Merge branch 'writeback-workqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq into for-3.10/core

Tejun writes:

-----

This is the pull request for the earlier patchset[1] with the same
name.  It's only three patches (the first one was committed to
workqueue tree) but the merge strategy is a bit involved due to the
dependencies.

* Because the conversion needs features from wq/for-3.10,
  block/for-3.10/core is based on rc3, and wq/for-3.10 has conflicts
  with rc3, I pulled mainline (rc5) into wq/for-3.10 to prevent those
  workqueue conflicts from flaring up in block tree.

* Resolving the issue that Jan and Dave raised about debugging
  requires arch-wide changes.  The patchset is being worked on[2] but
  it'll have to go through -mm after these changes show up in -next,
  and not included in this pull request.

The three commits are located in the following git branch.

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git writeback-workqueue

Pulling it into block/for-3.10/core produces a conflict in
drivers/md/raid5.c between the following two commits.

  e3620a3ad5 ("MD RAID5: Avoid accessing gendisk or queue structs when not available")
  2f6db2a707 ("raid5: use bio_reset()")

The conflict is trivial - one removes an "if ()" conditional while the
other removes "rbi->bi_next = NULL" right above it.  We just need to
remove both.  The merged branch is available at

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git block-test-merge

so that you can use it for verification.  The test merge commit has
proper merge description.

While these changes are a bit of pain to route, they make code simpler
and even have, while minute, measureable performance gain[3] even on a
workload which isn't particularly favorable to showing the benefits of
this conversion.

----

Fixed up the conflict.

Conflicts:
	drivers/md/raid5.c

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 30 insertions, 17 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 11e179826b60..6b2b039c191f 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1264,6 +1264,32 @@ static bool obj_request_done_test(struct rbd_obj_request *obj_request)
 	return atomic_read(&obj_request->done) != 0;
 }
 
+static void
+rbd_img_obj_request_read_callback(struct rbd_obj_request *obj_request)
+{
+	dout("%s: obj %p img %p result %d %llu/%llu\n", __func__,
+		obj_request, obj_request->img_request, obj_request->result,
+		obj_request->xferred, obj_request->length);
+	/*
+	 * ENOENT means a hole in the image.  We zero-fill the
+	 * entire length of the request.  A short read also implies
+	 * zero-fill to the end of the request.  Either way we
+	 * update the xferred count to indicate the whole request
+	 * was satisfied.
+	 */
+	BUG_ON(obj_request->type != OBJ_REQUEST_BIO);
+	if (obj_request->result == -ENOENT) {
+		zero_bio_chain(obj_request->bio_list, 0);
+		obj_request->result = 0;
+		obj_request->xferred = obj_request->length;
+	} else if (obj_request->xferred < obj_request->length &&
+			!obj_request->result) {
+		zero_bio_chain(obj_request->bio_list, obj_request->xferred);
+		obj_request->xferred = obj_request->length;
+	}
+	obj_request_done_set(obj_request);
+}
+
 static void rbd_obj_request_complete(struct rbd_obj_request *obj_request)
 {
 	dout("%s: obj %p cb %p\n", __func__, obj_request,
@@ -1284,23 +1310,10 @@ static void rbd_osd_read_callback(struct rbd_obj_request *obj_request)
 {
 	dout("%s: obj %p result %d %llu/%llu\n", __func__, obj_request,
 		obj_request->result, obj_request->xferred, obj_request->length);
-	/*
-	 * ENOENT means a hole in the object.  We zero-fill the
-	 * entire length of the request.  A short read also implies
-	 * zero-fill to the end of the request.  Either way we
-	 * update the xferred count to indicate the whole request
-	 * was satisfied.
-	 */
-	if (obj_request->result == -ENOENT) {
-		zero_bio_chain(obj_request->bio_list, 0);
-		obj_request->result = 0;
-		obj_request->xferred = obj_request->length;
-	} else if (obj_request->xferred < obj_request->length &&
-			!obj_request->result) {
-		zero_bio_chain(obj_request->bio_list, obj_request->xferred);
-		obj_request->xferred = obj_request->length;
-	}
-	obj_request_done_set(obj_request);
+	if (obj_request->img_request)
+		rbd_img_obj_request_read_callback(obj_request);
+	else
+		obj_request_done_set(obj_request);
 }
 
 static void rbd_osd_write_callback(struct rbd_obj_request *obj_request)