libceph: define struct ceph_sparse_extent and add some helpers

When the OSD sends back a sparse read reply, it contains an array of
these structures. Define the structure and add a couple of helpers for
dealing with them.

Also add a place in struct ceph_osd_req_op to store the extent buffer,
and code to free it if it's populated when the req is torn down.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-and-tested-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

include/linux/ceph/osd_client.h

@@ -29,6 +29,17 @@ typedef void (*ceph_osdc_callback_t)(struct ceph_osd_request *);
 
 #define CEPH_HOMELESS_OSD	-1
 
+/*
+ * A single extent in a SPARSE_READ reply.
+ *
+ * Note that these come from the OSD as little-endian values. On BE arches,
+ * we convert them in-place after receipt.
+ */
+struct ceph_sparse_extent {
+	u64	off;
+	u64	len;
+} __packed;
+
 /*
  * A given osd we're communicating with.
  *
@@ -104,6 +115,8 @@ struct ceph_osd_req_op {
 			u64 offset, length;
 			u64 truncate_size;
 			u32 truncate_seq;
+			int sparse_ext_cnt;
+			struct ceph_sparse_extent *sparse_ext;
 			struct ceph_osd_data osd_data;
 		} extent;
 		struct {
@@ -510,6 +523,20 @@ extern struct ceph_osd_request *ceph_osdc_new_request(struct ceph_osd_client *,
 				      u32 truncate_seq, u64 truncate_size,
 				      bool use_mempool);
 
+int __ceph_alloc_sparse_ext_map(struct ceph_osd_req_op *op, int cnt);
+
+/*
+ * How big an extent array should we preallocate for a sparse read? This is
+ * just a starting value.  If we get more than this back from the OSD, the
+ * receiver will reallocate.
+ */
+#define CEPH_SPARSE_EXT_ARRAY_INITIAL  16
+
+static inline int ceph_alloc_sparse_ext_map(struct ceph_osd_req_op *op)
+{
+	return __ceph_alloc_sparse_ext_map(op, CEPH_SPARSE_EXT_ARRAY_INITIAL);
+}
+
 extern void ceph_osdc_get_request(struct ceph_osd_request *req);
 extern void ceph_osdc_put_request(struct ceph_osd_request *req);
 
@@ -564,5 +591,19 @@ int ceph_osdc_list_watchers(struct ceph_osd_client *osdc,
 			    struct ceph_object_locator *oloc,
 			    struct ceph_watch_item **watchers,
 			    u32 *num_watchers);
-#endif
 
+/* Find offset into the buffer of the end of the extent map */
+static inline u64 ceph_sparse_ext_map_end(struct ceph_osd_req_op *op)
+{
+	struct ceph_sparse_extent *ext;
+
+	/* No extents? No data */
+	if (op->extent.sparse_ext_cnt == 0)
+		return 0;
+
+	ext = &op->extent.sparse_ext[op->extent.sparse_ext_cnt - 1];
+
+	return ext->off + ext->len - op->extent.offset;
+}
+
+#endif

net/ceph/osd_client.c

@@ -378,6 +378,7 @@ static void osd_req_op_data_release(struct ceph_osd_request *osd_req,
 	case CEPH_OSD_OP_READ:
 	case CEPH_OSD_OP_WRITE:
 	case CEPH_OSD_OP_WRITEFULL:
+		kfree(op->extent.sparse_ext);
 		ceph_osd_data_release(&op->extent.osd_data);
 		break;
 	case CEPH_OSD_OP_CALL:
@@ -1120,6 +1121,18 @@ fail:
 }
 EXPORT_SYMBOL(ceph_osdc_new_request);
 
+int __ceph_alloc_sparse_ext_map(struct ceph_osd_req_op *op, int cnt)
+{
+	op->extent.sparse_ext_cnt = cnt;
+	op->extent.sparse_ext = kmalloc_array(cnt,
+					      sizeof(*op->extent.sparse_ext),
+					      GFP_NOFS);
+	if (!op->extent.sparse_ext)
+		return -ENOMEM;
+	return 0;
+}
+EXPORT_SYMBOL(__ceph_alloc_sparse_ext_map);
+
 /*
  * We keep osd requests in an rbtree, sorted by ->r_tid.
  */