[PATCH v12 09/14] block: modify the comment for BDRV_REQ_PREFETCH flag

[Andrey Shinkevich via <qemu-devel@nongnu.org>]

Modify the comment for the flag BDRV_REQ_PREFETCH as we are going to
use it alone and pass it to the COR-filter driver for further
processing.

Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 include/block/block.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/block/block.h b/include/block/block.h
index ae7612f..1b6742f 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -81,9 +81,11 @@ typedef enum {
     BDRV_REQ_NO_FALLBACK        = 0x100,
 
     /*
-     * BDRV_REQ_PREFETCH may be used only together with BDRV_REQ_COPY_ON_READ
-     * on read request and means that caller doesn't really need data to be
-     * written to qiov parameter which may be NULL.
+     * BDRV_REQ_PREFETCH makes sense only in the context of copy-on-read
+     * (i.e., together with the BDRV_REQ_COPY_ON_READ flag or when a COR
+     * filter is involved), in which case it signals that the COR operation
+     * need not read the data into memory (qiov) but only ensure they are
+     * copied to the top layer (i.e., that COR operation is done).
      */
     BDRV_REQ_PREFETCH  = 0x200,
     /* Mask of valid flags */
-- 
1.8.3.1