* Peter Xu (pet...@redhat.com) wrote:
> When starting ram saving procedure (especially at the completion phase),
> always set last_seen_block to non-NULL to make sure we can always correctly
> detect the case where "we've migrated all the dirty pages".
>
> Then we'll guarantee both last_seen_block and pss.block will be valid
> always before the loop starts.
>
> See the comment in the code for some details.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
Yeh I guess it can currently only happen during restart?
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> migration/ram.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index dc1de9ddbc..1d42414ecc 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2546,14 +2546,22 @@ static int ram_find_and_save_block(RAMState *rs)
> return pages;
> }
>
> + /*
> + * Always keep last_seen_block/last_page valid during this procedure,
> + * because find_dirty_block() relies on these values (e.g., we compare
> + * last_seen_block with pss.block to see whether we searched all the
> + * ramblocks) to detect the completion of migration. Having NULL value
> + * of last_seen_block can conditionally cause below loop to run forever.
> + */
> + if (!rs->last_seen_block) {
> + rs->last_seen_block = QLIST_FIRST_RCU(&ram_list.blocks);
> + rs->last_page = 0;
> + }
> +
> pss.block = rs->last_seen_block;
> pss.page = rs->last_page;
> pss.complete_round = false;
>
> - if (!pss.block) {
> - pss.block = QLIST_FIRST_RCU(&ram_list.blocks);
> - }
> -
> do {
> again = true;
> found = get_queued_page(rs, &pss);
> --
> 2.32.0
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
