From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH REPOST 1/2] rbd: make exists flag atomic Date: Thu, 03 Jan 2013 16:53:54 -0600 Message-ID: <50E60C02.2090605@inktank.com> References: <50E60BD0.30408@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ie0-f173.google.com ([209.85.223.173]:56643 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754261Ab3ACWx4 (ORCPT ); Thu, 3 Jan 2013 17:53:56 -0500 Received: by mail-ie0-f173.google.com with SMTP id e13so19066983iej.18 for ; Thu, 03 Jan 2013 14:53:56 -0800 (PST) In-Reply-To: <50E60BD0.30408@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: "ceph-devel@vger.kernel.org" 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 --- 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 1348825..a3b0d43 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; } @@ -1670,7 +1670,7 @@ 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); } @@ -2292,6 +2292,7 @@ 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); @@ -2916,7 +2917,7 @@ 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 ? -- 1.7.9.5