Il 09/10/2014 04:50, Alexey Kardashevskiy ha scritto:
> When migrated using libvirt with "--copy-storage-all", at the end of
> migration there is race between NBD mirroring task trying to do flush
> and migration completion, both end up invalidating cache. Since qcow2
> driver does not handle this situation very well, random crashes happen.
>
> This disables the BDRV_O_INCOMING flag for the block device being migrated
> once the cache has been invalidated.
>
> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
> Changes:
> v1 (v0 was RFC):
> * added a comment to nbd_export_new() as suggested by Stefan
> ---
> block.c | 18 +++++-------------
> migration.c | 1 -
> nbd.c | 6 ++++++
> 3 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/block.c b/block.c
> index c5a251c..6314af7 100644
> --- a/block.c
> +++ b/block.c
> @@ -5048,6 +5048,11 @@ void bdrv_invalidate_cache(BlockDriverState *bs, Error
> **errp)
> return;
> }
>
> + if (!(bs->open_flags & BDRV_O_INCOMING)) {
> + return;
> + }
> + bs->open_flags &= ~(BDRV_O_INCOMING);
Unnecessary parentheses.
> +
> if (bs->drv->bdrv_invalidate_cache) {
> bs->drv->bdrv_invalidate_cache(bs, &local_err);
> } else if (bs->file) {
> @@ -5083,19 +5088,6 @@ void bdrv_invalidate_cache_all(Error **errp)
> }
> }
>
> -void bdrv_clear_incoming_migration_all(void)
> -{
> - BlockDriverState *bs;
> -
> - QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
> - AioContext *aio_context = bdrv_get_aio_context(bs);
> -
> - aio_context_acquire(aio_context);
> - bs->open_flags = bs->open_flags & ~(BDRV_O_INCOMING);
> - aio_context_release(aio_context);
> - }
> -}
> -
> int bdrv_flush(BlockDriverState *bs)
> {
> Coroutine *co;
> diff --git a/migration.c b/migration.c
> index 8d675b3..c49a05a 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -103,7 +103,6 @@ static void process_incoming_migration_co(void *opaque)
> }
> qemu_announce_self();
>
> - bdrv_clear_incoming_migration_all();
> /* Make sure all file formats flush their mutable metadata */
> bdrv_invalidate_cache_all(&local_err);
> if (local_err) {
> diff --git a/nbd.c b/nbd.c
> index e9b539b..a7bce45 100644
> --- a/nbd.c
> +++ b/nbd.c
> @@ -972,6 +972,12 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t
> dev_offset,
> exp->ctx = bdrv_get_aio_context(bs);
> bdrv_ref(bs);
> bdrv_add_aio_context_notifier(bs, bs_aio_attached, bs_aio_detach, exp);
> + /*
> + * NBD exports are used for non-shared storage migration. Make sure
> + * that BDRV_O_INCOMING is cleared and the image is ready for write
> + * access since the export could be available before migration handover.
> + */
> + bdrv_invalidate_cache(bs, NULL);
> return exp;
> }
>
>
Apart from the above style remark,
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
