Re: [PATCH] libceph: make message data be a pointer

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Reviewed-by: Josh Durgin <josh.durgin@xxxxxxxxxxx>

On 03/12/2013 06:10 PM, Alex Elder wrote:
Begin the transition from a single message data item to a list of
them by replacing the "data" structure in a message with a pointer
to a ceph_msg_data structure.

A null pointer will indicate the message has no data; replace the
use of ceph_msg_has_data() with a simple check for a null pointer.

Create functions ceph_msg_data_create() and ceph_msg_data_destroy()
to dynamically allocate and free a data item structure of a given type.

When a message has its data item "set," allocate one of these to
hold the data description, and free it when the last reference to
the message is dropped.

This partially resolves:
     http://tracker.ceph.com/issues/4429

Signed-off-by: Alex Elder <elder@xxxxxxxxxxx>
---
  include/linux/ceph/messenger.h |    5 +--
  net/ceph/messenger.c           |   91
+++++++++++++++++++++++++++-------------
  2 files changed, 62 insertions(+), 34 deletions(-)

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index 686df5b..3181321 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -64,8 +64,6 @@ struct ceph_messenger {
  	u32 required_features;
  };

-#define ceph_msg_has_data(m)		((m)->data.type != CEPH_MSG_DATA_NONE)
-
  enum ceph_msg_data_type {
  	CEPH_MSG_DATA_NONE,	/* message contains no data payload */
  	CEPH_MSG_DATA_PAGES,	/* data source/destination is a page array */
@@ -141,8 +139,7 @@ struct ceph_msg {
  	struct kvec front;              /* unaligned blobs of message */
  	struct ceph_buffer *middle;

-	/* data payload */
-	struct ceph_msg_data	data;
+	struct ceph_msg_data	*data;	/* data payload */

  	struct ceph_connection *con;
  	struct list_head list_head;	/* links for connection lists */
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 8e07ac4..d703813 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1086,7 +1086,7 @@ static void prepare_message_data(struct ceph_msg *msg)

  	/* Initialize data cursors */

-	ceph_msg_data_cursor_init(&msg->data, data_len);
+	ceph_msg_data_cursor_init(msg->data, data_len);
  }

  /*
@@ -1388,13 +1388,13 @@ 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;

  	dout("%s %p msg %p\n", __func__, con, msg);

-	if (WARN_ON(!ceph_msg_has_data(msg)))
+	if (WARN_ON(!msg->data))
  		return -EINVAL;

  	/*
@@ -1414,7 +1414,7 @@ static int write_partial_message_data(struct
ceph_connection *con)
  		bool need_crc;
  		int ret;

-		page = ceph_msg_data_next(&msg->data, &page_offset, &length,
+		page = ceph_msg_data_next(msg->data, &page_offset, &length,
  							&last_piece);
  		if (do_datacrc && cursor->need_crc)
  			crc = ceph_crc32c_page(crc, page, page_offset, length);
@@ -1425,7 +1425,7 @@ static int write_partial_message_data(struct
ceph_connection *con)

  			return ret;
  		}
-		need_crc = ceph_msg_data_advance(&msg->data, (size_t) ret);
+		need_crc = ceph_msg_data_advance(msg->data, (size_t) ret);
  	}
  	msg->footer.data_crc = cpu_to_le32(crc);

@@ -2075,7 +2075,7 @@ 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;
@@ -2084,12 +2084,12 @@ static int read_partial_msg_data(struct
ceph_connection *con)
  	int ret;

  	BUG_ON(!msg);
-	if (WARN_ON(!ceph_msg_has_data(msg)))
+	if (!msg->data)
  		return -EIO;

  	crc = con->in_data_crc;
  	while (cursor->resid) {
-		page = ceph_msg_data_next(&msg->data, &page_offset, &length,
+		page = ceph_msg_data_next(msg->data, &page_offset, &length,
  							NULL);
  		ret = ceph_tcp_recvpage(con->sock, page, page_offset, length);
  		if (ret <= 0) {
@@ -2100,7 +2100,7 @@ static int read_partial_msg_data(struct
ceph_connection *con)

  		if (do_datacrc)
  			crc = ceph_crc32c_page(crc, page, page_offset, ret);
-		(void) ceph_msg_data_advance(&msg->data, (size_t) ret);
+		(void) ceph_msg_data_advance(msg->data, (size_t) ret);
  	}
  	con->in_data_crc = crc;

@@ -2910,44 +2910,80 @@ void ceph_con_keepalive(struct ceph_connection *con)
  }
  EXPORT_SYMBOL(ceph_con_keepalive);

-static void ceph_msg_data_init(struct ceph_msg_data *data)
+static struct ceph_msg_data *ceph_msg_data_create(enum
ceph_msg_data_type type)
  {
-	data->type = CEPH_MSG_DATA_NONE;
+	struct ceph_msg_data *data;
+
+	if (WARN_ON(!ceph_msg_data_type_valid(type)))
+		return NULL;
+
+	data = kzalloc(sizeof (*data), GFP_NOFS);
+	if (data)
+		data->type = type;
+
+	return data;
+}
+
+static void ceph_msg_data_destroy(struct ceph_msg_data *data)
+{
+	if (!data)
+		return;
+
+	if (data->type == CEPH_MSG_DATA_PAGELIST) {
+		ceph_pagelist_release(data->pagelist);
+		kfree(data->pagelist);
+	}
+	kfree(data);
  }

  void ceph_msg_data_set_pages(struct ceph_msg *msg, struct page **pages,
  		size_t length, size_t alignment)
  {
+	struct ceph_msg_data *data;
+
  	BUG_ON(!pages);
  	BUG_ON(!length);
-	BUG_ON(msg->data.type != CEPH_MSG_DATA_NONE);
+	BUG_ON(msg->data != NULL);
+
+	data = ceph_msg_data_create(CEPH_MSG_DATA_PAGES);
+	BUG_ON(!data);
+	data->pages = pages;
+	data->length = length;
+	data->alignment = alignment & ~PAGE_MASK;

-	msg->data.type = CEPH_MSG_DATA_PAGES;
-	msg->data.pages = pages;
-	msg->data.length = length;
-	msg->data.alignment = alignment & ~PAGE_MASK;
+	msg->data = data;
  }
  EXPORT_SYMBOL(ceph_msg_data_set_pages);

  void ceph_msg_data_set_pagelist(struct ceph_msg *msg,
  				struct ceph_pagelist *pagelist)
  {
+	struct ceph_msg_data *data;
+
  	BUG_ON(!pagelist);
  	BUG_ON(!pagelist->length);
-	BUG_ON(msg->data.type != CEPH_MSG_DATA_NONE);
+	BUG_ON(msg->data != NULL);
+
+	data = ceph_msg_data_create(CEPH_MSG_DATA_PAGELIST);
+	BUG_ON(!data);
+	data->pagelist = pagelist;

-	msg->data.type = CEPH_MSG_DATA_PAGELIST;
-	msg->data.pagelist = pagelist;
+	msg->data = data;
  }
  EXPORT_SYMBOL(ceph_msg_data_set_pagelist);

  void ceph_msg_data_set_bio(struct ceph_msg *msg, struct bio *bio)
  {
+	struct ceph_msg_data *data;
+
  	BUG_ON(!bio);
-	BUG_ON(msg->data.type != CEPH_MSG_DATA_NONE);
+	BUG_ON(msg->data != NULL);
+
+	data = ceph_msg_data_create(CEPH_MSG_DATA_BIO);
+	BUG_ON(!data);
+	data->bio = bio;

-	msg->data.type = CEPH_MSG_DATA_BIO;
-	msg->data.bio = bio;
+	msg->data = data;
  }
  EXPORT_SYMBOL(ceph_msg_data_set_bio);

@@ -2971,8 +3007,6 @@ struct ceph_msg *ceph_msg_new(int type, int
front_len, gfp_t flags,
  	INIT_LIST_HEAD(&m->list_head);
  	kref_init(&m->kref);

-	ceph_msg_data_init(&m->data);
-
  	/* front */
  	m->front_max = front_len;
  	if (front_len) {
@@ -3127,11 +3161,8 @@ void ceph_msg_last_put(struct kref *kref)
  		m->middle = NULL;
  	}

-	if (ceph_msg_has_data(m) && m->data.type == CEPH_MSG_DATA_PAGELIST) {
-		ceph_pagelist_release(m->data.pagelist);
-		kfree(m->data.pagelist);
-		m->data.pagelist = NULL;
-	}
+	ceph_msg_data_destroy(m->data);
+	m->data = NULL;

  	if (m->pool)
  		ceph_msgpool_put(m->pool, m);
@@ -3143,7 +3174,7 @@ EXPORT_SYMBOL(ceph_msg_last_put);
  void ceph_msg_dump(struct ceph_msg *msg)
  {
  	pr_debug("msg_dump %p (front_max %d length %zd)\n", msg,
-		 msg->front_max, msg->data.length);
+		 msg->front_max, msg->data->length);
  	print_hex_dump(KERN_DEBUG, "header: ",
  		       DUMP_PREFIX_OFFSET, 16, 1,
  		       &msg->hdr, sizeof(msg->hdr), true);


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