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[PATCH v6 5/9] block: bdrv_reopen_parse_backing(): simplify handling imp
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
[PATCH v6 5/9] block: bdrv_reopen_parse_backing(): simplify handling implicit filters |
Date: |
Thu, 10 Jun 2021 15:05:33 +0300 |
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>
---
block.c | 53 ++++++++++++++++-------------------------------------
1 file changed, 16 insertions(+), 37 deletions(-)
diff --git a/block.c b/block.c
index d86e26299e..1717e5cb98 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);
}
/*
--
2.29.2
- [PATCH v6 0/9] Allow changing bs->file on reopen, Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 1/9] block: introduce bdrv_remove_file_or_backing_child(), Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 3/9] block: bdrv_reopen_parse_backing(): don't check aio context, Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 2/9] block: introduce bdrv_set_file_or_backing_noperm(), Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 5/9] block: bdrv_reopen_parse_backing(): simplify handling implicit filters,
Vladimir Sementsov-Ogievskiy <=
- [PATCH v6 6/9] block: move supports_backing check to bdrv_set_file_or_backing_noperm(), Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 9/9] iotests: Test replacing files with x-blockdev-reopen, Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 4/9] block: bdrv_reopen_parse_backing(): don't check frozen child, Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 7/9] block: BDRVReopenState: drop replace_backing_bs field, Vladimir Sementsov-Ogievskiy, 2021/06/10
- [PATCH v6 8/9] block: Allow changing bs->file on reopen, Vladimir Sementsov-Ogievskiy, 2021/06/10
- Re: [PATCH v6 0/9] Allow changing bs->file on reopen, Kevin Wolf, 2021/06/28