rbd: support for object-map and fast-diff

Speed up reads, discards and zeroouts through RBD_OBJ_FLAG_MAY_EXIST
and RBD_OBJ_FLAG_NOOP_FOR_NONEXISTENT based on object map.

Invalid object maps are not trusted, but still updated.  Note that we
never iterate, resize or invalidate object maps.  If object-map feature
is enabled but object map fails to load, we just fail the requester
(either "rbd map" or I/O, by way of post-acquire action).
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

drivers/block/rbd_types.h

@@ -18,6 +18,7 @@
 /* For format version 2, rbd image 'foo' consists of objects
  *   rbd_id.foo		- id of image
  *   rbd_header.<id>	- image metadata
+ *   rbd_object_map.<id> - optional image object map
  *   rbd_data.<id>.0000000000000000
  *   rbd_data.<id>.0000000000000001
  *   ...		- data
@@ -25,6 +26,7 @@
  */
 
 #define RBD_HEADER_PREFIX      "rbd_header."
+#define RBD_OBJECT_MAP_PREFIX  "rbd_object_map."
 #define RBD_ID_PREFIX          "rbd_id."
 #define RBD_V2_DATA_FORMAT     "%s.%016llx"
 
@@ -39,6 +41,14 @@ enum rbd_notify_op {
 	RBD_NOTIFY_OP_HEADER_UPDATE      = 3,
 };
 
+#define OBJECT_NONEXISTENT	0
+#define OBJECT_EXISTS		1
+#define OBJECT_PENDING		2
+#define OBJECT_EXISTS_CLEAN	3
+
+#define RBD_FLAG_OBJECT_MAP_INVALID	(1ULL << 0)
+#define RBD_FLAG_FAST_DIFF_INVALID	(1ULL << 1)
+
 /*
  * For format version 1, rbd image 'foo' consists of objects
  *   foo.rbd		- image metadata

include/linux/ceph/cls_lock_client.h

@@ -52,4 +52,7 @@ int ceph_cls_lock_info(struct ceph_osd_client *osdc,
 		       char *lock_name, u8 *type, char **tag,
 		       struct ceph_locker **lockers, u32 *num_lockers);
 
+int ceph_cls_assert_locked(struct ceph_osd_request *req, int which,
+			   char *lock_name, u8 type, char *cookie, char *tag);
+
 #endif

include/linux/ceph/striper.h

@@ -66,4 +66,6 @@ int ceph_extent_to_file(struct ceph_file_layout *l,
 			struct ceph_file_extent **file_extents,
 			u32 *num_file_extents);
 
+u64 ceph_get_num_objects(struct ceph_file_layout *l, u64 size);
+
 #endif

net/ceph/cls_lock_client.c

@@ -6,6 +6,7 @@
 
 #include <linux/ceph/cls_lock_client.h>
 #include <linux/ceph/decode.h>
+#include <linux/ceph/libceph.h>
 
 /**
  * ceph_cls_lock - grab rados lock for object
@@ -378,3 +379,47 @@ int ceph_cls_lock_info(struct ceph_osd_client *osdc,
 	return ret;
 }
 EXPORT_SYMBOL(ceph_cls_lock_info);
+
+int ceph_cls_assert_locked(struct ceph_osd_request *req, int which,
+			   char *lock_name, u8 type, char *cookie, char *tag)
+{
+	int assert_op_buf_size;
+	int name_len = strlen(lock_name);
+	int cookie_len = strlen(cookie);
+	int tag_len = strlen(tag);
+	struct page **pages;
+	void *p, *end;
+	int ret;
+
+	assert_op_buf_size = name_len + sizeof(__le32) +
+			     cookie_len + sizeof(__le32) +
+			     tag_len + sizeof(__le32) +
+			     sizeof(u8) + CEPH_ENCODING_START_BLK_LEN;
+	if (assert_op_buf_size > PAGE_SIZE)
+		return -E2BIG;
+
+	ret = osd_req_op_cls_init(req, which, "lock", "assert_locked");
+	if (ret)
+		return ret;
+
+	pages = ceph_alloc_page_vector(1, GFP_NOIO);
+	if (IS_ERR(pages))
+		return PTR_ERR(pages);
+
+	p = page_address(pages[0]);
+	end = p + assert_op_buf_size;
+
+	/* encode cls_lock_assert_op struct */
+	ceph_start_encoding(&p, 1, 1,
+			    assert_op_buf_size - CEPH_ENCODING_START_BLK_LEN);
+	ceph_encode_string(&p, end, lock_name, name_len);
+	ceph_encode_8(&p, type);
+	ceph_encode_string(&p, end, cookie, cookie_len);
+	ceph_encode_string(&p, end, tag, tag_len);
+	WARN_ON(p != end);
+
+	osd_req_op_cls_request_data_pages(req, which, pages, assert_op_buf_size,
+					  0, false, true);
+	return 0;
+}
+EXPORT_SYMBOL(ceph_cls_assert_locked);

net/ceph/striper.c

@@ -259,3 +259,20 @@ int ceph_extent_to_file(struct ceph_file_layout *l,
 	return 0;
 }
 EXPORT_SYMBOL(ceph_extent_to_file);
+
+u64 ceph_get_num_objects(struct ceph_file_layout *l, u64 size)
+{
+	u64 period = (u64)l->stripe_count * l->object_size;
+	u64 num_periods = DIV64_U64_ROUND_UP(size, period);
+	u64 remainder_bytes;
+	u64 remainder_objs = 0;
+
+	div64_u64_rem(size, period, &remainder_bytes);
+	if (remainder_bytes > 0 &&
+	    remainder_bytes < (u64)l->stripe_count * l->stripe_unit)
+		remainder_objs = l->stripe_count -
+			    DIV_ROUND_UP_ULL(remainder_bytes, l->stripe_unit);
+
+	return num_periods * l->stripe_count - remainder_objs;
+}
+EXPORT_SYMBOL(ceph_get_num_objects);