rbd: updates from Josh Durgin

This is updated whenever a snapshot is added or deleted, and the snapc pointer is changed with every refresh of the header.

Signed-off-by Josh Durgin <[email protected]>

Reviewed-by Alex Elder <[email protected]>

---
 drivers/block/rbd.c |    4 +++-

 1 file changed, 3 insertions(+), 1 deletion(-)

Index: b/drivers/block/rbd.c
===================================================================

drivers/block/rbd.c +3 -1

@@ -1685,7 +1685,9 @@
        if (ret < 0)
                return ret;
 
-       dev->header.snapc->seq =  new_snapid;
+       down_write(&dev->header_rwsem);
+       dev->header.snapc->seq = new_snapid;
+       up_write(&dev->header_rwsem);
 
        return 0;

 bad:

When a device was open at a snapshot, and snapshots were deleted or added, data from the wrong snapshot could be read. Instead of assuming the snap context is constant, store the actual snap id when the device is initialized, and rely on the OSDs to signal an error if we try reading from a snapshot that was deleted.

Signed-off-by Josh Durgin <[email protected]>

Reviewed-by Alex Elder <[email protected]>

---
 drivers/block/rbd.c |   27 +++++----------------------

 1 file changed, 5 insertions(+), 22 deletions(-)

Index: b/drivers/block/rbd.c
===================================================================

drivers/block/rbd.c +1 -17

@@ -175,8 +175,7 @@
        /* protects updating the header */
        struct rw_semaphore     header_rwsem;
        char                    snap_name[RBD_MAX_SNAP_NAME_LEN];
-       u32 cur_snap;   /* index+1 of current snapshot within snap context
-                          0 - for the head */
+       u64                     snap_id;        /* current snapshot id */
        int read_only;
 
        struct list_head        node;

@@ -554,21 +553,6 @@
        return -ENOMEM;
  }
 
-static int snap_index(struct rbd_image_header *header, int snap_num)
-{
-       return header->total_snaps - snap_num;
-}
-
-static u64 cur_snap_id(struct rbd_device *rbd_dev)
-{
-       struct rbd_image_header *header = &rbd_dev->header;
-
-       if (!rbd_dev->cur_snap)
-               return 0;
-
-       return header->snapc->snaps[snap_index(header, rbd_dev->cur_snap)];
-}
-

 static int snap_by_name(struct rbd_image_header *header, const char *snap_name,
                       u64 *seq, u64 *size)
 {

drivers/block/rbd.c +0 -0

@@ -607,7 +591,7 @@
                        snapc->seq = header->snap_seq;

               else
                       snapc->seq = 0;
-               dev->cur_snap = 0;
+               dev->snap_id = CEPH_NOSNAP; dev->read_only = 0;
               if (size)
                       *size = header->image_size;

drivers/block/rbd.c +1 -2

@@ -615,8 +599,7 @@
                ret = snap_by_name(header, dev->snap_name, &snapc->seq,
 size);
                if (ret < 0)
                        goto done;
-
-               dev->cur_snap = header->total_snaps - ret;
+               dev->snap_id = snapc->seq;
                dev->read_only = 1;
        }

@@ -1523,7 +1506,7 @@
                                              coll, cur_seg);

                       else
                               rbd_req_read(rq, rbd_dev,
-                                            cur_snap_id(rbd_dev),
+                                            rbd_dev->snap_id, ofs, op_size, bio, coll, cur_seg);

The snapid parameters passed to rbd_do_op() and rbd_req_sync_op() are now always either a valid snapid or an explicit CEPH_NOSNAP.

[[email protected]: Rephrased the description]

Signed-off-by Josh Durgin <[email protected]>

Reviewed-by Alex Elder <[email protected]>

---
 drivers/block/rbd.c |    4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

Index: b/drivers/block/rbd.c
===================================================================

drivers/block/rbd.c +1 -1

@@ -1153,7 +1153,7 @@
                         int coll_index)
  {
        return rbd_do_op(rq, rbd_dev, NULL,
-                        (snapid ? snapid : CEPH_NOSNAP),
+                        snapid,
                         CEPH_OSD_OP_READ,
                         CEPH_OSD_FLAG_READ,
                         2,

Snapshot sizes should be the same type as regular image sizes. This only affects their displayed size in sysfs, not the reported size of an actual block device sizes.

Signed-off-by Josh Durgin <[email protected]>

Reviewed-by Alex Elder <[email protected]>

---
 drivers/block/rbd.c |    6 +++---

 1 file changed, 3 insertions(+), 3 deletions(-)

Index: b/drivers/block/rbd.c
===================================================================

drivers/block/rbd.c +2 -2

@@ -141,7 +141,7 @@
  struct rbd_snap {
        struct  device          dev;
        const char              *name;
-       size_t                  size;
+       u64                     size;
        struct list_head        node;
        u64                     id;
  };

@@ -1936,7 +1936,7 @@
  {
        struct rbd_snap *snap = container_of(dev, struct rbd_snap, dev);
 
-       return sprintf(buf, "%zd\n", snap->size);
+       return sprintf(buf, "%llu\n", (unsigned long long)snap->size);
  }
 
  static ssize_t rbd_snap_id_show(struct device *dev,

This function rereads the entire header and handles any changes in it, not just changes in snapshots.

Signed-off-by Josh Durgin <[email protected]>

Reviewed-by Alex Elder <[email protected]>

---
 drivers/block/rbd.c |   12 ++++++------

 1 file changed, 6 insertions(+), 6 deletions(-)

Index: b/drivers/block/rbd.c
===================================================================

drivers/block/rbd.c +2 -2

@@ -240,7 +240,7 @@
        put_device(&rbd_dev->dev);
  }
 
-static int __rbd_update_snaps(struct rbd_device *rbd_dev);
+static int __rbd_refresh_header(struct rbd_device *rbd_dev);
 
  static int rbd_open(struct block_device *bdev, fmode_t mode)
  {

@@ -1223,7 +1223,7 @@
        dout("rbd_watch_cb %s notify_id=%lld opcode=%d\n", dev->obj_md_name,
                notify_id, (int)opcode);
        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
-       rc = __rbd_update_snaps(dev);
+       rc = __rbd_refresh_header(dev);
        mutex_unlock(&ctl_mutex);
        if (rc)

               pr_warning(RBD_DRV_NAME "%d got notification but failed to "

drivers/block/rbd.c +3 -3

@@ -1690,7 +1690,7 @@
  /*
  * only read the first part of the ondisk header, without the snaps info
  */
-static int __rbd_update_snaps(struct rbd_device *rbd_dev)
+static int __rbd_refresh_header(struct rbd_device *rbd_dev)
  {
        int ret;
        struct rbd_image_header h;

@@ -1877,7 +1877,7 @@
 
        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
 
-       rc = __rbd_update_snaps(rbd_dev);
+       rc = __rbd_refresh_header(rbd_dev);
        if (rc < 0)
                ret = rc;
 

@@ -2160,7 +2160,7 @@
                                         rbd_dev->header.obj_version);
                if (ret == -ERANGE) {
                        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
-                       rc = __rbd_update_snaps(rbd_dev);
+                       rc = __rbd_refresh_header(rbd_dev);
                        mutex_unlock(&ctl_mutex);
                        if (rc < 0)
                                return rc;

Each attribute is prefixed with "snap_".

Signed-off-by Josh Durgin <[email protected]>

Reviewed-by Alex Elder <[email protected]>

---
 Documentation/ABI/testing/sysfs-bus-rbd |    4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

Index: b/Documentation/ABI/testing/sysfs-bus-rbd
===================================================================

Documentation/ABI/testing/sysfs-bus-rbd +0 -0

@@ -65,11 +65,11 @@

 Entries under /sys/bus/rbd/devices/<dev-id>/snap_<snap-name>
 -------------------------------------------------------------

Documentation/ABI/testing/sysfs-bus-rbd +1 -1

-id
+snap_id

       The rados internal snapshot id assigned for this snapshot

Documentation/ABI/testing/sysfs-bus-rbd +1 -1

-size
+snap_size

       The size of the image when this snapshot was taken.