From: Vladimir Sementsov-Ogievskiy <[email protected]> Here is double bug:
First, return error but not set errp. This may lead to: qmp block-dirty-bitmap-remove may report success when actually failed block-dirty-bitmap-remove used in a transaction will crash, as qmp_transaction will think that it returned success and will call block_dirty_bitmap_remove_commit which will crash, as state->bitmap is NULL Second (like in anecdote), this case is not an error at all. As it is documented in the comment above bdrv_co_remove_persistent_dirty_bitmap definition, absence of bitmap is not an error, and similar case handled at start of qcow2_co_remove_persistent_dirty_bitmap, it returns 0 when there is no bitmaps at all. But when there are some bitmaps, but not the requested one, it return error with errp unset. Fix that. Trigger: 1. create persistent bitmap A 2. shutdown vm (bitmap A is synced) 3. start vm 4. create persistent bitmap B 5. remove bitmap B - it fails (and crashes if in transaction) Potential workaround (rather invasive to ask clients to implement it): 1. create persistent bitmap A 2. shutdown vm 3. start vm 4. create persistent bitmap B 5. remember, that we want to remove bitmap B after vm shutdown ... some other operations ... 6. vm shutdown 7. start vm in stopped mode, and remove all bitmaps marked for removing 8. stop vm Fixes: b56a1e31759b750 Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]> Message-Id: <[email protected]> Reviewed-by: Eric Blake <[email protected]> Reviewed-by: John Snow <[email protected]> [eblake: commit message tweaks] Signed-off-by: Eric Blake <[email protected]> --- block/qcow2-bitmap.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c index 8abaf632fc7d..c6c8ebbe89d4 100644 --- a/block/qcow2-bitmap.c +++ b/block/qcow2-bitmap.c @@ -1469,8 +1469,10 @@ int coroutine_fn qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs, Qcow2BitmapList *bm_list; if (s->nb_bitmaps == 0) { - /* Absence of the bitmap is not an error: see explanation above - * bdrv_remove_persistent_dirty_bitmap() definition. */ + /* + * Absence of the bitmap is not an error: see explanation above + * bdrv_co_remove_persistent_dirty_bitmap() definition. + */ return 0; } @@ -1485,7 +1487,8 @@ int coroutine_fn qcow2_co_remove_persistent_dirty_bitmap(BlockDriverState *bs, bm = find_bitmap_by_name(bm_list, name); if (bm == NULL) { - ret = -EINVAL; + /* Absence of the bitmap is not an error, see above. */ + ret = 0; goto out; } -- 2.21.0
