rbd: reference count parent requests (a2acd00e) · Commits · 戴 / test

drivers/block/rbd.c

+102 −2

Original line number	Diff line number	Diff line
		@@ -55,6 +55,39 @@
		#define SECTOR_SHIFT 9
		#define SECTOR_SIZE (1ULL << SECTOR_SHIFT)

		/*
		* Increment the given counter and return its updated value.
		* If the counter is already 0 it will not be incremented.
		* If the counter is already at its maximum value returns
		* -EINVAL without updating it.
		*/
		static int atomic_inc_return_safe(atomic_t *v)
		{
		unsigned int counter;

		counter = (unsigned int)__atomic_add_unless(v, 1, 0);
		if (counter <= (unsigned int)INT_MAX)
		return (int)counter;

		atomic_dec(v);

		return -EINVAL;
		}

		/* Decrement the counter. Return the resulting value, or -EINVAL */
		static int atomic_dec_return_safe(atomic_t *v)
		{
		int counter;

		counter = atomic_dec_return(v);
		if (counter >= 0)
		return counter;

		atomic_inc(v);

		return -EINVAL;
		}

		#define RBD_DRV_NAME "rbd"
		#define RBD_DRV_NAME_LONG "rbd (rados block device)"

		@@ -312,6 +345,7 @@ struct rbd_device {

		struct rbd_spec *parent_spec;
		u64 parent_overlap;
		atomic_t parent_ref;
		struct rbd_device *parent;

		/* protects updating the header */
		@@ -361,6 +395,7 @@ static ssize_t rbd_add(struct bus_type bus, const char buf,
		static ssize_t rbd_remove(struct bus_type bus, const char buf,
		size_t count);
		static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool mapping);
		static void rbd_spec_put(struct rbd_spec *spec);

		static struct bus_attribute rbd_bus_attrs[] = {
		__ATTR(add, S_IWUSR, NULL, rbd_add),
		@@ -1505,6 +1540,12 @@ static void img_request_layered_set(struct rbd_img_request *img_request)
		smp_mb();
		}

		static void img_request_layered_clear(struct rbd_img_request *img_request)
		{
		clear_bit(IMG_REQ_LAYERED, &img_request->flags);
		smp_mb();
		}

		static bool img_request_layered_test(struct rbd_img_request *img_request)
		{
		smp_mb();
		@@ -1859,6 +1900,58 @@ static void rbd_dev_unparent(struct rbd_device *rbd_dev)
		rbd_dev->parent_overlap = 0;
		}

		/*
		* Parent image reference counting is used to determine when an
		* image's parent fields can be safely torn down--after there are no
		* more in-flight requests to the parent image. When the last
		* reference is dropped, cleaning them up is safe.
		*/
		static void rbd_dev_parent_put(struct rbd_device *rbd_dev)
		{
		int counter;

		if (!rbd_dev->parent_spec)
		return;

		counter = atomic_dec_return_safe(&rbd_dev->parent_ref);
		if (counter > 0)
		return;

		/* Last reference; clean up parent data structures */

		if (!counter)
		rbd_dev_unparent(rbd_dev);
		else
		rbd_warn(rbd_dev, "parent reference underflow\n");
		}

		/*
		* If an image has a non-zero parent overlap, get a reference to its
		* parent.
		*
		* Returns true if the rbd device has a parent with a non-zero
		* overlap and a reference for it was successfully taken, or
		* false otherwise.
		*/
		static bool rbd_dev_parent_get(struct rbd_device *rbd_dev)
		{
		int counter;

		if (!rbd_dev->parent_spec)
		return false;

		counter = atomic_inc_return_safe(&rbd_dev->parent_ref);
		if (counter > 0 && rbd_dev->parent_overlap)
		return true;

		/* Image was flattened, but parent is not yet torn down */

		if (counter < 0)
		rbd_warn(rbd_dev, "parent reference overflow\n");

		return false;
		}

		/*
		* Caller is responsible for filling in the list of object requests
		* that comprises the image request, and the Linux request pointer
		@@ -1892,7 +1985,7 @@ static struct rbd_img_request *rbd_img_request_create(
		} else {
		img_request->snap_id = rbd_dev->spec->snap_id;
		}
		if (rbd_dev->parent_overlap)
		if (rbd_dev_parent_get(rbd_dev))
		img_request_layered_set(img_request);
		spin_lock_init(&img_request->completion_lock);
		img_request->next_completion = 0;
		@@ -1923,6 +2016,11 @@ static void rbd_img_request_destroy(struct kref *kref)
		rbd_img_obj_request_del(img_request, obj_request);
		rbd_assert(img_request->obj_request_count == 0);

		if (img_request_layered_test(img_request)) {
		img_request_layered_clear(img_request);
		rbd_dev_parent_put(img_request->rbd_dev);
		}

		if (img_request_write_test(img_request))
		ceph_put_snap_context(img_request->snapc);

		@@ -3502,6 +3600,7 @@ static struct rbd_device rbd_dev_create(struct rbd_client rbdc,

		spin_lock_init(&rbd_dev->lock);
		rbd_dev->flags = 0;
		atomic_set(&rbd_dev->parent_ref, 0);
		INIT_LIST_HEAD(&rbd_dev->node);
		init_rwsem(&rbd_dev->header_rwsem);

		@@ -4534,7 +4633,7 @@ static void rbd_dev_unprobe(struct rbd_device *rbd_dev)
		{
		struct rbd_image_header *header;

		rbd_dev_unparent(rbd_dev);
		rbd_dev_parent_put(rbd_dev);

		/* Free dynamic fields from the header, then zero it out */

		@@ -4606,6 +4705,7 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
		if (ret < 0)
		goto out_err;
		rbd_dev->parent = parent;
		atomic_set(&rbd_dev->parent_ref, 1);

		return 0;
		out_err:

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