Some Proxmox users reported an occasional assertion failure [0][1] in
busy VMs when using drive mirror with active mode. In particular, the
failure may occur for zero writes shorter than the job granularity:
> #0 0x00007b421154b507 in abort ()
> #1 0x00007b421154b420 in ?? ()
> #2 0x0000641c582e061f in bitmap_set (map=0x7b4204014e00, start=14, nr=-1)
> #3 0x0000641c58062824 in do_sync_target_write (job=0x641c7e73d1e0,
> method=MIRROR_METHOD_ZERO, offset=852480, bytes=4096, qiov=0x0, flags=0)
> #4 0x0000641c58062250 in bdrv_mirror_top_do_write (bs=0x641c7e62e1f0,
method=MIRROR_METHOD_ZERO, copy_to_target=true, offset=852480,
bytes=4096, qiov=0x0, flags=0)
> #5 0x0000641c58061f31 in bdrv_mirror_top_pwrite_zeroes (bs=0x641c7e62e1f0,
offset=852480, bytes=4096, flags=0)
The range for the dirty bitmap described by dirty_bitmap_offset and
dirty_bitmap_end is narrower than the original range and in fact,
dirty_bitmap_end might be smaller than dirty_bitmap_offset. There
already is a check for 'dirty_bitmap_offset < dirty_bitmap_end' before
resetting the dirty bitmap. Add such a check for setting the zero
bitmap too, which uses the same narrower range.
[0]: https://forum.proxmox.com/threads/177981/
[1]: https://bugzilla.proxmox.com/show_bug.cgi?id=7222
Cc: [email protected]
Fixes: 7e277545b9 ("mirror: Skip writing zeroes when target is already zero")
Signed-off-by: Fiona Ebner <[email protected]>
---
block/mirror.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/block/mirror.c b/block/mirror.c
index b344182c74..bc982cb99a 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1514,9 +1514,12 @@ do_sync_target_write(MirrorBlockJob *job, MirrorMethod
method,
assert(!qiov);
ret = blk_co_pwrite_zeroes(job->target, offset, bytes, flags);
if (job->zero_bitmap && ret >= 0) {
- bitmap_set(job->zero_bitmap, dirty_bitmap_offset /
job->granularity,
- (dirty_bitmap_end - dirty_bitmap_offset) /
- job->granularity);
+ if (dirty_bitmap_offset < dirty_bitmap_end) {
+ bitmap_set(job->zero_bitmap,
+ dirty_bitmap_offset / job->granularity,
+ (dirty_bitmap_end - dirty_bitmap_offset) /
+ job->granularity);
+ }
}
break;
--
2.47.3
