Commit 35ddd930 authored by Max Reitz's avatar Max Reitz Committed by Kevin Wolf
Browse files

qemu-img: Allow rebase with no input base 



Currently, without -u, you cannot add a backing file to an image when it
currently has none:

$ qemu-img rebase -b base.qcow2 foo.qcow2
qemu-img: Could not open old backing file '': The 'file' block driver
requires a file name

It is really simple to allow this, though (effectively by setting
old_backing_size to 0), so this patch does just that.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 433e8e3b

qemu-img.c

+34 −27
Original line number Diff line number Diff line
@@ -3312,6 +3312,7 @@ static int img_rebase(int argc, char **argv) 
        char backing_name[PATH_MAX];

        QDict *options = NULL;



        if (bs->backing) {

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

                options = qdict_new();

                qdict_put_str(options, "driver", bs->backing_format);
@@ -3333,6 +3334,9 @@ static int img_rebase(int argc, char **argv) 
                ret = -1;

                goto out;

            }

        } else {

            blk_old_backing = NULL;

        }



        if (out_baseimg[0]) {

            const char *overlay_filename;
@@ -3384,7 +3388,7 @@ static int img_rebase(int argc, char **argv) 
     */

    if (!unsafe) {

        int64_t size;

        int64_t old_backing_size;

        int64_t old_backing_size = 0;

        int64_t new_backing_size = 0;

        uint64_t offset;

        int64_t n;
@@ -3400,16 +3404,19 @@ static int img_rebase(int argc, char **argv) 
            ret = -1;

            goto out;

        }

        if (blk_old_backing) {

            old_backing_size = blk_getlength(blk_old_backing);

            if (old_backing_size < 0) {

                char backing_name[PATH_MAX];



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

                bdrv_get_backing_filename(bs, backing_name,

                                          sizeof(backing_name));

                error_report("Could not get size of '%s': %s",

                             backing_name, strerror(-old_backing_size));

                ret = -1;

                goto out;

            }

        }

        if (blk_new_backing) {

            new_backing_size = blk_getlength(blk_new_backing);

            if (new_backing_size < 0) {