block: reorganize request fetching functions
Impact: code reorganization
elv_next_request() and elv_dequeue_request() are public block layer
interface than actual elevator implementation. They mostly deal with
how requests interact with block layer and low level drivers at the
beginning of rqeuest processing whereas __elv_next_request() is the
actual eleveator request fetching interface.
Move the two functions to blk-core.c. This prepares for further
interface cleanup.
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/block/blk-core.c b/block/blk-core.c
index 406a93e..678ede2 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1712,6 +1712,101 @@
}
EXPORT_SYMBOL_GPL(blk_rq_cur_bytes);
+struct request *elv_next_request(struct request_queue *q)
+{
+ struct request *rq;
+ int ret;
+
+ while ((rq = __elv_next_request(q)) != NULL) {
+ if (!(rq->cmd_flags & REQ_STARTED)) {
+ /*
+ * This is the first time the device driver
+ * sees this request (possibly after
+ * requeueing). Notify IO scheduler.
+ */
+ if (blk_sorted_rq(rq))
+ elv_activate_rq(q, rq);
+
+ /*
+ * just mark as started even if we don't start
+ * it, a request that has been delayed should
+ * not be passed by new incoming requests
+ */
+ rq->cmd_flags |= REQ_STARTED;
+ trace_block_rq_issue(q, rq);
+ }
+
+ if (!q->boundary_rq || q->boundary_rq == rq) {
+ q->end_sector = rq_end_sector(rq);
+ q->boundary_rq = NULL;
+ }
+
+ if (rq->cmd_flags & REQ_DONTPREP)
+ break;
+
+ if (q->dma_drain_size && rq->data_len) {
+ /*
+ * make sure space for the drain appears we
+ * know we can do this because max_hw_segments
+ * has been adjusted to be one fewer than the
+ * device can handle
+ */
+ rq->nr_phys_segments++;
+ }
+
+ if (!q->prep_rq_fn)
+ break;
+
+ ret = q->prep_rq_fn(q, rq);
+ if (ret == BLKPREP_OK) {
+ break;
+ } else if (ret == BLKPREP_DEFER) {
+ /*
+ * the request may have been (partially) prepped.
+ * we need to keep this request in the front to
+ * avoid resource deadlock. REQ_STARTED will
+ * prevent other fs requests from passing this one.
+ */
+ if (q->dma_drain_size && rq->data_len &&
+ !(rq->cmd_flags & REQ_DONTPREP)) {
+ /*
+ * remove the space for the drain we added
+ * so that we don't add it again
+ */
+ --rq->nr_phys_segments;
+ }
+
+ rq = NULL;
+ break;
+ } else if (ret == BLKPREP_KILL) {
+ rq->cmd_flags |= REQ_QUIET;
+ __blk_end_request(rq, -EIO, blk_rq_bytes(rq));
+ } else {
+ printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
+ break;
+ }
+ }
+
+ return rq;
+}
+EXPORT_SYMBOL(elv_next_request);
+
+void elv_dequeue_request(struct request_queue *q, struct request *rq)
+{
+ BUG_ON(list_empty(&rq->queuelist));
+ BUG_ON(ELV_ON_HASH(rq));
+
+ list_del_init(&rq->queuelist);
+
+ /*
+ * the time frame between a request being removed from the lists
+ * and to it is freed is accounted as io that is in progress at
+ * the driver side.
+ */
+ if (blk_account_rq(rq))
+ q->in_flight++;
+}
+
/**
* __end_that_request_first - end I/O on a request
* @req: the request being processed