From d78b650a595e23e5a115d332e3c37e019baf7703 Mon Sep 17 00:00:00 2001 From: Alex Elder Date: Fri, 9 Nov 2012 08:43:15 -0600 Subject: [PATCH] rbd: make exists flag atomic The rbd_device->exists field can be updated asynchronously, changing from set to clear if a mapped snapshot disappears from the base image's snapshot context. Currently, value of the "exists" flag is only read and modified under protection of the header semaphore, but that will change with the next patch. Making it atomic ensures this won't be a problem because the a the non-existence of device will be immediately known. Signed-off-by: Alex Elder Reviewed-by: Josh Durgin --- drivers/block/rbd.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 9d49e5b888d8..2846536d446e 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -229,7 +229,7 @@ struct rbd_device { spinlock_t lock; /* queue lock */ struct rbd_image_header header; - bool exists; + atomic_t exists; struct rbd_spec *spec; char *header_name; @@ -751,7 +751,7 @@ static int rbd_dev_set_mapping(struct rbd_device *rbd_dev) goto done; rbd_dev->mapping.read_only = true; } - rbd_dev->exists = true; + atomic_set(&rbd_dev->exists, 1); done: return ret; } @@ -1671,7 +1671,7 @@ static void rbd_rq_fn(struct request_queue *q) /* Grab a reference to the snapshot context */ down_read(&rbd_dev->header_rwsem); - if (rbd_dev->exists) { + if (atomic_read(&rbd_dev->exists)) { snapc = ceph_get_snap_context(rbd_dev->header.snapc); rbd_assert(snapc != NULL); } @@ -2294,6 +2294,7 @@ struct rbd_device *rbd_dev_create(struct rbd_client *rbdc, return NULL; spin_lock_init(&rbd_dev->lock); + atomic_set(&rbd_dev->exists, 0); INIT_LIST_HEAD(&rbd_dev->node); INIT_LIST_HEAD(&rbd_dev->snaps); init_rwsem(&rbd_dev->header_rwsem); @@ -2918,7 +2919,7 @@ 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) - rbd_dev->exists = false; + atomic_set(&rbd_dev->exists, 0); rbd_remove_snap_dev(snap); dout("%ssnap id %llu has been removed\n", rbd_dev->spec->snap_id == snap->id ? -- 2.39.5