Commit 263a6f4c authored by Ren Kimura's avatar Ren Kimura Committed by Max Reitz
Browse files

qemu-img: check block status of backing file when converting. 



When converting images, check the block status of its backing file chain
to avoid needlessly reading zeros.

Signed-off-by: default avatarRen Kimura <rkx1209dev@gmail.com>
Message-id: 1461773098-20356-1-git-send-email-rkx1209dev@gmail.com
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent 9036e87c

qemu-img.c

+13 −2
Original line number Diff line number Diff line
@@ -1475,10 +1475,21 @@ static int convert_iteration_sectors(ImgConvertState *s, int64_t sector_num) 
        } else if (!s->target_has_backing) {

            /* Without a target backing file we must copy over the contents of

             * the backing file as well. */

            /* TODO Check block status of the backing file chain to avoid

            /* Check block status of the backing file chain to avoid

             * needlessly reading zeroes and limiting the iteration to the

             * buffer size */

            ret = bdrv_get_block_status_above(blk_bs(s->src[s->src_cur]), NULL,

                                              sector_num - s->src_cur_offset,

                                              n, &n, &file);

            if (ret < 0) {

                return ret;

            }



            if (ret & BDRV_BLOCK_ZERO) {

                s->status = BLK_ZERO;

            } else {

                s->status = BLK_DATA;

            }

        } else {

            s->status = BLK_BACKING_FILE;

        }