[TAPDISK] honor read-only attributes when creating tap-based VBDs

Signed-off-by: Jake Wires <jwires@xensource.com>

6 files changed, 38 insertions, 15 deletions

diff --git a/tools/blktap/drivers/blktapctrl.c b/tools/blktap/drivers/blktapctrl.c
index f2022fcc97..5f78cede2a 100644
--- a/tools/blktap/drivers/blktapctrl.c
+++ b/tools/blktap/drivers/blktapctrl.c
@@ -303,6 +303,7 @@ static int write_msg(int fd, int msgtype, void *ptr, void *ptr2)
 		msg->type = CTLMSG_PARAMS;
 		msg->len = msglen;
 		msg->drivertype = blkif->drivertype;
+		msg->readonly = blkif->readonly;
 
 		gettimeofday(&timeout, NULL);
 		msg->cookie = blkif->cookie;
@@ -410,7 +411,6 @@ static int read_msg(int fd, int msgtype, void *ptr)
 	if (select(fd+1, &readfds,  (fd_set *) 0,
 		  (fd_set *) 0, &timeout) > 0) {
 		ret = read(fd, buf, msglen);
-		
 	}			
 	if (ret > 0) {
 		msg = (msg_hdr_t *)buf;
diff --git a/tools/blktap/drivers/block-qcow.c b/tools/blktap/drivers/block-qcow.c
index 185c670111..36f77e6f05 100644
--- a/tools/blktap/drivers/block-qcow.c
+++ b/tools/blktap/drivers/block-qcow.c
@@ -422,7 +422,7 @@ static int qtruncate(int fd, off_t length, int sparse)
 		return -1;
 	if (S_ISBLK(st.st_mode))
 		return 0;
-	
+
 	sectors = (length + DEFAULT_SECTOR_SIZE - 1)/DEFAULT_SECTOR_SIZE;
 	current = (st.st_size + DEFAULT_SECTOR_SIZE - 1)/DEFAULT_SECTOR_SIZE;
 	rem     = st.st_size % DEFAULT_SECTOR_SIZE;
diff --git a/tools/blktap/drivers/tapdisk.c b/tools/blktap/drivers/tapdisk.c
index 965dbd9b7d..954901b2a8 100644
--- a/tools/blktap/drivers/tapdisk.c
+++ b/tools/blktap/drivers/tapdisk.c
@@ -268,7 +268,8 @@ static int map_new_dev(struct td_state *s, int minor)
 }
 
 static struct disk_driver *disk_init(struct td_state *s, 
-				     struct tap_disk *drv, char *name)
+				     struct tap_disk *drv, 
+				     char *name, td_flag_t flags)
 {
 	struct disk_driver *dd;
 
@@ -285,14 +286,17 @@ static struct disk_driver *disk_init(struct td_state *s,
 	dd->drv      = drv;
 	dd->td_state = s;
 	dd->name     = name;
+	dd->flags    = flags;
 
 	return dd;
 }
 
-static int open_disk(struct td_state *s, struct tap_disk *drv, char *path)
+static int open_disk(struct td_state *s, 
+		     struct tap_disk *drv, char *path, td_flag_t flags)
 {
 	int err;
 	char *dup;
+	td_flag_t pflags;
 	struct disk_id id;
 	struct disk_driver *d;
 
@@ -301,16 +305,17 @@ static int open_disk(struct td_state *s, struct tap_disk *drv, char *path)
 		return -ENOMEM;
 
 	memset(&id, 0, sizeof(struct disk_id));
-	s->disks = d = disk_init(s, drv, dup);
+	s->disks = d = disk_init(s, drv, dup, flags);
 	if (!d)
 		return -ENOMEM;
 
-	err = drv->td_open(d, path, 0);
+	err = drv->td_open(d, path, flags);
 	if (err) {
 		free_driver(d);
 		s->disks = NULL;
 		return -ENOMEM;
 	}
+	pflags = flags | TD_RDONLY;
 
 	/* load backing files as necessary */
 	while ((err = d->drv->td_get_parent_id(d, &id)) == 0) {
@@ -324,11 +329,11 @@ static int open_disk(struct td_state *s, struct tap_disk *drv, char *path)
 		if (!dup)
 			goto fail;
 
-		new = disk_init(s, get_driver(id.drivertype), dup);
+		new = disk_init(s, get_driver(id.drivertype), dup, pflags);
 		if (!new)
 			goto fail;
 
-		err = new->drv->td_open(new, new->name, TD_RDONLY);
+		err = new->drv->td_open(new, new->name, pflags);
 		if (err)
 			goto fail;
 
@@ -342,6 +347,8 @@ static int open_disk(struct td_state *s, struct tap_disk *drv, char *path)
 		free(id.name);
 	}
 
+	s->info |= ((flags & TD_RDONLY) ? VDISK_READONLY : 0);
+
 	if (err >= 0)
 		return 0;
 
@@ -404,7 +411,8 @@ static int read_msg(char *buf)
 				goto params_done;
 
 			/*Open file*/
-			ret = open_disk(s, drv, path);
+			ret = open_disk(s, drv, path, 
+					((msg->readonly) ? TD_RDONLY : 0));
 			if (ret)
 				goto params_done;
 
@@ -510,7 +518,8 @@ void io_done(struct disk_driver *dd, int sid)
 
 	if (!run) return; /*We have received signal to close*/
 
-	if (drv->td_do_callbacks(dd, sid) > 0) kick_responses(dd->td_state);
+	if (sid > MAX_IOFD || drv->td_do_callbacks(dd, sid) > 0)
+		kick_responses(dd->td_state);
 
 	return;
 }
@@ -661,6 +670,12 @@ static void get_io_request(struct td_state *s)
 			sector_nr = req->sector_number;
 		}
 
+		if ((dd->flags & TD_RDONLY) && 
+		    (req->operation == BLKIF_OP_WRITE)) {
+			blkif->pending_list[idx].status = BLKIF_RSP_ERROR;
+			goto send_response;
+		}
+
 		for (i = start_seg; i < req->nr_segments; i++) {
 			nsects = req->seg[i].last_sect - 
 				 req->seg[i].first_sect + 1;
@@ -726,10 +741,12 @@ static void get_io_request(struct td_state *s)
 			}
 			sector_nr += nsects;
 		}
+	send_response:
 		blkif->pending_list[idx].submitting = 0;
 		/* force write_rsp_to_ring for synchronous case */
 		if (blkif->pending_list[idx].secs_pending == 0)
-			dd->early += send_responses(dd, 0, 0, 0, idx, (void *)0);
+			dd->early += send_responses(dd, 0, 0, 0, idx, 
+						    (void *)(long)0);
 	}
 
  out:
@@ -737,7 +754,7 @@ static void get_io_request(struct td_state *s)
 	td_for_each_disk(s, dd) {
 		dd->early += dd->drv->td_submit(dd);
 		if (dd->early > 0) {
-			io_done(dd, 10);
+			io_done(dd, MAX_IOFD + 1);
 			dd->early = 0;
 		}
 	}
@@ -820,7 +837,8 @@ int main(int argc, char *argv[])
 						dd->early += 
 							dd->drv->td_submit(dd);
 						if (dd->early > 0) {
-							io_done(dd, 10);
+							io_done(dd, 
+								MAX_IOFD + 1);
 							dd->early = 0;
 						}
 					}
diff --git a/tools/blktap/drivers/tapdisk.h b/tools/blktap/drivers/tapdisk.h
index b76d46cce5..5c68a5e9c8 100644
--- a/tools/blktap/drivers/tapdisk.h
+++ b/tools/blktap/drivers/tapdisk.h
@@ -94,6 +94,7 @@ struct disk_driver {
 	int early;
 	char *name;
 	void *private;
+	td_flag_t flags;
 	int io_fd[MAX_IOFD];
 	struct tap_disk *drv;
 	struct td_state *td_state;
diff --git a/tools/blktap/lib/blktaplib.h b/tools/blktap/lib/blktaplib.h
index 0ba3c04ec8..078a293185 100644
--- a/tools/blktap/lib/blktaplib.h
+++ b/tools/blktap/lib/blktaplib.h
@@ -173,6 +173,7 @@ typedef struct msg_hdr {
 	uint16_t   len;
 	uint16_t   drivertype;
 	uint16_t   cookie;
+	uint8_t    readonly;
 } msg_hdr_t;
 
 typedef struct msg_newdev {
diff --git a/tools/blktap/lib/xenbus.c b/tools/blktap/lib/xenbus.c
index d50e492784..fb36e748fe 100644
--- a/tools/blktap/lib/xenbus.c
+++ b/tools/blktap/lib/xenbus.c
@@ -177,8 +177,11 @@ static void ueblktap_setup(struct xs_handle *h, char *bepath)
 	}
 
 	/* Check to see if device is to be opened read-only. */
-	asprintf(&path, "%s/%s", bepath, "read-only");
-	if (xs_exists(h, path))
+	deverr = xs_gather(h, bepath, "mode", NULL, &path, NULL);
+	if (deverr) {
+		DPRINTF("ERROR: could not find read/write mode\n");
+		goto fail;
+	} else if (path[0] == 'r')
 		be->readonly = 1;
 
 	if (be->blkif == NULL) {