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[PATCH v4 06/19] block: Add bdrv_recurse_can_replace()
From: |
Max Reitz |
Subject: |
[PATCH v4 06/19] block: Add bdrv_recurse_can_replace() |
Date: |
Tue, 18 Feb 2020 11:34:41 +0100 |
After a couple of follow-up patches, this function will replace
bdrv_recurse_is_first_non_filter() in check_to_replace_node().
bdrv_recurse_is_first_non_filter() is both not sufficiently specific for
check_to_replace_node() (it allows cases that should not be allowed,
like replacing child nodes of quorum with dissenting data that have more
parents than just quorum), and it is too restrictive (it is perfectly
fine to replace filters).
Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
block.c | 38 ++++++++++++++++++++++++++++++++++++++
include/block/block_int.h | 10 ++++++++++
2 files changed, 48 insertions(+)
diff --git a/block.c b/block.c
index f6731fa9be..553ccff216 100644
--- a/block.c
+++ b/block.c
@@ -6235,6 +6235,44 @@ bool bdrv_recurse_is_first_non_filter(BlockDriverState
*bs,
return false;
}
+/*
+ * This function checks whether the given @to_replace is allowed to be
+ * replaced by a node that always shows the same data as @bs. This is
+ * used for example to verify whether the mirror job can replace
+ * @to_replace by the target mirrored from @bs.
+ * To be replaceable, @bs and @to_replace may either be guaranteed to
+ * always show the same data (because they are only connected through
+ * filters), or some driver may allow replacing one of its children
+ * because it can guarantee that this child's data is not visible at
+ * all (for example, for dissenting quorum children that have no other
+ * parents).
+ */
+bool bdrv_recurse_can_replace(BlockDriverState *bs,
+ BlockDriverState *to_replace)
+{
+ if (!bs || !bs->drv) {
+ return false;
+ }
+
+ if (bs == to_replace) {
+ return true;
+ }
+
+ /* See what the driver can do */
+ if (bs->drv->bdrv_recurse_can_replace) {
+ return bs->drv->bdrv_recurse_can_replace(bs, to_replace);
+ }
+
+ /* For filters without an own implementation, we can recurse on our own */
+ if (bs->drv->is_filter) {
+ BdrvChild *child = bs->file ?: bs->backing;
+ return bdrv_recurse_can_replace(child->bs, to_replace);
+ }
+
+ /* Safe default */
+ return false;
+}
+
BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
const char *node_name, Error **errp)
{
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 640fb82c78..eaefac210e 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -102,6 +102,13 @@ struct BlockDriver {
*/
bool (*bdrv_recurse_is_first_non_filter)(BlockDriverState *bs,
BlockDriverState *candidate);
+ /*
+ * Return true if @to_replace can be replaced by a BDS with the
+ * same data as @bs without it affecting @bs's behavior (that is,
+ * without it being visible to @bs's parents).
+ */
+ bool (*bdrv_recurse_can_replace)(BlockDriverState *bs,
+ BlockDriverState *to_replace);
int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename);
int (*bdrv_probe_device)(const char *filename);
@@ -1263,6 +1270,9 @@ void bdrv_format_default_perms(BlockDriverState *bs,
BdrvChild *c,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared);
+bool bdrv_recurse_can_replace(BlockDriverState *bs,
+ BlockDriverState *to_replace);
+
/*
* Default implementation for drivers to pass bdrv_co_block_status() to
* their file.
--
2.24.1
- [PATCH v4 00/19] block: Fix check_to_replace_node(), Max Reitz, 2020/02/18
- [PATCH v4 01/19] blockdev: Allow external snapshots everywhere, Max Reitz, 2020/02/18
- [PATCH v4 02/19] blockdev: Allow resizing everywhere, Max Reitz, 2020/02/18
- [PATCH v4 03/19] block: Drop bdrv_is_first_non_filter(), Max Reitz, 2020/02/18
- [PATCH v4 04/19] iotests: Let 041 use -blockdev for quorum children, Max Reitz, 2020/02/18
- [PATCH v4 05/19] quorum: Fix child permissions, Max Reitz, 2020/02/18
- [PATCH v4 06/19] block: Add bdrv_recurse_can_replace(),
Max Reitz <=
- [PATCH v4 07/19] blkverify: Implement .bdrv_recurse_can_replace(), Max Reitz, 2020/02/18
- [PATCH v4 08/19] quorum: Implement .bdrv_recurse_can_replace(), Max Reitz, 2020/02/18
- [PATCH v4 10/19] block: Remove bdrv_recurse_is_first_non_filter(), Max Reitz, 2020/02/18
- [PATCH v4 09/19] block: Use bdrv_recurse_can_replace(), Max Reitz, 2020/02/18
- [PATCH v4 11/19] mirror: Double-check immediately before replacing, Max Reitz, 2020/02/18
- [PATCH v4 12/19] quorum: Stop marking it as a filter, Max Reitz, 2020/02/18
- [PATCH v4 13/19] iotests: Use complete_and_wait() in 155, Max Reitz, 2020/02/18
- [PATCH v4 14/19] iotests: Add VM.assert_block_path(), Max Reitz, 2020/02/18
- [PATCH v4 15/19] iotests/041: Drop superfluous shutdowns, Max Reitz, 2020/02/18
- [PATCH v4 16/19] iotests: Resolve TODOs in 041, Max Reitz, 2020/02/18