I see that set_bit is atomic, but I don't see that test_bit is. Am I
missing a subtlety?
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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