ram: Split host_from_stream_offset() into two helper functions

Split host_from_stream_offset() into two parts:
One is to get ram block, which the block idstr may be get from migration
stream, the other is to get hva (host) address from block and the offset.
Besides, we will do the check working in a new helper offset_in_ramblock().

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Message-Id: <1452829066-9764-2-git-send-email-zhang.zhanghailiang@huawei.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>

include/exec/ram_addr.h

@@ -38,10 +38,14 @@ struct RAMBlock {
     int fd;
 };
 
+static inline bool offset_in_ramblock(RAMBlock *b, ram_addr_t offset)
+{
+    return (b && b->host && offset < b->used_length) ? true : false;
+}
+
 static inline void *ramblock_ptr(RAMBlock *block, ram_addr_t offset)
 {
-    assert(offset < block->used_length);
-    assert(block->host);
+    assert(offset_in_ramblock(block, offset));
     return (char *)block->host + offset;
 }
 

migration/ram.c

@@ -2124,41 +2124,47 @@ static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
  * Returns a pointer from within the RCU-protected ram_list.
  */
 /*
- * Read a RAMBlock ID from the stream f, find the host address of the
- * start of that block and add on 'offset'
+ * Read a RAMBlock ID from the stream f.
  *
  * f: Stream to read from
- * offset: Offset within the block
  * flags: Page flags (mostly to see if it's a continuation of previous block)
  */
-static inline void *host_from_stream_offset(QEMUFile *f,
-                                            ram_addr_t offset,
-                                            int flags)
+static inline RAMBlock *ram_block_from_stream(QEMUFile *f,
+                                              int flags)
 {
     static RAMBlock *block = NULL;
     char id[256];
     uint8_t len;
 
     if (flags & RAM_SAVE_FLAG_CONTINUE) {
-        if (!block || block->max_length <= offset) {
+        if (!block) {
             error_report("Ack, bad migration stream!");
             return NULL;
         }
-
-        return block->host + offset;
+        return block;
     }
 
     len = qemu_get_byte(f);
     qemu_get_buffer(f, (uint8_t *)id, len);
     id[len] = 0;
 
     block = qemu_ram_block_by_name(id);
-    if (block && block->max_length > offset) {
-        return block->host + offset;
+    if (!block) {
+        error_report("Can't find block %s", id);
+        return NULL;
     }
 
-    error_report("Can't find block %s", id);
-    return NULL;
+    return block;
+}
+
+static inline void *host_from_ram_block_offset(RAMBlock *block,
+                                               ram_addr_t offset)
+{
+    if (!offset_in_ramblock(block, offset)) {
+        return NULL;
+    }
+
+    return block->host + offset;
 }
 
 /*
@@ -2302,7 +2308,9 @@ static int ram_load_postcopy(QEMUFile *f)
         trace_ram_load_postcopy_loop((uint64_t)addr, flags);
         place_needed = false;
         if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE)) {
-            host = host_from_stream_offset(f, addr, flags);
+            RAMBlock *block = ram_block_from_stream(f, flags);
+
+            host = host_from_ram_block_offset(block, addr);
             if (!host) {
                 error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
                 ret = -EINVAL;
@@ -2433,7 +2441,9 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
 
         if (flags & (RAM_SAVE_FLAG_COMPRESS | RAM_SAVE_FLAG_PAGE |
                      RAM_SAVE_FLAG_COMPRESS_PAGE | RAM_SAVE_FLAG_XBZRLE)) {
-            host = host_from_stream_offset(f, addr, flags);
+            RAMBlock *block = ram_block_from_stream(f, flags);
+
+            host = host_from_ram_block_offset(block, addr);
             if (!host) {
                 error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
                 ret = -EINVAL;