rbd: separate mapping info in rbd_dev

Several fields in a struct rbd_dev are related to what is mapped, as
opposed to the actual base rbd image.  If the base image is mapped
these are almost unneeded, but if a snapshot is mapped they describe
information about that snapshot.

In some contexts this can be a little bit confusing.  So group these
mapping-related field into a structure to make it clear what they
are describing.

This also includes a minor change that rearranges the fields in the
in-core image header structure so that invariant fields are at the
top, followed by those that change.

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

1 files changed, 45 insertions, 38 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index eb6b7723906b..dff621060432 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -81,13 +81,15 @@
  * block device image metadata (in-memory version)
  */
 struct rbd_image_header {
-        u64 image_size;
+        /* These four fields never change for a given rbd image */
         char *object_prefix;
         __u8 obj_order;
         __u8 crypt_type;
         __u8 comp_type;
-        struct ceph_snap_context *snapc;
 
+        /* The remaining fields need to be updated occasionally */
+        u64 image_size;
+        struct ceph_snap_context *snapc;
         char *snap_names;
         u64 *snap_sizes;
 
@@ -146,6 +148,13 @@ struct rbd_snap {
         u64                     id;
 };
 
+struct rbd_mapping {
+        char                    *snap_name;
+        u64                     snap_id;
+        bool                    snap_exists;
+        bool                    read_only;
+};
+
 /*
  * a single device
  */
@@ -174,13 +183,8 @@ struct rbd_device {
 
         /* protects updating the header */
         struct rw_semaphore     header_rwsem;
-        /* name of the snapshot this device reads from */
-        char                    *snap_name;
-        /* id of the snapshot this device reads from */
-        u64                     snap_id;        /* current snapshot id */
-        /* whether the snap_id this device reads from still exists */
-        bool                    snap_exists;
-        bool                    read_only;
+
+        struct rbd_mapping      mapping;
 
         struct list_head        node;
 
@@ -261,11 +265,11 @@ static int rbd_open(struct block_device *bdev, fmode_t mode)
 {
         struct rbd_device *rbd_dev = bdev->bd_disk->private_data;
 
-        if ((mode & FMODE_WRITE) && rbd_dev->read_only)
+        if ((mode & FMODE_WRITE) && rbd_dev->mapping.read_only)
                 return -EROFS;
 
         rbd_get_dev(rbd_dev);
-        set_device_ro(bdev, rbd_dev->read_only);
+        set_device_ro(bdev, rbd_dev->mapping.read_only);
 
         return 0;
 }
@@ -375,7 +379,7 @@ enum {
 static match_table_t rbd_opts_tokens = {
         /* int args above */
         /* string args above */
-        {Opt_read_only, "read_only"},
+        {Opt_read_only, "mapping.read_only"},
         {Opt_read_only, "ro"},          /* Alternate spelling */
         {Opt_read_write, "read_write"},
         {Opt_read_write, "rw"},         /* Alternate spelling */
@@ -583,13 +587,13 @@ static int rbd_header_from_disk(struct rbd_image_header *header,
                 header->snap_sizes = NULL;
         }
 
-        header->image_size = le64_to_cpu(ondisk->image_size);
         header->obj_order = ondisk->options.order;
         header->crypt_type = ondisk->options.crypt_type;
         header->comp_type = ondisk->options.comp_type;
 
         /* Allocate and fill in the snapshot context */
 
+        header->image_size = le64_to_cpu(ondisk->image_size);
         size = sizeof (struct ceph_snap_context);
         size += snap_count * sizeof (header->snapc->snaps[0]);
         header->snapc = kzalloc(size, GFP_KERNEL);
@@ -645,23 +649,24 @@ static int rbd_header_set_snap(struct rbd_device *rbd_dev, u64 *size)
 
         down_write(&rbd_dev->header_rwsem);
 
-        if (!memcmp(rbd_dev->snap_name, RBD_SNAP_HEAD_NAME,
+        if (!memcmp(rbd_dev->mapping.snap_name, RBD_SNAP_HEAD_NAME,
                     sizeof (RBD_SNAP_HEAD_NAME))) {
-                rbd_dev->snap_id = CEPH_NOSNAP;
-                rbd_dev->snap_exists = false;
-                rbd_dev->read_only = rbd_dev->rbd_opts.read_only;
+                rbd_dev->mapping.snap_id = CEPH_NOSNAP;
+                rbd_dev->mapping.snap_exists = false;
+                rbd_dev->mapping.read_only = rbd_dev->rbd_opts.read_only;
                 if (size)
                         *size = rbd_dev->header.image_size;
         } else {
                 u64 snap_id = 0;
 
-                ret = snap_by_name(&rbd_dev->header, rbd_dev->snap_name,
+                ret = snap_by_name(&rbd_dev->header,
+                                        rbd_dev->mapping.snap_name,
                                         &snap_id, size);
                 if (ret < 0)
                         goto done;
-                rbd_dev->snap_id = snap_id;
-                rbd_dev->snap_exists = true;
-                rbd_dev->read_only = true;      /* No choice for snapshots */
+                rbd_dev->mapping.snap_id = snap_id;
+                rbd_dev->mapping.snap_exists = true;
+                rbd_dev->mapping.read_only = true;
         }
 
         ret = 0;
@@ -1532,7 +1537,7 @@ static void rbd_rq_fn(struct request_queue *q)
                 size = blk_rq_bytes(rq);
                 ofs = blk_rq_pos(rq) * SECTOR_SIZE;
                 rq_bio = rq->bio;
-                if (do_write && rbd_dev->read_only) {
+                if (do_write && rbd_dev->mapping.read_only) {
                         __blk_end_request_all(rq, -EROFS);
                         continue;
                 }
@@ -1541,7 +1546,8 @@ static void rbd_rq_fn(struct request_queue *q)
 
                 down_read(&rbd_dev->header_rwsem);
 
-                if (rbd_dev->snap_id != CEPH_NOSNAP && !rbd_dev->snap_exists) {
+                if (rbd_dev->mapping.snap_id != CEPH_NOSNAP &&
+                                !rbd_dev->mapping.snap_exists) {
                         up_read(&rbd_dev->header_rwsem);
                         dout("request for non-existent snapshot");
                         spin_lock_irq(q->queue_lock);
@@ -1595,7 +1601,7 @@ static void rbd_rq_fn(struct request_queue *q)
                                               coll, cur_seg);
                         else
                                 rbd_req_read(rq, rbd_dev,
-                                             rbd_dev->snap_id,
+                                             rbd_dev->mapping.snap_id,
                                              ofs,
                                              op_size, bio,
                                              coll, cur_seg);
@@ -1767,7 +1773,7 @@ static int rbd_header_add_snap(struct rbd_device *rbd_dev,
         struct ceph_mon_client *monc;
 
         /* we should create a snapshot only if we're pointing at the head */
-        if (rbd_dev->snap_id != CEPH_NOSNAP)
+        if (rbd_dev->mapping.snap_id != CEPH_NOSNAP)
                 return -EINVAL;
 
         monc = &rbd_dev->rbd_client->client->monc;
@@ -1821,7 +1827,7 @@ static int __rbd_refresh_header(struct rbd_device *rbd_dev, u64 *hver)
         down_write(&rbd_dev->header_rwsem);
 
         /* resized? */
-        if (rbd_dev->snap_id == CEPH_NOSNAP) {
+        if (rbd_dev->mapping.snap_id == CEPH_NOSNAP) {
                 sector_t size = (sector_t) h.image_size / SECTOR_SIZE;
 
                 dout("setting size to %llu sectors", (unsigned long long) size);
@@ -2004,7 +2010,7 @@ static ssize_t rbd_snap_show(struct device *dev,
 {
         struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
 
-        return sprintf(buf, "%s\n", rbd_dev->snap_name);
+        return sprintf(buf, "%s\n", rbd_dev->mapping.snap_name);
 }
 
 static ssize_t rbd_image_refresh(struct device *dev,
@@ -2205,11 +2211,12 @@ static int rbd_dev_snap_devs_update(struct rbd_device *rbd_dev)
 
                         /* Existing snapshot not in the new snap context */
 
-                        if (rbd_dev->snap_id == snap->id)
-                                rbd_dev->snap_exists = false;
+                        if (rbd_dev->mapping.snap_id == snap->id)
+                                rbd_dev->mapping.snap_exists = false;
                         __rbd_remove_snap_dev(snap);
                         dout("%ssnap id %llu has been removed\n",
-                                rbd_dev->snap_id == snap->id ? "mapped " : "",
+                                rbd_dev->mapping.snap_id == snap->id ?
+                                                                "mapped " : "",
                                 (unsigned long long) snap->id);
 
                         /* Done with this list entry; advance */
@@ -2522,18 +2529,18 @@ static int rbd_add_parse_args(struct rbd_device *rbd_dev,
          * The snapshot name is optional.  If none is is supplied,
          * we use the default value.
          */
-        rbd_dev->snap_name = dup_token(&buf, &len);
-        if (!rbd_dev->snap_name)
+        rbd_dev->mapping.snap_name = dup_token(&buf, &len);
+        if (!rbd_dev->mapping.snap_name)
                 goto out_err;
         if (!len) {
                 /* Replace the empty name with the default */
-                kfree(rbd_dev->snap_name);
-                rbd_dev->snap_name
+                kfree(rbd_dev->mapping.snap_name);
+                rbd_dev->mapping.snap_name
                         = kmalloc(sizeof (RBD_SNAP_HEAD_NAME), GFP_KERNEL);
-                if (!rbd_dev->snap_name)
+                if (!rbd_dev->mapping.snap_name)
                         goto out_err;
 
-                memcpy(rbd_dev->snap_name, RBD_SNAP_HEAD_NAME,
+                memcpy(rbd_dev->mapping.snap_name, RBD_SNAP_HEAD_NAME,
                         sizeof (RBD_SNAP_HEAD_NAME));
         }
 
@@ -2642,7 +2649,7 @@ err_out_client:
         rbd_put_client(rbd_dev);
 err_put_id:
         if (rbd_dev->pool_name) {
-                kfree(rbd_dev->snap_name);
+                kfree(rbd_dev->mapping.snap_name);
                 kfree(rbd_dev->header_name);
                 kfree(rbd_dev->image_name);
                 kfree(rbd_dev->pool_name);
@@ -2695,7 +2702,7 @@ static void rbd_dev_release(struct device *dev)
         unregister_blkdev(rbd_dev->major, rbd_dev->name);
 
         /* done with the id, and with the rbd_dev */
-        kfree(rbd_dev->snap_name);
+        kfree(rbd_dev->mapping.snap_name);
         kfree(rbd_dev->header_name);
         kfree(rbd_dev->pool_name);
         kfree(rbd_dev->image_name);