[Qemu-devel] [PATCH v8 01/36] block: Add flag bits for image locking

[Fam Zheng]

Later the block layer will automatically lock the images to avoid unexpected
concurrent accesses to the same image, which will easily corrupt the metadata
or user data, unless in some very special cases, like migration.

The exceptional cases like shared storage migration and testing should
set BDRV_O_SHARED_LOCK or BDRV_O_NO_LOCK to advise an appropriate
locking mode.

Signed-off-by: Fam Zheng <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
---
 include/block/block.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/block/block.h b/include/block/block.h
index e18233a..cecab7a 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -98,7 +98,11 @@ typedef struct HDGeometry {
                                       select an appropriate protocol driver,
                                       ignoring the format layer */
 #define BDRV_O_NO_IO       0x10000 /* don't initialize for I/O */
+#define BDRV_O_NO_LOCK     0x20000 /* don't lock image file */
+#define BDRV_O_SHARED_LOCK 0x40000 /* lock the image file in shared mode */
+#define BDRV_O_EXCLUSIVE_LOCK 0x80000 /* lock the image file in exclusive mode 
*/
 
+#define BDRV_O_LOCK_MASK   (BDRV_O_NO_LOCK | BDRV_O_SHARED_LOCK | 
BDRV_O_EXCLUSIVE_LOCK)
 #define BDRV_O_CACHE_MASK  (BDRV_O_NOCACHE | BDRV_O_NO_FLUSH)
 
 
-- 
2.7.4