block: Consolidate command flag and queue limit checks for merges

 - blk_check_merge_flags() verifies that cmd_flags / bi_rw are
   compatible. This function is called for both req-req and req-bio
   merging.

 - blk_rq_get_max_sectors() and blk_queue_get_max_sectors() can be used
   to query the maximum sector count for a given request or queue. The
   calls will return the right value from the queue limits given the
   type of command (RW, discard, write same, etc.)

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 5cc29299f6ac63c429beba4485e1105a66bf5783..33eded00c5b1c9c80f44e62da2709750d4703c1b 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1866,8 +1866,7 @@ int blk_rq_check_limits(struct request_queue *q, struct request *rq)
        if (!rq_mergeable(rq))
                return 0;
 
-       if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
-           blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
+       if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, rq->cmd_flags)) {
                printk(KERN_ERR "%s: over max size limit.\n", __func__);
                return -EIO;
        }

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 86710ca408b862d38f1876c59332ff3753033ec4..642b862608a1b246196a26773efc257f7c9d5673 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -275,14 +275,8 @@ no_merge:
 int ll_back_merge_fn(struct request_queue *q, struct request *req,
                     struct bio *bio)
 {
-       unsigned short max_sectors;
-
-       if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
-               max_sectors = queue_max_hw_sectors(q);
-       else
-               max_sectors = queue_max_sectors(q);
-
-       if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
+       if (blk_rq_sectors(req) + bio_sectors(bio) >
+           blk_rq_get_max_sectors(req)) {
                req->cmd_flags |= REQ_NOMERGE;
                if (req == q->last_merge)
                        q->last_merge = NULL;
@@ -299,15 +293,8 @@ int ll_back_merge_fn(struct request_queue *q, struct request *req,
 int ll_front_merge_fn(struct request_queue *q, struct request *req,
                      struct bio *bio)
 {
-       unsigned short max_sectors;
-
-       if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
-               max_sectors = queue_max_hw_sectors(q);
-       else
-               max_sectors = queue_max_sectors(q);
-
-
-       if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
+       if (blk_rq_sectors(req) + bio_sectors(bio) >
+           blk_rq_get_max_sectors(req)) {
                req->cmd_flags |= REQ_NOMERGE;
                if (req == q->last_merge)
                        q->last_merge = NULL;
@@ -338,7 +325,8 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
        /*
         * Will it become too large?
         */
-       if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
+       if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
+           blk_rq_get_max_sectors(req))
                return 0;
 
        total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
@@ -417,6 +405,9 @@ static int attempt_merge(struct request_queue *q, struct request *req,
        if (!rq_mergeable(req) || !rq_mergeable(next))
                return 0;
 
+       if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
+               return 0;
+
        /*
         * not contiguous
         */
@@ -512,6 +503,9 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
        if (!rq_mergeable(rq) || !bio_mergeable(bio))
                return false;
 
+       if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
+               return false;
+
        /* different data direction or already started, don't merge */
        if (bio_data_dir(bio) != rq_data_dir(rq))
                return false;

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3a6fea7460f1f0309508432696609e3376b2195d..90f7abe8f183a1c2ae616931714b878127e4d1bf 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -605,6 +605,18 @@ static inline bool rq_mergeable(struct request *rq)
        return true;
 }
 
+static inline bool blk_check_merge_flags(unsigned int flags1,
+                                        unsigned int flags2)
+{
+       if ((flags1 & REQ_DISCARD) != (flags2 & REQ_DISCARD))
+               return false;
+
+       if ((flags1 & REQ_SECURE) != (flags2 & REQ_SECURE))
+               return false;
+
+       return true;
+}
+
 /*
  * q->prep_rq_fn return values
  */
@@ -800,6 +812,25 @@ static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
        return blk_rq_cur_bytes(rq) >> 9;
 }
 
+static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
+                                                    unsigned int cmd_flags)
+{
+       if (unlikely(cmd_flags & REQ_DISCARD))
+               return q->limits.max_discard_sectors;
+
+       return q->limits.max_sectors;
+}
+
+static inline unsigned int blk_rq_get_max_sectors(struct request *rq)
+{
+       struct request_queue *q = rq->q;
+
+       if (unlikely(rq->cmd_type == REQ_TYPE_BLOCK_PC))
+               return q->limits.max_hw_sectors;
+
+       return blk_queue_get_max_sectors(q, rq->cmd_flags);
+}
+
 /*
  * Request issue related functions.
  */