Workaround bhyve virtual disks operation on top of GEOM providers.

GEOM does not support scatter/gather lists in its I/Os.  Such requests
are cut in pieces by physio(), that may be problematic, if those pieces
are not multiple of provider's sector size.  If such case is detected,
move the data through temporary sequential buffer.

MFC after:	2 weeks

usr.sbin/bhyve/block_if.c

@@ -85,6 +85,7 @@ struct blockif_ctxt {
 	int			bc_magic;
 	int			bc_fd;
 	int			bc_ischr;
+	int			bc_isgeom;
 	int			bc_candelete;
 	int			bc_rdonly;
 	off_t			bc_size;
@@ -198,27 +199,93 @@ blockif_complete(struct blockif_ctxt *bc, struct blockif_elem *be)
 }
 
 static void
-blockif_proc(struct blockif_ctxt *bc, struct blockif_elem *be)
+blockif_proc(struct blockif_ctxt *bc, struct blockif_elem *be, uint8_t *buf)
 {
 	struct blockif_req *br;
 	off_t arg[2];
-	int err;
+	ssize_t clen, len, off, boff, voff;
+	int i, err;
 
 	br = be->be_req;
+	if (br->br_iovcnt <= 1)
+		buf = NULL;
 	err = 0;
-
 	switch (be->be_op) {
 	case BOP_READ:
-		if (preadv(bc->bc_fd, br->br_iov, br->br_iovcnt,
-			   br->br_offset) < 0)
-			err = errno;
+		if (buf == NULL) {
+			if ((len = preadv(bc->bc_fd, br->br_iov, br->br_iovcnt,
+				   br->br_offset)) < 0)
+				err = errno;
+			else
+				br->br_resid -= len;
+			break;
+		}
+		i = 0;
+		off = voff = 0;
+		while (br->br_resid > 0) {
+			len = MIN(br->br_resid, MAXPHYS);
+			if (pread(bc->bc_fd, buf, len, br->br_offset +
+			    off) < 0) {
+				err = errno;
+				break;
+			}
+			boff = 0;
+			do {
+				clen = MIN(len - boff, br->br_iov[i].iov_len -
+				    voff);
+				memcpy(br->br_iov[i].iov_base + voff,
+				    buf + boff, clen);
+				if (clen < br->br_iov[i].iov_len - voff)
+					voff += clen;
+				else {
+					i++;
+					voff = 0;
+				}
+				boff += clen;
+			} while (boff < len);
+			off += len;
+			br->br_resid -= len;
+		}
 		break;
 	case BOP_WRITE:
-		if (bc->bc_rdonly)
+		if (bc->bc_rdonly) {
 			err = EROFS;
-		else if (pwritev(bc->bc_fd, br->br_iov, br->br_iovcnt,
-			     br->br_offset) < 0)
-			err = errno;
+			break;
+		}
+		if (buf == NULL) {
+			if ((len = pwritev(bc->bc_fd, br->br_iov, br->br_iovcnt,
+				    br->br_offset)) < 0)
+				err = errno;
+			else
+				br->br_resid -= len;
+			break;
+		}
+		i = 0;
+		off = voff = 0;
+		while (br->br_resid > 0) {
+			len = MIN(br->br_resid, MAXPHYS);
+			boff = 0;
+			do {
+				clen = MIN(len - boff, br->br_iov[i].iov_len -
+				    voff);
+				memcpy(buf + boff,
+				    br->br_iov[i].iov_base + voff, clen);
+				if (clen < br->br_iov[i].iov_len - voff)
+					voff += clen;
+				else {
+					i++;
+					voff = 0;
+				}
+				boff += clen;
+			} while (boff < len);
+			if (pwrite(bc->bc_fd, buf, len, br->br_offset +
+			    off) < 0) {
+				err = errno;
+				break;
+			}
+			off += len;
+			br->br_resid -= len;
+		}
 		break;
 	case BOP_FLUSH:
 		if (bc->bc_ischr) {
@@ -234,9 +301,11 @@ blockif_proc(struct blockif_ctxt *bc, struct blockif_elem *be)
 			err = EROFS;
 		else if (bc->bc_ischr) {
 			arg[0] = br->br_offset;
-			arg[1] = br->br_iov[0].iov_len;
+			arg[1] = br->br_resid;
 			if (ioctl(bc->bc_fd, DIOCGDELETE, arg))
 				err = errno;
+			else
+				br->br_resid = 0;
 		} else
 			err = EOPNOTSUPP;
 		break;
@@ -256,15 +325,20 @@ blockif_thr(void *arg)
 	struct blockif_ctxt *bc;
 	struct blockif_elem *be;
 	pthread_t t;
+	uint8_t *buf;
 
 	bc = arg;
+	if (bc->bc_isgeom)
+		buf = malloc(MAXPHYS);
+	else
+		buf = NULL;
 	t = pthread_self();
 
 	pthread_mutex_lock(&bc->bc_mtx);
 	for (;;) {
 		while (blockif_dequeue(bc, t, &be)) {
 			pthread_mutex_unlock(&bc->bc_mtx);
-			blockif_proc(bc, be);
+			blockif_proc(bc, be, buf);
 			pthread_mutex_lock(&bc->bc_mtx);
 			blockif_complete(bc, be);
 		}
@@ -275,6 +349,8 @@ blockif_thr(void *arg)
 	}
 	pthread_mutex_unlock(&bc->bc_mtx);
 
+	if (buf)
+		free(buf);
 	pthread_exit(NULL);
 	return (NULL);
 }
@@ -315,13 +391,14 @@ struct blockif_ctxt *
 blockif_open(const char *optstr, const char *ident)
 {
 	char tname[MAXCOMLEN + 1];
+	char name[MAXPATHLEN];
 	char *nopt, *xopts;
 	struct blockif_ctxt *bc;
 	struct stat sbuf;
 	struct diocgattr_arg arg;
 	off_t size, psectsz, psectoff;
 	int extra, fd, i, sectsz;
-	int nocache, sync, ro, candelete;
+	int nocache, sync, ro, candelete, geom;
 
 	pthread_once(&blockif_once, blockif_init);
 
@@ -375,7 +452,7 @@ blockif_open(const char *optstr, const char *ident)
         size = sbuf.st_size;
 	sectsz = DEV_BSIZE;
 	psectsz = psectoff = 0;
-	candelete = 0;
+	candelete = geom = 0;
 	if (S_ISCHR(sbuf.st_mode)) {
 		if (ioctl(fd, DIOCGMEDIASIZE, &size) < 0 ||
 		    ioctl(fd, DIOCGSECTORSIZE, &sectsz)) {
@@ -391,6 +468,8 @@ blockif_open(const char *optstr, const char *ident)
 		arg.len = sizeof(arg.value.i);
 		if (ioctl(fd, DIOCGATTR, &arg) == 0)
 			candelete = arg.value.i;
+		if (ioctl(fd, DIOCGPROVIDERNAME, name) == 0)
+			geom = 1;
 	} else
 		psectsz = sbuf.st_blksize;
 
@@ -403,6 +482,7 @@ blockif_open(const char *optstr, const char *ident)
 	bc->bc_magic = BLOCKIF_SIG;
 	bc->bc_fd = fd;
 	bc->bc_ischr = S_ISCHR(sbuf.st_mode);
+	bc->bc_isgeom = geom;
 	bc->bc_candelete = candelete;
 	bc->bc_rdonly = ro;
 	bc->bc_size = size;

usr.sbin/bhyve/block_if.h

@@ -45,6 +45,7 @@ struct blockif_req {
 	struct iovec	br_iov[BLOCKIF_IOV_MAX];
 	int		br_iovcnt;
 	off_t		br_offset;
+	ssize_t		br_resid;
 	void		(*br_callback)(struct blockif_req *req, int err);
 	void		*br_param;
 };

usr.sbin/bhyve/pci_ahci.c

@@ -571,6 +571,7 @@ ahci_build_iov(struct ahci_port *p, struct ahci_ioreq *aior,
 	}
 
 	breq->br_iovcnt = j;
+	breq->br_resid = todo;
 	aior->done += todo;
 	aior->more = (aior->done < aior->len && i < prdtl);
 }
@@ -776,8 +777,7 @@ next:
 
 	breq = &aior->io_req;
 	breq->br_offset = elba * blockif_sectsz(p->bctx);
-	breq->br_iovcnt = 1;
-	breq->br_iov[0].iov_len = elen * blockif_sectsz(p->bctx);
+	breq->br_resid = elen * blockif_sectsz(p->bctx);
 
 	/*
 	 * Mark this command in-flight.

usr.sbin/bhyve/pci_virtio_block.c

@@ -198,7 +198,7 @@ pci_vtblk_proc(struct pci_vtblk_softc *sc, struct vqueue_info *vq)
 	struct pci_vtblk_ioreq *io;
 	int i, n;
 	int err;
-	int iolen;
+	ssize_t iolen;
 	int writeop, type;
 	off_t offset;
 	struct iovec iov[BLOCKIF_IOV_MAX + 2];
@@ -246,8 +246,9 @@ pci_vtblk_proc(struct pci_vtblk_softc *sc, struct vqueue_info *vq)
 		assert(((flags[i] & VRING_DESC_F_WRITE) == 0) == writeop);
 		iolen += iov[i].iov_len;
 	}
+	io->io_req.br_resid = iolen;
 
-	DPRINTF(("virtio-block: %s op, %d bytes, %d segs, offset %ld\n\r", 
+	DPRINTF(("virtio-block: %s op, %zd bytes, %d segs, offset %ld\n\r", 
 		 writeop ? "write" : "read/ident", iolen, i - 1, offset));
 
 	switch (type) {