block: loop: support DIO & AIO

[linux-2.6-block.git] / drivers / block / loop.c

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 75db3b98ec2b865a31b20a1c0705f73ed700884d..23376084a5cba7e631f101f15e227ded4da9132f 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -445,6 +445,90 @@ static int lo_req_flush(struct loop_device *lo, struct request *rq)
        return ret;
 }
 
+static inline void handle_partial_read(struct loop_cmd *cmd, long bytes)
+{
+       if (bytes < 0 || (cmd->rq->cmd_flags & REQ_WRITE))
+               return;
+
+       if (unlikely(bytes < blk_rq_bytes(cmd->rq))) {
+               struct bio *bio = cmd->rq->bio;
+
+               bio_advance(bio, bytes);
+               zero_fill_bio(bio);
+       }
+}
+
+static void lo_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
+{
+       struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb);
+       struct request *rq = cmd->rq;
+
+       handle_partial_read(cmd, ret);
+
+       if (ret > 0)
+               ret = 0;
+       else if (ret < 0)
+               ret = -EIO;
+
+       rq->errors = ret;
+       blk_mq_complete_request(rq);
+}
+
+static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
+                    loff_t pos, bool rw)
+{
+       struct iov_iter iter;
+       struct bio_vec *bvec;
+       struct bio *bio = cmd->rq->bio;
+       struct file *file = lo->lo_backing_file;
+       int ret;
+
+       /* nomerge for loop request queue */
+       WARN_ON(cmd->rq->bio != cmd->rq->biotail);
+
+       bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
+       iov_iter_bvec(&iter, ITER_BVEC | rw, bvec,
+                     bio_segments(bio), blk_rq_bytes(cmd->rq));
+
+       cmd->iocb.ki_pos = pos;
+       cmd->iocb.ki_filp = file;
+       cmd->iocb.ki_complete = lo_rw_aio_complete;
+       cmd->iocb.ki_flags = IOCB_DIRECT;
+
+       if (rw == WRITE)
+               ret = file->f_op->write_iter(&cmd->iocb, &iter);
+       else
+               ret = file->f_op->read_iter(&cmd->iocb, &iter);
+
+       if (ret != -EIOCBQUEUED)
+               cmd->iocb.ki_complete(&cmd->iocb, ret, 0);
+       return 0;
+}
+
+
+static inline int lo_rw_simple(struct loop_device *lo,
+               struct request *rq, loff_t pos, bool rw)
+{
+       struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
+
+       if (cmd->use_aio)
+               return lo_rw_aio(lo, cmd, pos, rw);
+
+       /*
+        * lo_write_simple and lo_read_simple should have been covered
+        * by io submit style function like lo_rw_aio(), one blocker
+        * is that lo_read_simple() need to call flush_dcache_page after
+        * the page is written from kernel, and it isn't easy to handle
+        * this in io submit style function which submits all segments
+        * of the req at one time. And direct read IO doesn't need to
+        * run flush_dcache_page().
+        */
+       if (rw == WRITE)
+               return lo_write_simple(lo, rq, pos);
+       else
+               return lo_read_simple(lo, rq, pos);
+}
+
 static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 {
        loff_t pos;
@@ -460,13 +544,13 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
                else if (lo->transfer)
                        ret = lo_write_transfer(lo, rq, pos);
                else
-                       ret = lo_write_simple(lo, rq, pos);
+                       ret = lo_rw_simple(lo, rq, pos, WRITE);
 
        } else {
                if (lo->transfer)
                        ret = lo_read_transfer(lo, rq, pos);
                else
-                       ret = lo_read_simple(lo, rq, pos);
+                       ret = lo_rw_simple(lo, rq, pos, READ);
        }
 
        return ret;
@@ -1570,6 +1654,12 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
        if (lo->lo_state != Lo_bound)
                return -EIO;
 
+       if (lo->use_dio && !(cmd->rq->cmd_flags & (REQ_FLUSH |
+                                       REQ_DISCARD)))
+               cmd->use_aio = true;
+       else
+               cmd->use_aio = false;
+
        queue_kthread_work(&lo->worker, &cmd->work);
 
        return BLK_MQ_RQ_QUEUE_OK;
@@ -1589,7 +1679,9 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
  failed:
        if (ret)
                cmd->rq->errors = -EIO;
-       blk_mq_complete_request(cmd->rq);
+       /* complete non-aio request */
+       if (!cmd->use_aio || ret)
+               blk_mq_complete_request(cmd->rq);
 }
 
 static void loop_queue_work(struct kthread_work *work)