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From 5774af5a3c713d0c93010c30453812eae6a749cd Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 13 Mar 2020 12:34:37 +0000
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Subject: [PATCH 17/20] block: Fix cross-AioContext blockdev-snapshot
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20200313123439.10548-12-kwolf@redhat.com>
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Patchwork-id: 94286
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O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH v2 11/13] block: Fix cross-AioContext blockdev-snapshot
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Bugzilla: 1790482 1805143
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Daniel P. Berrange <berrange@redhat.com>
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RH-Acked-by: Peter Krempa <pkrempa@redhat.com>
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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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(cherry picked from commit 30dd65f307b647eef8156c4a33bd007823ef85cb)
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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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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 354d388..ec29b1e 100644
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--- a/block.c
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+++ b/block.c
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@@ -4327,6 +4327,7 @@ 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 7918533..c8d4b51 100644
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--- a/blockdev.c
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+++ b/blockdev.c
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@@ -1535,9 +1535,7 @@ 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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uint64_t perm, shared;
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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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@@ -1678,20 +1676,6 @@ 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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1.8.3.1
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