rbd: expose the correct size of the device in sysfs

If an image was mapped to a snapshot, the size of the head version
would be shown. Protect capacity with header_rwsem, since it may
change.

Signed-off-by: Josh Durgin <josh.durgin@dreamhost.com>
Reviewed-by: Alex Elder <elder@inktank.com>
(cherry picked from commit a51aa0c042fa39946dd017d5f91a073300a71577)
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 52a045b11d4ecbdeddde7f4f2b15b5076850aeb7..0ac989cf240e517141c51e4b4ac2b393d44c142d 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1720,6 +1720,8 @@ static int __rbd_update_snaps(struct rbd_device *rbd_dev)
        if (ret < 0)
                return ret;
 
+       down_write(&rbd_dev->header_rwsem);
+
        /* resized? */
        if (rbd_dev->snap_id == CEPH_NOSNAP) {
                sector_t size = (sector_t) h.image_size / SECTOR_SIZE;
@@ -1728,8 +1730,6 @@ static int __rbd_update_snaps(struct rbd_device *rbd_dev)
                set_capacity(rbd_dev->disk, size);
        }
 
-       down_write(&rbd_dev->header_rwsem);
-
        snap_seq = rbd_dev->header.snapc->seq;
        if (rbd_dev->header.total_snaps &&
            rbd_dev->header.snapc->snaps[0] == snap_seq)
@@ -1844,8 +1844,13 @@ static ssize_t rbd_size_show(struct device *dev,
                             struct device_attribute *attr, char *buf)
 {
        struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
+       sector_t size;
+
+       down_read(&rbd_dev->header_rwsem);
+       size = get_capacity(rbd_dev->disk);
+       up_read(&rbd_dev->header_rwsem);
 
-       return sprintf(buf, "%llu\n", (unsigned long long)rbd_dev->header.image_size);
+       return sprintf(buf, "%llu\n", (unsigned long long) size * SECTOR_SIZE);
 }
 
 static ssize_t rbd_major_show(struct device *dev,