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From: Fiona Ebner <f.ebner@proxmox.com>
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Date: Thu, 11 Apr 2024 11:29:23 +0200
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Subject: [pve-devel] [PATCH qemu v3 02/22] block/copy-before-write: support
unligned snapshot-discard
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From: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
First thing that crashes on unligned access here is
bdrv_reset_dirty_bitmap(). Correct way is to align-down the
snapshot-discard request.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
block/copy-before-write.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index a2dddf6f57..0a219c2b75 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -325,14 +325,24 @@ static int coroutine_fn GRAPH_RDLOCK
cbw_co_pdiscard_snapshot(BlockDriverState *bs, int64_t offset, int64_t bytes)
{
BDRVCopyBeforeWriteState *s = bs->opaque;
+ uint32_t cluster_size = block_copy_cluster_size(s->bcs);
+ int64_t aligned_offset = QEMU_ALIGN_UP(offset, cluster_size);
+ int64_t aligned_end = QEMU_ALIGN_DOWN(offset + bytes, cluster_size);
+ int64_t aligned_bytes;
+
+ if (aligned_end <= aligned_offset) {
+ return 0;
+ }
+ aligned_bytes = aligned_end - aligned_offset;
WITH_QEMU_LOCK_GUARD(&s->lock) {
- bdrv_reset_dirty_bitmap(s->access_bitmap, offset, bytes);
+ bdrv_reset_dirty_bitmap(s->access_bitmap, aligned_offset,
+ aligned_bytes);
}
- block_copy_reset(s->bcs, offset, bytes);
+ block_copy_reset(s->bcs, aligned_offset, aligned_bytes);
- return bdrv_co_pdiscard(s->target, offset, bytes);
+ return bdrv_co_pdiscard(s->target, aligned_offset, aligned_bytes);
}
static void cbw_refresh_filename(BlockDriverState *bs)
--
2.39.2