern void drbd_csum_bio(struct drbd_conf *, struct crypto_hash *, struct bio *, void *);
+extern void drbd_csum_ee(struct drbd_conf *, struct crypto_hash *, struct drbd_epoch_entry *, void *);
 /* worker callbacks */
 extern int w_req_cancel_conflict(struct drbd_conf *, struct drbd_work *, int);
 extern int w_read_retry_remote(struct drbd_conf *, struct drbd_work *, int);
@@ -1438,6 +1488,8 @@ extern int w_e_reissue(struct drbd_conf *, struct drbd_work *, int);
 extern void resync_timer_fn(unsigned long data);
 
 /* drbd_receiver.c */
+extern int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
+		const unsigned rw, const int fault_type);
 extern int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list);
 extern struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
 					    u64 id,
@@ -1593,6 +1645,41 @@ void drbd_bcast_ee(struct drbd_conf *mdev,
  * inline helper functions
  *************************/
 
+/* see also page_chain_add and friends in drbd_receiver.c */
+static inline struct page *page_chain_next(struct page *page)
+{
+	return (struct page *)page_private(page);
+}
+#define page_chain_for_each(page) \
+	for (; page && ({ prefetch(page_chain_next(page)); 1; }); \
+			page = page_chain_next(page))
+#define page_chain_for_each_safe(page, n) \
+	for (; page && ({ n = page_chain_next(page); 1; }); page = n)
+
+static inline int drbd_bio_has_active_page(struct bio *bio)
+{
+	struct bio_vec *bvec;
+	int i;
+
+	__bio_for_each_segment(bvec, bio, i, 0) {
+		if (page_count(bvec->bv_page) > 1)
+			return 1;
+	}
+
+	return 0;
+}
+
+static inline int drbd_ee_has_active_page(struct drbd_epoch_entry *e)
+{
+	struct page *page = e->pages;
+	page_chain_for_each(page) {
+		if (page_count(page) > 1)
+			return 1;
+	}
+	return 0;
+}
+
+
 static inline void drbd_state_lock(struct drbd_conf *mdev)
 {
 	wait_event(mdev->misc_wait,
@@ -2132,13 +2219,15 @@ static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
 		return 0;
 	if (test_bit(BITMAP_IO, &mdev->flags))
 		return 0;
+	if (atomic_read(&mdev->new_c_uuid))
+		return 0;
 	return 1;
 }
 
 /* I'd like to use wait_event_lock_irq,
  * but I'm not sure when it got introduced,
  * and not sure when it has 3 or 4 arguments */
-static inline void inc_ap_bio(struct drbd_conf *mdev, int one_or_two)
+static inline void inc_ap_bio(struct drbd_conf *mdev, int count)
 {
 	/* compare with after_state_ch,
 	 * os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S */
@@ -2152,6 +2241,9 @@ static inline void inc_ap_bio(struct drbd_conf *mdev, int one_or_two)
 	 * to avoid races with the reconnect code,
 	 * we need to atomic_inc within the spinlock. */
 
+	if (atomic_read(&mdev->new_c_uuid) && atomic_add_unless(&mdev->new_c_uuid, -1, 1))
+		drbd_queue_work_front(&mdev->data.work, &mdev->uuid_work);
+
 	spin_lock_irq(&mdev->req_lock);
 	while (!__inc_ap_bio_cond(mdev)) {
 		prepare_to_wait(&mdev->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
@@ -2160,7 +2252,7 @@ static inline void inc_ap_bio(struct drbd_conf *mdev, int one_or_two)
 		finish_wait(&mdev->misc_wait, &wait);
 		spin_lock_irq(&mdev->req_lock);
 	}
-	atomic_add(one_or_two, &mdev->ap_bio_cnt);
+	atomic_add(count, &mdev->ap_bio_cnt);
 	spin_unlock_irq(&mdev->req_lock);
 }
 
@@ -2251,7 +2343,8 @@ static inline void drbd_md_flush(struct drbd_conf *mdev)
 	if (test_bit(MD_NO_BARRIER, &mdev->flags))
 		return;
 
-	r = blkdev_issue_flush(mdev->ldev->md_bdev, NULL);
+	r = blkdev_issue_flush(mdev->ldev->md_bdev, GFP_KERNEL, NULL,
+			BLKDEV_IFL_WAIT);
 	if (r) {
 		set_bit(MD_NO_BARRIER, &mdev->flags);
 		dev_err(DEV, "meta data flush failed with status %d, disabling md-flushes\n", r);
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 93d1f9b469d4..be2d2da9cdba 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -684,6 +684,9 @@ static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
 	else if (ns.conn > C_CONNECTED && ns.pdsk < D_INCONSISTENT)
 		rv = SS_NO_REMOTE_DISK;
 
+	else if (ns.conn > C_CONNECTED && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE)
+		rv = SS_NO_UP_TO_DATE_DISK;
+
 	else if ((ns.conn == C_CONNECTED ||
 		  ns.conn == C_WF_BITMAP_S ||
 		  ns.conn == C_SYNC_SOURCE ||
@@ -840,7 +843,12 @@ static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state
 			break;
 		case C_WF_BITMAP_S:
 		case C_PAUSED_SYNC_S:
-			ns.pdsk = D_OUTDATED;
+			/* remap any consistent state to D_OUTDATED,
+			 * but disallow "upgrade" of not even consistent states.
+			 */
+			ns.pdsk =
+				(D_DISKLESS < os.pdsk && os.pdsk < D_OUTDATED)
+				? os.pdsk : D_OUTDATED;
 			break;
 		case C_SYNC_SOURCE:
 			ns.pdsk = D_INCONSISTENT;
@@ -1205,21 +1213,20 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 	&&  (ns.pdsk < D_INCONSISTENT ||
 	     ns.pdsk == D_UNKNOWN ||
 	     ns.pdsk == D_OUTDATED)) {
-		kfree(mdev->p_uuid);
-		mdev->p_uuid = NULL;
 		if (get_ldev(mdev)) {
 			if ((ns.role == R_PRIMARY || ns.peer == R_PRIMARY) &&
-			    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
-				drbd_uuid_new_current(mdev);
-				drbd_send_uuids(mdev);
-			}
+			    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE &&
+			    !atomic_read(&mdev->new_c_uuid))
+				atomic_set(&mdev->new_c_uuid, 2);
 			put_ldev(mdev);
 		}
 	}
 
 	if (ns.pdsk < D_INCONSISTENT && get_ldev(mdev)) {
-		if (ns.peer == R_PRIMARY && mdev->ldev->md.uuid[UI_BITMAP] == 0)
-			drbd_uuid_new_current(mdev);
+		/* Diskless peer becomes primary or got connected do diskless, primary peer. */
+		if (ns.peer == R_PRIMARY && mdev->ldev->md.uuid[UI_BITMAP] == 0 &&
+		    !atomic_read(&mdev->new_c_uuid))
+			atomic_set(&mdev->new_c_uuid, 2);
 
 		/* D_DISKLESS Peer becomes secondary */
 		if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
@@ -1232,7 +1239,7 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 	    os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
 		kfree(mdev->p_uuid); /* We expect to receive up-to-date UUIDs soon. */
 		mdev->p_uuid = NULL; /* ...to not use the old ones in the mean time */
-		drbd_send_sizes(mdev, 0);  /* to start sync... */
+		drbd_send_sizes(mdev, 0, 0);  /* to start sync... */
 		drbd_send_uuids(mdev);
 		drbd_send_state(mdev);
 	}
@@ -1343,6 +1350,24 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 	drbd_md_sync(mdev);
 }
 
+static int w_new_current_uuid(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	if (get_ldev(mdev)) {
+		if (mdev->ldev->md.uuid[UI_BITMAP] == 0) {
+			drbd_uuid_new_current(mdev);
+			if (get_net_conf(mdev)) {
+				drbd_send_uuids(mdev);
+				put_net_conf(mdev);
+			}
+			drbd_md_sync(mdev);
+		}
+		put_ldev(mdev);
+	}
+	atomic_dec(&mdev->new_c_uuid);
+	wake_up(&mdev->misc_wait);
+
+	return 1;
+}
 
 static int drbd_thread_setup(void *arg)
 {
@@ -1755,7 +1780,7 @@ int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val)
 			     (struct p_header *)&p, sizeof(p));
 }
 
-int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply)
+int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply, enum dds_flags flags)
 {
 	struct p_sizes p;
 	sector_t d_size, u_size;
@@ -1767,7 +1792,6 @@ int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply)
 		d_size = drbd_get_max_capacity(mdev->ldev);
 		u_size = mdev->ldev->dc.disk_size;
 		q_order_type = drbd_queue_order_type(mdev);
-		p.queue_order_type = cpu_to_be32(drbd_queue_order_type(mdev));
 		put_ldev(mdev);
 	} else {
 		d_size = 0;
@@ -1779,7 +1803,8 @@ int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply)
 	p.u_size = cpu_to_be64(u_size);
 	p.c_size = cpu_to_be64(trigger_reply ? 0 : drbd_get_capacity(mdev->this_bdev));
 	p.max_segment_size = cpu_to_be32(queue_max_segment_size(mdev->rq_queue));
-	p.queue_order_type = cpu_to_be32(q_order_type);
+	p.queue_order_type = cpu_to_be16(q_order_type);
+	p.dds_flags = cpu_to_be16(flags);
 
 	ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SIZES,
 			   (struct p_header *)&p, sizeof(p));
@@ -2180,6 +2205,43 @@ int drbd_send_ov_request(struct drbd_conf *mdev, sector_t sector, int size)
 	return ok;
 }
 
+static int drbd_send_delay_probe(struct drbd_conf *mdev, struct drbd_socket *ds)
+{
+	struct p_delay_probe dp;
+	int offset, ok = 0;
+	struct timeval now;
+
+	mutex_lock(&ds->mutex);
+	if (likely(ds->socket)) {
+		do_gettimeofday(&now);
+		offset = now.tv_usec - mdev->dps_time.tv_usec +
+			 (now.tv_sec - mdev->dps_time.tv_sec) * 1000000;
+		dp.seq_num  = cpu_to_be32(mdev->delay_seq);
+		dp.offset   = cpu_to_be32(offset);
+
+		ok = _drbd_send_cmd(mdev, ds->socket, P_DELAY_PROBE,
+				    (struct p_header *)&dp, sizeof(dp), 0);
+	}
+	mutex_unlock(&ds->mutex);
+
+	return ok;
+}
+
+static int drbd_send_delay_probes(struct drbd_conf *mdev)
+{
+	int ok;
+
+	mdev->delay_seq++;
+	do_gettimeofday(&mdev->dps_time);
+	ok = drbd_send_delay_probe(mdev, &mdev->meta);
+	ok = ok && drbd_send_delay_probe(mdev, &mdev->data);
+
+	mdev->dp_volume_last = mdev->send_cnt;
+	mod_timer(&mdev->delay_probe_timer, jiffies + mdev->sync_conf.dp_interval * HZ / 10);
+
+	return ok;
+}
+
 /* called on sndtimeo
  * returns FALSE if we should retry,
  * TRUE if we think connection is dead
@@ -2309,6 +2371,44 @@ static int _drbd_send_zc_bio(struct drbd_conf *mdev, struct bio *bio)
 	return 1;
 }
 
+static int _drbd_send_zc_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
+{
+	struct page *page = e->pages;
+	unsigned len = e->size;
+	page_chain_for_each(page) {
+		unsigned l = min_t(unsigned, len, PAGE_SIZE);
+		if (!_drbd_send_page(mdev, page, 0, l))
+			return 0;
+		len -= l;
+	}
+	return 1;
+}
+
+static void consider_delay_probes(struct drbd_conf *mdev)
+{
+	if (mdev->state.conn != C_SYNC_SOURCE || mdev->agreed_pro_version < 93)
+		return;
+
+	if (mdev->dp_volume_last + mdev->sync_conf.dp_volume * 2 < mdev->send_cnt)
+		drbd_send_delay_probes(mdev);
+}
+
+static int w_delay_probes(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+	if (!cancel && mdev->state.conn == C_SYNC_SOURCE)
+		drbd_send_delay_probes(mdev);
+
+	return 1;
+}
+
+static void delay_probe_timer_fn(unsigned long data)
+{
+	struct drbd_conf *mdev = (struct drbd_conf *) data;
+
+	if (list_empty(&mdev->delay_probe_work.list))
+		drbd_queue_work(&mdev->data.work, &mdev->delay_probe_work);
+}
+
 /* Used to send write requests
  * R_PRIMARY -> Peer	(P_DATA)
  */
@@ -2360,7 +2460,7 @@ int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
 		drbd_send(mdev, mdev->data.socket, &p, sizeof(p), MSG_MORE));
 	if (ok && dgs) {
 		dgb = mdev->int_dig_out;
-		drbd_csum(mdev, mdev->integrity_w_tfm, req->master_bio, dgb);
+		drbd_csum_bio(mdev, mdev->integrity_w_tfm, req->master_bio, dgb);
 		ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, MSG_MORE);
 	}
 	if (ok) {
@@ -2371,6 +2471,10 @@ int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
 	}
 
 	drbd_put_data_sock(mdev);
+
+	if (ok)
+		consider_delay_probes(mdev);
+
 	return ok;
 }
 
@@ -2409,13 +2513,17 @@ int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
 					sizeof(p), MSG_MORE);
 	if (ok && dgs) {
 		dgb = mdev->int_dig_out;
-		drbd_csum(mdev, mdev->integrity_w_tfm, e->private_bio, dgb);
+		drbd_csum_ee(mdev, mdev->integrity_w_tfm, e, dgb);
 		ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, MSG_MORE);
 	}
 	if (ok)
-		ok = _drbd_send_zc_bio(mdev, e->private_bio);
+		ok = _drbd_send_zc_ee(mdev, e);
 
 	drbd_put_data_sock(mdev);
+
+	if (ok)
+		consider_delay_probes(mdev);
+
 	return ok;
 }
 
@@ -2600,6 +2708,7 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	atomic_set(&mdev->net_cnt, 0);
 	atomic_set(&mdev->packet_seq, 0);
 	atomic_set(&mdev->pp_in_use, 0);
+	atomic_set(&mdev->new_c_uuid, 0);
 
 	mutex_init(&mdev->md_io_mutex);
 	mutex_init(&mdev->data.mutex);
@@ -2628,16 +2737,26 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	INIT_LIST_HEAD(&mdev->unplug_work.list);
 	INIT_LIST_HEAD(&mdev->md_sync_work.list);
 	INIT_LIST_HEAD(&mdev->bm_io_work.w.list);
+	INIT_LIST_HEAD(&mdev->delay_probes);
+	INIT_LIST_HEAD(&mdev->delay_probe_work.list);
+	INIT_LIST_HEAD(&mdev->uuid_work.list);
+
 	mdev->resync_work.cb  = w_resync_inactive;
 	mdev->unplug_work.cb  = w_send_write_hint;
 	mdev->md_sync_work.cb = w_md_sync;
 	mdev->bm_io_work.w.cb = w_bitmap_io;
+	mdev->delay_probe_work.cb = w_delay_probes;
+	mdev->uuid_work.cb = w_new_current_uuid;
 	init_timer(&mdev->resync_timer);
 	init_timer(&mdev->md_sync_timer);
+	init_timer(&mdev->delay_probe_timer);
 	mdev->resync_timer.function = resync_timer_fn;
 	mdev->resync_timer.data = (unsigned long) mdev;
 	mdev->md_sync_timer.function = md_sync_timer_fn;
 	mdev->md_sync_timer.data = (unsigned long) mdev;
+	mdev->delay_probe_timer.function = delay_probe_timer_fn;
+	mdev->delay_probe_timer.data = (unsigned long) mdev;
+
 
 	init_waitqueue_head(&mdev->misc_wait);
 	init_waitqueue_head(&mdev->state_wait);
@@ -2680,7 +2799,7 @@ void drbd_mdev_cleanup(struct drbd_conf *mdev)
 	drbd_set_my_capacity(mdev, 0);
 	if (mdev->bitmap) {
 		/* maybe never allocated. */
-		drbd_bm_resize(mdev, 0);
+		drbd_bm_resize(mdev, 0, 1);
 		drbd_bm_cleanup(mdev);
 	}
 
@@ -3129,7 +3248,7 @@ int __init drbd_init(void)
 	if (err)
 		goto Enomem;
 
-	drbd_proc = proc_create("drbd", S_IFREG | S_IRUGO , NULL, &drbd_proc_fops);
+	drbd_proc = proc_create_data("drbd", S_IFREG | S_IRUGO , NULL, &drbd_proc_fops, NULL);
 	if (!drbd_proc)	{
 		printk(KERN_ERR "drbd: unable to register proc file\n");
 		goto Enomem;
@@ -3660,7 +3779,8 @@ _drbd_fault_str(unsigned int type) {
 		[DRBD_FAULT_DT_RD] = "Data read",
 		[DRBD_FAULT_DT_RA] = "Data read ahead",
 		[DRBD_FAULT_BM_ALLOC] = "BM allocation",
-		[DRBD_FAULT_AL_EE] = "EE allocation"
+		[DRBD_FAULT_AL_EE] = "EE allocation",
+		[DRBD_FAULT_RECEIVE] = "receive data corruption",
 	};
 
 	return (type < DRBD_FAULT_MAX) ? _faults[type] : "**Unknown**";
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 6429d2b19e06..632e3245d1bb 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -510,7 +510,7 @@ void drbd_resume_io(struct drbd_conf *mdev)
  * Returns 0 on success, negative return values indicate errors.
  * You should call drbd_md_sync() after calling this function.
  */
-enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *mdev, int force) __must_hold(local)
+enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *mdev, enum dds_flags flags) __must_hold(local)
 {
 	sector_t prev_first_sect, prev_size; /* previous meta location */
 	sector_t la_size;
@@ -541,12 +541,12 @@ enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *mdev, int force
 	/* TODO: should only be some assert here, not (re)init... */
 	drbd_md_set_sector_offsets(mdev, mdev->ldev);
 
-	size = drbd_new_dev_size(mdev, mdev->ldev, force);
+	size = drbd_new_dev_size(mdev, mdev->ldev, flags & DDSF_FORCED);
 
 	if (drbd_get_capacity(mdev->this_bdev) != size ||
 	    drbd_bm_capacity(mdev) != size) {
 		int err;
-		err = drbd_bm_resize(mdev, size);
+		err = drbd_bm_resize(mdev, size, !(flags & DDSF_NO_RESYNC));
 		if (unlikely(err)) {
 			/* currently there is only one error: ENOMEM! */
 			size = drbd_bm_capacity(mdev)>>1;
@@ -704,9 +704,6 @@ void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int max_seg_s) __mu
 	struct request_queue * const b = mdev->ldev->backing_bdev->bd_disk->queue;
 	int max_segments = mdev->ldev->dc.max_bio_bvecs;
 
-	if (b->merge_bvec_fn && !mdev->ldev->dc.use_bmbv)
-		max_seg_s = PAGE_SIZE;
-
 	max_seg_s = min(queue_max_sectors(b) * queue_logical_block_size(b), max_seg_s);
 
 	blk_queue_max_hw_sectors(q, max_seg_s >> 9);
@@ -1199,13 +1196,12 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 	}
 
 	/* allocation not in the IO path, cqueue thread context */
-	new_conf = kmalloc(sizeof(struct net_conf), GFP_KERNEL);
+	new_conf = kzalloc(sizeof(struct net_conf), GFP_KERNEL);
 	if (!new_conf) {
 		retcode = ERR_NOMEM;
 		goto fail;
 	}
 
-	memset(new_conf, 0, sizeof(struct net_conf));
 	new_conf->timeout	   = DRBD_TIMEOUT_DEF;
 	new_conf->try_connect_int  = DRBD_CONNECT_INT_DEF;
 	new_conf->ping_int	   = DRBD_PING_INT_DEF;
@@ -1477,8 +1473,8 @@ static int drbd_nl_resize(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 {
 	struct resize rs;
 	int retcode = NO_ERROR;
-	int ldsc = 0; /* local disk size changed */
 	enum determine_dev_size dd;
+	enum dds_flags ddsf;
 
 	memset(&rs, 0, sizeof(struct resize));
 	if (!resize_from_tags(mdev, nlp->tag_list, &rs)) {
@@ -1502,13 +1498,17 @@ static int drbd_nl_resize(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 		goto fail;
 	}
 
-	if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
-		mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
-		ldsc = 1;
+	if (rs.no_resync && mdev->agreed_pro_version < 93) {
+		retcode = ERR_NEED_APV_93;
+		goto fail;
 	}
 
+	if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev))
+		mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
+
 	mdev->ldev->dc.disk_size = (sector_t)rs.resize_size;
-	dd = drbd_determin_dev_size(mdev, rs.resize_force);
+	ddsf = (rs.resize_force ? DDSF_FORCED : 0) | (rs.no_resync ? DDSF_NO_RESYNC : 0);
+	dd = drbd_determin_dev_size(mdev, ddsf);
 	drbd_md_sync(mdev);
 	put_ldev(mdev);
 	if (dd == dev_size_error) {
@@ -1516,12 +1516,12 @@ static int drbd_nl_resize(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 		goto fail;
 	}
 
-	if (mdev->state.conn == C_CONNECTED && (dd != unchanged || ldsc)) {
+	if (mdev->state.conn == C_CONNECTED) {
 		if (dd == grew)
 			set_bit(RESIZE_PENDING, &mdev->flags);
 
 		drbd_send_uuids(mdev);
-		drbd_send_sizes(mdev, 1);
+		drbd_send_sizes(mdev, 1, ddsf);
 	}
 
  fail:
@@ -1551,6 +1551,10 @@ static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n
 		sc.rate       = DRBD_RATE_DEF;
 		sc.after      = DRBD_AFTER_DEF;
 		sc.al_extents = DRBD_AL_EXTENTS_DEF;
+		sc.dp_volume  = DRBD_DP_VOLUME_DEF;
+		sc.dp_interval = DRBD_DP_INTERVAL_DEF;
+		sc.throttle_th = DRBD_RS_THROTTLE_TH_DEF;
+		sc.hold_off_th = DRBD_RS_HOLD_OFF_TH_DEF;
 	} else
 		memcpy(&sc, &mdev->sync_conf, sizeof(struct syncer_conf));
 
@@ -2207,9 +2211,9 @@ void drbd_bcast_ee(struct drbd_conf *mdev,
 {
 	struct cn_msg *cn_reply;
 	struct drbd_nl_cfg_reply *reply;
-	struct bio_vec *bvec;
 	unsigned short *tl;
-	int i;
+	struct page *page;
+	unsigned len;
 
 	if (!e)
 		return;
@@ -2247,11 +2251,15 @@ void drbd_bcast_ee(struct drbd_conf *mdev,
 	put_unaligned(T_ee_data, tl++);
 	put_unaligned(e->size, tl++);
 
-	__bio_for_each_segment(bvec, e->private_bio, i, 0) {
-		void *d = kmap(bvec->bv_page);
-		memcpy(tl, d + bvec->bv_offset, bvec->bv_len);
-		kunmap(bvec->bv_page);
-		tl=(unsigned short*)((char*)tl + bvec->bv_len);
+	len = e->size;
+	page = e->pages;
+	page_chain_for_each(page) {
+		void *d = kmap_atomic(page, KM_USER0);
+		unsigned l = min_t(unsigned, len, PAGE_SIZE);
+		memcpy(tl, d, l);
+		kunmap_atomic(d, KM_USER0);
+		tl = (unsigned short*)((char*)tl + l);
+		len -= l;
 	}
 	put_unaligned(TT_END, tl++); /* Close the tag list */
 
diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
index be3374b68460..d0f1767ea4c3 100644
--- a/drivers/block/drbd/drbd_proc.c
+++ b/drivers/block/drbd/drbd_proc.c
@@ -73,14 +73,21 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 	seq_printf(seq, "sync'ed:%3u.%u%% ", res / 10, res % 10);
 	/* if more than 1 GB display in MB */
 	if (mdev->rs_total > 0x100000L)
-		seq_printf(seq, "(%lu/%lu)M\n\t",
+		seq_printf(seq, "(%lu/%lu)M",
 			    (unsigned long) Bit2KB(rs_left >> 10),
 			    (unsigned long) Bit2KB(mdev->rs_total >> 10));
 	else
-		seq_printf(seq, "(%lu/%lu)K\n\t",
+		seq_printf(seq, "(%lu/%lu)K",
 			    (unsigned long) Bit2KB(rs_left),
 			    (unsigned long) Bit2KB(mdev->rs_total));
 
+	if (mdev->state.conn == C_SYNC_TARGET)
+		seq_printf(seq, " queue_delay: %d.%d ms\n\t",
+			   mdev->data_delay / 1000,
+			   (mdev->data_delay % 1000) / 100);
+	else if (mdev->state.conn == C_SYNC_SOURCE)
+		seq_printf(seq, " delay_probe: %u\n\t", mdev->delay_seq);
+
 	/* see drivers/md/md.c
 	 * We do not want to overflow, so the order of operands and
 	 * the * 100 / 100 trick are important. We do a +1 to be
@@ -128,6 +135,14 @@ static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
 	else
 		seq_printf(seq, " (%ld)", dbdt);
 
+	if (mdev->state.conn == C_SYNC_TARGET) {
+		if (mdev->c_sync_rate > 1000)
+			seq_printf(seq, " want: %d,%03d",
+				   mdev->c_sync_rate / 1000, mdev->c_sync_rate % 1000);
+		else
+			seq_printf(seq, " want: %d", mdev->c_sync_rate);
+	}
+
 	seq_printf(seq, " K/sec\n");
 }
 
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 3f096e7959b4..bc9ab7fb2cc7 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -80,30 +80,128 @@ static struct drbd_epoch *previous_epoch(struct drbd_conf *mdev, struct drbd_epo
 
 #define GFP_TRY	(__GFP_HIGHMEM | __GFP_NOWARN)
 
-static struct page *drbd_pp_first_page_or_try_alloc(struct drbd_conf *mdev)
+/*
+ * some helper functions to deal with single linked page lists,
+ * page->private being our "next" pointer.
+ */
+
+/* If at least n pages are linked at head, get n pages off.
+ * Otherwise, don't modify head, and return NULL.
+ * Locking is the responsibility of the caller.
+ */
+static struct page *page_chain_del(struct page **head, int n)
+{
+	struct page *page;
+	struct page *tmp;
+
+	BUG_ON(!n);
+	BUG_ON(!head);
+
+	page = *head;
+
+	if (!page)
+		return NULL;
+
+	while (page) {
+		tmp = page_chain_next(page);
+		if (--n == 0)
+			break; /* found sufficient pages */
+		if (tmp == NULL)
+			/* insufficient pages, don't use any of them. */
+			return NULL;
+		page = tmp;
+	}
+
+	/* add end of list marker for the returned list */
+	set_page_private(page, 0);
+	/* actual return value, and adjustment of head */
+	page = *head;
+	*head = tmp;
+	return page;
+}
+
+/* may be used outside of locks to find the tail of a (usually short)
+ * "private" page chain, before adding it back to a global chain head
+ * with page_chain_add() under a spinlock. */
+static struct page *page_chain_tail(struct page *page, int *len)
+{
+	struct page *tmp;
+	int i = 1;
+	while ((tmp = page_chain_next(page)))
+		++i, page = tmp;
+	if (len)
+		*len = i;
+	return page;
+}
+
+static int page_chain_free(struct page *page)
+{
+	struct page *tmp;
+	int i = 0;
+	page_chain_for_each_safe(page, tmp) {
+		put_page(page);
+		++i;
+	}
+	return i;
+}
+
+static void page_chain_add(struct page **head,
+		struct page *chain_first, struct page *chain_last)
+{
+#if 1
+	struct page *tmp;
+	tmp = page_chain_tail(chain_first, NULL);
+	BUG_ON(tmp != chain_last);
+#endif
+
+	/* add chain to head */
+	set_page_private(chain_last, (unsigned long)*head);
+	*head = chain_first;
+}
+
+static struct page *drbd_pp_first_pages_or_try_alloc(struct drbd_conf *mdev, int number)
 {
 	struct page *page = NULL;
+	struct page *tmp = NULL;
+	int i = 0;
 
 	/* Yes, testing drbd_pp_vacant outside the lock is racy.
 	 * So what. It saves a spin_lock. */
-	if (drbd_pp_vacant > 0) {
+	if (drbd_pp_vacant >= number) {
 		spin_lock(&drbd_pp_lock);
-		page = drbd_pp_pool;
-		if (page) {
-			drbd_pp_pool = (struct page *)page_private(page);
-			set_page_private(page, 0); /* just to be polite */
-			drbd_pp_vacant--;
-		}
+		page = page_chain_del(&drbd_pp_pool, number);
+		if (page)
+			drbd_pp_vacant -= number;
 		spin_unlock(&drbd_pp_lock);
+		if (page)
+			return page;
 	}
+
 	/* GFP_TRY, because we must not cause arbitrary write-out: in a DRBD
 	 * "criss-cross" setup, that might cause write-out on some other DRBD,
 	 * which in turn might block on the other node at this very place.  */
-	if (!page)
-		page = alloc_page(GFP_TRY);
-	if (page)
-		atomic_inc(&mdev->pp_in_use);
-	return page;
+	for (i = 0; i < number; i++) {
+		tmp = alloc_page(GFP_TRY);
+		if (!tmp)
+			break;
+		set_page_private(tmp, (unsigned long)page);
+		page = tmp;
+	}
+
+	if (i == number)
+		return page;
+
+	/* Not enough pages immediately available this time.
+	 * No need to jump around here, drbd_pp_alloc will retry this
+	 * function "soon". */
+	if (page) {
+		tmp = page_chain_tail(page, NULL);
+		spin_lock(&drbd_pp_lock);
+		page_chain_add(&drbd_pp_pool, page, tmp);
+		drbd_pp_vacant += i;
+		spin_unlock(&drbd_pp_lock);
+	}
+	return NULL;
 }
 
 /* kick lower level device, if we have more than (arbitrary number)
@@ -127,7 +225,7 @@ static void reclaim_net_ee(struct drbd_conf *mdev, struct list_head *to_be_freed
 
 	list_for_each_safe(le, tle, &mdev->net_ee) {
 		e = list_entry(le, struct drbd_epoch_entry, w.list);
-		if (drbd_bio_has_active_page(e->private_bio))
+		if (drbd_ee_has_active_page(e))
 			break;
 		list_move(le, to_be_freed);
 	}
@@ -148,32 +246,34 @@ static void drbd_kick_lo_and_reclaim_net(struct drbd_conf *mdev)
 }
 
 /**
- * drbd_pp_alloc() - Returns a page, fails only if a signal comes in
+ * drbd_pp_alloc() - Returns @number pages, retries forever (or until signalled)
  * @mdev:	DRBD device.
- * @retry:	whether or not to retry allocation forever (or until signalled)
+ * @number:	number of pages requested
+ * @retry:	whether to retry, if not enough pages are available right now
+ *
+ * Tries to allocate number pages, first from our own page pool, then from
+ * the kernel, unless this allocation would exceed the max_buffers setting.
+ * Possibly retry until DRBD frees sufficient pages somewhere else.
  *
- * Tries to allocate a page, first from our own page pool, then from the
- * kernel, unless this allocation would exceed the max_buffers setting.
- * If @retry is non-zero, retry until DRBD frees a page somewhere else.
+ * Returns a page chain linked via page->private.
  */
-static struct page *drbd_pp_alloc(struct drbd_conf *mdev, int retry)
+static struct page *drbd_pp_alloc(struct drbd_conf *mdev, unsigned number, bool retry)
 {
 	struct page *page = NULL;
 	DEFINE_WAIT(wait);
 
-	if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers) {
-		page = drbd_pp_first_page_or_try_alloc(mdev);
-		if (page)
-			return page;
-	}
+	/* Yes, we may run up to @number over max_buffers. If we
+	 * follow it strictly, the admin will get it wrong anyways. */
+	if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers)
+		page = drbd_pp_first_pages_or_try_alloc(mdev, number);
 
-	for (;;) {
+	while (page == NULL) {
 		prepare_to_wait(&drbd_pp_wait, &wait, TASK_INTERRUPTIBLE);
 
 		drbd_kick_lo_and_reclaim_net(mdev);
 
 		if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers) {
-			page = drbd_pp_first_page_or_try_alloc(mdev);
+			page = drbd_pp_first_pages_or_try_alloc(mdev, number);
 			if (page)
 				break;
 		}
@@ -190,62 +290,32 @@ static struct page *drbd_pp_alloc(struct drbd_conf *mdev, int retry)
 	}
 	finish_wait(&drbd_pp_wait, &wait);
 
+	if (page)
+		atomic_add(number, &mdev->pp_in_use);
 	return page;
 }
 
 /* Must not be used from irq, as that may deadlock: see drbd_pp_alloc.
- * Is also used from inside an other spin_lock_irq(&mdev->req_lock) */
+ * Is also used from inside an other spin_lock_irq(&mdev->req_lock);
+ * Either links the page chain back to the global pool,
+ * or returns all pages to the system. */
 static void drbd_pp_free(struct drbd_conf *mdev, struct page *page)
 {
-	int free_it;
-
-	spin_lock(&drbd_pp_lock);
-	if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count) {
-		free_it = 1;
-	} else {
-		set_page_private(page, (unsigned long)drbd_pp_pool);
-		drbd_pp_pool = page;
-		drbd_pp_vacant++;
-		free_it = 0;
-	}
-	spin_unlock(&drbd_pp_lock);
-
-	atomic_dec(&mdev->pp_in_use);
-
-	if (free_it)
-		__free_page(page);
-
-	wake_up(&drbd_pp_wait);
-}
-
-static void drbd_pp_free_bio_pages(struct drbd_conf *mdev, struct bio *bio)
-{
-	struct page *p_to_be_freed = NULL;
-	struct page *page;
-	struct bio_vec *bvec;
 	int i;
-
-	spin_lock(&drbd_pp_lock);
-	__bio_for_each_segment(bvec, bio, i, 0) {
-		if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count) {
-			set_page_private(bvec->bv_page, (unsigned long)p_to_be_freed);
-			p_to_be_freed = bvec->bv_page;
-		} else {
-			set_page_private(bvec->bv_page, (unsigned long)drbd_pp_pool);
-			drbd_pp_pool = bvec->bv_page;
-			drbd_pp_vacant++;
-		}
-	}
-	spin_unlock(&drbd_pp_lock);
-	atomic_sub(bio->bi_vcnt, &mdev->pp_in_use);
-
-	while (p_to_be_freed) {
-		page = p_to_be_freed;
-		p_to_be_freed = (struct page *)page_private(page);
-		set_page_private(page, 0); /* just to be polite */
-		put_page(page);
+	if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count)
+		i = page_chain_free(page);
+	else {
+		struct page *tmp;
+		tmp = page_chain_tail(page, &i);
+		spin_lock(&drbd_pp_lock);
+		page_chain_add(&drbd_pp_pool, page, tmp);
+		drbd_pp_vacant += i;
+		spin_unlock(&drbd_pp_lock);
 	}
-
+	atomic_sub(i, &mdev->pp_in_use);
+	i = atomic_read(&mdev->pp_in_use);
+	if (i < 0)
+		dev_warn(DEV, "ASSERTION FAILED: pp_in_use: %d < 0\n", i);
 	wake_up(&drbd_pp_wait);
 }
 
@@ -270,11 +340,9 @@ struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
 				     unsigned int data_size,
 				     gfp_t gfp_mask) __must_hold(local)
 {
-	struct request_queue *q;
 	struct drbd_epoch_entry *e;
 	struct page *page;
-	struct bio *bio;
-	unsigned int ds;
+	unsigned nr_pages = (data_size + PAGE_SIZE -1) >> PAGE_SHIFT;
 
 	if (FAULT_ACTIVE(mdev, DRBD_FAULT_AL_EE))
 		return NULL;
@@ -286,84 +354,32 @@ struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
 		return NULL;
 	}
 
-	bio = bio_alloc(gfp_mask & ~__GFP_HIGHMEM, div_ceil(data_size, PAGE_SIZE));
-	if (!bio) {
-		if (!(gfp_mask & __GFP_NOWARN))
-			dev_err(DEV, "alloc_ee: Allocation of a bio failed\n");
-		goto fail1;
-	}
-
-	bio->bi_bdev = mdev->ldev->backing_bdev;
-	bio->bi_sector = sector;
-
-	ds = data_size;
-	while (ds) {
-		page = drbd_pp_alloc(mdev, (gfp_mask & __GFP_WAIT));
-		if (!page) {
-			if (!(gfp_mask & __GFP_NOWARN))
-				dev_err(DEV, "alloc_ee: Allocation of a page failed\n");
-			goto fail2;
-		}
-		if (!bio_add_page(bio, page, min_t(int, ds, PAGE_SIZE), 0)) {
-			drbd_pp_free(mdev, page);
-			dev_err(DEV, "alloc_ee: bio_add_page(s=%llu,"
-			    "data_size=%u,ds=%u) failed\n",
-			    (unsigned long long)sector, data_size, ds);
-
-			q = bdev_get_queue(bio->bi_bdev);
-			if (q->merge_bvec_fn) {
-				struct bvec_merge_data bvm = {
-					.bi_bdev = bio->bi_bdev,
-					.bi_sector = bio->bi_sector,
-					.bi_size = bio->bi_size,
-					.bi_rw = bio->bi_rw,
-				};
-				int l = q->merge_bvec_fn(q, &bvm,
-						&bio->bi_io_vec[bio->bi_vcnt]);
-				dev_err(DEV, "merge_bvec_fn() = %d\n", l);
-			}
-
-			/* dump more of the bio. */
-			dev_err(DEV, "bio->bi_max_vecs = %d\n", bio->bi_max_vecs);
-			dev_err(DEV, "bio->bi_vcnt = %d\n", bio->bi_vcnt);
-			dev_err(DEV, "bio->bi_size = %d\n", bio->bi_size);
-			dev_err(DEV, "bio->bi_phys_segments = %d\n", bio->bi_phys_segments);
-
-			goto fail2;
-			break;
-		}
-		ds -= min_t(int, ds, PAGE_SIZE);
-	}
-
-	D_ASSERT(data_size == bio->bi_size);
-
-	bio->bi_private = e;
-	e->mdev = mdev;
-	e->sector = sector;
-	e->size = bio->bi_size;
+	page = drbd_pp_alloc(mdev, nr_pages, (gfp_mask & __GFP_WAIT));
+	if (!page)
+		goto fail;
 
-	e->private_bio = bio;
-	e->block_id = id;
 	INIT_HLIST_NODE(&e->colision);
 	e->epoch = NULL;
+	e->mdev = mdev;
+	e->pages = page;
+	atomic_set(&e->pending_bios, 0);
+	e->size = data_size;
 	e->flags = 0;
+	e->sector = sector;
+	e->sector = sector;
+	e->block_id = id;
 
 	return e;
 
- fail2:
-	drbd_pp_free_bio_pages(mdev, bio);
-	bio_put(bio);
- fail1:
+ fail:
 	mempool_free(e, drbd_ee_mempool);
-
 	return NULL;
 }
 
 void drbd_free_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
 {
-	struct bio *bio = e->private_bio;
-	drbd_pp_free_bio_pages(mdev, bio);
-	bio_put(bio);
+	drbd_pp_free(mdev, e->pages);
+	D_ASSERT(atomic_read(&e->pending_bios) == 0);
 	D_ASSERT(hlist_unhashed(&e->colision));
 	mempool_free(e, drbd_ee_mempool);
 }
@@ -902,7 +918,7 @@ retry:
 	if (!drbd_send_protocol(mdev))
 		return -1;
 	drbd_send_sync_param(mdev, &mdev->sync_conf);
-	drbd_send_sizes(mdev, 0);
+	drbd_send_sizes(mdev, 0, 0);
 	drbd_send_uuids(mdev);
 	drbd_send_state(mdev);
 	clear_bit(USE_DEGR_WFC_T, &mdev->flags);
@@ -946,7 +962,8 @@ static enum finish_epoch drbd_flush_after_epoch(struct drbd_conf *mdev, struct d
 	int rv;
 
 	if (mdev->write_ordering >= WO_bdev_flush && get_ldev(mdev)) {
-		rv = blkdev_issue_flush(mdev->ldev->backing_bdev, NULL);
+		rv = blkdev_issue_flush(mdev->ldev->backing_bdev, GFP_KERNEL,
+					NULL, BLKDEV_IFL_WAIT);
 		if (rv) {
 			dev_err(DEV, "local disk flush failed with status %d\n", rv);
 			/* would rather check on EOPNOTSUPP, but that is not reliable.
@@ -1120,6 +1137,101 @@ void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo)
 }
 
 /**
+ * drbd_submit_ee()
+ * @mdev:	DRBD device.
+ * @e:		epoch entry
+ * @rw:		flag field, see bio->bi_rw
+ */
+/* TODO allocate from our own bio_set. */
+int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
+		const unsigned rw, const int fault_type)
+{
+	struct bio *bios = NULL;
+	struct bio *bio;
+	struct page *page = e->pages;
+	sector_t sector = e->sector;
+	unsigned ds = e->size;
+	unsigned n_bios = 0;
+	unsigned nr_pages = (ds + PAGE_SIZE -1) >> PAGE_SHIFT;
+
+	if (atomic_read(&mdev->new_c_uuid)) {
+		if (atomic_add_unless(&mdev->new_c_uuid, -1, 1)) {
+			drbd_uuid_new_current(mdev);
+			drbd_md_sync(mdev);
+
+			atomic_dec(&mdev->new_c_uuid);
+			wake_up(&mdev->misc_wait);
+		}
+		wait_event(mdev->misc_wait, !atomic_read(&mdev->new_c_uuid));
+	}
+
+	/* In most cases, we will only need one bio.  But in case the lower
+	 * level restrictions happen to be different at this offset on this
+	 * side than those of the sending peer, we may need to submit the
+	 * request in more than one bio. */
+next_bio:
+	bio = bio_alloc(GFP_NOIO, nr_pages);
+	if (!bio) {
+		dev_err(DEV, "submit_ee: Allocation of a bio failed\n");
+		goto fail;
+	}
+	/* > e->sector, unless this is the first bio */
+	bio->bi_sector = sector;
+	bio->bi_bdev = mdev->ldev->backing_bdev;
+	/* we special case some flags in the multi-bio case, see below
+	 * (BIO_RW_UNPLUG, BIO_RW_BARRIER) */
+	bio->bi_rw = rw;
+	bio->bi_private = e;
+	bio->bi_end_io = drbd_endio_sec;
+
+	bio->bi_next = bios;
+	bios = bio;
+	++n_bios;
+
+	page_chain_for_each(page) {
+		unsigned len = min_t(unsigned, ds, PAGE_SIZE);
+		if (!bio_add_page(bio, page, len, 0)) {
+			/* a single page must always be possible! */
+			BUG_ON(bio->bi_vcnt == 0);
+			goto next_bio;
+		}
+		ds -= len;
+		sector += len >> 9;
+		--nr_pages;
+	}
+	D_ASSERT(page == NULL);
+	D_ASSERT(ds == 0);
+
+	atomic_set(&e->pending_bios, n_bios);
+	do {
+		bio = bios;
+		bios = bios->bi_next;
+		bio->bi_next = NULL;
+
+		/* strip off BIO_RW_UNPLUG unless it is the last bio */
+		if (bios)
+			bio->bi_rw &= ~(1<<BIO_RW_UNPLUG);
+
+		drbd_generic_make_request(mdev, fault_type, bio);
+
+		/* strip off BIO_RW_BARRIER,
+		 * unless it is the first or last bio */
+		if (bios && bios->bi_next)
+			bios->bi_rw &= ~(1<<BIO_RW_BARRIER);
+	} while (bios);
+	maybe_kick_lo(mdev);
+	return 0;
+
+fail:
+	while (bios) {
+		bio = bios;
+		bios = bios->bi_next;
+		bio_put(bio);
+	}
+	return -ENOMEM;
+}
+
+/**
  * w_e_reissue() - Worker callback; Resubmit a bio, without BIO_RW_BARRIER set
  * @mdev:	DRBD device.
  * @w:		work object.
@@ -1128,8 +1240,6 @@ void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo)
 int w_e_reissue(struct drbd_conf *mdev, struct drbd_work *w, int cancel) __releases(local)
 {
 	struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
-	struct bio *bio = e->private_bio;
-
 	/* We leave DE_CONTAINS_A_BARRIER and EE_IS_BARRIER in place,
 	   (and DE_BARRIER_IN_NEXT_EPOCH_ISSUED in the previous Epoch)
 	   so that we can finish that epoch in drbd_may_finish_epoch().
@@ -1143,33 +1253,17 @@ int w_e_reissue(struct drbd_conf *mdev, struct drbd_work *w, int cancel) __relea
 	if (previous_epoch(mdev, e->epoch))
 		dev_warn(DEV, "Write ordering was not enforced (one time event)\n");
 
-	/* prepare bio for re-submit,
-	 * re-init volatile members */
 	/* we still have a local reference,
 	 * get_ldev was done in receive_Data. */
-	bio->bi_bdev = mdev->ldev->backing_bdev;
-	bio->bi_sector = e->sector;
-	bio->bi_size = e->size;
-	bio->bi_idx = 0;
-
-	bio->bi_flags &= ~(BIO_POOL_MASK - 1);
-	bio->bi_flags |= 1 << BIO_UPTODATE;
-
-	/* don't know whether this is necessary: */
-	bio->bi_phys_segments = 0;
-	bio->bi_next = NULL;
-
-	/* these should be unchanged: */
-	/* bio->bi_end_io = drbd_endio_write_sec; */
-	/* bio->bi_vcnt = whatever; */
 
 	e->w.cb = e_end_block;
-
-	/* This is no longer a barrier request. */
-	bio->bi_rw &= ~(1UL << BIO_RW_BARRIER);
-
-	drbd_generic_make_request(mdev, DRBD_FAULT_DT_WR, bio);
-
+	if (drbd_submit_ee(mdev, e, WRITE, DRBD_FAULT_DT_WR) != 0) {
+		/* drbd_submit_ee fails for one reason only:
+		 * if was not able to allocate sufficient bios.
+		 * requeue, try again later. */
+		e->w.cb = w_e_reissue;
+		drbd_queue_work(&mdev->data.work, &e->w);
+	}
 	return 1;
 }
 
@@ -1261,13 +1355,13 @@ static int receive_Barrier(struct drbd_conf *mdev, struct p_header *h)
 static struct drbd_epoch_entry *
 read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __must_hold(local)
 {
+	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
 	struct drbd_epoch_entry *e;
-	struct bio_vec *bvec;
 	struct page *page;
-	struct bio *bio;
-	int dgs, ds, i, rr;
+	int dgs, ds, rr;
 	void *dig_in = mdev->int_dig_in;
 	void *dig_vv = mdev->int_dig_vv;
+	unsigned long *data;
 
 	dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
 		crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
@@ -1286,29 +1380,44 @@ read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __
 	ERR_IF(data_size &  0x1ff) return NULL;
 	ERR_IF(data_size >  DRBD_MAX_SEGMENT_SIZE) return NULL;
 
+	/* even though we trust out peer,
+	 * we sometimes have to double check. */
+	if (sector + (data_size>>9) > capacity) {
+		dev_err(DEV, "capacity: %llus < sector: %llus + size: %u\n",
+			(unsigned long long)capacity,
+			(unsigned long long)sector, data_size);
+		return NULL;
+	}
+
 	/* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
 	 * "criss-cross" setup, that might cause write-out on some other DRBD,
 	 * which in turn might block on the other node at this very place.  */
 	e = drbd_alloc_ee(mdev, id, sector, data_size, GFP_NOIO);
 	if (!e)
 		return NULL;
-	bio = e->private_bio;
+
 	ds = data_size;
-	bio_for_each_segment(bvec, bio, i) {
-		page = bvec->bv_page;
-		rr = drbd_recv(mdev, kmap(page), min_t(int, ds, PAGE_SIZE));
+	page = e->pages;
+	page_chain_for_each(page) {
+		unsigned len = min_t(int, ds, PAGE_SIZE);
+		data = kmap(page);
+		rr = drbd_recv(mdev, data, len);
+		if (FAULT_ACTIVE(mdev, DRBD_FAULT_RECEIVE)) {
+			dev_err(DEV, "Fault injection: Corrupting data on receive\n");
+			data[0] = data[0] ^ (unsigned long)-1;
+		}
 		kunmap(page);
-		if (rr != min_t(int, ds, PAGE_SIZE)) {
+		if (rr != len) {
 			drbd_free_ee(mdev, e);
 			dev_warn(DEV, "short read receiving data: read %d expected %d\n",
-			     rr, min_t(int, ds, PAGE_SIZE));
+			     rr, len);
 			return NULL;
 		}
 		ds -= rr;
 	}
 
 	if (dgs) {
-		drbd_csum(mdev, mdev->integrity_r_tfm, bio, dig_vv);
+		drbd_csum_ee(mdev, mdev->integrity_r_tfm, e, dig_vv);
 		if (memcmp(dig_in, dig_vv, dgs)) {
 			dev_err(DEV, "Digest integrity check FAILED.\n");
 			drbd_bcast_ee(mdev, "digest failed",
@@ -1330,7 +1439,10 @@ static int drbd_drain_block(struct drbd_conf *mdev, int data_size)
 	int rr, rv = 1;
 	void *data;
 
-	page = drbd_pp_alloc(mdev, 1);
+	if (!data_size)
+		return TRUE;
+
+	page = drbd_pp_alloc(mdev, 1, 1);
 
 	data = kmap(page);
 	while (data_size) {
@@ -1394,7 +1506,7 @@ static int recv_dless_read(struct drbd_conf *mdev, struct drbd_request *req,
 	}
 
 	if (dgs) {
-		drbd_csum(mdev, mdev->integrity_r_tfm, bio, dig_vv);
+		drbd_csum_bio(mdev, mdev->integrity_r_tfm, bio, dig_vv);
 		if (memcmp(dig_in, dig_vv, dgs)) {
 			dev_err(DEV, "Digest integrity check FAILED. Broken NICs?\n");
 			return 0;
@@ -1415,7 +1527,7 @@ static int e_end_resync_block(struct drbd_conf *mdev, struct drbd_work *w, int u
 
 	D_ASSERT(hlist_unhashed(&e->colision));
 
-	if (likely(drbd_bio_uptodate(e->private_bio))) {
+	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 		drbd_set_in_sync(mdev, sector, e->size);
 		ok = drbd_send_ack(mdev, P_RS_WRITE_ACK, e);
 	} else {
@@ -1434,30 +1546,28 @@ static int recv_resync_read(struct drbd_conf *mdev, sector_t sector, int data_si
 	struct drbd_epoch_entry *e;
 
 	e = read_in_block(mdev, ID_SYNCER, sector, data_size);
-	if (!e) {
-		put_ldev(mdev);
-		return FALSE;
-	}
+	if (!e)
+		goto fail;
 
 	dec_rs_pending(mdev);
 
-	e->private_bio->bi_end_io = drbd_endio_write_sec;
-	e->private_bio->bi_rw = WRITE;
-	e->w.cb = e_end_resync_block;
-
 	inc_unacked(mdev);
 	/* corresponding dec_unacked() in e_end_resync_block()
 	 * respective _drbd_clear_done_ee */
 
+	e->w.cb = e_end_resync_block;
+
 	spin_lock_irq(&mdev->req_lock);
 	list_add(&e->w.list, &mdev->sync_ee);
 	spin_unlock_irq(&mdev->req_lock);
 
-	drbd_generic_make_request(mdev, DRBD_FAULT_RS_WR, e->private_bio);
-	/* accounting done in endio */
+	if (drbd_submit_ee(mdev, e, WRITE, DRBD_FAULT_RS_WR) == 0)
+		return TRUE;
 
-	maybe_kick_lo(mdev);
-	return TRUE;
+	drbd_free_ee(mdev, e);
+fail:
+	put_ldev(mdev);
+	return FALSE;
 }
 
 static int receive_DataReply(struct drbd_conf *mdev, struct p_header *h)
@@ -1552,7 +1662,7 @@ static int e_end_block(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 	}
 
 	if (mdev->net_conf->wire_protocol == DRBD_PROT_C) {
-		if (likely(drbd_bio_uptodate(e->private_bio))) {
+		if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 			pcmd = (mdev->state.conn >= C_SYNC_SOURCE &&
 				mdev->state.conn <= C_PAUSED_SYNC_T &&
 				e->flags & EE_MAY_SET_IN_SYNC) ?
@@ -1698,7 +1808,6 @@ static int receive_Data(struct drbd_conf *mdev, struct p_header *h)
 		return FALSE;
 	}
 
-	e->private_bio->bi_end_io = drbd_endio_write_sec;
 	e->w.cb = e_end_block;
 
 	spin_lock(&mdev->epoch_lock);
@@ -1894,12 +2003,8 @@ static int receive_Data(struct drbd_conf *mdev, struct p_header *h)
 		drbd_al_begin_io(mdev, e->sector);
 	}
 
-	e->private_bio->bi_rw = rw;
-	drbd_generic_make_request(mdev, DRBD_FAULT_DT_WR, e->private_bio);
-	/* accounting done in endio */
-
-	maybe_kick_lo(mdev);
-	return TRUE;
+	if (drbd_submit_ee(mdev, e, rw, DRBD_FAULT_DT_WR) == 0)
+		return TRUE;
 
 out_interrupted:
 	/* yes, the epoch_size now is imbalanced.
@@ -1945,7 +2050,7 @@ static int receive_DataRequest(struct drbd_conf *mdev, struct p_header *h)
 			    "no local data.\n");
 		drbd_send_ack_rp(mdev, h->command == P_DATA_REQUEST ? P_NEG_DREPLY :
 				 P_NEG_RS_DREPLY , p);
-		return TRUE;
+		return drbd_drain_block(mdev, h->length - brps);
 	}
 
 	/* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
@@ -1957,9 +2062,6 @@ static int receive_DataRequest(struct drbd_conf *mdev, struct p_header *h)
 		return FALSE;
 	}
 
-	e->private_bio->bi_rw = READ;
-	e->private_bio->bi_end_io = drbd_endio_read_sec;
-
 	switch (h->command) {
 	case P_DATA_REQUEST:
 		e->w.cb = w_e_end_data_req;
@@ -2053,10 +2155,8 @@ static int receive_DataRequest(struct drbd_conf *mdev, struct p_header *h)
 
 	inc_unacked(mdev);
 
-	drbd_generic_make_request(mdev, fault_type, e->private_bio);
-	maybe_kick_lo(mdev);
-
-	return TRUE;
+	if (drbd_submit_ee(mdev, e, READ, fault_type) == 0)
+		return TRUE;
 
 out_free_e:
 	kfree(di);
@@ -2473,6 +2573,9 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_rol
 		     hg > 0 ? "source" : "target");
 	}
 
+	if (abs(hg) == 100)
+		drbd_khelper(mdev, "initial-split-brain");
+
 	if (hg == 100 || (hg == -100 && mdev->net_conf->always_asbp)) {
 		int pcount = (mdev->state.role == R_PRIMARY)
 			   + (peer_role == R_PRIMARY);
@@ -2518,7 +2621,7 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_rol
 		 * after an attempted attach on a diskless node.
 		 * We just refuse to attach -- well, we drop the "connection"
 		 * to that disk, in a way... */
-		dev_alert(DEV, "Split-Brain detected, dropping connection!\n");
+		dev_alert(DEV, "Split-Brain detected but unresolved, dropping connection!\n");
 		drbd_khelper(mdev, "split-brain");
 		return C_MASK;
 	}
@@ -2849,7 +2952,7 @@ static int receive_sizes(struct drbd_conf *mdev, struct p_header *h)
 	unsigned int max_seg_s;
 	sector_t p_size, p_usize, my_usize;
 	int ldsc = 0; /* local disk size changed */
-	enum drbd_conns nconn;
+	enum dds_flags ddsf;
 
 	ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
 	if (drbd_recv(mdev, h->payload, h->length) != h->length)
@@ -2905,8 +3008,9 @@ static int receive_sizes(struct drbd_conf *mdev, struct p_header *h)
 	}
 #undef min_not_zero
 
+	ddsf = be16_to_cpu(p->dds_flags);
 	if (get_ldev(mdev)) {
-	  dd = drbd_determin_dev_size(mdev, 0);
+		dd = drbd_determin_dev_size(mdev, ddsf);
 		put_ldev(mdev);
 		if (dd == dev_size_error)
 			return FALSE;
@@ -2916,33 +3020,21 @@ static int receive_sizes(struct drbd_conf *mdev, struct p_header *h)
 		drbd_set_my_capacity(mdev, p_size);
 	}
 
-	if (mdev->p_uuid && mdev->state.conn <= C_CONNECTED && get_ldev(mdev)) {
-		nconn = drbd_sync_handshake(mdev,
-				mdev->state.peer, mdev->state.pdsk);
-		put_ldev(mdev);
-
-		if (nconn == C_MASK) {
-			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-			return FALSE;
-		}
-
-		if (drbd_request_state(mdev, NS(conn, nconn)) < SS_SUCCESS) {
-			drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
-			return FALSE;
-		}
-	}
-
 	if (get_ldev(mdev)) {
 		if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
 			mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
 			ldsc = 1;
 		}
 
-		max_seg_s = be32_to_cpu(p->max_segment_size);
+		if (mdev->agreed_pro_version < 94)
+			max_seg_s = be32_to_cpu(p->max_segment_size);
+		else /* drbd 8.3.8 onwards */
+			max_seg_s = DRBD_MAX_SEGMENT_SIZE;
+
 		if (max_seg_s != queue_max_segment_size(mdev->rq_queue))
 			drbd_setup_queue_param(mdev, max_seg_s);
 
-		drbd_setup_order_type(mdev, be32_to_cpu(p->queue_order_type));
+		drbd_setup_order_type(mdev, be16_to_cpu(p->queue_order_type));
 		put_ldev(mdev);
 	}
 
@@ -2951,14 +3043,17 @@ static int receive_sizes(struct drbd_conf *mdev, struct p_header *h)
 		    drbd_get_capacity(mdev->this_bdev) || ldsc) {
 			/* we have different sizes, probably peer
 			 * needs to know my new size... */
-			drbd_send_sizes(mdev, 0);
+			drbd_send_sizes(mdev, 0, ddsf);
 		}
 		if (test_and_clear_bit(RESIZE_PENDING, &mdev->flags) ||
 		    (dd == grew && mdev->state.conn == C_CONNECTED)) {
 			if (mdev->state.pdsk >= D_INCONSISTENT &&
-			    mdev->state.disk >= D_INCONSISTENT)
-				resync_after_online_grow(mdev);
-			else
+			    mdev->state.disk >= D_INCONSISTENT) {
+				if (ddsf & DDSF_NO_RESYNC)
+					dev_info(DEV, "Resync of new storage suppressed with --assume-clean\n");
+				else
+					resync_after_online_grow(mdev);
+			} else
 				set_bit(RESYNC_AFTER_NEG, &mdev->flags);
 		}
 	}
@@ -3490,6 +3585,92 @@ static int receive_UnplugRemote(struct drbd_conf *mdev, struct p_header *h)
 	return TRUE;
 }
 
+static void timeval_sub_us(struct timeval* tv, unsigned int us)
+{
+	tv->tv_sec -= us / 1000000;
+	us = us % 1000000;
+	if (tv->tv_usec > us) {
+		tv->tv_usec += 1000000;
+		tv->tv_sec--;
+	}
+	tv->tv_usec -= us;
+}
+
+static void got_delay_probe(struct drbd_conf *mdev, int from, struct p_delay_probe *p)
+{
+	struct delay_probe *dp;
+	struct list_head *le;
+	struct timeval now;
+	int seq_num;
+	int offset;
+	int data_delay;
+
+	seq_num = be32_to_cpu(p->seq_num);
+	offset  = be32_to_cpu(p->offset);
+
+	spin_lock(&mdev->peer_seq_lock);
+	if (!list_empty(&mdev->delay_probes)) {
+		if (from == USE_DATA_SOCKET)
+			le = mdev->delay_probes.next;
+		else
+			le = mdev->delay_probes.prev;
+
+		dp = list_entry(le, struct delay_probe, list);
+
+		if (dp->seq_num == seq_num) {
+			list_del(le);
+			spin_unlock(&mdev->peer_seq_lock);
+			do_gettimeofday(&now);
+			timeval_sub_us(&now, offset);
+			data_delay =
+				now.tv_usec - dp->time.tv_usec +
+				(now.tv_sec - dp->time.tv_sec) * 1000000;
+
+			if (data_delay > 0)
+				mdev->data_delay = data_delay;
+
+			kfree(dp);
+			return;
+		}
+
+		if (dp->seq_num > seq_num) {
+			spin_unlock(&mdev->peer_seq_lock);
+			dev_warn(DEV, "Previous allocation failure of struct delay_probe?\n");
+			return; /* Do not alloca a struct delay_probe.... */
+		}
+	}
+	spin_unlock(&mdev->peer_seq_lock);
+
+	dp = kmalloc(sizeof(struct delay_probe), GFP_NOIO);
+	if (!dp) {
+		dev_warn(DEV, "Failed to allocate a struct delay_probe, do not worry.\n");
+		return;
+	}
+
+	dp->seq_num = seq_num;
+	do_gettimeofday(&dp->time);
+	timeval_sub_us(&dp->time, offset);
+
+	spin_lock(&mdev->peer_seq_lock);
+	if (from == USE_DATA_SOCKET)
+		list_add(&dp->list, &mdev->delay_probes);
+	else
+		list_add_tail(&dp->list, &mdev->delay_probes);
+	spin_unlock(&mdev->peer_seq_lock);
+}
+
+static int receive_delay_probe(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_delay_probe *p = (struct p_delay_probe *)h;
+
+	ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+	if (drbd_recv(mdev, h->payload, h->length) != h->length)
+		return FALSE;
+
+	got_delay_probe(mdev, USE_DATA_SOCKET, p);
+	return TRUE;
+}
+
 typedef int (*drbd_cmd_handler_f)(struct drbd_conf *, struct p_header *);
 
 static drbd_cmd_handler_f drbd_default_handler[] = {
@@ -3513,6 +3694,7 @@ static drbd_cmd_handler_f drbd_default_handler[] = {
 	[P_OV_REQUEST]      = receive_DataRequest,
 	[P_OV_REPLY]        = receive_DataRequest,
 	[P_CSUM_RS_REQUEST]    = receive_DataRequest,
+	[P_DELAY_PROBE]     = receive_delay_probe,
 	/* anything missing from this table is in
 	 * the asender_tbl, see get_asender_cmd */
 	[P_MAX_CMD]	    = NULL,
@@ -3739,7 +3921,7 @@ static void drbd_disconnect(struct drbd_conf *mdev)
 		dev_info(DEV, "net_ee not empty, killed %u entries\n", i);
 	i = atomic_read(&mdev->pp_in_use);
 	if (i)
-		dev_info(DEV, "pp_in_use = %u, expected 0\n", i);
+		dev_info(DEV, "pp_in_use = %d, expected 0\n", i);
 
 	D_ASSERT(list_empty(&mdev->read_ee));
 	D_ASSERT(list_empty(&mdev->active_ee));
@@ -4232,7 +4414,6 @@ static int got_NegRSDReply(struct drbd_conf *mdev, struct p_header *h)
 
 	sector = be64_to_cpu(p->sector);
 	size = be32_to_cpu(p->blksize);
-	D_ASSERT(p->block_id == ID_SYNCER);
 
 	update_peer_seq(mdev, be32_to_cpu(p->seq_num));
 
@@ -4290,6 +4471,14 @@ static int got_OVResult(struct drbd_conf *mdev, struct p_header *h)
 	return TRUE;
 }
 
+static int got_delay_probe_m(struct drbd_conf *mdev, struct p_header *h)
+{
+	struct p_delay_probe *p = (struct p_delay_probe *)h;
+
+	got_delay_probe(mdev, USE_META_SOCKET, p);
+	return TRUE;
+}
+
 struct asender_cmd {
 	size_t pkt_size;
 	int (*process)(struct drbd_conf *mdev, struct p_header *h);
@@ -4314,6 +4503,7 @@ static struct asender_cmd *get_asender_cmd(int cmd)
 	[P_BARRIER_ACK]	    = { sizeof(struct p_barrier_ack), got_BarrierAck },
 	[P_STATE_CHG_REPLY] = { sizeof(struct p_req_state_reply), got_RqSReply },
 	[P_RS_IS_IN_SYNC]   = { sizeof(struct p_block_ack), got_IsInSync },
+	[P_DELAY_PROBE]     = { sizeof(struct p_delay_probe), got_delay_probe_m },
 	[P_MAX_CMD]	    = { 0, NULL },
 	};
 	if (cmd > P_MAX_CMD || asender_tbl[cmd].process == NULL)
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index de81ab7b4627..3397f11d0ba9 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -722,6 +722,7 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
 	struct drbd_request *req;
 	int local, remote;
 	int err = -EIO;
+	int ret = 0;
 
 	/* allocate outside of all locks; */
 	req = drbd_req_new(mdev, bio);
@@ -784,7 +785,7 @@ static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
 			    (mdev->state.pdsk == D_INCONSISTENT &&
 			     mdev->state.conn >= C_CONNECTED));
 
-	if (!(local || remote)) {
+	if (!(local || remote) && !mdev->state.susp) {
 		dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
 		goto fail_free_complete;
 	}
@@ -810,6 +811,16 @@ allocate_barrier:
 	/* GOOD, everything prepared, grab the spin_lock */
 	spin_lock_irq(&mdev->req_lock);
 
+	if (mdev->state.susp) {
+		/* If we got suspended, use the retry mechanism of
+		   generic_make_request() to restart processing of this
+		   bio. In the next call to drbd_make_request_26
+		   we sleep in inc_ap_bio() */
+		ret = 1;
+		spin_unlock_irq(&mdev->req_lock);
+		goto fail_free_complete;
+	}
+
 	if (remote) {
 		remote = (mdev->state.pdsk == D_UP_TO_DATE ||
 			    (mdev->state.pdsk == D_INCONSISTENT &&
@@ -947,12 +958,14 @@ fail_and_free_req:
 		req->private_bio = NULL;
 		put_ldev(mdev);
 	}
-	bio_endio(bio, err);
+	if (!ret)
+		bio_endio(bio, err);
+
 	drbd_req_free(req);
 	dec_ap_bio(mdev);
 	kfree(b);
 
-	return 0;
+	return ret;
 }
 
 /* helper function for drbd_make_request
@@ -962,11 +975,6 @@ fail_and_free_req:
  */
 static int drbd_fail_request_early(struct drbd_conf *mdev, int is_write)
 {
-	/* Unconfigured */
-	if (mdev->state.conn == C_DISCONNECTING &&
-	    mdev->state.disk == D_DISKLESS)
-		return 1;
-
 	if (mdev->state.role != R_PRIMARY &&
 		(!allow_oos || is_write)) {
 		if (__ratelimit(&drbd_ratelimit_state)) {
@@ -1070,15 +1078,21 @@ int drbd_make_request_26(struct request_queue *q, struct bio *bio)
 
 		/* we need to get a "reference count" (ap_bio_cnt)
 		 * to avoid races with the disconnect/reconnect/suspend code.
-		 * In case we need to split the bio here, we need to get two references
+		 * In case we need to split the bio here, we need to get three references
 		 * atomically, otherwise we might deadlock when trying to submit the
 		 * second one! */
-		inc_ap_bio(mdev, 2);
+		inc_ap_bio(mdev, 3);
 
 		D_ASSERT(e_enr == s_enr + 1);
 
-		drbd_make_request_common(mdev, &bp->bio1);
-		drbd_make_request_common(mdev, &bp->bio2);
+		while (drbd_make_request_common(mdev, &bp->bio1))
+			inc_ap_bio(mdev, 1);
+
+		while (drbd_make_request_common(mdev, &bp->bio2))
+			inc_ap_bio(mdev, 1);
+
+		dec_ap_bio(mdev);
+
 		bio_pair_release(bp);
 	}
 	return 0;
@@ -1115,7 +1129,7 @@ int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct
 	} else if (limit && get_ldev(mdev)) {
 		struct request_queue * const b =
 			mdev->ldev->backing_bdev->bd_disk->queue;
-		if (b->merge_bvec_fn && mdev->ldev->dc.use_bmbv) {
+		if (b->merge_bvec_fn) {
 			backing_limit = b->merge_bvec_fn(b, bvm, bvec);
 			limit = min(limit, backing_limit);
 		}
diff --git a/drivers/block/drbd/drbd_strings.c b/drivers/block/drbd/drbd_strings.c
index 76863e3f05be..85179e1fb50a 100644
--- a/drivers/block/drbd/drbd_strings.c
+++ b/drivers/block/drbd/drbd_strings.c
@@ -70,7 +70,7 @@ static const char *drbd_disk_s_names[] = {
 
 static const char *drbd_state_sw_errors[] = {
 	[-SS_TWO_PRIMARIES] = "Multiple primaries not allowed by config",
-	[-SS_NO_UP_TO_DATE_DISK] = "Refusing to be Primary without at least one UpToDate disk",
+	[-SS_NO_UP_TO_DATE_DISK] = "Need access to UpToDate data",
 	[-SS_NO_LOCAL_DISK] = "Can not resync without local disk",
 	[-SS_NO_REMOTE_DISK] = "Can not resync without remote disk",
 	[-SS_CONNECTED_OUTDATES] = "Refusing to be Outdated while Connected",
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index d48a1dfd7b24..727ff6339754 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -47,8 +47,7 @@ static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int ca
 
 /* defined here:
    drbd_md_io_complete
-   drbd_endio_write_sec
-   drbd_endio_read_sec
+   drbd_endio_sec
    drbd_endio_pri
 
  * more endio handlers:
@@ -85,27 +84,10 @@ void drbd_md_io_complete(struct bio *bio, int error)
 /* reads on behalf of the partner,
  * "submitted" by the receiver
  */
-void drbd_endio_read_sec(struct bio *bio, int error) __releases(local)
+void drbd_endio_read_sec_final(struct drbd_epoch_entry *e) __releases(local)
 {
 	unsigned long flags = 0;
-	struct drbd_epoch_entry *e = NULL;
-	struct drbd_conf *mdev;
-	int uptodate = bio_flagged(bio, BIO_UPTODATE);
-
-	e = bio->bi_private;
-	mdev = e->mdev;
-
-	if (error)
-		dev_warn(DEV, "read: error=%d s=%llus\n", error,
-				(unsigned long long)e->sector);
-	if (!error && !uptodate) {
-		dev_warn(DEV, "read: setting error to -EIO s=%llus\n",
-				(unsigned long long)e->sector);
-		/* strange behavior of some lower level drivers...
-		 * fail the request by clearing the uptodate flag,
-		 * but do not return any error?! */
-		error = -EIO;
-	}
+	struct drbd_conf *mdev = e->mdev;
 
 	D_ASSERT(e->block_id != ID_VACANT);
 
@@ -114,49 +96,38 @@ void drbd_endio_read_sec(struct bio *bio, int error) __releases(local)
 	list_del(&e->w.list);
 	if (list_empty(&mdev->read_ee))
 		wake_up(&mdev->ee_wait);
+	if (test_bit(__EE_WAS_ERROR, &e->flags))
+		__drbd_chk_io_error(mdev, FALSE);
 	spin_unlock_irqrestore(&mdev->req_lock, flags);
 
-	drbd_chk_io_error(mdev, error, FALSE);
 	drbd_queue_work(&mdev->data.work, &e->w);
 	put_ldev(mdev);
 }
 
+static int is_failed_barrier(int ee_flags)
+{
+	return (ee_flags & (EE_IS_BARRIER|EE_WAS_ERROR|EE_RESUBMITTED))
+			== (EE_IS_BARRIER|EE_WAS_ERROR);
+}
+
 /* writes on behalf of the partner, or resync writes,
- * "submitted" by the receiver.
- */
-void drbd_endio_write_sec(struct bio *bio, int error) __releases(local)
+ * "submitted" by the receiver, final stage.  */
+static void drbd_endio_write_sec_final(struct drbd_epoch_entry *e) __releases(local)
 {
 	unsigned long flags = 0;
-	struct drbd_epoch_entry *e = NULL;
-	struct drbd_conf *mdev;
+	struct drbd_conf *mdev = e->mdev;
 	sector_t e_sector;
 	int do_wake;
 	int is_syncer_req;
 	int do_al_complete_io;
-	int uptodate = bio_flagged(bio, BIO_UPTODATE);
-	int is_barrier = bio_rw_flagged(bio, BIO_RW_BARRIER);
-
-	e = bio->bi_private;
-	mdev = e->mdev;
 
-	if (error)
-		dev_warn(DEV, "write: error=%d s=%llus\n", error,
-				(unsigned long long)e->sector);
-	if (!error && !uptodate) {
-		dev_warn(DEV, "write: setting error to -EIO s=%llus\n",
-				(unsigned long long)e->sector);
-		/* strange behavior of some lower level drivers...
-		 * fail the request by clearing the uptodate flag,
-		 * but do not return any error?! */
-		error = -EIO;
-	}
-
-	/* error == -ENOTSUPP would be a better test,
-	 * alas it is not reliable */
-	if (error && is_barrier && e->flags & EE_IS_BARRIER) {
+	/* if this is a failed barrier request, disable use of barriers,
+	 * and schedule for resubmission */
+	if (is_failed_barrier(e->flags)) {
 		drbd_bump_write_ordering(mdev, WO_bdev_flush);
 		spin_lock_irqsave(&mdev->req_lock, flags);
 		list_del(&e->w.list);
+		e->flags = (e->flags & ~EE_WAS_ERROR) | EE_RESUBMITTED;
 		e->w.cb = w_e_reissue;
 		/* put_ldev actually happens below, once we come here again. */
 		__release(local);
@@ -167,17 +138,16 @@ void drbd_endio_write_sec(struct bio *bio, int error) __releases(local)
 
 	D_ASSERT(e->block_id != ID_VACANT);
 
-	spin_lock_irqsave(&mdev->req_lock, flags);
-	mdev->writ_cnt += e->size >> 9;
-	is_syncer_req = is_syncer_block_id(e->block_id);
-
 	/* after we moved e to done_ee,
 	 * we may no longer access it,
 	 * it may be freed/reused already!
 	 * (as soon as we release the req_lock) */
 	e_sector = e->sector;
 	do_al_complete_io = e->flags & EE_CALL_AL_COMPLETE_IO;
+	is_syncer_req = is_syncer_block_id(e->block_id);
 
+	spin_lock_irqsave(&mdev->req_lock, flags);
+	mdev->writ_cnt += e->size >> 9;
 	list_del(&e->w.list); /* has been on active_ee or sync_ee */
 	list_add_tail(&e->w.list, &mdev->done_ee);
 
@@ -190,7 +160,7 @@ void drbd_endio_write_sec(struct bio *bio, int error) __releases(local)
 		? list_empty(&mdev->sync_ee)
 		: list_empty(&mdev->active_ee);
 
-	if (error)
+	if (test_bit(__EE_WAS_ERROR, &e->flags))
 		__drbd_chk_io_error(mdev, FALSE);
 	spin_unlock_irqrestore(&mdev->req_lock, flags);
 
@@ -205,7 +175,42 @@ void drbd_endio_write_sec(struct bio *bio, int error) __releases(local)
 
 	wake_asender(mdev);
 	put_ldev(mdev);
+}
+
+/* writes on behalf of the partner, or resync writes,
+ * "submitted" by the receiver.
+ */
+void drbd_endio_sec(struct bio *bio, int error)
+{
+	struct drbd_epoch_entry *e = bio->bi_private;
+	struct drbd_conf *mdev = e->mdev;
+	int uptodate = bio_flagged(bio, BIO_UPTODATE);
+	int is_write = bio_data_dir(bio) == WRITE;
+
+	if (error)
+		dev_warn(DEV, "%s: error=%d s=%llus\n",
+				is_write ? "write" : "read", error,
+				(unsigned long long)e->sector);
+	if (!error && !uptodate) {
+		dev_warn(DEV, "%s: setting error to -EIO s=%llus\n",
+				is_write ? "write" : "read",
+				(unsigned long long)e->sector);
+		/* strange behavior of some lower level drivers...
+		 * fail the request by clearing the uptodate flag,
+		 * but do not return any error?! */
+		error = -EIO;
+	}
+
+	if (error)
+		set_bit(__EE_WAS_ERROR, &e->flags);
 
+	bio_put(bio); /* no need for the bio anymore */
+	if (atomic_dec_and_test(&e->pending_bios)) {
+		if (is_write)
+			drbd_endio_write_sec_final(e);
+		else
+			drbd_endio_read_sec_final(e);
+	}
 }
 
 /* read, readA or write requests on R_PRIMARY coming from drbd_make_request
@@ -295,7 +300,34 @@ int w_resync_inactive(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 	return 1; /* Simply ignore this! */
 }
 
-void drbd_csum(struct drbd_conf *mdev, struct crypto_hash *tfm, struct bio *bio, void *digest)
+void drbd_csum_ee(struct drbd_conf *mdev, struct crypto_hash *tfm, struct drbd_epoch_entry *e, void *digest)
+{
+	struct hash_desc desc;
+	struct scatterlist sg;
+	struct page *page = e->pages;
+	struct page *tmp;
+	unsigned len;
+
+	desc.tfm = tfm;
+	desc.flags = 0;
+
+	sg_init_table(&sg, 1);
+	crypto_hash_init(&desc);
+
+	while ((tmp = page_chain_next(page))) {
+		/* all but the last page will be fully used */
+		sg_set_page(&sg, page, PAGE_SIZE, 0);
+		crypto_hash_update(&desc, &sg, sg.length);
+		page = tmp;
+	}
+	/* and now the last, possibly only partially used page */
+	len = e->size & (PAGE_SIZE - 1);
+	sg_set_page(&sg, page, len ?: PAGE_SIZE, 0);
+	crypto_hash_update(&desc, &sg, sg.length);
+	crypto_hash_final(&desc, digest);
+}
+
+void drbd_csum_bio(struct drbd_conf *mdev, struct crypto_hash *tfm, struct bio *bio, void *digest)
 {
 	struct hash_desc desc;
 	struct scatterlist sg;
@@ -329,11 +361,11 @@ static int w_e_send_csum(struct drbd_conf *mdev, struct drbd_work *w, int cancel
 		return 1;
 	}
 
-	if (likely(drbd_bio_uptodate(e->private_bio))) {
+	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 		digest_size = crypto_hash_digestsize(mdev->csums_tfm);
 		digest = kmalloc(digest_size, GFP_NOIO);
 		if (digest) {
-			drbd_csum(mdev, mdev->csums_tfm, e->private_bio, digest);
+			drbd_csum_ee(mdev, mdev->csums_tfm, e, digest);
 
 			inc_rs_pending(mdev);
 			ok = drbd_send_drequest_csum(mdev,
@@ -369,23 +401,21 @@ static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size)
 	/* GFP_TRY, because if there is no memory available right now, this may
 	 * be rescheduled for later. It is "only" background resync, after all. */
 	e = drbd_alloc_ee(mdev, DRBD_MAGIC+0xbeef, sector, size, GFP_TRY);
-	if (!e) {
-		put_ldev(mdev);
-		return 2;
-	}
+	if (!e)
+		goto fail;
 
 	spin_lock_irq(&mdev->req_lock);
 	list_add(&e->w.list, &mdev->read_ee);
 	spin_unlock_irq(&mdev->req_lock);
 
-	e->private_bio->bi_end_io = drbd_endio_read_sec;
-	e->private_bio->bi_rw = READ;
 	e->w.cb = w_e_send_csum;
+	if (drbd_submit_ee(mdev, e, READ, DRBD_FAULT_RS_RD) == 0)
+		return 1;
 
-	mdev->read_cnt += size >> 9;
-	drbd_generic_make_request(mdev, DRBD_FAULT_RS_RD, e->private_bio);
-
-	return 1;
+	drbd_free_ee(mdev, e);
+fail:
+	put_ldev(mdev);
+	return 2;
 }
 
 void resync_timer_fn(unsigned long data)
@@ -414,13 +444,25 @@ void resync_timer_fn(unsigned long data)
 		drbd_queue_work(&mdev->data.work, &mdev->resync_work);
 }
 
+static int calc_resync_rate(struct drbd_conf *mdev)
+{
+	int d = mdev->data_delay / 1000; /* us -> ms */
+	int td = mdev->sync_conf.throttle_th * 100;  /* 0.1s -> ms */
+	int hd = mdev->sync_conf.hold_off_th * 100;  /* 0.1s -> ms */
+	int cr = mdev->sync_conf.rate;
+
+	return d <= td ? cr :
+		d >= hd ? 0 :
+		cr + (cr * (td - d) / (hd - td));
+}
+
 int w_make_resync_request(struct drbd_conf *mdev,
 		struct drbd_work *w, int cancel)
 {
 	unsigned long bit;
 	sector_t sector;
 	const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
-	int max_segment_size = queue_max_segment_size(mdev->rq_queue);
+	int max_segment_size;
 	int number, i, size, pe, mx;
 	int align, queued, sndbuf;
 
@@ -446,7 +488,13 @@ int w_make_resync_request(struct drbd_conf *mdev,
 		return 1;
 	}
 
-	number = SLEEP_TIME * mdev->sync_conf.rate / ((BM_BLOCK_SIZE/1024)*HZ);
+	/* starting with drbd 8.3.8, we can handle multi-bio EEs,
+	 * if it should be necessary */
+	max_segment_size = mdev->agreed_pro_version < 94 ?
+		queue_max_segment_size(mdev->rq_queue) : DRBD_MAX_SEGMENT_SIZE;
+
+	mdev->c_sync_rate = calc_resync_rate(mdev);
+	number = SLEEP_TIME * mdev->c_sync_rate  / ((BM_BLOCK_SIZE / 1024) * HZ);
 	pe = atomic_read(&mdev->rs_pending_cnt);
 
 	mutex_lock(&mdev->data.mutex);
@@ -509,12 +557,6 @@ next_sector:
 		 *
 		 * Additionally always align bigger requests, in order to
 		 * be prepared for all stripe sizes of software RAIDs.
-		 *
-		 * we _do_ care about the agreed-upon q->max_segment_size
-		 * here, as splitting up the requests on the other side is more
-		 * difficult.  the consequence is, that on lvm and md and other
-		 * "indirect" devices, this is dead code, since
-		 * q->max_segment_size will be PAGE_SIZE.
 		 */
 		align = 1;
 		for (;;) {
@@ -806,7 +848,7 @@ out:
 /* helper */
 static void move_to_net_ee_or_free(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
 {
-	if (drbd_bio_has_active_page(e->private_bio)) {
+	if (drbd_ee_has_active_page(e)) {
 		/* This might happen if sendpage() has not finished */
 		spin_lock_irq(&mdev->req_lock);
 		list_add_tail(&e->w.list, &mdev->net_ee);
@@ -832,7 +874,7 @@ int w_e_end_data_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 		return 1;
 	}
 
-	if (likely(drbd_bio_uptodate(e->private_bio))) {
+	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 		ok = drbd_send_block(mdev, P_DATA_REPLY, e);
 	} else {
 		if (__ratelimit(&drbd_ratelimit_state))
@@ -873,7 +915,7 @@ int w_e_end_rsdata_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 		put_ldev(mdev);
 	}
 
-	if (likely(drbd_bio_uptodate(e->private_bio))) {
+	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 		if (likely(mdev->state.pdsk >= D_INCONSISTENT)) {
 			inc_rs_pending(mdev);
 			ok = drbd_send_block(mdev, P_RS_DATA_REPLY, e);
@@ -921,7 +963,7 @@ int w_e_end_csum_rs_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 
 	di = (struct digest_info *)(unsigned long)e->block_id;
 
-	if (likely(drbd_bio_uptodate(e->private_bio))) {
+	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 		/* quick hack to try to avoid a race against reconfiguration.
 		 * a real fix would be much more involved,
 		 * introducing more locking mechanisms */
@@ -931,7 +973,7 @@ int w_e_end_csum_rs_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 			digest = kmalloc(digest_size, GFP_NOIO);
 		}
 		if (digest) {
-			drbd_csum(mdev, mdev->csums_tfm, e->private_bio, digest);
+			drbd_csum_ee(mdev, mdev->csums_tfm, e, digest);
 			eq = !memcmp(digest, di->digest, digest_size);
 			kfree(digest);
 		}
@@ -973,14 +1015,14 @@ int w_e_end_ov_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 	if (unlikely(cancel))
 		goto out;
 
-	if (unlikely(!drbd_bio_uptodate(e->private_bio)))
+	if (unlikely((e->flags & EE_WAS_ERROR) != 0))
 		goto out;
 
 	digest_size = crypto_hash_digestsize(mdev->verify_tfm);
 	/* FIXME if this allocation fails, online verify will not terminate! */
 	digest = kmalloc(digest_size, GFP_NOIO);
 	if (digest) {
-		drbd_csum(mdev, mdev->verify_tfm, e->private_bio, digest);
+		drbd_csum_ee(mdev, mdev->verify_tfm, e, digest);
 		inc_rs_pending(mdev);
 		ok = drbd_send_drequest_csum(mdev, e->sector, e->size,
 					     digest, digest_size, P_OV_REPLY);
@@ -1029,11 +1071,11 @@ int w_e_end_ov_reply(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
 
 	di = (struct digest_info *)(unsigned long)e->block_id;
 
-	if (likely(drbd_bio_uptodate(e->private_bio))) {
+	if (likely((e->flags & EE_WAS_ERROR) == 0)) {
 		digest_size = crypto_hash_digestsize(mdev->verify_tfm);
 		digest = kmalloc(digest_size, GFP_NOIO);
 		if (digest) {
-			drbd_csum(mdev, mdev->verify_tfm, e->private_bio, digest);
+			drbd_csum_ee(mdev, mdev->verify_tfm, e, digest);
 
 			D_ASSERT(digest_size == di->digest_size);
 			eq = !memcmp(digest, di->digest, digest_size);
diff --git a/drivers/block/drbd/drbd_wrappers.h b/drivers/block/drbd/drbd_wrappers.h
index f93fa111ce50..defdb5013ea3 100644
--- a/drivers/block/drbd/drbd_wrappers.h
+++ b/drivers/block/drbd/drbd_wrappers.h
@@ -18,23 +18,9 @@ static inline void drbd_set_my_capacity(struct drbd_conf *mdev,
 
 #define drbd_bio_uptodate(bio) bio_flagged(bio, BIO_UPTODATE)
 
-static inline int drbd_bio_has_active_page(struct bio *bio)
-{
-	struct bio_vec *bvec;
-	int i;
-
-	__bio_for_each_segment(bvec, bio, i, 0) {
-		if (page_count(bvec->bv_page) > 1)
-			return 1;
-	}
-
-	return 0;
-}
-
 /* bi_end_io handlers */
 extern void drbd_md_io_complete(struct bio *bio, int error);
-extern void drbd_endio_read_sec(struct bio *bio, int error);
-extern void drbd_endio_write_sec(struct bio *bio, int error);
+extern void drbd_endio_sec(struct bio *bio, int error);
 extern void drbd_endio_pri(struct bio *bio, int error);
 
 /*
diff --git a/drivers/ide/ide-disk.c b/drivers/ide/ide-disk.c
index 3b128dce9c3a..33d65039cce9 100644
--- a/drivers/ide/ide-disk.c
+++ b/drivers/ide/ide-disk.c
@@ -407,32 +407,24 @@ static int ide_disk_get_capacity(ide_drive_t *drive)
 	return 0;
 }
 
-static u64 ide_disk_set_capacity(ide_drive_t *drive, u64 capacity)
+static void ide_disk_unlock_native_capacity(ide_drive_t *drive)
 {
-	u64 set = min(capacity, drive->probed_capacity);
 	u16 *id = drive->id;
 	int lba48 = ata_id_lba48_enabled(id);
 
 	if ((drive->dev_flags & IDE_DFLAG_LBA) == 0 ||
 	    ata_id_hpa_enabled(id) == 0)
-		goto out;
+		return;
 
 	/*
 	 * according to the spec the SET MAX ADDRESS command shall be
 	 * immediately preceded by a READ NATIVE MAX ADDRESS command
 	 */
-	capacity = ide_disk_hpa_get_native_capacity(drive, lba48);
-	if (capacity == 0)
-		goto out;
-
-	set = ide_disk_hpa_set_capacity(drive, set, lba48);
-	if (set) {
-		/* needed for ->resume to disable HPA */
-		drive->dev_flags |= IDE_DFLAG_NOHPA;
-		return set;
-	}
-out:
-	return drive->capacity64;
+	if (!ide_disk_hpa_get_native_capacity(drive, lba48))
+		return;
+
+	if (ide_disk_hpa_set_capacity(drive, drive->probed_capacity, lba48))
+		drive->dev_flags |= IDE_DFLAG_NOHPA; /* disable HPA on resume */
 }
 
 static void idedisk_prepare_flush(struct request_queue *q, struct request *rq)
@@ -783,13 +775,13 @@ static int ide_disk_set_doorlock(ide_drive_t *drive, struct gendisk *disk,
 }
 
 const struct ide_disk_ops ide_ata_disk_ops = {
-	.check		= ide_disk_check,
-	.set_capacity	= ide_disk_set_capacity,
-	.get_capacity	= ide_disk_get_capacity,
-	.setup		= ide_disk_setup,
-	.flush		= ide_disk_flush,
-	.init_media	= ide_disk_init_media,
-	.set_doorlock	= ide_disk_set_doorlock,
-	.do_request	= ide_do_rw_disk,
-	.ioctl		= ide_disk_ioctl,
+	.check			= ide_disk_check,
+	.unlock_native_capacity	= ide_disk_unlock_native_capacity,
+	.get_capacity		= ide_disk_get_capacity,
+	.setup			= ide_disk_setup,
+	.flush			= ide_disk_flush,
+	.init_media		= ide_disk_init_media,
+	.set_doorlock		= ide_disk_set_doorlock,
+	.do_request		= ide_do_rw_disk,
+	.ioctl			= ide_disk_ioctl,
 };
diff --git a/drivers/ide/ide-gd.c b/drivers/ide/ide-gd.c
index c32d83996ae1..c102d23d9b38 100644
--- a/drivers/ide/ide-gd.c
+++ b/drivers/ide/ide-gd.c
@@ -288,17 +288,14 @@ static int ide_gd_media_changed(struct gendisk *disk)
 	return ret;
 }
 
-static unsigned long long ide_gd_set_capacity(struct gendisk *disk,
-					      unsigned long long capacity)
+static void ide_gd_unlock_native_capacity(struct gendisk *disk)
 {
 	struct ide_disk_obj *idkp = ide_drv_g(disk, ide_disk_obj);
 	ide_drive_t *drive = idkp->drive;
 	const struct ide_disk_ops *disk_ops = drive->disk_ops;
 
-	if (disk_ops->set_capacity)
-		return disk_ops->set_capacity(drive, capacity);
-
-	return drive->capacity64;
+	if (disk_ops->unlock_native_capacity)
+		disk_ops->unlock_native_capacity(drive);
 }
 
 static int ide_gd_revalidate_disk(struct gendisk *disk)
@@ -329,7 +326,7 @@ static const struct block_device_operations ide_gd_ops = {
 	.locked_ioctl		= ide_gd_ioctl,
 	.getgeo			= ide_gd_getgeo,
 	.media_changed		= ide_gd_media_changed,
-	.set_capacity		= ide_gd_set_capacity,
+	.unlock_native_capacity	= ide_gd_unlock_native_capacity,
 	.revalidate_disk	= ide_gd_revalidate_disk
 };