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authorPeter Xu2022-10-04 20:24:26 +0200
committerJuan Quintela2022-11-21 11:58:10 +0100
commit4934a5dd7c68f5ab15f17498db4fc20ed6db9578 (patch)
tree6c7a43e0acaf1706ae878c1caecf2ca0d5f4940f
parentmigration/multifd/zero-copy: Create helper function for flushing (diff)
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migration: Fix possible infinite loop of ram save process
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. Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Signed-off-by: Juan Quintela <quintela@redhat.com>
-rw-r--r--migration/ram.c16
1 files 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);