bdev/rbd: support readv/writev with multiple iovs

Previously, the RBD bdev only supported a single iovec entry, which is
not sufficient for the bdev API.

Change-Id: Ic18257bae0363b9c01e091547e5b41bae0a21e9a
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-on: https://review.gerrithub.io/401259
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

lib/bdev/rbd/bdev_rbd.c

@@ -45,6 +45,7 @@
 #include "spdk/io_channel.h"
 #include "spdk/json.h"
 #include "spdk/string.h"
+#include "spdk/util.h"
 
 #include "spdk_internal/bdev.h"
 #include "spdk_internal/log.h"
@@ -70,6 +71,12 @@ struct bdev_rbd_io_channel {
 	struct spdk_poller *poller;
 };
 
+struct bdev_rbd_io {
+	uint64_t remaining_len;
+	int num_segments;
+	bool failed;
+};
+
 static void
 bdev_rbd_free(struct bdev_rbd *rbd)
 {
@@ -199,21 +206,56 @@ bdev_rbd_start_aio(rbd_image_t image, struct spdk_bdev_io *bdev_io,
 
 static int bdev_rbd_library_init(void);
 
+static int
+bdev_rbd_get_ctx_size(void)
+{
+	return sizeof(struct bdev_rbd_io);
+}
+
 SPDK_BDEV_MODULE_REGISTER(rbd, bdev_rbd_library_init, NULL, NULL,
-			  NULL, NULL)
+			  bdev_rbd_get_ctx_size, NULL)
 
 static int64_t
 bdev_rbd_rw(struct bdev_rbd *disk, struct spdk_io_channel *ch,
 	    struct spdk_bdev_io *bdev_io, struct iovec *iov,
 	    int iovcnt, size_t len, uint64_t offset)
 {
+	struct bdev_rbd_io *rbd_io = (struct bdev_rbd_io *)bdev_io->driver_ctx;
 	struct bdev_rbd_io_channel *rbdio_ch = spdk_io_channel_get_ctx(ch);
+	size_t remaining = len;
+	int i, rc;
 
-	if (iovcnt != 1 || iov->iov_len != len) {
+	rbd_io->remaining_len = 0;
-		return -1;
+	rbd_io->num_segments = 0;
+	rbd_io->failed = false;
+
+	for (i = 0; i < iovcnt && remaining > 0; i++) {
+		size_t seg_len = spdk_min(remaining, iov[i].iov_len);
+
+		rc = bdev_rbd_start_aio(rbdio_ch->image, bdev_io, iov[i].iov_base, offset, seg_len);
+		if (rc) {
+			/*
+			 * This bdev_rbd_start_aio() call failed, but if any previous ones were
+			 * submitted, we need to wait for them to finish.
+			 */
+			if (rbd_io->num_segments == 0) {
+				/* No previous I/O submitted - return error code immediately. */
+				return rc;
+			}
+
+			/* Return and wait for outstanding I/O to complete. */
+			rbd_io->failed = true;
+			return 0;
+		}
+
+		rbd_io->num_segments++;
+		rbd_io->remaining_len += seg_len;
+
+		offset += seg_len;
+		remaining -= seg_len;
 	}
 
-	return bdev_rbd_start_aio(rbdio_ch->image, bdev_io, iov->iov_base, offset, len);
+	return 0;
 }
 
 static int64_t
@@ -308,7 +350,7 @@ bdev_rbd_io_poll(void *arg)
 	int i, io_status, rc;
 	rbd_completion_t comps[SPDK_RBD_QUEUE_DEPTH];
 	struct spdk_bdev_io *bdev_io;
-	enum spdk_bdev_io_status status;
+	struct bdev_rbd_io *rbd_io;
 
 	rc = poll(&ch->pfd, 1, 0);
 
@@ -320,23 +362,34 @@ bdev_rbd_io_poll(void *arg)
 	rc = rbd_poll_io_events(ch->image, comps, SPDK_RBD_QUEUE_DEPTH);
 	for (i = 0; i < rc; i++) {
 		bdev_io = rbd_aio_get_arg(comps[i]);
+		rbd_io = (struct bdev_rbd_io *)bdev_io->driver_ctx;
 		io_status = rbd_aio_get_return_value(comps[i]);
+
+		assert(rbd_io->num_segments > 0);
+		rbd_io->num_segments--;
+
 		if (bdev_io->type == SPDK_BDEV_IO_TYPE_READ) {
-			if ((int)(bdev_io->u.bdev.num_blocks * bdev_io->bdev->blocklen) == io_status) {
+			if (io_status > 0) {
-				status = SPDK_BDEV_IO_STATUS_SUCCESS;
+				/* For reads, io_status is the length */
-			} else {
+				rbd_io->remaining_len -= io_status;
-				status = SPDK_BDEV_IO_STATUS_FAILED;
+			}
+
+			if (rbd_io->num_segments == 0 && rbd_io->remaining_len != 0) {
+				rbd_io->failed = true;
 			}
 		} else {
 			/* For others, 0 means success */
-			if (!io_status) {
+			if (io_status != 0) {
-				status = SPDK_BDEV_IO_STATUS_SUCCESS;
+				rbd_io->failed = true;
-			} else {
-				status = SPDK_BDEV_IO_STATUS_FAILED;
 			}
 		}
+
 		rbd_aio_release(comps[i]);
-		spdk_bdev_io_complete(bdev_io, status);
+
+		if (rbd_io->num_segments == 0) {
+			spdk_bdev_io_complete(bdev_io,
+					      rbd_io->failed ? SPDK_BDEV_IO_STATUS_FAILED : SPDK_BDEV_IO_STATUS_SUCCESS);
+		}
 	}
 }