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From 6123c29fcf385010a683061fd7f948f256713b48 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 17 May 2019 14:23:15 +0100
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Subject: [PATCH 4/5] block: Fix invalidate_cache error path for parent
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activation
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20190517142315.16266-2-kwolf@redhat.com>
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Patchwork-id: 88024
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O-Subject: [RHEL-8.1 qemu-kvm PATCH 1/1] block: Fix invalidate_cache error path for parent activation
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Bugzilla: 1673010
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Sergio Lopez Pascual <slp@redhat.com>
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RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
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bdrv_co_invalidate_cache() clears the BDRV_O_INACTIVE flag before
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actually activating a node so that the correct permissions etc. are
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taken. In case of errors, the flag must be restored so that the next
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call to bdrv_co_invalidate_cache() retries activation.
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Restoring the flag was missing in the error path for a failed
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parent->role->activate() call. The consequence is that this attempt to
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activate all images correctly fails because we still set errp, however
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on the next attempt BDRV_O_INACTIVE is already clear, so we return
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success without actually retrying the failed action.
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An example where this is observable in practice is migration to a QEMU
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instance that has a raw format block node attached to a guest device
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with share-rw=off (the default) while another process holds
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BLK_PERM_WRITE for the same image. In this case, all activation steps
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before parent->role->activate() succeed because raw can tolerate other
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writers to the image. Only the parent callback (in particular
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blk_root_activate()) tries to implement the share-rw=on property and
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requests exclusive write permissions. This fails when the migration
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completes and correctly displays an error. However, a manual 'cont' will
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incorrectly resume the VM without calling blk_root_activate() again.
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This case is described in more detail in the following bug report:
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https://bugzilla.redhat.com/show_bug.cgi?id=1531888
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Fix this by correctly restoring the BDRV_O_INACTIVE flag in the error
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path.
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Cc: qemu-stable@nongnu.org
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Tested-by: Markus Armbruster <armbru@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 78fc3b3a26c145eebcdee992988644974b243a74)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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block.c | 1 +
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1 file changed, 1 insertion(+)
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diff --git a/block.c b/block.c
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index d0f0dc6..82b16df 100644
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--- a/block.c
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+++ b/block.c
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@@ -4417,6 +4417,7 @@ static void coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs,
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if (parent->role->activate) {
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parent->role->activate(parent, &local_err);
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if (local_err) {
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+ bs->open_flags |= BDRV_O_INACTIVE;
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error_propagate(errp, local_err);
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return;
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}
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--
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1.8.3.1
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