rbd: snap names are pointer to constant data

Make explicit that snapshot names don't change by making functions
return and take parameters that that point to const qualified data.

This resolves:
    http://tracker.ceph.com/issues/4867

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index ab2c788a22adc7ca300bd50aed54798292d7d739..4be3b2a1be8e97216d22359b9a0f41f99082b699 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -3435,10 +3435,10 @@ static struct rbd_snap *rbd_snap_create(struct rbd_device *rbd_dev,
  * Returns a dynamically-allocated snapshot name if successful, or a
  * pointer-coded error otherwise.
  */
-static char *rbd_dev_v1_snap_info(struct rbd_device *rbd_dev, u32 which,
+static const char *rbd_dev_v1_snap_info(struct rbd_device *rbd_dev, u32 which,
                u64 *snap_size, u64 *snap_features)
 {
-       char *snap_name;
+       const char *snap_name;
        int i;
 
        rbd_assert(which < rbd_dev->header.snapc->num_snaps);
@@ -3907,7 +3907,7 @@ out:
        return ret;
 }
 
-static char *rbd_dev_v2_snap_name(struct rbd_device *rbd_dev, u32 which)
+static const char *rbd_dev_v2_snap_name(struct rbd_device *rbd_dev, u32 which)
 {
        size_t size;
        void *reply_buf;
@@ -3948,13 +3948,13 @@ out:
        return snap_name;
 }
 
-static char *rbd_dev_v2_snap_info(struct rbd_device *rbd_dev, u32 which,
+static const char *rbd_dev_v2_snap_info(struct rbd_device *rbd_dev, u32 which,
                u64 *snap_size, u64 *snap_features)
 {
        u64 snap_id;
        u64 size;
        u64 features;
-       char *snap_name;
+       const char *snap_name;
        int ret;
 
        rbd_assert(which < rbd_dev->header.snapc->num_snaps);
@@ -3978,7 +3978,7 @@ out_err:
        return ERR_PTR(ret);
 }
 
-static char *rbd_dev_snap_info(struct rbd_device *rbd_dev, u32 which,
+static const char *rbd_dev_snap_info(struct rbd_device *rbd_dev, u32 which,
                u64 *snap_size, u64 *snap_features)
 {
        if (rbd_dev->image_format == 1)
@@ -4045,7 +4045,7 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev)
        while (index < snap_count || links != head) {
                u64 snap_id;
                struct rbd_snap *snap;
-               char *snap_name;
+               const char *snap_name;
                u64 snap_size = 0;
                u64 snap_features = 0;