[Qemu-devel] [PATCH 1/3 v4] Expose a mechanisem to trace block writes

[lirans@il.ibm.com]

To support live migration without shared storage we need to be able to trace
writes to disk while migrating. This Patch expose handler registration for 
above components to be notified about block writes.

diff --git a/block.c b/block.c
index 33f3d65..bf5f7a6 100644
--- a/block.c
+++ b/block.c
@@ -61,6 +61,8 @@ BlockDriverState *bdrv_first;
 
 static BlockDriver *first_drv;
 
+static BlockDriverDirtyHandler *bdrv_dirty_handler = NULL;
+
 int path_is_absolute(const char *path)
 {
     const char *p;
@@ -626,6 +628,10 @@ int bdrv_write(BlockDriverState *bs, int64_t sector_num,
     if (bdrv_check_request(bs, sector_num, nb_sectors))
         return -EIO;
 
+    if(bdrv_dirty_handler != NULL) {
+      bdrv_dirty_handler(bs, sector_num, nb_sectors);
+    }
+    
     return drv->bdrv_write(bs, sector_num, buf, nb_sectors);
 }
 
@@ -1162,6 +1168,11 @@ int bdrv_write_compressed(BlockDriverState *bs, int64_t sector_num,
         return -ENOTSUP;
     if (bdrv_check_request(bs, sector_num, nb_sectors))
         return -EIO;
+    
+    if(bdrv_dirty_handler != NULL) {
+      bdrv_dirty_handler(bs, sector_num, nb_sectors);
+    }
+    
     return drv->bdrv_write_compressed(bs, sector_num, buf, nb_sectors);
 }
 
@@ -1359,6 +1370,10 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState *bs, int64_t sector_num,
     if (bdrv_check_request(bs, sector_num, nb_sectors))
         return NULL;
 
+    if(bdrv_dirty_handler != NULL) {
+      bdrv_dirty_handler(bs, sector_num, nb_sectors);
+    }
+    
     ret = drv->bdrv_aio_writev(bs, sector_num, qiov, nb_sectors,
                                cb, opaque);
 
@@ -1869,7 +1884,19 @@ BlockDriverAIOCB *bdrv_aio_ioctl(BlockDriverState *bs,
     return NULL;
 }
 
+
+
 void *qemu_blockalign(BlockDriverState *bs, size_t size)
 {
     return qemu_memalign((bs && bs->buffer_alignment) ? bs->buffer_alignment : 512, size);
 }
+
+void register_bdrv_dirty_tracking(BlockDriverDirtyHandler *dirty_handler)
+{
+  bdrv_dirty_handler = dirty_handler;
+}
+
+void unregister_bdrv_dirty_tracking(void)
+{
+  bdrv_dirty_handler = NULL;
+}
diff --git a/block.h b/block.h
index a966afb..9757a42 100644
--- a/block.h
+++ b/block.h
@@ -78,7 +78,8 @@ void bdrv_register(BlockDriver *bdrv);
 /* async block I/O */
 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
 typedef void BlockDriverCompletionFunc(void *opaque, int ret);
-
+typedef void BlockDriverDirtyHandler(BlockDriverState *bs, int64_t sector,
+				     int sector_num);
 BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState *bs, int64_t sector_num,
                                  QEMUIOVector *iov, int nb_sectors,
                                  BlockDriverCompletionFunc *cb, void *opaque);
@@ -184,4 +185,7 @@ int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
 int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
                       int64_t pos, int size);
 
+void register_bdrv_dirty_tracking(BlockDriverDirtyHandler *dirty_handler);
+void unregister_bdrv_dirty_tracking(void);
+
 #endif
diff --git a/block_int.h b/block_int.h
index 8e72abe..c524860 100644
--- a/block_int.h
+++ b/block_int.h
@@ -168,6 +168,7 @@ struct BlockDriverState {
     int cyls, heads, secs, translation;
     int type;
     char device_name[32];
+    void *dirty_control;
     BlockDriverState *next;
     void *private;
 };