rbd: add read_only rbd map option

Add the ability to map an rbd image read-only, by specifying either
"read_only" or "ro" as an option on the rbd "command line."  Also
allow the inverse to be explicitly specified using "read_write" or
"rw".

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>

1 files changed, 24 insertions, 4 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 839ab730a1f3..2db51cef9560 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -69,7 +69,8 @@
 #define DEV_NAME_LEN            32
 #define MAX_INT_FORMAT_WIDTH    ((5 * sizeof (int)) / 2 + 1)
 
-#define RBD_NOTIFY_TIMEOUT_DEFAULT 10
+#define RBD_NOTIFY_TIMEOUT_DEFAULT      10
+#define RBD_READ_ONLY_DEFAULT           false
 
 /*
  * block device image metadata (in-memory version)
@@ -91,6 +92,7 @@ struct rbd_image_header {
 
 struct rbd_options {
         int     notify_timeout;
+        bool    read_only;
 };
 
 /*
@@ -176,7 +178,7 @@ struct rbd_device {
         u64                     snap_id;        /* current snapshot id */
         /* whether the snap_id this device reads from still exists */
         bool                    snap_exists;
-        int                     read_only;
+        bool                    read_only;
 
         struct list_head        node;
 
@@ -351,12 +353,21 @@ enum {
         /* int args above */
         Opt_last_string,
         /* string args above */
+        Opt_read_only,
+        Opt_read_write,
+        /* Boolean args above */
+        Opt_last_bool,
 };
 
 static match_table_t rbd_opts_tokens = {
         {Opt_notify_timeout, "notify_timeout=%d"},
         /* int args above */
         /* string args above */
+        {Opt_read_only, "read_only"},
+        {Opt_read_only, "ro"},          /* Alternate spelling */
+        {Opt_read_write, "read_write"},
+        {Opt_read_write, "rw"},         /* Alternate spelling */
+        /* Boolean args above */
         {-1, NULL}
 };
 
@@ -381,6 +392,8 @@ static int parse_rbd_opts_token(char *c, void *private)
         } else if (token > Opt_last_int && token < Opt_last_string) {
                 dout("got string token %d val %s\n", token,
                      argstr[0].from);
+        } else if (token > Opt_last_string && token < Opt_last_bool) {
+                dout("got Boolean token %d\n", token);
         } else {
                 dout("got token %d\n", token);
         }
@@ -389,6 +402,12 @@ static int parse_rbd_opts_token(char *c, void *private)
         case Opt_notify_timeout:
                 rbd_opts->notify_timeout = intval;
                 break;
+        case Opt_read_only:
+                rbd_opts->read_only = true;
+                break;
+        case Opt_read_write:
+                rbd_opts->read_only = false;
+                break;
         default:
                 BUG_ON(token);
         }
@@ -407,6 +426,7 @@ static int rbd_get_client(struct rbd_device *rbd_dev, const char *mon_addr,
         struct rbd_client *rbdc;
 
         rbd_opts->notify_timeout = RBD_NOTIFY_TIMEOUT_DEFAULT;
+        rbd_opts->read_only = RBD_READ_ONLY_DEFAULT;
 
         ceph_opts = ceph_parse_options(options, mon_addr,
                                         mon_addr + mon_addr_len,
@@ -620,7 +640,7 @@ static int rbd_header_set_snap(struct rbd_device *rbd_dev, u64 *size)
                     sizeof (RBD_SNAP_HEAD_NAME))) {
                 rbd_dev->snap_id = CEPH_NOSNAP;
                 rbd_dev->snap_exists = false;
-                rbd_dev->read_only = 0;
+                rbd_dev->read_only = rbd_dev->rbd_opts.read_only;
                 if (size)
                         *size = rbd_dev->header.image_size;
         } else {
@@ -632,7 +652,7 @@ static int rbd_header_set_snap(struct rbd_device *rbd_dev, u64 *size)
                         goto done;
                 rbd_dev->snap_id = snap_id;
                 rbd_dev->snap_exists = true;
-                rbd_dev->read_only = 1;
+                rbd_dev->read_only = true;      /* No choice for snapshots */
         }
 
         ret = 0;