Merge branch 'for-4.6/core' of git://git.kernel.dk/linux-block

Pull core block updates from Jens Axboe:
 "Here are the core block changes for this merge window.  Not a lot of
  exciting stuff going on in this round, most of the changes have been
  on the driver side of things.  That pull request is coming next.  This
  pull request contains:

   - A set of fixes for chained bio handling from Christoph.

   - A tag bounds check for blk-mq from Hannes, ensuring that we don't
     do something stupid if a device reports an invalid tag value.

   - A set of fixes/updates for the CFQ IO scheduler from Jan Kara.

   - A set of blk-mq fixes from Keith, adding support for dynamic
     hardware queues, and fixing init of max_dev_sectors for stacking
     devices.

   - A fix for the dynamic hw context from Ming.

   - Enabling of cgroup writeback support on a block device, from
     Shaohua"

* 'for-4.6/core' of git://git.kernel.dk/linux-block:
  blk-mq: add bounds check on tag-to-rq conversion
  block: bio_remaining_done() isn't unlikely
  block: cleanup bio_endio
  block: factor out chained bio completion
  block: don't unecessarily clobber bi_error for chained bios
  block-dev: enable writeback cgroup support
  blk-mq: Fix NULL pointer updating nr_requests
  blk-mq: mark request queue as mq asap
  block: Initialize max_dev_sectors to 0
  blk-mq: dynamic h/w context count
  cfq-iosched: Allow parent cgroup to preempt its child
  cfq-iosched: Allow sync noidle workloads to preempt each other
  cfq-iosched: Reorder checks in cfq_should_preempt()
  cfq-iosched: Don't group_idle if cfqq has big thinktime

1 files changed, 26 insertions, 24 deletions

diff --git a/block/bio.c b/block/bio.c
index cf75915..f124a0a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -296,13 +296,19 @@ void bio_reset(struct bio *bio)
 }
 EXPORT_SYMBOL(bio_reset);
 
-static void bio_chain_endio(struct bio *bio)
+static struct bio *__bio_chain_endio(struct bio *bio)
 {
 	struct bio *parent = bio->bi_private;
 
-	parent->bi_error = bio->bi_error;
-	bio_endio(parent);
+	if (!parent->bi_error)
+		parent->bi_error = bio->bi_error;
 	bio_put(bio);
+	return parent;
+}
+
+static void bio_chain_endio(struct bio *bio)
+{
+	bio_endio(__bio_chain_endio(bio));
 }
 
 /*
@@ -1742,29 +1748,25 @@ static inline bool bio_remaining_done(struct bio *bio)
  **/
 void bio_endio(struct bio *bio)
 {
-	while (bio) {
-		if (unlikely(!bio_remaining_done(bio)))
-			break;
+again:
+	if (!bio_remaining_done(bio))
+		return;
 
-		/*
-		 * Need to have a real endio function for chained bios,
-		 * otherwise various corner cases will break (like stacking
-		 * block devices that save/restore bi_end_io) - however, we want
-		 * to avoid unbounded recursion and blowing the stack. Tail call
-		 * optimization would handle this, but compiling with frame
-		 * pointers also disables gcc's sibling call optimization.
-		 */
-		if (bio->bi_end_io == bio_chain_endio) {
-			struct bio *parent = bio->bi_private;
-			parent->bi_error = bio->bi_error;
-			bio_put(bio);
-			bio = parent;
-		} else {
-			if (bio->bi_end_io)
-				bio->bi_end_io(bio);
-			bio = NULL;
-		}
+	/*
+	 * Need to have a real endio function for chained bios, otherwise
+	 * various corner cases will break (like stacking block devices that
+	 * save/restore bi_end_io) - however, we want to avoid unbounded
+	 * recursion and blowing the stack. Tail call optimization would
+	 * handle this, but compiling with frame pointers also disables
+	 * gcc's sibling call optimization.
+	 */
+	if (bio->bi_end_io == bio_chain_endio) {
+		bio = __bio_chain_endio(bio);
+		goto again;
 	}
+
+	if (bio->bi_end_io)
+		bio->bi_end_io(bio);
 }
 EXPORT_SYMBOL(bio_endio);