From d32f35cbc5a87af5e1100dd55074a79fc2cb5307 Mon Sep 17 00:00:00 2001 From: Peter Lieven Date: Thu, 24 Oct 2013 12:06:52 +0200 Subject: block: introduce BDRV_REQ_MAY_UNMAP request flag Reviewed-by: Eric Blake Signed-off-by: Peter Lieven Signed-off-by: Stefan Hajnoczi --- include/block/block.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include') diff --git a/include/block/block.h b/include/block/block.h index 8ba9f0c80f..1f30a56fb0 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -65,6 +65,13 @@ typedef struct BlockDevOps { typedef enum { BDRV_REQ_COPY_ON_READ = 0x1, BDRV_REQ_ZERO_WRITE = 0x2, + /* The BDRV_REQ_MAY_UNMAP flag is used to indicate that the block driver + * is allowed to optimize a write zeroes request by unmapping (discarding) + * blocks if it is guaranteed that the result will read back as + * zeroes. The flag is only passed to the driver if the block device is + * opened with BDRV_O_UNMAP. + */ + BDRV_REQ_MAY_UNMAP = 0x4, } BdrvRequestFlags; #define BDRV_O_RDWR 0x0002 -- cgit v1.2.3-55-g7522