56 lines
2.3 KiB
Diff
56 lines
2.3 KiB
Diff
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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
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Date: Thu, 11 Apr 2024 11:29:22 +0200
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Subject: [PATCH] block/copy-before-write: fix permission
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In case when source node does not have any parents, the condition still
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works as required: backup job do create the parent by
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block_job_create -> block_job_add_bdrv -> bdrv_root_attach_child
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Still, in this case checking @perm variable doesn't work, as backup job
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creates the root blk with empty permissions (as it rely on CBW filter
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to require correct permissions and don't want to create extra
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conflicts).
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So, we should not check @perm.
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The hack may be dropped entirely when transactional insertion of
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filter (when we don't try to recalculate permissions in intermediate
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state, when filter does conflict with original parent of the source
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node) merged (old big series
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"[PATCH v5 00/45] Transactional block-graph modifying API"[1] and it's
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current in-flight part is "[PATCH v8 0/7] blockdev-replace"[2])
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[1] https://patchew.org/QEMU/20220330212902.590099-1-vsementsov@openvz.org/
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[2] https://patchew.org/QEMU/20231017184444.932733-1-vsementsov@yandex-team.ru/
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Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
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Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
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Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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---
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block/copy-before-write.c | 10 +++++++---
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1 file changed, 7 insertions(+), 3 deletions(-)
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diff --git a/block/copy-before-write.c b/block/copy-before-write.c
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index b866e42271..a2dddf6f57 100644
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--- a/block/copy-before-write.c
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+++ b/block/copy-before-write.c
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@@ -364,9 +364,13 @@ static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
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perm, shared, nperm, nshared);
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if (!QLIST_EMPTY(&bs->parents)) {
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- if (perm & BLK_PERM_WRITE) {
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- *nperm = *nperm | BLK_PERM_CONSISTENT_READ;
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- }
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+ /*
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+ * Note, that source child may be shared with backup job. Backup job
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+ * does create own blk parent on copy-before-write node, so this
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+ * works even if source node does not have any parents before backup
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+ * start
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+ */
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+ *nperm = *nperm | BLK_PERM_CONSISTENT_READ;
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*nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
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}
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}
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