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qemu-img: rebase: Reuse parent BlockDriverState

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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: Karl Heubaum <karl.heubaum@oracle.com>
Reviewed-by: Eyal Moscovici <eyal.moscovici@oracle.com>
Signed-off-by: Sagi Amit <sagi.amit@oracle.com>
Co-developed-by: Sagi Amit <sagi.amit@oracle.com>
Signed-off-by: Sam Eiderman <shmuel.eiderman@oracle.com>
Message-id: 20190523163337.4497-2-shmuel.eiderman@oracle.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Sam Eiderman 2019-05-23 19:33:35 +03:00 committed by Max Reitz
parent b441dc71c0
commit 4ebe061726
1 changed files with 9 additions and 20 deletions
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29
qemu-img.c
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@ -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 {