5 files changed, 43 insertions, 42 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index d1a9a0a64f9..36c0deebc2d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1490,9 +1490,9 @@ end_io:
 /*
  * We only want one ->make_request_fn to be active at a time,
  * else stack usage with stacked devices could be a problem.
- * So use current->bio_{list,tail} to keep a list of requests
+ * So use current->bio_list to keep a list of requests
  * submited by a make_request_fn function.
- * current->bio_tail is also used as a flag to say if
+ * current->bio_list is also used as a flag to say if
  * generic_make_request is currently active in this task or not.
  * If it is NULL, then no make_request is active.  If it is non-NULL,
  * then a make_request is active, and new requests should be added
@@ -1500,11 +1500,11 @@ end_io:
  */
 void generic_make_request(struct bio *bio)
 {
-        if (current->bio_tail) {
+        struct bio_list bio_list_on_stack;
+
+        if (current->bio_list) {
                 /* make_request is active */
-                *(current->bio_tail) = bio;
-                bio->bi_next = NULL;
-                current->bio_tail = &bio->bi_next;
+                bio_list_add(current->bio_list, bio);
                 return;
         }
         /* following loop may be a bit non-obvious, and so deserves some
@@ -1512,30 +1512,27 @@ void generic_make_request(struct bio *bio)
          * Before entering the loop, bio->bi_next is NULL (as all callers
          * ensure that) so we have a list with a single bio.
          * We pretend that we have just taken it off a longer list, so
-         * we assign bio_list to the next (which is NULL) and bio_tail
-         * to &bio_list, thus initialising the bio_list of new bios to be
+         * we assign bio_list to a pointer to the bio_list_on_stack,
+         * thus initialising the bio_list of new bios to be
          * added.  __generic_make_request may indeed add some more bios
          * through a recursive call to generic_make_request.  If it
          * did, we find a non-NULL value in bio_list and re-enter the loop
          * from the top.  In this case we really did just take the bio
-         * of the top of the list (no pretending) and so fixup bio_list and
-         * bio_tail or bi_next, and call into __generic_make_request again.
+         * of the top of the list (no pretending) and so remove it from
+         * bio_list, and call into __generic_make_request again.
          *
          * The loop was structured like this to make only one call to
          * __generic_make_request (which is important as it is large and
          * inlined) and to keep the structure simple.
          */
         BUG_ON(bio->bi_next);
+        bio_list_init(&bio_list_on_stack);
+        current->bio_list = &bio_list_on_stack;
         do {
-                current->bio_list = bio->bi_next;
-                if (bio->bi_next == NULL)
-                        current->bio_tail = &current->bio_list;
-                else
-                        bio->bi_next = NULL;
                 __generic_make_request(bio);
-                bio = current->bio_list;
+                bio = bio_list_pop(current->bio_list);
         } while (bio);
-        current->bio_tail = NULL; /* deactivate */
+        current->bio_list = NULL; /* deactivate */
 }
 EXPORT_SYMBOL(generic_make_request);
 
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 5eeb9e0d256..78549c72378 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -507,7 +507,7 @@ static unsigned int lcm(unsigned int a, unsigned int b)
  * blk_stack_limits - adjust queue_limits for stacked devices
  * @t:  the stacking driver limits (top device)
  * @b:  the underlying queue limits (bottom, component device)
- * @offset:  offset to beginning of data within component device
+ * @start:  first data sector within component device
  *
  * Description:
  *    This function is used by stacking drivers like MD and DM to ensure
@@ -525,10 +525,9 @@ static unsigned int lcm(unsigned int a, unsigned int b)
  *    the alignment_offset is undefined.
  */
 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
-                     sector_t offset)
+                     sector_t start)
 {
-        sector_t alignment;
-        unsigned int top, bottom, ret = 0;
+        unsigned int top, bottom, alignment, ret = 0;
 
         t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
         t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
@@ -548,7 +547,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 
         t->misaligned |= b->misaligned;
 
-        alignment = queue_limit_alignment_offset(b, offset);
+        alignment = queue_limit_alignment_offset(b, start);
 
         /* Bottom device has different alignment.  Check that it is
          * compatible with the current top alignment.
@@ -611,11 +610,7 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 
         /* Discard alignment and granularity */
         if (b->discard_granularity) {
-                unsigned int granularity = b->discard_granularity;
-                offset &= granularity - 1;
-
-                alignment = (granularity + b->discard_alignment - offset)
-                        & (granularity - 1);
+                alignment = queue_limit_discard_alignment(b, start);
 
                 if (t->discard_granularity != 0 &&
                     t->discard_alignment != alignment) {
@@ -657,7 +652,7 @@ int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
 
         start += get_start_sect(bdev);
 
-        return blk_stack_limits(t, &bq->limits, start << 9);
+        return blk_stack_limits(t, &bq->limits, start);
 }
 EXPORT_SYMBOL(bdev_stack_limits);
 
@@ -668,9 +663,8 @@ EXPORT_SYMBOL(bdev_stack_limits);
  * @offset:  offset to beginning of data within component device
  *
  * Description:
- *    Merges the limits for two queues.  Returns 0 if alignment
- *    didn't change.  Returns -1 if adding the bottom device caused
- *    misalignment.
+ *    Merges the limits for a top level gendisk and a bottom level
+ *    block_device.
  */
 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
                        sector_t offset)
@@ -678,9 +672,7 @@ void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
         struct request_queue *t = disk->queue;
         struct request_queue *b = bdev_get_queue(bdev);
 
-        offset += get_start_sect(bdev) << 9;
-
-        if (blk_stack_limits(&t->limits, &b->limits, offset) < 0) {
+        if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
                 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
 
                 disk_name(disk, 0, top);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 8606c9543fd..e85442415db 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -189,7 +189,8 @@ static ssize_t queue_nonrot_store(struct request_queue *q, const char *page,
 
 static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
 {
-        return queue_var_show(blk_queue_nomerges(q), page);
+        return queue_var_show((blk_queue_nomerges(q) << 1) |
+                               blk_queue_noxmerges(q), page);
 }
 
 static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
@@ -199,10 +200,12 @@ static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
         ssize_t ret = queue_var_store(&nm, page, count);
 
         spin_lock_irq(q->queue_lock);
-        if (nm)
+        queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
+        queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
+        if (nm == 2)
                 queue_flag_set(QUEUE_FLAG_NOMERGES, q);
-        else
-                queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
+        else if (nm)
+                queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
         spin_unlock_irq(q->queue_lock);
 
         return ret;
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 023f4e69a33..e3dedfd3bcb 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -115,11 +115,11 @@ struct cfq_queue {
         /* time when queue got scheduled in to dispatch first request. */
         unsigned long dispatch_start;
         unsigned int allocated_slice;
+        unsigned int slice_dispatch;
         /* time when first request from queue completed and slice started. */
         unsigned long slice_start;
         unsigned long slice_end;
         long slice_resid;
-        unsigned int slice_dispatch;
 
         /* pending metadata requests */
         int meta_pending;
@@ -130,13 +130,13 @@ struct cfq_queue {
         unsigned short ioprio, org_ioprio;
         unsigned short ioprio_class, org_ioprio_class;
 
+        pid_t pid;
+
         unsigned int seek_samples;
         u64 seek_total;
         sector_t seek_mean;
         sector_t last_request_pos;
 
-        pid_t pid;
-
         struct cfq_rb_root *service_tree;
         struct cfq_queue *new_cfqq;
         struct cfq_group *cfqg;
diff --git a/block/elevator.c b/block/elevator.c
index 9ad5ccc4c5e..ee3a883840f 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -474,6 +474,15 @@ int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
         int ret;
 
         /*
+         * Levels of merges:
+         *      nomerges:  No merges at all attempted
+         *      noxmerges: Only simple one-hit cache try
+         *      merges:    All merge tries attempted
+         */
+        if (blk_queue_nomerges(q))
+                return ELEVATOR_NO_MERGE;
+
+        /*
          * First try one-hit cache.
          */
         if (q->last_merge) {
@@ -484,7 +493,7 @@ int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
                 }
         }
 
-        if (blk_queue_nomerges(q))
+        if (blk_queue_noxmerges(q))
                 return ELEVATOR_NO_MERGE;
 
         /*