libceph: move cursor into message

A message will only be processing a single data item at a time, so
there's no need for each data item to have its own cursor.

Move the cursor embedded in the message data structure into the
message itself.  To minimize the impact, keep the data->cursor
field, but make it be a pointer to the cursor in the message.

Move the definition of ceph_msg_data above ceph_msg_data_cursor so
the cursor can point to the data without a forward definition rather
than vice-versa.

This and the upcoming patches are part of:
    http://tracker.ceph.com/issues/3761

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

include/linux/ceph/messenger.h

@@ -88,6 +88,25 @@ static __inline__ bool ceph_msg_data_type_valid(enum ceph_msg_data_type type)
 	}
 }
 
+struct ceph_msg_data {
+	enum ceph_msg_data_type		type;
+	union {
+#ifdef CONFIG_BLOCK
+		struct {
+			struct bio	*bio;
+			size_t		bio_length;
+		};
+#endif /* CONFIG_BLOCK */
+		struct {
+			struct page	**pages;	/* NOT OWNER. */
+			size_t		length;		/* total # bytes */
+			unsigned int	alignment;	/* first page */
+		};
+		struct ceph_pagelist	*pagelist;
+	};
+	struct ceph_msg_data_cursor	*cursor;
+};
+
 struct ceph_msg_data_cursor {
 	size_t		resid;		/* bytes not yet consumed */
 	bool		last_piece;	/* now at last piece of data item */
@@ -112,25 +131,6 @@ struct ceph_msg_data_cursor {
 	};
 };
 
-struct ceph_msg_data {
-	enum ceph_msg_data_type		type;
-	union {
-#ifdef CONFIG_BLOCK
-		struct {
-			struct bio	*bio;
-			size_t		bio_length;
-		};
-#endif /* CONFIG_BLOCK */
-		struct {
-			struct page	**pages;	/* NOT OWNER. */
-			size_t		length;		/* total # bytes */
-			unsigned int	alignment;	/* first page */
-		};
-		struct ceph_pagelist	*pagelist;
-	};
-	struct ceph_msg_data_cursor	cursor;		/* pagelist only */
-};
-
 /*
  * a single message.  it contains a header (src, dest, message type, etc.),
  * footer (crc values, mainly), a "front" message body, and possibly a
@@ -142,8 +142,9 @@ struct ceph_msg {
 	struct kvec front;              /* unaligned blobs of message */
 	struct ceph_buffer *middle;
 
-	size_t			data_length;
-	struct ceph_msg_data	*data;	/* data payload */
+	size_t				data_length;
+	struct ceph_msg_data		*data;
+	struct ceph_msg_data_cursor	cursor;
 
 	struct ceph_connection *con;
 	struct list_head list_head;	/* links for connection lists */

net/ceph/messenger.c

@@ -725,7 +725,7 @@ static void con_out_kvec_add(struct ceph_connection *con,
 static void ceph_msg_data_bio_cursor_init(struct ceph_msg_data *data,
 					size_t length)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	struct bio *bio;
 
 	BUG_ON(data->type != CEPH_MSG_DATA_BIO);
@@ -745,7 +745,7 @@ static struct page *ceph_msg_data_bio_next(struct ceph_msg_data *data,
 						size_t *page_offset,
 						size_t *length)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	struct bio *bio;
 	struct bio_vec *bio_vec;
 	unsigned int index;
@@ -774,7 +774,7 @@ static struct page *ceph_msg_data_bio_next(struct ceph_msg_data *data,
 
 static bool ceph_msg_data_bio_advance(struct ceph_msg_data *data, size_t bytes)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	struct bio *bio;
 	struct bio_vec *bio_vec;
 	unsigned int index;
@@ -826,7 +826,7 @@ static bool ceph_msg_data_bio_advance(struct ceph_msg_data *data, size_t bytes)
 static void ceph_msg_data_pages_cursor_init(struct ceph_msg_data *data,
 					size_t length)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	int page_count;
 
 	BUG_ON(data->type != CEPH_MSG_DATA_PAGES);
@@ -849,7 +849,7 @@ static struct page *ceph_msg_data_pages_next(struct ceph_msg_data *data,
 					size_t *page_offset,
 					size_t *length)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 
 	BUG_ON(data->type != CEPH_MSG_DATA_PAGES);
 
@@ -868,7 +868,7 @@ static struct page *ceph_msg_data_pages_next(struct ceph_msg_data *data,
 static bool ceph_msg_data_pages_advance(struct ceph_msg_data *data,
 						size_t bytes)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 
 	BUG_ON(data->type != CEPH_MSG_DATA_PAGES);
 
@@ -897,7 +897,7 @@ static bool ceph_msg_data_pages_advance(struct ceph_msg_data *data,
 static void ceph_msg_data_pagelist_cursor_init(struct ceph_msg_data *data,
 					size_t length)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	struct ceph_pagelist *pagelist;
 	struct page *page;
 
@@ -923,7 +923,7 @@ static struct page *ceph_msg_data_pagelist_next(struct ceph_msg_data *data,
 						size_t *page_offset,
 						size_t *length)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	struct ceph_pagelist *pagelist;
 
 	BUG_ON(data->type != CEPH_MSG_DATA_PAGELIST);
@@ -941,13 +941,13 @@ static struct page *ceph_msg_data_pagelist_next(struct ceph_msg_data *data,
 	else
 		*length = PAGE_SIZE - *page_offset;
 
-	return data->cursor.page;
+	return data->cursor->page;
 }
 
 static bool ceph_msg_data_pagelist_advance(struct ceph_msg_data *data,
 						size_t bytes)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	struct ceph_pagelist *pagelist;
 
 	BUG_ON(data->type != CEPH_MSG_DATA_PAGELIST);
@@ -1003,7 +1003,7 @@ static void ceph_msg_data_cursor_init(struct ceph_msg_data *data,
 		/* BUG(); */
 		break;
 	}
-	data->cursor.need_crc = true;
+	data->cursor->need_crc = true;
 }
 
 /*
@@ -1039,7 +1039,7 @@ static struct page *ceph_msg_data_next(struct ceph_msg_data *data,
 	BUG_ON(*page_offset + *length > PAGE_SIZE);
 	BUG_ON(!*length);
 	if (last_piece)
-		*last_piece = data->cursor.last_piece;
+		*last_piece = data->cursor->last_piece;
 
 	return page;
 }
@@ -1050,7 +1050,7 @@ static struct page *ceph_msg_data_next(struct ceph_msg_data *data,
  */
 static bool ceph_msg_data_advance(struct ceph_msg_data *data, size_t bytes)
 {
-	struct ceph_msg_data_cursor *cursor = &data->cursor;
+	struct ceph_msg_data_cursor *cursor = data->cursor;
 	bool new_piece;
 
 	BUG_ON(bytes > cursor->resid);
@@ -1071,7 +1071,7 @@ static bool ceph_msg_data_advance(struct ceph_msg_data *data, size_t bytes)
 		BUG();
 		break;
 	}
-	data->cursor.need_crc = new_piece;
+	data->cursor->need_crc = new_piece;
 
 	return new_piece;
 }
@@ -1404,7 +1404,7 @@ static u32 ceph_crc32c_page(u32 crc, struct page *page,
 static int write_partial_message_data(struct ceph_connection *con)
 {
 	struct ceph_msg *msg = con->out_msg;
-	struct ceph_msg_data_cursor *cursor = &msg->data->cursor;
+	struct ceph_msg_data_cursor *cursor = msg->data->cursor;
 	bool do_datacrc = !con->msgr->nocrc;
 	u32 crc;
 
@@ -2102,7 +2102,7 @@ static int read_partial_message_section(struct ceph_connection *con,
 static int read_partial_msg_data(struct ceph_connection *con)
 {
 	struct ceph_msg *msg = con->in_msg;
-	struct ceph_msg_data_cursor *cursor = &msg->data->cursor;
+	struct ceph_msg_data_cursor *cursor = msg->data->cursor;
 	const bool do_datacrc = !con->msgr->nocrc;
 	struct page *page;
 	size_t page_offset;
@@ -2991,6 +2991,7 @@ void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
 
 	data = ceph_msg_data_create(CEPH_MSG_DATA_PAGES);
 	BUG_ON(!data);
+	data->cursor = &msg->cursor;
 	data->pages = pages;
 	data->length = length;
 	data->alignment = alignment & ~PAGE_MASK;
@@ -3012,6 +3013,7 @@ void ceph_msg_data_set_pagelist(struct ceph_msg *msg,
 
 	data = ceph_msg_data_create(CEPH_MSG_DATA_PAGELIST);
 	BUG_ON(!data);
+	data->cursor = &msg->cursor;
 	data->pagelist = pagelist;
 
 	msg->data = data;
@@ -3031,6 +3033,7 @@ void ceph_msg_data_set_bio(struct ceph_msg *msg, struct bio *bio,
 
 	data = ceph_msg_data_create(CEPH_MSG_DATA_BIO);
 	BUG_ON(!data);
+	data->cursor = &msg->cursor;
 	data->bio = bio;
 	data->bio_length = length;