On Thu, 6 Sep 2012, Alex Elder wrote:
> 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@xxxxxxxxxxx>
> ---
> v2: - Made the read_only/ro flag explicitly make the mapping
> read-only rather than having it toggle.
> - Added read_write/rw flags to allow a writable mapping to
> be explicitly requested. Snapshot mappings are silently
> mapped read-only (even if read_write was requested).
If rw is the default, and rw is silently ignored if the image itself is a
snapshot, what is the value in rw? Would it make more sense to fail with
EROFS if you specify rw on a snapshot (or otherwise read-only image)?
sage
>
> drivers/block/rbd.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> Index: b/drivers/block/rbd.c
> ===================================================================
> --- 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,
> } 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,
> 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_dev
> 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 rb
> 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 rb
> 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;
> --
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