79 lines
2.8 KiB
Diff
79 lines
2.8 KiB
Diff
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From ec96b9f64c239736003413d70dc3999ad0b8271c Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Tue, 10 Mar 2020 12:38:29 +0100
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Subject: [PATCH] block: Fix cross-AioContext blockdev-snapshot
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external_snapshot_prepare() tries to move the overlay to the AioContext
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of the backing file (the snapshotted node). However, it's possible that
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this doesn't work, but the backing file can instead be moved to the
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overlay's AioContext (e.g. opening the backing chain for a mirror
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target).
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bdrv_append() already indirectly uses bdrv_attach_node(), which takes
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care to move nodes to make sure they use the same AioContext and which
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tries both directions.
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So the problem has a simple fix: Just delete the unnecessary extra
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bdrv_try_set_aio_context() call in external_snapshot_prepare() and
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instead assert in bdrv_append() that both nodes were indeed moved to the
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same AioContext.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Message-Id: <20200310113831.27293-6-kwolf@redhat.com>
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Tested-by: Peter Krempa <pkrempa@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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block.c | 1 +
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blockdev.c | 16 ----------------
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2 files changed, 1 insertion(+), 16 deletions(-)
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diff --git a/block.c b/block.c
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index ba36b53a00..824025f781 100644
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--- a/block.c
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+++ b/block.c
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@@ -4165,6 +4165,7 @@ void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
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bdrv_ref(from);
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assert(qemu_get_current_aio_context() == qemu_get_aio_context());
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+ assert(bdrv_get_aio_context(from) == bdrv_get_aio_context(to));
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bdrv_drained_begin(from);
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/* Put all parents into @list and calculate their cumulative permissions */
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diff --git a/blockdev.c b/blockdev.c
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index 79112be2e6..d1a3b6a630 100644
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--- a/blockdev.c
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+++ b/blockdev.c
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@@ -1578,8 +1578,6 @@ static void external_snapshot_prepare(BlkActionState *common,
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DO_UPCAST(ExternalSnapshotState, common, common);
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TransactionAction *action = common->action;
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AioContext *aio_context;
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- AioContext *old_context;
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- int ret;
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/* 'blockdev-snapshot' and 'blockdev-snapshot-sync' have similar
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* purpose but a different set of parameters */
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@@ -1719,20 +1717,6 @@ static void external_snapshot_prepare(BlkActionState *common,
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goto out;
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}
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- /* Honor bdrv_try_set_aio_context() context acquisition requirements. */
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- old_context = bdrv_get_aio_context(state->new_bs);
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- aio_context_release(aio_context);
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- aio_context_acquire(old_context);
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-
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- ret = bdrv_try_set_aio_context(state->new_bs, aio_context, errp);
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-
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- aio_context_release(old_context);
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- aio_context_acquire(aio_context);
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-
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- if (ret < 0) {
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- goto out;
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- }
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-
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/* This removes our old bs and adds the new bs. This is an operation that
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* can fail, so we need to do it in .prepare; undoing it for abort is
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* always possible. */
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--
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2.27.0
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