[Qemu-devel] loading bitmaps in invalidate_cache fails

[Vladimir Sementsov-Ogievskiy]

Hi Kevin!

I'm confused with relations of permissions and invalidation, can you 
please help?

Now dirty bitmaps are loaded in invalidate_cache. Here is a problem with 
migration:

1. destination starts (inactive)

2. load bitmaps readonly

...

3. invalidate_cache: here we should make our loaded bitmaps RW, ie set 
BdrvDirtyBitmap->readonly

  to false and set IN_USE bit in the image. But the latter goes into 
"bdrv_aligned_pwritev: Assertion `child->perm & BLK_PERM_WRITE' failed",

  because in bdrv_invalidate_cache we call bdrv_set_perm after 
drv->bdrv_invalidate_cache.


What is the true way of fixing this?


PS: actually current code calls qcow2_load_autoloading_dirty_bitmaps in 
(3.) instead of qcow2_reopen_bitmaps_rw, which leads to

"Bitmap already exists" error - it's a bug which I am now fixing.


--
Best regards,
Vladimir