block: Fix documentation for BDRV_REQ_MAY_UNMAP

BDRV_REQ_MAY_UNMAP in a write_zeroes request does not only allow the
driver to unmap the blocks, but it actively requests that the blocks be
unmapped afterwards if at all possible.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/include/block/block.h b/include/block/block.h
index f85e3a6ed33455df75fe6cf6f40970e58721d07b..4e0871aaf9463e03b52f7579315aacaba6765d82 100644 (file)
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -43,11 +43,12 @@ typedef struct BlockFragInfo {
 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.
+
+    /*
+     * The BDRV_REQ_MAY_UNMAP flag is used in write_zeroes requests to indicate
+     * that the block driver should unmap (discard) 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,