diff mbox

[v4,4/8] block: Fix dirty bitmap in bdrv_co_discard

Message ID 1432266060-22104-5-git-send-email-famz@redhat.com
State New
Headers show

Commit Message

Fam Zheng May 22, 2015, 3:40 a.m. UTC 
Unsetting dirty globally with discard is not very correct. The discard may zero
out sectors (depending on can_write_zeroes_with_unmap), we should replicate
this change to destinition side to make sure that the guest sees the same data.

Calling bdrv_reset_dirty also troubles mirror job because the hbitmap iterator
doesn't expect unsetting of bits after current position.

So let's do it the opposite way which fixes both problems: set the dirty bits
if we are to discard it.

Reported-by: wangxiaolong@ucloud.cn
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/io.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Eric Blake May 22, 2015, 8:22 p.m. UTC | #1 
On 05/21/2015 09:40 PM, Fam Zheng wrote:
> Unsetting dirty globally with discard is not very correct. The discard may zero
> out sectors (depending on can_write_zeroes_with_unmap), we should replicate
> this change to destinition side to make sure that the guest sees the same data.

s/destinition/destination/

> 
> Calling bdrv_reset_dirty also troubles mirror job because the hbitmap iterator
> doesn't expect unsetting of bits after current position.
> 
> So let's do it the opposite way which fixes both problems: set the dirty bits
> if we are to discard it.
> 
> Reported-by: wangxiaolong@ucloud.cn
> Signed-off-by: Fam Zheng <famz@redhat.com>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  block/io.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>
diff mbox

Patch

diff --git a/block/io.c b/block/io.c
index 36a4007..a1ff943 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2368,8 +2368,6 @@  int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
         return -EROFS;
     }
 
-    bdrv_reset_dirty(bs, sector_num, nb_sectors);
-
     /* Do nothing if disabled.  */
     if (!(bs->open_flags & BDRV_O_UNMAP)) {
         return 0;
@@ -2379,6 +2377,8 @@  int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
         return 0;
     }
 
+    bdrv_set_dirty(bs, sector_num, nb_sectors);
+
     max_discard = MIN_NON_ZERO(bs->bl.max_discard, BDRV_REQUEST_MAX_SECTORS);
     while (nb_sectors > 0) {
         int ret;