Commit 4ebe0617 authored by Sam Eiderman's avatar Sam Eiderman Committed by Max Reitz
Browse files

qemu-img: rebase: Reuse parent BlockDriverState 



In safe mode we open the entire chain, including the parent backing
file of the rebased file.
Do not open a new BlockBackend for the parent backing file, which
saves opening the rest of the chain twice, which for long chains
saves many "pricy" bdrv_open() calls.

Permissions for blk_new() were copied from blk_new_open() when
flags = 0.

Reviewed-by: default avatarKarl Heubaum <karl.heubaum@oracle.com>
Reviewed-by: default avatarEyal Moscovici <eyal.moscovici@oracle.com>
Signed-off-by: default avatarSagi Amit <sagi.amit@oracle.com>
Co-developed-by: default avatarSagi Amit <sagi.amit@oracle.com>
Signed-off-by: default avatarSam Eiderman <shmuel.eiderman@oracle.com>
Message-id: 20190523163337.4497-2-shmuel.eiderman@oracle.com
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent b441dc71

qemu-img.c

+9 −20
Original line number Diff line number Diff line
@@ -3309,29 +3309,18 @@ static int img_rebase(int argc, char **argv) 


    /* For safe rebasing we need to compare old and new backing file */

    if (!unsafe) {

        char backing_name[PATH_MAX];

        QDict *options = NULL;

        BlockDriverState *base_bs = backing_bs(bs);



        if (bs->backing) {

            if (bs->backing_format[0] != '\0') {

                options = qdict_new();

                qdict_put_str(options, "driver", bs->backing_format);

            }



            if (force_share) {

                if (!options) {

                    options = qdict_new();

                }

                qdict_put_bool(options, BDRV_OPT_FORCE_SHARE, true);

            }

            bdrv_get_backing_filename(bs, backing_name, sizeof(backing_name));

            blk_old_backing = blk_new_open(backing_name, NULL,

                                           options, src_flags, &local_err);

            if (!blk_old_backing) {

        if (base_bs) {

            blk_old_backing = blk_new(BLK_PERM_CONSISTENT_READ,

                                      BLK_PERM_ALL);

            ret = blk_insert_bs(blk_old_backing, base_bs,

                                &local_err);

            if (ret < 0) {

                error_reportf_err(local_err,

                                  "Could not open old backing file '%s': ",

                                  backing_name);

                ret = -1;

                                  "Could not reuse old backing file '%s': ",

                                  base_bs->filename);

                goto out;

            }

        } else {