blk-mq: support partial I/O completions

Add a new blk_mq_end_io_partial function to partially complete requests
as needed by the SCSI layer.  We do this by reusing blk_update_request
to advance the bio instead of having a simplified version of it in
the blk-mq code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

2 files changed, 12 insertions, 33 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2af840594dc1..1b8b50df3655 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -283,38 +283,10 @@ void blk_mq_free_request(struct request *rq)
         __blk_mq_free_request(hctx, ctx, rq);
 }
 
-static void blk_mq_bio_endio(struct request *rq, struct bio *bio, int error)
+bool blk_mq_end_io_partial(struct request *rq, int error, unsigned int nr_bytes)
 {
-        if (error)
-                clear_bit(BIO_UPTODATE, &bio->bi_flags);
-        else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
-                error = -EIO;
-
-        if (unlikely(rq->cmd_flags & REQ_QUIET))
-                set_bit(BIO_QUIET, &bio->bi_flags);
-
-        /* don't actually finish bio if it's part of flush sequence */
-        if (!(rq->cmd_flags & REQ_FLUSH_SEQ))
-                bio_endio(bio, error);
-}
-
-void blk_mq_end_io(struct request *rq, int error)
-{
-        struct bio *bio = rq->bio;
-        unsigned int bytes = 0;
-
-        trace_block_rq_complete(rq->q, rq);
-
-        while (bio) {
-                struct bio *next = bio->bi_next;
-
-                bio->bi_next = NULL;
-                bytes += bio->bi_iter.bi_size;
-                blk_mq_bio_endio(rq, bio, error);
-                bio = next;
-        }
-
-        blk_account_io_completion(rq, bytes);
+        if (blk_update_request(rq, error, blk_rq_bytes(rq)))
+                return true;
 
         blk_account_io_done(rq);
 
@@ -322,8 +294,9 @@ void blk_mq_end_io(struct request *rq, int error)
                 rq->end_io(rq, error);
         else
                 blk_mq_free_request(rq);
+        return false;
 }
-EXPORT_SYMBOL(blk_mq_end_io);
+EXPORT_SYMBOL(blk_mq_end_io_partial);
 
 static void __blk_mq_complete_request_remote(void *data)
 {
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index ff28fe37ddda..2ff2e8d982be 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -133,7 +133,13 @@ struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *, const int ctx_ind
 struct blk_mq_hw_ctx *blk_mq_alloc_single_hw_queue(struct blk_mq_reg *, unsigned int);
 void blk_mq_free_single_hw_queue(struct blk_mq_hw_ctx *, unsigned int);
 
-void blk_mq_end_io(struct request *rq, int error);
+bool blk_mq_end_io_partial(struct request *rq, int error,
+                unsigned int nr_bytes);
+static inline void blk_mq_end_io(struct request *rq, int error)
+{
+        bool done = !blk_mq_end_io_partial(rq, error, blk_rq_bytes(rq));
+        BUG_ON(!done);
+}
 
 void blk_mq_complete_request(struct request *rq);