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[PULL 10/24] block: bdrv_reopen_parse_backing(): simplify handling impli
From: |
Kevin Wolf |
Subject: |
[PULL 10/24] block: bdrv_reopen_parse_backing(): simplify handling implicit filters |
Date: |
Wed, 30 Jun 2021 18:01:52 +0200 |
From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
The logic around finding overlay here is not obvious. Actually it does
two simple things:
1. If new bs is already in backing chain, split from parent bs by
several implicit filters we are done, do nothing.
2. Otherwise, don't try to replace implicit filter.
Let's rewrite this in more obvious way.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-6-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block.c | 53 ++++++++++++++++-------------------------------------
1 file changed, 16 insertions(+), 37 deletions(-)
diff --git a/block.c b/block.c
index 6472866283..d047cae43c 100644
--- a/block.c
+++ b/block.c
@@ -4237,7 +4237,7 @@ static int bdrv_reopen_parse_backing(BDRVReopenState
*reopen_state,
Error **errp)
{
BlockDriverState *bs = reopen_state->bs;
- BlockDriverState *overlay_bs, *below_bs, *new_backing_bs;
+ BlockDriverState *new_backing_bs;
QObject *value;
const char *str;
@@ -4266,6 +4266,18 @@ static int bdrv_reopen_parse_backing(BDRVReopenState
*reopen_state,
g_assert_not_reached();
}
+ if (bs->backing) {
+ if (bdrv_skip_implicit_filters(bs->backing->bs) == new_backing_bs) {
+ return 0;
+ }
+
+ if (bs->backing->bs->implicit) {
+ error_setg(errp, "Cannot change backing link if '%s' has "
+ "an implicit backing file", bs->node_name);
+ return -EPERM;
+ }
+ }
+
/*
* Ensure that @bs can really handle backing files, because we are
* about to give it one (or swap the existing one)
@@ -4283,42 +4295,9 @@ static int bdrv_reopen_parse_backing(BDRVReopenState
*reopen_state,
return -EINVAL;
}
- /*
- * Find the "actual" backing file by skipping all links that point
- * to an implicit node, if any (e.g. a commit filter node).
- * We cannot use any of the bdrv_skip_*() functions here because
- * those return the first explicit node, while we are looking for
- * its overlay here.
- */
- overlay_bs = bs;
- for (below_bs = bdrv_filter_or_cow_bs(overlay_bs);
- below_bs && below_bs->implicit;
- below_bs = bdrv_filter_or_cow_bs(overlay_bs))
- {
- overlay_bs = below_bs;
- }
-
- /* If we want to replace the backing file we need some extra checks */
- if (new_backing_bs != bdrv_filter_or_cow_bs(overlay_bs)) {
- int ret;
-
- /* Check for implicit nodes between bs and its backing file */
- if (bs != overlay_bs) {
- error_setg(errp, "Cannot change backing link if '%s' has "
- "an implicit backing file", bs->node_name);
- return -EPERM;
- }
-
- reopen_state->replace_backing_bs = true;
- reopen_state->old_backing_bs = bs->backing ? bs->backing->bs : NULL;
- ret = bdrv_set_backing_noperm(bs, new_backing_bs, set_backings_tran,
- errp);
- if (ret < 0) {
- return ret;
- }
- }
-
- return 0;
+ reopen_state->replace_backing_bs = true;
+ reopen_state->old_backing_bs = bs->backing ? bs->backing->bs : NULL;
+ return bdrv_set_backing_noperm(bs, new_backing_bs, set_backings_tran,
errp);
}
/*
--
2.31.1
- [PULL 00/24] Block layer patches, Kevin Wolf, 2021/06/30
- [PULL 01/24] Prevent compiler warning on block.c, Kevin Wolf, 2021/06/30
- [PULL 03/24] block: BDRV_O_NO_IO for backing file on creation, Kevin Wolf, 2021/06/30
- [PULL 02/24] block: Move read-only check during truncation earlier, Kevin Wolf, 2021/06/30
- [PULL 06/24] block: introduce bdrv_remove_file_or_backing_child(), Kevin Wolf, 2021/06/30
- [PULL 08/24] block: bdrv_reopen_parse_backing(): don't check aio context, Kevin Wolf, 2021/06/30
- [PULL 07/24] block: introduce bdrv_set_file_or_backing_noperm(), Kevin Wolf, 2021/06/30
- [PULL 12/24] block: BDRVReopenState: drop replace_backing_bs field, Kevin Wolf, 2021/06/30
- [PULL 09/24] block: bdrv_reopen_parse_backing(): don't check frozen child, Kevin Wolf, 2021/06/30
- [PULL 10/24] block: bdrv_reopen_parse_backing(): simplify handling implicit filters,
Kevin Wolf <=
- [PULL 11/24] block: move supports_backing check to bdrv_set_file_or_backing_noperm(), Kevin Wolf, 2021/06/30
- [PULL 13/24] block: Allow changing bs->file on reopen, Kevin Wolf, 2021/06/30
- [PULL 04/24] block: rename bdrv_replace_child to bdrv_replace_child_tran, Kevin Wolf, 2021/06/30
- [PULL 17/24] block/ssh: add support for sha256 host key fingerprints, Kevin Wolf, 2021/06/30
- [PULL 15/24] introduce QEMU_AUTO_VFREE, Kevin Wolf, 2021/06/30
- [PULL 18/24] vhost: Add Error parameter to vhost_dev_init(), Kevin Wolf, 2021/06/30
- [PULL 16/24] block/commit: use QEMU_AUTO_VFREE, Kevin Wolf, 2021/06/30
- [PULL 22/24] vhost: Distinguish errors in vhost_dev_get_config(), Kevin Wolf, 2021/06/30
- [PULL 23/24] vhost-user-blk: Factor out vhost_user_blk_realize_connect(), Kevin Wolf, 2021/06/30
- [PULL 14/24] iotests: Test replacing files with x-blockdev-reopen, Kevin Wolf, 2021/06/30