block, aio: batch completion for bios/kiocbs

When completing a kiocb, there's some fixed overhead from touching the
kioctx's ring buffer the kiocb belongs to.  Some newer high end block
devices can complete multiple IOs per interrupt, much like many network
interfaces have been for some time.

This plumbs through infrastructure so we can take advantage of multiple
completions at the interrupt level, and complete multiple kiocbs at the
same time.

Drivers have to be converted to take advantage of this, but it's a simple
change and the next patches will convert a few drivers.

To use it, an interrupt handler (or any code that completes bios or
requests) declares and initializes a struct batch_complete:

struct batch_complete batch;
batch_complete_init(&batch);

Then, instead of calling bio_endio(), it calls
bio_endio_batch(bio, err, &batch). This just adds the bio to a list in
the batch_complete.

At the end, it calls

batch_complete(&batch);

This completes all the bios all at once, building up a list of kiocbs;
then the list of kiocbs are completed all at once.

[akpm@linux-foundation.org: fix warning]
[akpm@linux-foundation.org: fs/aio.c needs bio.h, move bio_endio_batch() declaration somewhere rational]
[akpm@linux-foundation.org: fix warnings]
[minchan@kernel.org: fix build error due to bio_endio_batch]
[akpm@linux-foundation.org: fix tracepoint in batch_complete()]
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 18 insertions, 14 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index f224d1793ee5..b557900466ba 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -152,7 +152,8 @@ void blk_rq_init(struct request_queue *q, struct request *rq)
 EXPORT_SYMBOL(blk_rq_init);
 
 static void req_bio_endio(struct request *rq, struct bio *bio,
-			  unsigned int nbytes, int error)
+			  unsigned int nbytes, int error,
+			  struct batch_complete *batch)
 {
 	if (error)
 		clear_bit(BIO_UPTODATE, &bio->bi_flags);
@@ -166,7 +167,7 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
 
 	/* don't actually finish bio if it's part of flush sequence */
 	if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
-		bio_endio(bio, error);
+		bio_endio_batch(bio, error, batch);
 }
 
 void blk_dump_rq_flags(struct request *rq, char *msg)
@@ -2280,7 +2281,8 @@ EXPORT_SYMBOL(blk_fetch_request);
  *     %false - this request doesn't have any more data
  *     %true  - this request has more data
  **/
-bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
+bool blk_update_request(struct request *req, int error, unsigned int nr_bytes,
+			struct batch_complete *batch)
 {
 	int total_bytes;
 
@@ -2336,7 +2338,7 @@ bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
 		if (bio_bytes == bio->bi_size)
 			req->bio = bio->bi_next;
 
-		req_bio_endio(req, bio, bio_bytes, error);
+		req_bio_endio(req, bio, bio_bytes, error, batch);
 
 		total_bytes += bio_bytes;
 		nr_bytes -= bio_bytes;
@@ -2389,14 +2391,15 @@ EXPORT_SYMBOL_GPL(blk_update_request);
 
 static bool blk_update_bidi_request(struct request *rq, int error,
 				    unsigned int nr_bytes,
-				    unsigned int bidi_bytes)
+				    unsigned int bidi_bytes,
+				    struct batch_complete *batch)
 {
-	if (blk_update_request(rq, error, nr_bytes))
+	if (blk_update_request(rq, error, nr_bytes, batch))
 		return true;
 
 	/* Bidi request must be completed as a whole */
 	if (unlikely(blk_bidi_rq(rq)) &&
-	    blk_update_request(rq->next_rq, error, bidi_bytes))
+	    blk_update_request(rq->next_rq, error, bidi_bytes, batch))
 		return true;
 
 	if (blk_queue_add_random(rq->q))
@@ -2479,7 +2482,7 @@ static bool blk_end_bidi_request(struct request *rq, int error,
 	struct request_queue *q = rq->q;
 	unsigned long flags;
 
-	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
+	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes, NULL))
 		return true;
 
 	spin_lock_irqsave(q->queue_lock, flags);
@@ -2505,9 +2508,10 @@ static bool blk_end_bidi_request(struct request *rq, int error,
  *     %true  - still buffers pending for this request
  **/
 bool __blk_end_bidi_request(struct request *rq, int error,
-				   unsigned int nr_bytes, unsigned int bidi_bytes)
+				   unsigned int nr_bytes, unsigned int bidi_bytes,
+				   struct batch_complete *batch)
 {
-	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
+	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes, batch))
 		return true;
 
 	blk_finish_request(rq, error);
@@ -2608,7 +2612,7 @@ EXPORT_SYMBOL_GPL(blk_end_request_err);
  **/
 bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
 {
-	return __blk_end_bidi_request(rq, error, nr_bytes, 0);
+	return __blk_end_bidi_request(rq, error, nr_bytes, 0, NULL);
 }
 EXPORT_SYMBOL(__blk_end_request);
 
@@ -2620,7 +2624,7 @@ EXPORT_SYMBOL(__blk_end_request);
  * Description:
  *     Completely finish @rq.  Must be called with queue lock held.
  */
-void __blk_end_request_all(struct request *rq, int error)
+void blk_end_request_all_batch(struct request *rq, int error, struct batch_complete *batch)
 {
 	bool pending;
 	unsigned int bidi_bytes = 0;
@@ -2628,10 +2632,10 @@ void __blk_end_request_all(struct request *rq, int error)
 	if (unlikely(blk_bidi_rq(rq)))
 		bidi_bytes = blk_rq_bytes(rq->next_rq);
 
-	pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
+	pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes, batch);
 	BUG_ON(pending);
 }
-EXPORT_SYMBOL(__blk_end_request_all);
+EXPORT_SYMBOL(blk_end_request_all_batch);
 
 /**
  * __blk_end_request_cur - Helper function to finish the current request chunk.