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rbd: define flags field, use it for exists flag

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Define a new rbd device flags field, manipulated using bit
operations.  Replace the use of the current "exists" flag with a bit
in this new "flags" field.  Add a little commentary about the
"exists" flag, which does not need to be manipulated atomically.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
This commit is contained in:
Alex Elder 2013-01-14 12:43:31 -06:00 committed by Sage Weil
parent 8eb8756530
commit 6d292906f8
1 changed files with 28 additions and 9 deletions
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37
drivers/block/rbd.c
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@ -264,7 +264,7 @@ 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;
@ -292,6 +292,12 @@ 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 */
@ -782,7 +788,8 @@ 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;
}
@ -1877,9 +1884,14 @@ static void rbd_request_fn(struct request_queue *q)
rbd_assert(rbd_dev->spec->snap_id == CEPH_NOSNAP);
}
/* Quit early if the snapshot has disappeared */
if (!atomic_read(&rbd_dev->exists)) {
/*
* Quit early if the mapped snapshot no longer
* exists. It's still possible the snapshot will
* have disappeared by the time our request arrives
* at the osd, but there's no sense in sending it if
* we already know.
*/
if (!test_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags)) {
dout("request for non-existent snapshot");
rbd_assert(rbd_dev->spec->snap_id != CEPH_NOSNAP);
result = -ENXIO;
@ -2571,7 +2583,7 @@ 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);
@ -3200,10 +3212,17 @@ static int rbd_dev_snaps_update(struct rbd_device *rbd_dev)
if (snap_id == CEPH_NOSNAP || (snap && snap->id > snap_id)) {
struct list_head *next = links->next;
/* Existing snapshot not in the new snap context */
/*
* A previously-existing snapshot is not in
* the new snap context.
*
* If the now missing snapshot is the one the
* image is mapped to, clear its exists flag
* so we can avoid sending any more requests
* to it.
*/
if (rbd_dev->spec->snap_id == snap->id)
atomic_set(&rbd_dev->exists, 0);
clear_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 ?