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>
(based on commit cc0538b62c839c2df7b9f8378bb37e3b35faa608)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index cce3e5f..78996d0 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -71,7 +71,8 @@
 #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)
@@ -95,6 +96,7 @@ struct rbd_image_header {
 
 struct rbd_options {
        int     notify_timeout;
+       bool    read_only;
 };
 
 /*
@@ -180,7 +182,7 @@ 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;
 
@@ -346,12 +348,21 @@ 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 rbdopt_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}
 };
 
@@ -376,6 +387,8 @@ 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);
        }
@@ -384,6 +397,12 @@ static int parse_rbd_opts_token(char *c, void *private)
        case Opt_notify_timeout:
                rbdopt->notify_timeout = intval;
                break;
+       case Opt_read_only:
+               rbdopt->read_only = true;
+               break;
+       case Opt_read_write:
+               rbdopt->read_only = false;
+               break;
        default:
                BUG_ON(token);
        }
@@ -407,6 +426,7 @@ static struct rbd_client *rbd_get_client(const char *mon_addr,
                return ERR_PTR(-ENOMEM);
 
        rbd_opts->notify_timeout = RBD_NOTIFY_TIMEOUT_DEFAULT;
+       rbd_opts->read_only = RBD_READ_ONLY_DEFAULT;
 
        opt = ceph_parse_options(options, mon_addr,
                                mon_addr + mon_addr_len,
@@ -590,7 +610,7 @@ static int rbd_header_set_snap(struct rbd_device *dev, u64 *size)
                        snapc->seq = 0;
                dev->snap_id = CEPH_NOSNAP;
                dev->snap_exists = false;
-               dev->read_only = 0;
+               dev->read_only = dev->rbd_client->rbd_opts->read_only;
                if (size)
                        *size = header->image_size;
        } else {
@@ -599,7 +619,7 @@ static int rbd_header_set_snap(struct rbd_device *dev, u64 *size)
                        goto done;
                dev->snap_id = snapc->seq;
                dev->snap_exists = true;
-               dev->read_only = 1;
+               dev->read_only = true;  /* No choice for snapshots */
        }
 
        ret = 0;