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block/monitor: allow dropping a bitmap never stored on disk

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block-dirty-bitmap-remove refuses any readonly bitmap outright, via
the generic BDRV_BITMAP_RO check in bdrv_dirty_bitmap_check(). That
check cannot tell whether the bitmap is actually on disk, so it also
blocks dropping one that only ever existed in memory, which needs no
write at all.

Drop the blanket check and let qcow2 decide: bdrv_remove_persistent_
dirty_bitmap() already treats an absent on-disk entry as a no-op, so
such a bitmap is now released with no write attempted. For one that
is genuinely stored, qcow2_co_remove_persistent_dirty_bitmap_locked()
now checks can_write() before it would update the on-disk directory,
so removal still fails there, with a message naming the actual
reason instead of just the bitmap's readonly flag.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Eric Blake <eblake@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
CC: John Snow <jsnow@redhat.com>
CC: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Message-ID: <20260716112242.3000035-4-den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
This commit is contained in:
Denis V. Lunev 2026-07-16 13:22:42 +02:00 • committed by Vladimir Sementsov-Ogievskiy
parent 3f3f5cdb92
commit 9a77ef813f
3 changed files with 12 additions and 3 deletions
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4
block/monitor/bitmap-qmp-cmds.c
View file

@ -165,11 +165,11 @@ BdrvDirtyBitmap *block_dirty_bitmap_remove(const char *node, const char *name,
return NULL;
}
if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_BUSY | BDRV_BITMAP_RO,
errp)) {
if (bdrv_dirty_bitmap_check(bitmap, BDRV_BITMAP_BUSY, errp)) {
return NULL;
}
/* Dropping a bitmap needs no write access unless it is actually stored. */
if (bdrv_dirty_bitmap_get_persistence(bitmap) &&
bdrv_remove_persistent_dirty_bitmap(bs, name, errp) < 0)
{

9
block/qcow2-bitmap.c
View file

@ -1487,6 +1487,15 @@ int coroutine_fn qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs,
goto out;
}
if (!can_write(bs)) {
error_setg(errp, "Cannot remove persistent bitmap '%s': "
"no write access to node '%s'", name,
bdrv_get_node_name(bs));
ret = -EACCES;
bm = NULL;
goto out;
}
QSIMPLEQ_REMOVE(bm_list, bm, Qcow2Bitmap, entry);
ret = update_ext_header_and_dir(bs, bm_list);

2
tests/qemu-iotests/tests/remove-bitmap-from-backing.out
View file

@ -1,6 +1,6 @@
Trying to remove persistent bitmap from r-o base node, should fail:
{"execute": "block-dirty-bitmap-remove", "arguments": {"name": "bitmap0", "node": "base"}}
{"error": {"class": "GenericError", "desc": "Bitmap 'bitmap0' is readonly and cannot be modified"}}
{"error": {"class": "GenericError", "desc": "Cannot remove persistent bitmap 'bitmap0': no write access to node 'base'"}}
Remove persistent bitmap from base node reopened to RW:
{"execute": "block-dirty-bitmap-remove", "arguments": {"name": "bitmap0", "node": "base"}}
{"return": {}}