libceph: abstract message data

Group the types of message data into an abstract structure with a
type indicator and a union containing fields appropriate to the
type of data it represents.  Use this to represent the pages,
pagelist, bio, and trail in a ceph message.

Verify message data is of type NONE in ceph_msg_data_set_*()
routines.  Since information about message data of type NONE really
should not be interpreted, get rid of the other assertions in those
functions.

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

1 files changed, 51 insertions, 20 deletions

diff --git a/include/linux/ceph/messenger.h b/include/linux/ceph/messenger.h
index fb2b18a20c13..5860dd0c2caf 100644
--- a/include/linux/ceph/messenger.h
+++ b/include/linux/ceph/messenger.h
@@ -64,12 +64,55 @@ struct ceph_messenger {
         u32 required_features;
 };
 
-#define ceph_msg_has_pages(m)           ((m)->p.pages != NULL)
-#define ceph_msg_has_pagelist(m)        ((m)->l.pagelist != NULL)
+#define ceph_msg_has_pages(m)           ((m)->p.type == CEPH_MSG_DATA_PAGES)
+#define ceph_msg_has_pagelist(m)        ((m)->l.type == CEPH_MSG_DATA_PAGELIST)
 #ifdef CONFIG_BLOCK
-#define ceph_msg_has_bio(m)             ((m)->b.bio != NULL)
+#define ceph_msg_has_bio(m)             ((m)->b.type == CEPH_MSG_DATA_BIO)
 #endif /* CONFIG_BLOCK */
-#define ceph_msg_has_trail(m)           ((m)->t.trail != NULL)
+#define ceph_msg_has_trail(m)           ((m)->t.type == CEPH_MSG_DATA_PAGELIST)
+
+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 */
+        CEPH_MSG_DATA_PAGELIST, /* data source/destination is a pagelist */
+#ifdef CONFIG_BLOCK
+        CEPH_MSG_DATA_BIO,      /* data source/destination is a bio list */
+#endif /* CONFIG_BLOCK */
+};
+
+static __inline__ bool ceph_msg_data_type_valid(enum ceph_msg_data_type type)
+{
+        switch (type) {
+        case CEPH_MSG_DATA_NONE:
+        case CEPH_MSG_DATA_PAGES:
+        case CEPH_MSG_DATA_PAGELIST:
+#ifdef CONFIG_BLOCK
+        case CEPH_MSG_DATA_BIO:
+#endif /* CONFIG_BLOCK */
+                return true;
+        default:
+                return false;
+        }
+}
+
+struct ceph_msg_data {
+        enum ceph_msg_data_type         type;
+        union {
+#ifdef CONFIG_BLOCK
+                struct {
+                        struct bio      *bio_iter;      /* iterator */
+                        struct bio      *bio;
+                        unsigned int    bio_seg;        /* current seg in bio */
+                };
+#endif /* CONFIG_BLOCK */
+                struct {
+                        struct page     **pages;        /* NOT OWNER. */
+                        size_t          length;         /* total # bytes */
+                        unsigned int    alignment;      /* first page */
+                };
+                struct ceph_pagelist    *pagelist;
+        };
+};
 
 /*
  * a single message.  it contains a header (src, dest, message type, etc.),
@@ -83,24 +126,12 @@ struct ceph_msg {
         struct ceph_buffer *middle;
 
         /* data payload */
-        struct {
-                struct page     **pages;        /* NOT OWNER. */
-                size_t          length;         /* # data bytes in array */
-                unsigned int    alignment;      /* first page */
-        } p;
-        struct {
-                struct ceph_pagelist    *pagelist;
-        } l;
+        struct ceph_msg_data    p;      /* pages */
+        struct ceph_msg_data    l;      /* pagelist */
 #ifdef CONFIG_BLOCK
-        struct {
-                struct bio      *bio_iter;      /* iterator */
-                struct bio      *bio;
-                unsigned int    bio_seg;        /* current seg in bio */
-        } b;
+        struct ceph_msg_data    b;      /* bio */
 #endif /* CONFIG_BLOCK */
-        struct {
-                struct ceph_pagelist *trail;    /* trailing part of data */
-        } t;
+        struct ceph_msg_data    t;      /* trail */
 
         struct ceph_connection *con;
         struct list_head list_head;     /* links for connection lists */