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authorAlex Elder <elder@dreamhost.com>2012-01-29 13:57:44 -0600
committerAlex Elder <elder@dreamhost.com>2012-03-22 10:47:47 -0500
commitd184f6bfde1428ad4a690d49b28afc9ab4d57b35 (patch)
treefd3156df944edc90146143e5cea416d34c8fcd47 /drivers/block/rbd.c
parent499afd5b8e742792fda6bd7730c738ad83aecf6b (diff)
rbd: restore previous rbd id sequence behavior
It used to be that selecting a new unique identifier for an added rbd device required searching all existing ones to find the highest id is used. A recent change made that unnecessary, but made it so that id's used were monotonically non-decreasing. It's a bit more pleasant to have smaller rbd id's though, and this change makes ids get allocated as they were before--each new id is one more than the maximum currently in use. Signed-off-by: Alex Elder <elder@dreamhost.com> Signed-off-by: Sage Weil <sage@newdream.net>
Diffstat (limited to 'drivers/block/rbd.c')
-rw-r--r--drivers/block/rbd.c40
1 files changed, 34 insertions, 6 deletions
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index e7727e8337f..9ac1484a95a 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2172,18 +2172,46 @@ static void rbd_id_get(struct rbd_device *rbd_dev)
*/
static void rbd_id_put(struct rbd_device *rbd_dev)
{
- BUG_ON(rbd_dev->id < 1);
+ struct list_head *tmp;
+ int rbd_id = rbd_dev->id;
+ int max_id;
+
+ BUG_ON(rbd_id < 1);
spin_lock(&rbd_dev_list_lock);
list_del_init(&rbd_dev->node);
+
+ /*
+ * If the id being "put" is not the current maximum, there
+ * is nothing special we need to do.
+ */
+ if (rbd_id != atomic64_read(&rbd_id_max)) {
+ spin_unlock(&rbd_dev_list_lock);
+ return;
+ }
+
+ /*
+ * We need to update the current maximum id. Search the
+ * list to find out what it is. We're more likely to find
+ * the maximum at the end, so search the list backward.
+ */
+ max_id = 0;
+ list_for_each_prev(tmp, &rbd_dev_list) {
+ struct rbd_device *rbd_dev;
+
+ rbd_dev = list_entry(tmp, struct rbd_device, node);
+ if (rbd_id > max_id)
+ max_id = rbd_id;
+ }
spin_unlock(&rbd_dev_list_lock);
/*
- * New id's are always one more than the current maximum.
- * If the id being "put" *is* that maximum, decrement the
- * maximum so the next one requested just reuses this one.
+ * The max id could have been updated by rbd_id_get(), in
+ * which case it now accurately reflects the new maximum.
+ * Be careful not to overwrite the maximum value in that
+ * case.
*/
- atomic64_cmpxchg(&rbd_id_max, rbd_dev->id, rbd_dev->id - 1);
+ atomic64_cmpxchg(&rbd_id_max, rbd_id, max_id);
}
static ssize_t rbd_add(struct bus_type *bus,
@@ -2220,7 +2248,7 @@ static ssize_t rbd_add(struct bus_type *bus,
init_rwsem(&rbd_dev->header.snap_rwsem);
- /* generate unique id: one more than highest used so far */
+ /* generate unique id: find highest unique id, add one */
rbd_id_get(rbd_dev);
/* parse add command */