Re: [PATCH 1/2] rbd: define flags field, use it for exists flag

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Reviewed-by: Dan Mick <dan.mick@xxxxxxxxxxx>

On 01/14/2013 10:50 AM, Alex Elder wrote:
Define a new rbd device flags field, manipulated using atomic bit
operations.  Replace the use of the current "exists" flag with a
bit in this new "flags" field.

Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
---
  drivers/block/rbd.c |   17 ++++++++++++-----
  1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 02002b1..9eb1631 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -232,7 +232,7 @@ struct rbd_device {
  	spinlock_t		lock;		/* queue lock */

  	struct rbd_image_header	header;
-	atomic_t		exists;
+	unsigned long		flags;
  	struct rbd_spec		*spec;

  	char			*header_name;
@@ -260,6 +260,12 @@ struct rbd_device {
  	unsigned long		open_count;
  };

+/* Flag bits for rbd_dev->flags */
+
+enum rbd_dev_flags {
+	rbd_dev_flag_exists,	/* mapped snapshot has not been deleted */
+};
+
  static DEFINE_MUTEX(ctl_mutex);	  /* Serialize open/close/setup/teardown */

  static LIST_HEAD(rbd_dev_list);    /* devices */
@@ -756,7 +762,8 @@ static int rbd_dev_set_mapping(struct rbd_device
*rbd_dev)
  			goto done;
  		rbd_dev->mapping.read_only = true;
  	}
-	atomic_set(&rbd_dev->exists, 1);
+	set_bit(rbd_dev_flag_exists, &rbd_dev->flags);
+
  done:
  	return ret;
  }
@@ -1654,7 +1661,7 @@ static void rbd_rq_fn(struct request_queue *q)
  			snapc = ceph_get_snap_context(rbd_dev->header.snapc);
  			up_read(&rbd_dev->header_rwsem);
  			rbd_assert(snapc != NULL);
-		} else if (!atomic_read(&rbd_dev->exists)) {
+		} else if (!test_bit(rbd_dev_flag_exists, &rbd_dev->flags)) {
  			rbd_assert(rbd_dev->spec->snap_id != CEPH_NOSNAP);
  			dout("request for non-existent snapshot");
  			result = -ENXIO;
@@ -2270,7 +2277,7 @@ struct rbd_device *rbd_dev_create(struct
rbd_client *rbdc,
  		return NULL;

  	spin_lock_init(&rbd_dev->lock);
-	atomic_set(&rbd_dev->exists, 0);
+	rbd_dev->flags = 0;
  	INIT_LIST_HEAD(&rbd_dev->node);
  	INIT_LIST_HEAD(&rbd_dev->snaps);
  	init_rwsem(&rbd_dev->header_rwsem);
@@ -2902,7 +2909,7 @@ static int rbd_dev_snaps_update(struct rbd_device
*rbd_dev)
  			/* Existing snapshot not in the new snap context */

  			if (rbd_dev->spec->snap_id == snap->id)
-				atomic_set(&rbd_dev->exists, 0);
+				set_bit(rbd_dev_flag_exists, &rbd_dev->flags);
  			rbd_remove_snap_dev(snap);
  			dout("%ssnap id %llu has been removed\n",
  				rbd_dev->spec->snap_id == snap->id ?

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