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Commit cfbf6377 authored by Alex Elder's avatar Alex Elder Committed by Sage Weil
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rbd: use rwsem to protect header updates 

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: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarJosh Durgin <josh.durgin@inktank.com>
parent 1ba0f1e7

drivers/block/rbd.c

+10 −16
Original line number Diff line number Diff line
@@ -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);
@@ -516,7 +516,7 @@ 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)

{
@@ -673,13 +673,13 @@ 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;

}
@@ -833,7 +833,6 @@ 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;
@@ -862,8 +861,6 @@ 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;
@@ -3333,7 +3330,7 @@ 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);
@@ -3343,7 +3340,8 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev) 
	/* If it's a mapped snapshot, validate its EXISTS flag */



	rbd_exists_validate(rbd_dev);

	mutex_unlock(&ctl_mutex);

	up_write(&rbd_dev->header_rwsem);



	if (mapping_size != rbd_dev->mapping.size) {

		sector_t size;
@@ -4272,16 +4270,14 @@ 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);



	ret = rbd_dev_v2_image_size(rbd_dev);

	if (ret)

		goto out;

		return ret;



	if (first_time) {

		ret = rbd_dev_v2_header_onetime(rbd_dev);

		if (ret)

			goto out;

			return ret;

	}



	/*
@@ -4296,7 +4292,7 @@ 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
@@ -4317,8 +4313,6 @@ 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;

}