[PATCH] block: unmap (discard) blocks only if discard_zeros flag is true

[luzhipeng]

From: lu zhipeng <luzhipeng@cestc.cn>

we can unmap(discard) blocks for block devices of supporting discard zeros
or regular file.

Signed-off-by: lu zhipeng <luzhipeng@cestc.cn>
---
 block/file-posix.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 48cd096624..c35dbc0d88 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -799,7 +799,8 @@ static int raw_open_common(BlockDriverState *bs, QDict 
*options,
 #endif
     s->needs_alignment = raw_needs_alignment(bs);
 
-    bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK;
+    bs->supported_zero_flags = s->discard_zeroes ?
+                               BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK : 0;
     if (S_ISREG(st.st_mode)) {
         /* When extending regular files, we get zeros from the OS */
         bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
-- 
2.31.1