69 lines
2.6 KiB
Diff
69 lines
2.6 KiB
Diff
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From 6f4a7e3489a104137f60e034157cf687e4c3158f Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Tue, 4 Feb 2025 22:13:54 +0100
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Subject: [PATCH 10/23] block: Inactivate external snapshot overlays when
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necessary
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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RH-MergeRequest: 339: QMP command for block device reactivation after migration
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RH-Jira: RHEL-54296 RHEL-78397
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RH-Acked-by: Eric Blake <eblake@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Commit: [9/22] 59b39138f0da734d497f3a58d458992abc348978 (kmwolf/centos-qemu-kvm)
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Putting an active block node on top of an inactive one is strictly
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speaking an invalid configuration and the next patch will turn it into a
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hard error.
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However, taking a snapshot while disk images are inactive after
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completing migration has an important use case: After migrating to a
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file, taking an external snapshot is what is needed to take a full VM
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snapshot.
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In order for this to keep working after the later patches, change
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creating a snapshot such that it automatically inactivates an overlay
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that is added on top of an already inactive node.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Acked-by: Fabiano Rosas <farosas@suse.de>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Message-ID: <20250204211407.381505-4-kwolf@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit e80210ffb24c4e47650344ba77ce3ed354af596c)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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blockdev.c | 16 ++++++++++++++++
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1 file changed, 16 insertions(+)
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diff --git a/blockdev.c b/blockdev.c
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index 835064ed03..81430122df 100644
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--- a/blockdev.c
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+++ b/blockdev.c
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@@ -1497,6 +1497,22 @@ static void external_snapshot_action(TransactionAction *action,
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return;
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}
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+ /*
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+ * Older QEMU versions have allowed adding an active parent node to an
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+ * inactive child node. This is unsafe in the general case, but there is an
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+ * important use case, which is taking a VM snapshot with migration to file
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+ * and then adding an external snapshot while the VM is still stopped and
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+ * images are inactive. Requiring the user to explicitly create the overlay
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+ * as inactive would break compatibility, so just do it automatically here
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+ * to keep this working.
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+ */
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+ if (bdrv_is_inactive(state->old_bs) && !bdrv_is_inactive(state->new_bs)) {
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+ ret = bdrv_inactivate(state->new_bs, errp);
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+ if (ret < 0) {
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+ return;
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+ }
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+ }
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+
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ret = bdrv_append(state->new_bs, state->old_bs, errp);
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if (ret < 0) {
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return;
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--
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2.48.1
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