diff mbox series

[PULL,03/27] qemu-img: rebase: use backing files' BlockBackend for buffer alignment

Message ID 20231031185918.346940-4-kwolf@redhat.com (mailing list archive)
State New, archived
Headers show
Series [PULL,01/27] qemu-img: rebase: stop when reaching EOF of old backing file | expand

Commit Message

Kevin Wolf Oct. 31, 2023, 6:58 p.m. UTC 
From: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>

Since commit bb1c05973cf ("qemu-img: Use qemu_blockalign"), buffers for
the data read from the old and new backing files are aligned using
BlockDriverState (or BlockBackend later on) referring to the target image.
However, this isn't quite right, because buf_new is only being used for
reading from the new backing, while buf_old is being used for both reading
from the old backing and writing to the target.  Let's take that into account
and use more appropriate values as alignments.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Message-ID: <20230919165804.439110-4-andrey.drobyshev@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 qemu-img.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/qemu-img.c b/qemu-img.c
index 2b2a3a86ca..e61d996e0f 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -3759,8 +3759,13 @@  static int img_rebase(int argc, char **argv)
         int64_t n;
         float local_progress = 0;
 
-        buf_old = blk_blockalign(blk, IO_BUF_SIZE);
-        buf_new = blk_blockalign(blk, IO_BUF_SIZE);
+        if (blk_old_backing && bdrv_opt_mem_align(blk_bs(blk_old_backing)) >
+            bdrv_opt_mem_align(blk_bs(blk))) {
+            buf_old = blk_blockalign(blk_old_backing, IO_BUF_SIZE);
+        } else {
+            buf_old = blk_blockalign(blk, IO_BUF_SIZE);
+        }
+        buf_new = blk_blockalign(blk_new_backing, IO_BUF_SIZE);
 
         size = blk_getlength(blk);
         if (size < 0) {