Merge tag 'dm-3.11-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm

Pull device-mapper changes from Alasdair G Kergon:
 "Add a device-mapper target called dm-switch to provide a multipath
  framework for storage arrays that dynamically reconfigure their
  preferred paths for different device regions.

  Fix a bug in the verity target that prevented its use with some
  specific sizes of devices.

  Improve some locking mechanisms in the device-mapper core and bufio.

  Add Mike Snitzer as a device-mapper maintainer.

  A few more clean-ups and fixes"

* tag 'dm-3.11-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm:
  dm: add switch target
  dm: update maintainers
  dm: optimize reorder structure
  dm: optimize use SRCU and RCU
  dm bufio: submit writes outside lock
  dm cache: fix arm link errors with inline
  dm verity: use __ffs and __fls
  dm flakey: correct ctr alloc failure mesg
  dm verity: remove pointless comparison
  dm: use __GFP_HIGHMEM in __vmalloc
  dm verity: fix inability to use a few specific devices sizes
  dm ioctl: set noio flag to avoid __vmalloc deadlock
  dm mpath: fix ioctl deadlock when no paths

15 files changed, 951 insertions, 185 deletions

diff --git a/Documentation/device-mapper/switch.txt b/Documentation/device-mapper/switch.txt
new file mode 100644
index 000000000000..2fa749387be8
--- /dev/null
+++ b/Documentation/device-mapper/switch.txt
@@ -0,0 +1,126 @@
+dm-switch
+=========
+
+The device-mapper switch target creates a device that supports an
+arbitrary mapping of fixed-size regions of I/O across a fixed set of
+paths.  The path used for any specific region can be switched
+dynamically by sending the target a message.
+
+It maps I/O to underlying block devices efficiently when there is a large
+number of fixed-sized address regions but there is no simple pattern
+that would allow for a compact representation of the mapping such as
+dm-stripe.
+
+Background
+----------
+
+Dell EqualLogic and some other iSCSI storage arrays use a distributed
+frameless architecture.  In this architecture, the storage group
+consists of a number of distinct storage arrays ("members") each having
+independent controllers, disk storage and network adapters.  When a LUN
+is created it is spread across multiple members.  The details of the
+spreading are hidden from initiators connected to this storage system.
+The storage group exposes a single target discovery portal, no matter
+how many members are being used.  When iSCSI sessions are created, each
+session is connected to an eth port on a single member.  Data to a LUN
+can be sent on any iSCSI session, and if the blocks being accessed are
+stored on another member the I/O will be forwarded as required.  This
+forwarding is invisible to the initiator.  The storage layout is also
+dynamic, and the blocks stored on disk may be moved from member to
+member as needed to balance the load.
+
+This architecture simplifies the management and configuration of both
+the storage group and initiators.  In a multipathing configuration, it
+is possible to set up multiple iSCSI sessions to use multiple network
+interfaces on both the host and target to take advantage of the
+increased network bandwidth.  An initiator could use a simple round
+robin algorithm to send I/O across all paths and let the storage array
+members forward it as necessary, but there is a performance advantage to
+sending data directly to the correct member.
+
+A device-mapper table already lets you map different regions of a
+device onto different targets.  However in this architecture the LUN is
+spread with an address region size on the order of 10s of MBs, which
+means the resulting table could have more than a million entries and
+consume far too much memory.
+
+Using this device-mapper switch target we can now build a two-layer
+device hierarchy:
+
+    Upper Tier – Determine which array member the I/O should be sent to.
+    Lower Tier – Load balance amongst paths to a particular member.
+
+The lower tier consists of a single dm multipath device for each member.
+Each of these multipath devices contains the set of paths directly to
+the array member in one priority group, and leverages existing path
+selectors to load balance amongst these paths.  We also build a
+non-preferred priority group containing paths to other array members for
+failover reasons.
+
+The upper tier consists of a single dm-switch device.  This device uses
+a bitmap to look up the location of the I/O and choose the appropriate
+lower tier device to route the I/O.  By using a bitmap we are able to
+use 4 bits for each address range in a 16 member group (which is very
+large for us).  This is a much denser representation than the dm table
+b-tree can achieve.
+
+Construction Parameters
+=======================
+
+    <num_paths> <region_size> <num_optional_args> [<optional_args>...]
+    [<dev_path> <offset>]+
+
+<num_paths>
+    The number of paths across which to distribute the I/O.
+
+<region_size>
+    The number of 512-byte sectors in a region. Each region can be redirected
+    to any of the available paths.
+
+<num_optional_args>
+    The number of optional arguments. Currently, no optional arguments
+    are supported and so this must be zero.
+
+<dev_path>
+    The block device that represents a specific path to the device.
+
+<offset>
+    The offset of the start of data on the specific <dev_path> (in units
+    of 512-byte sectors). This number is added to the sector number when
+    forwarding the request to the specific path. Typically it is zero.
+
+Messages
+========
+
+set_region_mappings <index>:<path_nr> [<index>]:<path_nr> [<index>]:<path_nr>...
+
+Modify the region table by specifying which regions are redirected to
+which paths.
+
+<index>
+    The region number (region size was specified in constructor parameters).
+    If index is omitted, the next region (previous index + 1) is used.
+    Expressed in hexadecimal (WITHOUT any prefix like 0x).
+
+<path_nr>
+    The path number in the range 0 ... (<num_paths> - 1).
+    Expressed in hexadecimal (WITHOUT any prefix like 0x).
+
+Status
+======
+
+No status line is reported.
+
+Example
+=======
+
+Assume that you have volumes vg1/switch0 vg1/switch1 vg1/switch2 with
+the same size.
+
+Create a switch device with 64kB region size:
+    dmsetup create switch --table "0 `blockdev --getsize /dev/vg1/switch0`
+        switch 3 128 0 /dev/vg1/switch0 0 /dev/vg1/switch1 0 /dev/vg1/switch2 0"
+
+Set mappings for the first 7 entries to point to devices switch0, switch1,
+switch2, switch0, switch1, switch2, switch1:
+    dmsetup message switch 0 set_region_mappings 0:0 :1 :2 :0 :1 :2 :1
diff --git a/MAINTAINERS b/MAINTAINERS
index 3a81b6d08833..9d771d9825cf 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2574,6 +2574,7 @@ S:	Maintained
 
 DEVICE-MAPPER  (LVM)
 M:      Alasdair Kergon <agk@redhat.com>
+M:      Mike Snitzer <snitzer@redhat.com>
 M:      dm-devel@redhat.com
 L:      dm-devel@redhat.com
 W:      http://sources.redhat.com/dm
@@ -2585,6 +2586,7 @@ F:	drivers/md/dm*
 F:      drivers/md/persistent-data/
 F:      include/linux/device-mapper.h
 F:      include/linux/dm-*.h
+F:      include/uapi/linux/dm-*.h
 
 DIOLAN U2C-12 I2C DRIVER
 M:      Guenter Roeck <linux@roeck-us.net>
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 3bfc8f1da9fe..30b426ed744b 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -412,4 +412,18 @@ config DM_VERITY
 
           If unsure, say N.
 
+config DM_SWITCH
+        tristate "Switch target support (EXPERIMENTAL)"
+        depends on BLK_DEV_DM
+        ---help---
+          This device-mapper target creates a device that supports an arbitrary
+          mapping of fixed-size regions of I/O across a fixed set of paths.
+          The path used for any specific region can be switched dynamically
+          by sending the target a message.
+
+          To compile this code as a module, choose M here: the module will
+          be called dm-switch.
+
+          If unsure, say N.
+
 endif # MD
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 1439fd4ad9b1..5ef78efc27f2 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_DM_FLAKEY)		+= dm-flakey.o
 obj-$(CONFIG_DM_MULTIPATH)      += dm-multipath.o dm-round-robin.o
 obj-$(CONFIG_DM_MULTIPATH_QL)   += dm-queue-length.o
 obj-$(CONFIG_DM_MULTIPATH_ST)   += dm-service-time.o
+obj-$(CONFIG_DM_SWITCH)         += dm-switch.o
 obj-$(CONFIG_DM_SNAPSHOT)       += dm-snapshot.o
 obj-$(CONFIG_DM_PERSISTENT_DATA)        += persistent-data/
 obj-$(CONFIG_DM_MIRROR)         += dm-mirror.o dm-log.o dm-region-hash.o
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 0387e05cdb98..5227e079a6e3 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -145,6 +145,7 @@ struct dm_buffer {
         unsigned long state;
         unsigned long last_accessed;
         struct dm_bufio_client *c;
+        struct list_head write_list;
         struct bio bio;
         struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS];
 };
@@ -349,7 +350,7 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
         if (gfp_mask & __GFP_NORETRY)
                 noio_flag = memalloc_noio_save();
 
-        ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
+        ptr = __vmalloc(c->block_size, gfp_mask | __GFP_HIGHMEM, PAGE_KERNEL);
 
         if (gfp_mask & __GFP_NORETRY)
                 memalloc_noio_restore(noio_flag);
@@ -630,7 +631,8 @@ static int do_io_schedule(void *word)
  * - Submit our write and don't wait on it. We set B_WRITING indicating
  *   that there is a write in progress.
  */
-static void __write_dirty_buffer(struct dm_buffer *b)
+static void __write_dirty_buffer(struct dm_buffer *b,
+                                 struct list_head *write_list)
 {
         if (!test_bit(B_DIRTY, &b->state))
                 return;
@@ -639,7 +641,24 @@ static void __write_dirty_buffer(struct dm_buffer *b)
         wait_on_bit_lock(&b->state, B_WRITING,
                          do_io_schedule, TASK_UNINTERRUPTIBLE);
 
-        submit_io(b, WRITE, b->block, write_endio);
+        if (!write_list)
+                submit_io(b, WRITE, b->block, write_endio);
+        else
+                list_add_tail(&b->write_list, write_list);
+}
+
+static void __flush_write_list(struct list_head *write_list)
+{
+        struct blk_plug plug;
+        blk_start_plug(&plug);
+        while (!list_empty(write_list)) {
+                struct dm_buffer *b =
+                        list_entry(write_list->next, struct dm_buffer, write_list);
+                list_del(&b->write_list);
+                submit_io(b, WRITE, b->block, write_endio);
+                dm_bufio_cond_resched();
+        }
+        blk_finish_plug(&plug);
 }
 
 /*
@@ -655,7 +674,7 @@ static void __make_buffer_clean(struct dm_buffer *b)
                 return;
 
         wait_on_bit(&b->state, B_READING, do_io_schedule, TASK_UNINTERRUPTIBLE);
-        __write_dirty_buffer(b);
+        __write_dirty_buffer(b, NULL);
         wait_on_bit(&b->state, B_WRITING, do_io_schedule, TASK_UNINTERRUPTIBLE);
 }
 
@@ -802,7 +821,8 @@ static void __free_buffer_wake(struct dm_buffer *b)
         wake_up(&c->free_buffer_wait);
 }
 
-static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait)
+static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
+                                        struct list_head *write_list)
 {
         struct dm_buffer *b, *tmp;
 
@@ -818,7 +838,7 @@ static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait)
                 if (no_wait && test_bit(B_WRITING, &b->state))
                         return;
 
-                __write_dirty_buffer(b);
+                __write_dirty_buffer(b, write_list);
                 dm_bufio_cond_resched();
         }
 }
@@ -853,7 +873,8 @@ static void __get_memory_limit(struct dm_bufio_client *c,
  * If we are over threshold_buffers, start freeing buffers.
  * If we're over "limit_buffers", block until we get under the limit.
  */
-static void __check_watermark(struct dm_bufio_client *c)
+static void __check_watermark(struct dm_bufio_client *c,
+                              struct list_head *write_list)
 {
         unsigned long threshold_buffers, limit_buffers;
 
@@ -872,7 +893,7 @@ static void __check_watermark(struct dm_bufio_client *c)
         }
 
         if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
-                __write_dirty_buffers_async(c, 1);
+                __write_dirty_buffers_async(c, 1, write_list);
 }
 
 /*
@@ -897,7 +918,8 @@ static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
  *--------------------------------------------------------------*/
 
 static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
-                                     enum new_flag nf, int *need_submit)
+                                     enum new_flag nf, int *need_submit,
+                                     struct list_head *write_list)
 {
         struct dm_buffer *b, *new_b = NULL;
 
@@ -924,7 +946,7 @@ static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
                 goto found_buffer;
         }
 
-        __check_watermark(c);
+        __check_watermark(c, write_list);
 
         b = new_b;
         b->hold_count = 1;
@@ -992,10 +1014,14 @@ static void *new_read(struct dm_bufio_client *c, sector_t block,
         int need_submit;
         struct dm_buffer *b;
 
+        LIST_HEAD(write_list);
+
         dm_bufio_lock(c);
-        b = __bufio_new(c, block, nf, &need_submit);
+        b = __bufio_new(c, block, nf, &need_submit, &write_list);
         dm_bufio_unlock(c);
 
+        __flush_write_list(&write_list);
+
         if (!b)
                 return b;
 
@@ -1047,6 +1073,8 @@ void dm_bufio_prefetch(struct dm_bufio_client *c,
 {
         struct blk_plug plug;
 
+        LIST_HEAD(write_list);
+
         BUG_ON(dm_bufio_in_request());
 
         blk_start_plug(&plug);
@@ -1055,7 +1083,15 @@ void dm_bufio_prefetch(struct dm_bufio_client *c,
         for (; n_blocks--; block++) {
                 int need_submit;
                 struct dm_buffer *b;
-                b = __bufio_new(c, block, NF_PREFETCH, &need_submit);
+                b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
+                                &write_list);
+                if (unlikely(!list_empty(&write_list))) {
+                        dm_bufio_unlock(c);
+                        blk_finish_plug(&plug);
+                        __flush_write_list(&write_list);
+                        blk_start_plug(&plug);
+                        dm_bufio_lock(c);
+                }
                 if (unlikely(b != NULL)) {
                         dm_bufio_unlock(c);
 
@@ -1069,7 +1105,6 @@ void dm_bufio_prefetch(struct dm_bufio_client *c,
                                 goto flush_plug;
                         dm_bufio_lock(c);
                 }
-
         }
 
         dm_bufio_unlock(c);
@@ -1126,11 +1161,14 @@ EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
 
 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
 {
+        LIST_HEAD(write_list);
+
         BUG_ON(dm_bufio_in_request());
 
         dm_bufio_lock(c);
-        __write_dirty_buffers_async(c, 0);
+        __write_dirty_buffers_async(c, 0, &write_list);
         dm_bufio_unlock(c);
+        __flush_write_list(&write_list);
 }
 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
 
@@ -1147,8 +1185,13 @@ int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
         unsigned long buffers_processed = 0;
         struct dm_buffer *b, *tmp;
 
+        LIST_HEAD(write_list);
+
+        dm_bufio_lock(c);
+        __write_dirty_buffers_async(c, 0, &write_list);
+        dm_bufio_unlock(c);
+        __flush_write_list(&write_list);
         dm_bufio_lock(c);
-        __write_dirty_buffers_async(c, 0);
 
 again:
         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
@@ -1274,7 +1317,7 @@ retry:
         BUG_ON(!b->hold_count);
         BUG_ON(test_bit(B_READING, &b->state));
 
-        __write_dirty_buffer(b);
+        __write_dirty_buffer(b, NULL);
         if (b->hold_count == 1) {
                 wait_on_bit(&b->state, B_WRITING,
                             do_io_schedule, TASK_UNINTERRUPTIBLE);
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index df44b60e66f2..0df3ec085ebb 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -425,6 +425,10 @@ static bool block_size_is_power_of_two(struct cache *cache)
         return cache->sectors_per_block_shift >= 0;
 }
 
+/* gcc on ARM generates spurious references to __udivdi3 and __umoddi3 */
+#if defined(CONFIG_ARM) && __GNUC__ == 4 && __GNUC_MINOR__ <= 6
+__always_inline
+#endif
 static dm_block_t block_div(dm_block_t b, uint32_t n)
 {
         do_div(b, n);
diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index 7fcf21cb4ff8..c80a0ec5f126 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -176,7 +176,7 @@ static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
         fc = kzalloc(sizeof(*fc), GFP_KERNEL);
         if (!fc) {
-                ti->error = "Cannot allocate linear context";
+                ti->error = "Cannot allocate context";
                 return -ENOMEM;
         }
         fc->start_time = jiffies;
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index aa04f0224642..f1b758675ec7 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -36,6 +36,14 @@ struct hash_cell {
         struct dm_table *new_map;
 };
 
+/*
+ * A dummy definition to make RCU happy.
+ * struct dm_table should never be dereferenced in this file.
+ */
+struct dm_table {
+        int undefined__;
+};
+
 struct vers_iter {
     size_t param_size;
     struct dm_target_versions *vers, *old_vers;
@@ -242,9 +250,10 @@ static int dm_hash_insert(const char *name, const char *uuid, struct mapped_devi
         return -EBUSY;
 }
 
-static void __hash_remove(struct hash_cell *hc)
+static struct dm_table *__hash_remove(struct hash_cell *hc)
 {
         struct dm_table *table;
+        int srcu_idx;
 
         /* remove from the dev hash */
         list_del(&hc->uuid_list);
@@ -253,16 +262,18 @@ static void __hash_remove(struct hash_cell *hc)
         dm_set_mdptr(hc->md, NULL);
         mutex_unlock(&dm_hash_cells_mutex);
 
-        table = dm_get_live_table(hc->md);
-        if (table) {
+        table = dm_get_live_table(hc->md, &srcu_idx);
+        if (table)
                 dm_table_event(table);
-                dm_table_put(table);
-        }
+        dm_put_live_table(hc->md, srcu_idx);
 
+        table = NULL;
         if (hc->new_map)
-                dm_table_destroy(hc->new_map);
+                table = hc->new_map;
         dm_put(hc->md);
         free_cell(hc);
+
+        return table;
 }
 
 static void dm_hash_remove_all(int keep_open_devices)
@@ -270,6 +281,7 @@ static void dm_hash_remove_all(int keep_open_devices)
         int i, dev_skipped;
         struct hash_cell *hc;
         struct mapped_device *md;
+        struct dm_table *t;
 
 retry:
         dev_skipped = 0;
@@ -287,10 +299,14 @@ retry:
                                 continue;
                         }
 
-                        __hash_remove(hc);
+                        t = __hash_remove(hc);
 
                         up_write(&_hash_lock);
 
+                        if (t) {
+                                dm_sync_table(md);
+                                dm_table_destroy(t);
+                        }
                         dm_put(md);
                         if (likely(keep_open_devices))
                                 dm_destroy(md);
@@ -356,6 +372,7 @@ static struct mapped_device *dm_hash_rename(struct dm_ioctl *param,
         struct dm_table *table;
         struct mapped_device *md;
         unsigned change_uuid = (param->flags & DM_UUID_FLAG) ? 1 : 0;
+        int srcu_idx;
 
         /*
          * duplicate new.
@@ -418,11 +435,10 @@ static struct mapped_device *dm_hash_rename(struct dm_ioctl *param,
         /*
          * Wake up any dm event waiters.
          */
-        table = dm_get_live_table(hc->md);
-        if (table) {
+        table = dm_get_live_table(hc->md, &srcu_idx);
+        if (table)
                 dm_table_event(table);
-                dm_table_put(table);
-        }
+        dm_put_live_table(hc->md, srcu_idx);
 
         if (!dm_kobject_uevent(hc->md, KOBJ_CHANGE, param->event_nr))
                 param->flags |= DM_UEVENT_GENERATED_FLAG;
@@ -620,11 +636,14 @@ static int check_name(const char *name)
  * _hash_lock without first calling dm_table_put, because dm_table_destroy
  * waits for this dm_table_put and could be called under this lock.
  */
-static struct dm_table *dm_get_inactive_table(struct mapped_device *md)
+static struct dm_table *dm_get_inactive_table(struct mapped_device *md, int *srcu_idx)
 {
         struct hash_cell *hc;
         struct dm_table *table = NULL;
 
+        /* increment rcu count, we don't care about the table pointer */
+        dm_get_live_table(md, srcu_idx);
+
         down_read(&_hash_lock);
         hc = dm_get_mdptr(md);
         if (!hc || hc->md != md) {
@@ -633,8 +652,6 @@ static struct dm_table *dm_get_inactive_table(struct mapped_device *md)
         }
 
         table = hc->new_map;
-        if (table)
-                dm_table_get(table);
 
 out:
         up_read(&_hash_lock);
@@ -643,10 +660,11 @@ out:
 }
 
 static struct dm_table *dm_get_live_or_inactive_table(struct mapped_device *md,
-                                                      struct dm_ioctl *param)
+                                                      struct dm_ioctl *param,
+                                                      int *srcu_idx)
 {
         return (param->flags & DM_QUERY_INACTIVE_TABLE_FLAG) ?
-                dm_get_inactive_table(md) : dm_get_live_table(md);
+                dm_get_inactive_table(md, srcu_idx) : dm_get_live_table(md, srcu_idx);
 }
 
 /*
@@ -657,6 +675,7 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param)
 {
         struct gendisk *disk = dm_disk(md);
         struct dm_table *table;
+        int srcu_idx;
 
         param->flags &= ~(DM_SUSPEND_FLAG | DM_READONLY_FLAG |
                           DM_ACTIVE_PRESENT_FLAG);
@@ -676,26 +695,27 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param)
         param->event_nr = dm_get_event_nr(md);
         param->target_count = 0;
 
-        table = dm_get_live_table(md);
+        table = dm_get_live_table(md, &srcu_idx);
         if (table) {
                 if (!(param->flags & DM_QUERY_INACTIVE_TABLE_FLAG)) {
                         if (get_disk_ro(disk))
                                 param->flags |= DM_READONLY_FLAG;
                         param->target_count = dm_table_get_num_targets(table);
                 }
-                dm_table_put(table);
 
                 param->flags |= DM_ACTIVE_PRESENT_FLAG;
         }
+        dm_put_live_table(md, srcu_idx);
 
         if (param->flags & DM_QUERY_INACTIVE_TABLE_FLAG) {
-                table = dm_get_inactive_table(md);
+                int srcu_idx;
+                table = dm_get_inactive_table(md, &srcu_idx);
                 if (table) {
                         if (!(dm_table_get_mode(table) & FMODE_WRITE))
                                 param->flags |= DM_READONLY_FLAG;
                         param->target_count = dm_table_get_num_targets(table);
-                        dm_table_put(table);
                 }
+                dm_put_live_table(md, srcu_idx);
         }
 }
 
@@ -796,6 +816,7 @@ static int dev_remove(struct dm_ioctl *param, size_t param_size)
         struct hash_cell *hc;
         struct mapped_device *md;
         int r;
+        struct dm_table *t;
 
         down_write(&_hash_lock);
         hc = __find_device_hash_cell(param);
@@ -819,9 +840,14 @@ static int dev_remove(struct dm_ioctl *param, size_t param_size)
                 return r;
         }
 
-        __hash_remove(hc);
+        t = __hash_remove(hc);
         up_write(&_hash_lock);
 
+        if (t) {
+                dm_sync_table(md);
+                dm_table_destroy(t);
+        }
+
         if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr))
                 param->flags |= DM_UEVENT_GENERATED_FLAG;
 
@@ -986,6 +1012,7 @@ static int do_resume(struct dm_ioctl *param)
 
                 old_map = dm_swap_table(md, new_map);
                 if (IS_ERR(old_map)) {
+                        dm_sync_table(md);
                         dm_table_destroy(new_map);
                         dm_put(md);
                         return PTR_ERR(old_map);
@@ -1003,6 +1030,10 @@ static int do_resume(struct dm_ioctl *param)
                         param->flags |= DM_UEVENT_GENERATED_FLAG;
         }
 
+        /*
+         * Since dm_swap_table synchronizes RCU, nobody should be in
+         * read-side critical section already.
+         */
         if (old_map)
                 dm_table_destroy(old_map);
 
@@ -1125,6 +1156,7 @@ static int dev_wait(struct dm_ioctl *param, size_t param_size)
         int r = 0;
         struct mapped_device *md;
         struct dm_table *table;
+        int srcu_idx;
 
         md = find_device(param);
         if (!md)
@@ -1145,11 +1177,10 @@ static int dev_wait(struct dm_ioctl *param, size_t param_size)
          */
         __dev_status(md, param);
 
-        table = dm_get_live_or_inactive_table(md, param);
-        if (table) {
+        table = dm_get_live_or_inactive_table(md, param, &srcu_idx);
+        if (table)
                 retrieve_status(table, param, param_size);
-                dm_table_put(table);
-        }
+        dm_put_live_table(md, srcu_idx);
 
 out:
         dm_put(md);
@@ -1221,7 +1252,7 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
 {
         int r;
         struct hash_cell *hc;
-        struct dm_table *t;
+        struct dm_table *t, *old_map = NULL;
         struct mapped_device *md;
         struct target_type *immutable_target_type;
 
@@ -1277,14 +1308,14 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
         hc = dm_get_mdptr(md);
         if (!hc || hc->md != md) {
                 DMWARN("device has been removed from the dev hash table.");
-                dm_table_destroy(t);
                 up_write(&_hash_lock);
+                dm_table_destroy(t);
                 r = -ENXIO;
                 goto out;
         }
 
         if (hc->new_map)
-                dm_table_destroy(hc->new_map);
+                old_map = hc->new_map;
         hc->new_map = t;
         up_write(&_hash_lock);
 
@@ -1292,6 +1323,11 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
         __dev_status(md, param);
 
 out:
+        if (old_map) {
+                dm_sync_table(md);
+                dm_table_destroy(old_map);
+        }
+
         dm_put(md);
 
         return r;
@@ -1301,6 +1337,7 @@ static int table_clear(struct dm_ioctl *param, size_t param_size)
 {
         struct hash_cell *hc;
         struct mapped_device *md;
+        struct dm_table *old_map = NULL;
 
         down_write(&_hash_lock);
 
@@ -1312,7 +1349,7 @@ static int table_clear(struct dm_ioctl *param, size_t param_size)
         }
 
         if (hc->new_map) {
-                dm_table_destroy(hc->new_map);
+                old_map = hc->new_map;
                 hc->new_map = NULL;
         }
 
@@ -1321,6 +1358,10 @@ static int table_clear(struct dm_ioctl *param, size_t param_size)
         __dev_status(hc->md, param);
         md = hc->md;
         up_write(&_hash_lock);
+        if (old_map) {
+                dm_sync_table(md);
+                dm_table_destroy(old_map);
+        }
         dm_put(md);
 
         return 0;
@@ -1370,6 +1411,7 @@ static int table_deps(struct dm_ioctl *param, size_t param_size)
 {
         struct mapped_device *md;
         struct dm_table *table;
+        int srcu_idx;
 
         md = find_device(param);
         if (!md)
@@ -1377,11 +1419,10 @@ static int table_deps(struct dm_ioctl *param, size_t param_size)
 
         __dev_status(md, param);
 
-        table = dm_get_live_or_inactive_table(md, param);
-        if (table) {
+        table = dm_get_live_or_inactive_table(md, param, &srcu_idx);
+        if (table)
                 retrieve_deps(table, param, param_size);
-                dm_table_put(table);
-        }
+        dm_put_live_table(md, srcu_idx);
 
         dm_put(md);
 
@@ -1396,6 +1437,7 @@ static int table_status(struct dm_ioctl *param, size_t param_size)
 {
         struct mapped_device *md;
         struct dm_table *table;
+        int srcu_idx;
 
         md = find_device(param);
         if (!md)
@@ -1403,11 +1445,10 @@ static int table_status(struct dm_ioctl *param, size_t param_size)
 
         __dev_status(md, param);
 
-        table = dm_get_live_or_inactive_table(md, param);
-        if (table) {
+        table = dm_get_live_or_inactive_table(md, param, &srcu_idx);
+        if (table)
                 retrieve_status(table, param, param_size);
-                dm_table_put(table);
-        }
+        dm_put_live_table(md, srcu_idx);
 
         dm_put(md);
 
@@ -1443,6 +1484,7 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
         struct dm_target_msg *tmsg = (void *) param + param->data_start;
         size_t maxlen;
         char *result = get_result_buffer(param, param_size, &maxlen);
+        int srcu_idx;
 
         md = find_device(param);
         if (!md)
@@ -1470,9 +1512,9 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
         if (r <= 1)
                 goto out_argv;
 
-        table = dm_get_live_table(md);
+        table = dm_get_live_table(md, &srcu_idx);
         if (!table)
-                goto out_argv;
+                goto out_table;
 
         if (dm_deleting_md(md)) {
                 r = -ENXIO;
@@ -1491,7 +1533,7 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
         }
 
  out_table:
-        dm_table_put(table);
+        dm_put_live_table(md, srcu_idx);
  out_argv:
         kfree(argv);
  out:
@@ -1644,7 +1686,10 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
         }
 
         if (!dmi) {
-                dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH, PAGE_KERNEL);
+                unsigned noio_flag;
+                noio_flag = memalloc_noio_save();
+                dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
+                memalloc_noio_restore(noio_flag);
                 if (dmi)
                         *param_flags |= DM_PARAMS_VMALLOC;
         }
diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index bdf26f5bd326..5adede17ddf6 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -1561,7 +1561,6 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
         unsigned long flags;
         int r;
 
-again:
         bdev = NULL;
         mode = 0;
         r = 0;
@@ -1579,7 +1578,7 @@ again:
         }
 
         if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
-                r = -EAGAIN;
+                r = -ENOTCONN;
         else if (!bdev)
                 r = -EIO;
 
@@ -1591,11 +1590,8 @@ again:
         if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
                 r = scsi_verify_blk_ioctl(NULL, cmd);
 
-        if (r == -EAGAIN && !fatal_signal_pending(current)) {
+        if (r == -ENOTCONN && !fatal_signal_pending(current))
                 queue_work(kmultipathd, &m->process_queued_ios);
-                msleep(10);
-                goto again;
-        }
 
         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
 }
diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
new file mode 100644
index 000000000000..ff9ac4be4721
--- /dev/null
+++ b/drivers/md/dm-switch.c
@@ -0,0 +1,538 @@
+/*
+ * Copyright (C) 2010-2012 by Dell Inc.  All rights reserved.
+ * Copyright (C) 2011-2013 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ *
+ * dm-switch is a device-mapper target that maps IO to underlying block
+ * devices efficiently when there are a large number of fixed-sized
+ * address regions but there is no simple pattern to allow for a compact
+ * mapping representation such as dm-stripe.
+ */
+
+#include <linux/device-mapper.h>
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/vmalloc.h>
+
+#define DM_MSG_PREFIX "switch"
+
+/*
+ * One region_table_slot_t holds <region_entries_per_slot> region table
+ * entries each of which is <region_table_entry_bits> in size.
+ */
+typedef unsigned long region_table_slot_t;
+
+/*
+ * A device with the offset to its start sector.
+ */
+struct switch_path {
+        struct dm_dev *dmdev;
+        sector_t start;
+};
+
+/*
+ * Context block for a dm switch device.
+ */
+struct switch_ctx {
+        struct dm_target *ti;
+
+        unsigned nr_paths;              /* Number of paths in path_list. */
+
+        unsigned region_size;           /* Region size in 512-byte sectors */
+        unsigned long nr_regions;       /* Number of regions making up the device */
+        signed char region_size_bits;   /* log2 of region_size or -1 */
+
+        unsigned char region_table_entry_bits;  /* Number of bits in one region table entry */
+        unsigned char region_entries_per_slot;  /* Number of entries in one region table slot */
+        signed char region_entries_per_slot_bits;       /* log2 of region_entries_per_slot or -1 */
+
+        region_table_slot_t *region_table;      /* Region table */
+
+        /*
+         * Array of dm devices to switch between.
+         */
+        struct switch_path path_list[0];
+};
+
+static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_paths,
+                                           unsigned region_size)
+{
+        struct switch_ctx *sctx;
+
+        sctx = kzalloc(sizeof(struct switch_ctx) + nr_paths * sizeof(struct switch_path),
+                       GFP_KERNEL);
+        if (!sctx)
+                return NULL;
+
+        sctx->ti = ti;
+        sctx->region_size = region_size;
+
+        ti->private = sctx;
+
+        return sctx;
+}
+
+static int alloc_region_table(struct dm_target *ti, unsigned nr_paths)
+{
+        struct switch_ctx *sctx = ti->private;
+        sector_t nr_regions = ti->len;
+        sector_t nr_slots;
+
+        if (!(sctx->region_size & (sctx->region_size - 1)))
+                sctx->region_size_bits = __ffs(sctx->region_size);
+        else
+                sctx->region_size_bits = -1;
+
+        sctx->region_table_entry_bits = 1;
+        while (sctx->region_table_entry_bits < sizeof(region_table_slot_t) * 8 &&
+               (region_table_slot_t)1 << sctx->region_table_entry_bits < nr_paths)
+                sctx->region_table_entry_bits++;
+
+        sctx->region_entries_per_slot = (sizeof(region_table_slot_t) * 8) / sctx->region_table_entry_bits;
+        if (!(sctx->region_entries_per_slot & (sctx->region_entries_per_slot - 1)))
+                sctx->region_entries_per_slot_bits = __ffs(sctx->region_entries_per_slot);
+        else
+                sctx->region_entries_per_slot_bits = -1;
+
+        if (sector_div(nr_regions, sctx->region_size))
+                nr_regions++;
+
+        sctx->nr_regions = nr_regions;
+        if (sctx->nr_regions != nr_regions || sctx->nr_regions >= ULONG_MAX) {
+                ti->error = "Region table too large";
+                return -EINVAL;
+        }
+
+        nr_slots = nr_regions;
+        if (sector_div(nr_slots, sctx->region_entries_per_slot))
+                nr_slots++;
+
+        if (nr_slots > ULONG_MAX / sizeof(region_table_slot_t)) {
+                ti->error = "Region table too large";
+                return -EINVAL;
+        }
+
+        sctx->region_table = vmalloc(nr_slots * sizeof(region_table_slot_t));
+        if (!sctx->region_table) {
+                ti->error = "Cannot allocate region table";
+                return -ENOMEM;
+        }
+
+        return 0;
+}
+
+static void switch_get_position(struct switch_ctx *sctx, unsigned long region_nr,
+                                unsigned long *region_index, unsigned *bit)
+{
+        if (sctx->region_entries_per_slot_bits >= 0) {
+                *region_index = region_nr >> sctx->region_entries_per_slot_bits;
+                *bit = region_nr & (sctx->region_entries_per_slot - 1);
+        } else {
+                *region_index = region_nr / sctx->region_entries_per_slot;
+                *bit = region_nr % sctx->region_entries_per_slot;
+        }
+
+        *bit *= sctx->region_table_entry_bits;
+}
+
+/*
+ * Find which path to use at given offset.
+ */
+static unsigned switch_get_path_nr(struct switch_ctx *sctx, sector_t offset)
+{
+        unsigned long region_index;
+        unsigned bit, path_nr;
+        sector_t p;
+
+        p = offset;
+        if (sctx->region_size_bits >= 0)
+                p >>= sctx->region_size_bits;
+        else
+                sector_div(p, sctx->region_size);
+
+        switch_get_position(sctx, p, &region_index, &bit);
+        path_nr = (ACCESS_ONCE(sctx->region_table[region_index]) >> bit) &
+               ((1 << sctx->region_table_entry_bits) - 1);
+
+        /* This can only happen if the processor uses non-atomic stores. */
+        if (unlikely(path_nr >= sctx->nr_paths))
+                path_nr = 0;
+
+        return path_nr;
+}
+
+static void switch_region_table_write(struct switch_ctx *sctx, unsigned long region_nr,
+                                      unsigned value)
+{
+        unsigned long region_index;
+        unsigned bit;
+        region_table_slot_t pte;
+
+        switch_get_position(sctx, region_nr, &region_index, &bit);
+
+        pte = sctx->region_table[region_index];
+        pte &= ~((((region_table_slot_t)1 << sctx->region_table_entry_bits) - 1) << bit);
+        pte |= (region_table_slot_t)value << bit;
+        sctx->region_table[region_index] = pte;
+}
+
+/*
+ * Fill the region table with an initial round robin pattern.
+ */
+static void initialise_region_table(struct switch_ctx *sctx)
+{
+        unsigned path_nr = 0;
+        unsigned long region_nr;
+
+        for (region_nr = 0; region_nr < sctx->nr_regions; region_nr++) {
+                switch_region_table_write(sctx, region_nr, path_nr);
+                if (++path_nr >= sctx->nr_paths)
+                        path_nr = 0;
+        }
+}
+
+static int parse_path(struct dm_arg_set *as, struct dm_target *ti)
+{
+        struct switch_ctx *sctx = ti->private;
+        unsigned long long start;
+        int r;
+
+        r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
+                          &sctx->path_list[sctx->nr_paths].dmdev);
+        if (r) {
+                ti->error = "Device lookup failed";
+                return r;
+        }
+
+        if (kstrtoull(dm_shift_arg(as), 10, &start) || start != (sector_t)start) {
+                ti->error = "Invalid device starting offset";
+                dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev);
+                return -EINVAL;
+        }
+
+        sctx->path_list[sctx->nr_paths].start = start;
+
+        sctx->nr_paths++;
+
+        return 0;
+}
+
+/*
+ * Destructor: Don't free the dm_target, just the ti->private data (if any).
+ */
+static void switch_dtr(struct dm_target *ti)
+{
+        struct switch_ctx *sctx = ti->private;
+
+        while (sctx->nr_paths--)
+                dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev);
+
+        vfree(sctx->region_table);
+        kfree(sctx);
+}
+
+/*
+ * Constructor arguments:
+ *   <num_paths> <region_size> <num_optional_args> [<optional_args>...]
+ *   [<dev_path> <offset>]+
+ *
+ * Optional args are to allow for future extension: currently this
+ * parameter must be 0.
+ */
+static int switch_ctr(struct dm_target *ti, unsigned argc, char **argv)
+{
+        static struct dm_arg _args[] = {
+                {1, (KMALLOC_MAX_SIZE - sizeof(struct switch_ctx)) / sizeof(struct switch_path), "Invalid number of paths"},
+                {1, UINT_MAX, "Invalid region size"},
+                {0, 0, "Invalid number of optional args"},
+        };
+
+        struct switch_ctx *sctx;
+        struct dm_arg_set as;
+        unsigned nr_paths, region_size, nr_optional_args;
+        int r;
+
+        as.argc = argc;
+        as.argv = argv;
+
+        r = dm_read_arg(_args, &as, &nr_paths, &ti->error);
+        if (r)
+                return -EINVAL;
+
+        r = dm_read_arg(_args + 1, &as, &region_size, &ti->error);
+        if (r)
+                return r;
+
+        r = dm_read_arg_group(_args + 2, &as, &nr_optional_args, &ti->error);
+        if (r)
+                return r;
+        /* parse optional arguments here, if we add any */
+
+        if (as.argc != nr_paths * 2) {
+                ti->error = "Incorrect number of path arguments";
+                return -EINVAL;
+        }
+
+        sctx = alloc_switch_ctx(ti, nr_paths, region_size);
+        if (!sctx) {
+                ti->error = "Cannot allocate redirection context";
+                return -ENOMEM;
+        }
+
+        r = dm_set_target_max_io_len(ti, region_size);
+        if (r)
+                goto error;
+
+        while (as.argc) {
+                r = parse_path(&as, ti);
+                if (r)
+                        goto error;
+        }
+
+        r = alloc_region_table(ti, nr_paths);
+        if (r)
+                goto error;
+
+        initialise_region_table(sctx);
+
+        /* For UNMAP, sending the request down any path is sufficient */
+        ti->num_discard_bios = 1;
+
+        return 0;
+
+error:
+        switch_dtr(ti);
+
+        return r;
+}
+
+static int switch_map(struct dm_target *ti, struct bio *bio)
+{
+        struct switch_ctx *sctx = ti->private;
+        sector_t offset = dm_target_offset(ti, bio->bi_sector);
+        unsigned path_nr = switch_get_path_nr(sctx, offset);
+
+        bio->bi_bdev = sctx->path_list[path_nr].dmdev->bdev;
+        bio->bi_sector = sctx->path_list[path_nr].start + offset;
+
+        return DM_MAPIO_REMAPPED;
+}
+
+/*
+ * We need to parse hex numbers in the message as quickly as possible.
+ *
+ * This table-based hex parser improves performance.
+ * It improves a time to load 1000000 entries compared to the condition-based
+ * parser.
+ *              table-based parser      condition-based parser
+ * PA-RISC      0.29s                   0.31s
+ * Opteron      0.0495s                 0.0498s
+ */
+static const unsigned char hex_table[256] = {
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255,
+255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
+};
+
+static __always_inline unsigned long parse_hex(const char **string)
+{
+        unsigned char d;
+        unsigned long r = 0;
+
+        while ((d = hex_table[(unsigned char)**string]) < 16) {
+                r = (r << 4) | d;
+                (*string)++;
+        }
+
+        return r;
+}
+
+static int process_set_region_mappings(struct switch_ctx *sctx,
+                             unsigned argc, char **argv)
+{
+        unsigned i;
+        unsigned long region_index = 0;
+
+        for (i = 1; i < argc; i++) {
+                unsigned long path_nr;
+                const char *string = argv[i];
+
+                if (*string == ':')
+                        region_index++;
+                else {
+                        region_index = parse_hex(&string);
+                        if (unlikely(*string != ':')) {
+                                DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+                                return -EINVAL;
+                        }
+                }
+
+                string++;
+                if (unlikely(!*string)) {
+                        DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+                        return -EINVAL;
+                }
+
+                path_nr = parse_hex(&string);
+                if (unlikely(*string)) {
+                        DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+                        return -EINVAL;
+                }
+                if (unlikely(region_index >= sctx->nr_regions)) {
+                        DMWARN("invalid set_region_mappings region number: %lu >= %lu", region_index, sctx->nr_regions);
+                        return -EINVAL;
+                }
+                if (unlikely(path_nr >= sctx->nr_paths)) {
+                        DMWARN("invalid set_region_mappings device: %lu >= %u", path_nr, sctx->nr_paths);
+                        return -EINVAL;
+                }
+
+                switch_region_table_write(sctx, region_index, path_nr);
+        }
+
+        return 0;
+}
+
+/*
+ * Messages are processed one-at-a-time.
+ *
+ * Only set_region_mappings is supported.
+ */
+static int switch_message(struct dm_target *ti, unsigned argc, char **argv)
+{
+        static DEFINE_MUTEX(message_mutex);
+
+        struct switch_ctx *sctx = ti->private;
+        int r = -EINVAL;
+
+        mutex_lock(&message_mutex);
+
+        if (!strcasecmp(argv[0], "set_region_mappings"))
+                r = process_set_region_mappings(sctx, argc, argv);
+        else
+                DMWARN("Unrecognised message received.");
+
+        mutex_unlock(&message_mutex);
+
+        return r;
+}
+
+static void switch_status(struct dm_target *ti, status_type_t type,
+                          unsigned status_flags, char *result, unsigned maxlen)
+{
+        struct switch_ctx *sctx = ti->private;
+        unsigned sz = 0;
+        int path_nr;
+
+        switch (type) {
+        case STATUSTYPE_INFO:
+                result[0] = '\0';
+                break;
+
+        case STATUSTYPE_TABLE:
+                DMEMIT("%u %u 0", sctx->nr_paths, sctx->region_size);
+                for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++)
+                        DMEMIT(" %s %llu", sctx->path_list[path_nr].dmdev->name,
+                               (unsigned long long)sctx->path_list[path_nr].start);
+                break;
+        }
+}
+
+/*
+ * Switch ioctl:
+ *
+ * Passthrough all ioctls to the path for sector 0
+ */
+static int switch_ioctl(struct dm_target *ti, unsigned cmd,
+                        unsigned long arg)
+{
+        struct switch_ctx *sctx = ti->private;
+        struct block_device *bdev;
+        fmode_t mode;
+        unsigned path_nr;
+        int r = 0;
+
+        path_nr = switch_get_path_nr(sctx, 0);
+
+        bdev = sctx->path_list[path_nr].dmdev->bdev;
+        mode = sctx->path_list[path_nr].dmdev->mode;
+
+        /*
+         * Only pass ioctls through if the device sizes match exactly.
+         */
+        if (ti->len + sctx->path_list[path_nr].start != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
+                r = scsi_verify_blk_ioctl(NULL, cmd);
+
+        return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
+}
+
+static int switch_iterate_devices(struct dm_target *ti,
+                                  iterate_devices_callout_fn fn, void *data)
+{
+        struct switch_ctx *sctx = ti->private;
+        int path_nr;
+        int r;
+
+        for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++) {
+                r = fn(ti, sctx->path_list[path_nr].dmdev,
+                         sctx->path_list[path_nr].start, ti->len, data);
+                if (r)
+                        return r;
+        }
+
+        return 0;
+}
+
+static struct target_type switch_target = {
+        .name = "switch",
+        .version = {1, 0, 0},
+        .module = THIS_MODULE,
+        .ctr = switch_ctr,
+        .dtr = switch_dtr,
+        .map = switch_map,
+        .message = switch_message,
+        .status = switch_status,
+        .ioctl = switch_ioctl,
+        .iterate_devices = switch_iterate_devices,
+};
+
+static int __init dm_switch_init(void)
+{
+        int r;
+
+        r = dm_register_target(&switch_target);
+        if (r < 0)
+                DMERR("dm_register_target() failed %d", r);
+
+        return r;
+}
+
+static void __exit dm_switch_exit(void)
+{
+        dm_unregister_target(&switch_target);
+}
+
+module_init(dm_switch_init);
+module_exit(dm_switch_exit);
+
+MODULE_DESCRIPTION(DM_NAME " dynamic path switching target");
+MODULE_AUTHOR("Kevin D. O'Kelley <Kevin_OKelley@dell.com>");
+MODULE_AUTHOR("Narendran Ganapathy <Narendran_Ganapathy@dell.com>");
+MODULE_AUTHOR("Jim Ramsay <Jim_Ramsay@dell.com>");
+MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 1ff252ab7d46..f221812b7dbc 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -26,22 +26,8 @@
 #define KEYS_PER_NODE (NODE_SIZE / sizeof(sector_t))
 #define CHILDREN_PER_NODE (KEYS_PER_NODE + 1)
 
-/*
- * The table has always exactly one reference from either mapped_device->map
- * or hash_cell->new_map. This reference is not counted in table->holders.
- * A pair of dm_create_table/dm_destroy_table functions is used for table
- * creation/destruction.
- *
- * Temporary references from the other code increase table->holders. A pair
- * of dm_table_get/dm_table_put functions is used to manipulate it.
- *
- * When the table is about to be destroyed, we wait for table->holders to
- * drop to zero.
- */
-
 struct dm_table {
         struct mapped_device *md;
-        atomic_t holders;
         unsigned type;
 
         /* btree table */
@@ -208,7 +194,6 @@ int dm_table_create(struct dm_table **result, fmode_t mode,
 
         INIT_LIST_HEAD(&t->devices);
         INIT_LIST_HEAD(&t->target_callbacks);
-        atomic_set(&t->holders, 0);
 
         if (!num_targets)
                 num_targets = KEYS_PER_NODE;
@@ -246,10 +231,6 @@ void dm_table_destroy(struct dm_table *t)
         if (!t)
                 return;
 
-        while (atomic_read(&t->holders))
-                msleep(1);
-        smp_mb();
-
         /* free the indexes */
         if (t->depth >= 2)
                 vfree(t->index[t->depth - 2]);
@@ -274,22 +255,6 @@ void dm_table_destroy(struct dm_table *t)
         kfree(t);
 }
 
-void dm_table_get(struct dm_table *t)
-{
-        atomic_inc(&t->holders);
-}
-EXPORT_SYMBOL(dm_table_get);
-
-void dm_table_put(struct dm_table *t)
-{
-        if (!t)
-                return;
-
-        smp_mb__before_atomic_dec();
-        atomic_dec(&t->holders);
-}
-EXPORT_SYMBOL(dm_table_put);
-
 /*
  * Checks to see if we need to extend highs or targets.
  */
diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index b948fd864d45..4b7941db3aff 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -451,7 +451,7 @@ static void verity_prefetch_io(struct work_struct *work)
                                 goto no_prefetch_cluster;
 
                         if (unlikely(cluster & (cluster - 1)))
-                                cluster = 1 << (fls(cluster) - 1);
+                                cluster = 1 << __fls(cluster);
 
                         hash_block_start &= ~(sector_t)(cluster - 1);
                         hash_block_end |= cluster - 1;
@@ -695,8 +695,8 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 goto bad;
         }
 
-        if (sscanf(argv[0], "%d%c", &num, &dummy) != 1 ||
-            num < 0 || num > 1) {
+        if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
+            num > 1) {
                 ti->error = "Invalid version";
                 r = -EINVAL;
                 goto bad;
@@ -723,7 +723,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 r = -EINVAL;
                 goto bad;
         }
-        v->data_dev_block_bits = ffs(num) - 1;
+        v->data_dev_block_bits = __ffs(num);
 
         if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
             !num || (num & (num - 1)) ||
@@ -733,7 +733,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
                 r = -EINVAL;
                 goto bad;
         }
-        v->hash_dev_block_bits = ffs(num) - 1;
+        v->hash_dev_block_bits = __ffs(num);
 
         if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
             (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
@@ -812,7 +812,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
         }
 
         v->hash_per_block_bits =
-                fls((1 << v->hash_dev_block_bits) / v->digest_size) - 1;
+                __fls((1 << v->hash_dev_block_bits) / v->digest_size);
 
         v->levels = 0;
         if (v->data_blocks)
@@ -831,9 +831,8 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
         for (i = v->levels - 1; i >= 0; i--) {
                 sector_t s;
                 v->hash_level_block[i] = hash_position;
-                s = verity_position_at_level(v, v->data_blocks, i);
-                s = (s >> v->hash_per_block_bits) +
-                    !!(s & ((1 << v->hash_per_block_bits) - 1));
+                s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
+                                        >> ((i + 1) * v->hash_per_block_bits);
                 if (hash_position + s < hash_position) {
                         ti->error = "Hash device offset overflow";
                         r = -E2BIG;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index d5370a94b2c1..9e39d2b64bf8 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -117,15 +117,29 @@ EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo);
 #define DMF_MERGE_IS_OPTIONAL 6
 
 /*
+ * A dummy definition to make RCU happy.
+ * struct dm_table should never be dereferenced in this file.
+ */
+struct dm_table {
+        int undefined__;
+};
+
+/*
  * Work processed by per-device workqueue.
  */
 struct mapped_device {
-        struct rw_semaphore io_lock;
+        struct srcu_struct io_barrier;
         struct mutex suspend_lock;
-        rwlock_t map_lock;
         atomic_t holders;
         atomic_t open_count;
 
+        /*
+         * The current mapping.
+         * Use dm_get_live_table{_fast} or take suspend_lock for
+         * dereference.
+         */
+        struct dm_table *map;
+
         unsigned long flags;
 
         struct request_queue *queue;
@@ -155,11 +169,6 @@ struct mapped_device {
         struct workqueue_struct *wq;
 
         /*
-         * The current mapping.
-         */
-        struct dm_table *map;
-
-        /*
          * io objects are allocated from here.
          */
         mempool_t *io_pool;
@@ -386,10 +395,14 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
                         unsigned int cmd, unsigned long arg)
 {
         struct mapped_device *md = bdev->bd_disk->private_data;
-        struct dm_table *map = dm_get_live_table(md);
+        int srcu_idx;
+        struct dm_table *map;
         struct dm_target *tgt;
         int r = -ENOTTY;
 
+retry:
+        map = dm_get_live_table(md, &srcu_idx);
+
         if (!map || !dm_table_get_size(map))
                 goto out;
 
@@ -408,7 +421,12 @@ static int dm_blk_ioctl(struct block_device *bdev, fmode_t mode,
                 r = tgt->type->ioctl(tgt, cmd, arg);
 
 out:
-        dm_table_put(map);
+        dm_put_live_table(md, srcu_idx);
+
+        if (r == -ENOTCONN) {
+                msleep(10);
+                goto retry;
+        }
 
         return r;
 }
@@ -502,20 +520,39 @@ static void queue_io(struct mapped_device *md, struct bio *bio)
 /*
  * Everyone (including functions in this file), should use this
  * function to access the md->map field, and make sure they call
- * dm_table_put() when finished.
+ * dm_put_live_table() when finished.
  */
-struct dm_table *dm_get_live_table(struct mapped_device *md)
+struct dm_table *dm_get_live_table(struct mapped_device *md, int *srcu_idx) __acquires(md->io_barrier)
 {
-        struct dm_table *t;
-        unsigned long flags;
+        *srcu_idx = srcu_read_lock(&md->io_barrier);
+
+        return srcu_dereference(md->map, &md->io_barrier);
+}
 
-        read_lock_irqsave(&md->map_lock, flags);
-        t = md->map;
-        if (t)
-                dm_table_get(t);
-        read_unlock_irqrestore(&md->map_lock, flags);
+void dm_put_live_table(struct mapped_device *md, int srcu_idx) __releases(md->io_barrier)
+{
+        srcu_read_unlock(&md->io_barrier, srcu_idx);
+}
 
-        return t;
+void dm_sync_table(struct mapped_device *md)
+{
+        synchronize_srcu(&md->io_barrier);
+        synchronize_rcu_expedited();
+}
+
+/*
+ * A fast alternative to dm_get_live_table/dm_put_live_table.
+ * The caller must not block between these two functions.
+ */
+static struct dm_table *dm_get_live_table_fast(struct mapped_device *md) __acquires(RCU)
+{
+        rcu_read_lock();
+        return rcu_dereference(md->map);
+}
+
+static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU)
+{
+        rcu_read_unlock();
 }
 
 /*
@@ -1349,17 +1386,18 @@ static int __split_and_process_non_flush(struct clone_info *ci)
 /*
  * Entry point to split a bio into clones and submit them to the targets.
  */
-static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
+static void __split_and_process_bio(struct mapped_device *md,
+                                    struct dm_table *map, struct bio *bio)
 {
         struct clone_info ci;
         int error = 0;
 
-        ci.map = dm_get_live_table(md);
-        if (unlikely(!ci.map)) {
+        if (unlikely(!map)) {
                 bio_io_error(bio);
                 return;
         }
 
+        ci.map = map;
         ci.md = md;
         ci.io = alloc_io(md);
         ci.io->error = 0;
@@ -1386,7 +1424,6 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
 
         /* drop the extra reference count */
         dec_pending(ci.io, error);
-        dm_table_put(ci.map);
 }
 /*-----------------------------------------------------------------
  * CRUD END
@@ -1397,7 +1434,7 @@ static int dm_merge_bvec(struct request_queue *q,
                          struct bio_vec *biovec)
 {
         struct mapped_device *md = q->queuedata;
-        struct dm_table *map = dm_get_live_table(md);
+        struct dm_table *map = dm_get_live_table_fast(md);
         struct dm_target *ti;
         sector_t max_sectors;
         int max_size = 0;
@@ -1407,7 +1444,7 @@ static int dm_merge_bvec(struct request_queue *q,
 
         ti = dm_table_find_target(map, bvm->bi_sector);
         if (!dm_target_is_valid(ti))
-                goto out_table;
+                goto out;
 
         /*
          * Find maximum amount of I/O that won't need splitting
@@ -1436,10 +1473,8 @@ static int dm_merge_bvec(struct request_queue *q,
 
                 max_size = 0;
 
-out_table:
-        dm_table_put(map);
-
 out:
+        dm_put_live_table_fast(md);
         /*
          * Always allow an entire first page
          */
@@ -1458,8 +1493,10 @@ static void _dm_request(struct request_queue *q, struct bio *bio)
         int rw = bio_data_dir(bio);
         struct mapped_device *md = q->queuedata;
         int cpu;
+        int srcu_idx;
+        struct dm_table *map;
 
-        down_read(&md->io_lock);
+        map = dm_get_live_table(md, &srcu_idx);
 
         cpu = part_stat_lock();
         part_stat_inc(cpu, &dm_disk(md)->part0, ios[rw]);
@@ -1468,7 +1505,7 @@ static void _dm_request(struct request_queue *q, struct bio *bio)
 
         /* if we're suspended, we have to queue this io for later */
         if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))) {
-                up_read(&md->io_lock);
+                dm_put_live_table(md, srcu_idx);
 
                 if (bio_rw(bio) != READA)
                         queue_io(md, bio);
@@ -1477,8 +1514,8 @@ static void _dm_request(struct request_queue *q, struct bio *bio)
                 return;
         }
 
-        __split_and_process_bio(md, bio);
-        up_read(&md->io_lock);
+        __split_and_process_bio(md, map, bio);
+        dm_put_live_table(md, srcu_idx);
         return;
 }
 
@@ -1664,7 +1701,8 @@ static struct request *dm_start_request(struct mapped_device *md, struct request
 static void dm_request_fn(struct request_queue *q)
 {
         struct mapped_device *md = q->queuedata;
-        struct dm_table *map = dm_get_live_table(md);
+        int srcu_idx;
+        struct dm_table *map = dm_get_live_table(md, &srcu_idx);
         struct dm_target *ti;
         struct request *rq, *clone;
         sector_t pos;
@@ -1719,7 +1757,7 @@ requeued:
 delay_and_out:
         blk_delay_queue(q, HZ / 10);
 out:
-        dm_table_put(map);
+        dm_put_live_table(md, srcu_idx);
 }
 
 int dm_underlying_device_busy(struct request_queue *q)
@@ -1732,14 +1770,14 @@ static int dm_lld_busy(struct request_queue *q)
 {
         int r;
         struct mapped_device *md = q->queuedata;
-        struct dm_table *map = dm_get_live_table(md);
+        struct dm_table *map = dm_get_live_table_fast(md);
 
         if (!map || test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))
                 r = 1;
         else
                 r = dm_table_any_busy_target(map);
 
-        dm_table_put(map);
+        dm_put_live_table_fast(md);
 
         return r;
 }
@@ -1751,7 +1789,7 @@ static int dm_any_congested(void *congested_data, int bdi_bits)
         struct dm_table *map;
 
         if (!test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) {
-                map = dm_get_live_table(md);
+                map = dm_get_live_table_fast(md);
                 if (map) {
                         /*
                          * Request-based dm cares about only own queue for
@@ -1762,9 +1800,8 @@ static int dm_any_congested(void *congested_data, int bdi_bits)
                                     bdi_bits;
                         else
                                 r = dm_table_any_congested(map, bdi_bits);
-
-                        dm_table_put(map);
                 }
+                dm_put_live_table_fast(md);
         }
 
         return r;
@@ -1869,12 +1906,14 @@ static struct mapped_device *alloc_dev(int minor)
         if (r < 0)
                 goto bad_minor;
 
+        r = init_srcu_struct(&md->io_barrier);
+        if (r < 0)
+                goto bad_io_barrier;
+
         md->type = DM_TYPE_NONE;
-        init_rwsem(&md->io_lock);
         mutex_init(&md->suspend_lock);
         mutex_init(&md->type_lock);
         spin_lock_init(&md->deferred_lock);
-        rwlock_init(&md->map_lock);
         atomic_set(&md->holders, 1);
         atomic_set(&md->open_count, 0);
         atomic_set(&md->event_nr, 0);
@@ -1937,6 +1976,8 @@ bad_thread:
 bad_disk:
         blk_cleanup_queue(md->queue);
 bad_queue:
+        cleanup_srcu_struct(&md->io_barrier);
+bad_io_barrier:
         free_minor(minor);
 bad_minor:
         module_put(THIS_MODULE);
@@ -1960,6 +2001,7 @@ static void free_dev(struct mapped_device *md)
                 bioset_free(md->bs);
         blk_integrity_unregister(md->disk);
         del_gendisk(md->disk);
+        cleanup_srcu_struct(&md->io_barrier);
         free_minor(minor);
 
         spin_lock(&_minor_lock);
@@ -2102,7 +2144,6 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
         struct dm_table *old_map;
         struct request_queue *q = md->queue;
         sector_t size;
-        unsigned long flags;
         int merge_is_optional;
 
         size = dm_table_get_size(t);
@@ -2131,9 +2172,8 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
 
         merge_is_optional = dm_table_merge_is_optional(t);
 
-        write_lock_irqsave(&md->map_lock, flags);
         old_map = md->map;
-        md->map = t;
+        rcu_assign_pointer(md->map, t);
         md->immutable_target_type = dm_table_get_immutable_target_type(t);
 
         dm_table_set_restrictions(t, q, limits);
@@ -2141,7 +2181,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
                 set_bit(DMF_MERGE_IS_OPTIONAL, &md->flags);
         else
                 clear_bit(DMF_MERGE_IS_OPTIONAL, &md->flags);
-        write_unlock_irqrestore(&md->map_lock, flags);
+        dm_sync_table(md);
 
         return old_map;
 }
@@ -2152,15 +2192,13 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
 static struct dm_table *__unbind(struct mapped_device *md)
 {
         struct dm_table *map = md->map;
-        unsigned long flags;
 
         if (!map)
                 return NULL;
 
         dm_table_event_callback(map, NULL, NULL);
-        write_lock_irqsave(&md->map_lock, flags);
-        md->map = NULL;
-        write_unlock_irqrestore(&md->map_lock, flags);
+        rcu_assign_pointer(md->map, NULL);
+        dm_sync_table(md);
 
         return map;
 }
@@ -2312,11 +2350,12 @@ EXPORT_SYMBOL_GPL(dm_device_name);
 static void __dm_destroy(struct mapped_device *md, bool wait)
 {
         struct dm_table *map;
+        int srcu_idx;
 
         might_sleep();
 
         spin_lock(&_minor_lock);
-        map = dm_get_live_table(md);
+        map = dm_get_live_table(md, &srcu_idx);
         idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md))));
         set_bit(DMF_FREEING, &md->flags);
         spin_unlock(&_minor_lock);
@@ -2326,6 +2365,9 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
                 dm_table_postsuspend_targets(map);
         }
 
+        /* dm_put_live_table must be before msleep, otherwise deadlock is possible */
+        dm_put_live_table(md, srcu_idx);
+
         /*
          * Rare, but there may be I/O requests still going to complete,
          * for example.  Wait for all references to disappear.
@@ -2340,7 +2382,6 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
                        dm_device_name(md), atomic_read(&md->holders));
 
         dm_sysfs_exit(md);
-        dm_table_put(map);
         dm_table_destroy(__unbind(md));
         free_dev(md);
 }
@@ -2397,8 +2438,10 @@ static void dm_wq_work(struct work_struct *work)
         struct mapped_device *md = container_of(work, struct mapped_device,
                                                 work);
         struct bio *c;
+        int srcu_idx;
+        struct dm_table *map;
 
-        down_read(&md->io_lock);
+        map = dm_get_live_table(md, &srcu_idx);
 
         while (!test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) {
                 spin_lock_irq(&md->deferred_lock);
@@ -2408,17 +2451,13 @@ static void dm_wq_work(struct work_struct *work)
                 if (!c)
                         break;
 
-                up_read(&md->io_lock);
-
                 if (dm_request_based(md))
                         generic_make_request(c);
                 else
-                        __split_and_process_bio(md, c);
-
-                down_read(&md->io_lock);
+                        __split_and_process_bio(md, map, c);
         }
 
-        up_read(&md->io_lock);
+        dm_put_live_table(md, srcu_idx);
 }
 
 static void dm_queue_flush(struct mapped_device *md)
@@ -2450,10 +2489,10 @@ struct dm_table *dm_swap_table(struct mapped_device *md, struct dm_table *table)
          * reappear.
          */
         if (dm_table_has_no_data_devices(table)) {
-                live_map = dm_get_live_table(md);
+                live_map = dm_get_live_table_fast(md);
                 if (live_map)
                         limits = md->queue->limits;
-                dm_table_put(live_map);
+                dm_put_live_table_fast(md);
         }
 
         if (!live_map) {
@@ -2533,7 +2572,7 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
                 goto out_unlock;
         }
 
-        map = dm_get_live_table(md);
+        map = md->map;
 
         /*
          * DMF_NOFLUSH_SUSPENDING must be set before presuspend.
@@ -2554,7 +2593,7 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
         if (!noflush && do_lockfs) {
                 r = lock_fs(md);
                 if (r)
-                        goto out;
+                        goto out_unlock;
         }
 
         /*
@@ -2569,9 +2608,8 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
          * (dm_wq_work), we set BMF_BLOCK_IO_FOR_SUSPEND and call
          * flush_workqueue(md->wq).
          */
-        down_write(&md->io_lock);
         set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags);
-        up_write(&md->io_lock);
+        synchronize_srcu(&md->io_barrier);
 
         /*
          * Stop md->queue before flushing md->wq in case request-based
@@ -2589,10 +2627,9 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
          */
         r = dm_wait_for_completion(md, TASK_INTERRUPTIBLE);
 
-        down_write(&md->io_lock);
         if (noflush)
                 clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
-        up_write(&md->io_lock);
+        synchronize_srcu(&md->io_barrier);
 
         /* were we interrupted ? */
         if (r < 0) {
@@ -2602,7 +2639,7 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
                         start_queue(md->queue);
 
                 unlock_fs(md);
-                goto out; /* pushback list is already flushed, so skip flush */
+                goto out_unlock; /* pushback list is already flushed, so skip flush */
         }
 
         /*
@@ -2615,9 +2652,6 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
 
         dm_table_postsuspend_targets(map);
 
-out:
-        dm_table_put(map);
-
 out_unlock:
         mutex_unlock(&md->suspend_lock);
         return r;
@@ -2632,7 +2666,7 @@ int dm_resume(struct mapped_device *md)
         if (!dm_suspended_md(md))
                 goto out;
 
-        map = dm_get_live_table(md);
+        map = md->map;
         if (!map || !dm_table_get_size(map))
                 goto out;
 
@@ -2656,7 +2690,6 @@ int dm_resume(struct mapped_device *md)
 
         r = 0;
 out:
-        dm_table_put(map);
         mutex_unlock(&md->suspend_lock);
 
         return r;
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 3cd32478f2fd..e151d4c9298d 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -446,9 +446,9 @@ int __must_check dm_set_target_max_io_len(struct dm_target *ti, sector_t len);
 /*
  * Table reference counting.
  */
-struct dm_table *dm_get_live_table(struct mapped_device *md);
-void dm_table_get(struct dm_table *t);
-void dm_table_put(struct dm_table *t);
+struct dm_table *dm_get_live_table(struct mapped_device *md, int *srcu_idx);
+void dm_put_live_table(struct mapped_device *md, int srcu_idx);
+void dm_sync_table(struct mapped_device *md);
 
 /*
  * Queries
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 7e75b6fd8d45..afd0cbd52edb 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -267,9 +267,9 @@ enum {
 #define DM_DEV_SET_GEOMETRY     _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR        4
-#define DM_VERSION_MINOR        24
+#define DM_VERSION_MINOR        25
 #define DM_VERSION_PATCHLEVEL   0
-#define DM_VERSION_EXTRA        "-ioctl (2013-01-15)"
+#define DM_VERSION_EXTRA        "-ioctl (2013-06-26)"
 
 /* Status bits */
 #define DM_READONLY_FLAG        (1 << 0) /* In/Out */