libceph: record message data byte length

Record the number of bytes of data in a page array rather than the
number of pages in the array.  It can be assumed that the page array
is of sufficient size to hold the number of bytes indicated (and
offset by the indicated alignment).
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

include/linux/ceph/messenger.h

@@ -77,7 +77,7 @@ struct ceph_msg {
 
 	struct page **pages;		/* data payload.  NOT OWNER. */
 	unsigned int page_alignment;	/* io offset in first page */
-	unsigned int page_count;	/* # pages in array or list */
+	size_t length;			/* # data bytes in array or list */
 	struct ceph_pagelist *pagelist; /* instead of pages */
 #ifdef CONFIG_BLOCK
 	unsigned int bio_seg;		/* current bio segment */

net/ceph/messenger.c

@@ -809,11 +809,10 @@ static void prepare_write_message(struct ceph_connection *con)
 		m->bio_iter = NULL;
 #endif
 
-	dout("prepare_write_message %p seq %lld type %d len %d+%d+%d %d pgs\n",
+	dout("prepare_write_message %p seq %lld type %d len %d+%d+%d (%zd)\n",
 	     m, con->out_seq, le16_to_cpu(m->hdr.type),
 	     le32_to_cpu(m->hdr.front_len), le32_to_cpu(m->hdr.middle_len),
-	     le32_to_cpu(m->hdr.data_len),
-	     m->page_count);
+	     le32_to_cpu(m->hdr.data_len), m->length);
 	BUG_ON(le32_to_cpu(m->hdr.front_len) != m->front.iov_len);
 
 	/* tag + hdr + front + middle */
@@ -1091,9 +1090,8 @@ static int write_partial_msg_pages(struct ceph_connection *con)
 	const size_t trail_len = (msg->trail ? msg->trail->length : 0);
 	const size_t trail_off = data_len - trail_len;
 
-	dout("write_partial_msg_pages %p msg %p page %d/%d offset %d\n",
-	     con, msg, con->out_msg_pos.page, msg->page_count,
-	     con->out_msg_pos.page_pos);
+	dout("write_partial_msg_pages %p msg %p page %d offset %d\n",
+	     con, msg, con->out_msg_pos.page, con->out_msg_pos.page_pos);
 
 	/*
 	 * Iterate through each page that contains data to be
@@ -2695,10 +2693,10 @@ void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
 	/* BUG_ON(!pages); */
 	/* BUG_ON(!length); */
 	/* BUG_ON(msg->pages); */
-	/* BUG_ON(msg->page_count); */
+	/* BUG_ON(msg->length); */
 
 	msg->pages = pages;
-	msg->page_count = calc_pages_for((u64)alignment, (u64)length);
+	msg->length = length;
 	msg->page_alignment = alignment & ~PAGE_MASK;
 }
 EXPORT_SYMBOL(ceph_msg_data_set_pages);
@@ -2906,7 +2904,7 @@ void ceph_msg_last_put(struct kref *kref)
 		ceph_buffer_put(m->middle);
 		m->middle = NULL;
 	}
-	m->page_count = 0;
+	m->length = 0;
 	m->pages = NULL;
 
 	if (m->pagelist) {
@@ -2926,8 +2924,8 @@ EXPORT_SYMBOL(ceph_msg_last_put);
 
 void ceph_msg_dump(struct ceph_msg *msg)
 {
-	pr_debug("msg_dump %p (front_max %d page_count %d)\n", msg,
-		 msg->front_max, msg->page_count);
+	pr_debug("msg_dump %p (front_max %d length %zd)\n", msg,
+		 msg->front_max, msg->length);
 	print_hex_dump(KERN_DEBUG, "header: ",
 		       DUMP_PREFIX_OFFSET, 16, 1,
 		       &msg->hdr, sizeof(msg->hdr), true);