blk-core: use BIO list management functions

Now that the bio list management stuff is generic, convert
generic_make_request to use bio lists instead of its own private bio
list implementation.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 16 insertions, 19 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 718897e6d37f..44b6d691728d 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/include/linux/sched.h b/include/linux/sched.h
index 78efe7c485ac..7eb82975e1ee 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -97,7 +97,7 @@ struct sched_param {
 struct exec_domain;
 struct futex_pi_state;
 struct robust_list_head;
-struct bio;
+struct bio_list;
 struct fs_struct;
 struct bts_context;
 struct perf_event_context;
@@ -1466,7 +1466,7 @@ struct task_struct {
         void *journal_info;
 
 /* stacked block device info */
-        struct bio *bio_list, **bio_tail;
+        struct bio_list *bio_list;
 
 /* VM state */
         struct reclaim_state *reclaim_state;