On 05/31/2013 06:20 PM, Alex Elder wrote:
Updating an image header needs to be protected to ensure it's
done consistently. However distinct headers can be updated
concurrently without a problem. Instead of using the global
control lock to serialize headder updates, just rely on the header
semaphore. (It's already used, this just moves it out to cover
a broader section of the code.)
That leaves the control mutex protecting only the creation of rbd
clients, so rename it.
This resolves:
http://tracker.ceph.com/issues/5222
Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
---
drivers/block/rbd.c | 25 +++++++++----------------
1 file changed, 9 insertions(+), 16 deletions(-)
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 9c81a5c..107e1e5 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -372,7 +372,7 @@ enum rbd_dev_flags {
RBD_DEV_FLAG_REMOVING, /* this mapping is being removed */
};
-static DEFINE_MUTEX(ctl_mutex); /* Serialize open/close/setup/teardown */
+static DEFINE_MUTEX(client_mutex); /* Serialize client creation */
static LIST_HEAD(rbd_dev_list); /* devices */
static DEFINE_SPINLOCK(rbd_dev_list_lock);
@@ -518,7 +518,7 @@ static const struct block_device_operations
rbd_bd_ops = {
/*
* Initialize an rbd client instance. Success or not, this function
- * consumes ceph_opts. Caller holds ctl_mutex.
+ * consumes ceph_opts. Caller holds client_mutex.
*/
static struct rbd_client *rbd_client_create(struct ceph_options *ceph_opts)
{
@@ -675,13 +675,13 @@ static struct rbd_client *rbd_get_client(struct
ceph_options *ceph_opts)
{
struct rbd_client *rbdc;
- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+ mutex_lock_nested(&client_mutex, SINGLE_DEPTH_NESTING);
rbdc = rbd_client_find(ceph_opts);
if (rbdc) /* using an existing client */
ceph_destroy_options(ceph_opts);
else
rbdc = rbd_client_create(ceph_opts);
- mutex_unlock(&ctl_mutex);
+ mutex_unlock(&client_mutex);
return rbdc;
}
@@ -835,7 +835,6 @@ static int rbd_header_from_disk(struct rbd_device
*rbd_dev,
/* We won't fail any more, fill in the header */
- down_write(&rbd_dev->header_rwsem);
if (first_time) {
header->object_prefix = object_prefix;
header->obj_order = ondisk->options.order;
@@ -864,8 +863,6 @@ static int rbd_header_from_disk(struct rbd_device
*rbd_dev,
if (rbd_dev->mapping.size != header->image_size)
rbd_dev->mapping.size = header->image_size;
- up_write(&rbd_dev->header_rwsem);
-
return 0;
out_2big:
ret = -EIO;
@@ -3349,17 +3346,17 @@ static int rbd_dev_refresh(struct rbd_device
*rbd_dev)
int ret;
rbd_assert(rbd_image_format_valid(rbd_dev->image_format));
- mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+ down_write(&rbd_dev->header_rwsem);
mapping_size = rbd_dev->mapping.size;
if (rbd_dev->image_format == 1)
ret = rbd_dev_v1_header_info(rbd_dev);
else
ret = rbd_dev_v2_header_info(rbd_dev);
+ up_write(&rbd_dev->header_rwsem);
I think this needs to happen after rbd_exists_validate() so that
reading the snapshot context via rbd_dev_snap_index() is protected.
Looks good otherwise.
Reviewed-by: Josh Durgin <josh.durgin@xxxxxxxxxxx>
/* If it's a mapped snapshot, validate its EXISTS flag */
rbd_exists_validate(rbd_dev);
- mutex_unlock(&ctl_mutex);
if (mapping_size != rbd_dev->mapping.size) {
sector_t size;
@@ -4288,12 +4285,10 @@ static int rbd_dev_v2_header_info(struct
rbd_device *rbd_dev)
bool first_time = rbd_dev->header.object_prefix == NULL;
int ret;
- down_write(&rbd_dev->header_rwsem);
-
if (first_time) {
ret = rbd_dev_v2_header_onetime(rbd_dev);
if (ret)
- goto out;
+ return ret;
}
/*
@@ -4308,7 +4303,7 @@ static int rbd_dev_v2_header_info(struct
rbd_device *rbd_dev)
ret = rbd_dev_v2_parent_info(rbd_dev);
if (ret)
- goto out;
+ return ret;
/*
* Print a warning if this is the initial probe and
@@ -4325,7 +4320,7 @@ static int rbd_dev_v2_header_info(struct
rbd_device *rbd_dev)
ret = rbd_dev_v2_image_size(rbd_dev);
if (ret)
- goto out;
+ return ret;
if (rbd_dev->spec->snap_id == CEPH_NOSNAP)
if (rbd_dev->mapping.size != rbd_dev->header.image_size)
@@ -4333,8 +4328,6 @@ static int rbd_dev_v2_header_info(struct
rbd_device *rbd_dev)
ret = rbd_dev_v2_snap_context(rbd_dev);
dout("rbd_dev_v2_snap_context returned %d\n", ret);
-out:
- up_write(&rbd_dev->header_rwsem);
return ret;
}
--
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