On 03.03.25 13:13, Brendan Jackman wrote:
Since the migratetype hygiene patches [0], the locking here is
a bit more formalised.
For other stuff, it's pretty obvious that it would be protected by the
zone lock. But it didn't seem totally self-evident that it should
protect the pageblock type. So it seems particularly helpful to have it
written in the code.
[...]
+
u64 max_mem_size = U64_MAX;
/* add this memory to iomem resource */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 579789600a3c7bfb7b0d847d51af702a9d4b139a..1ed21179676d05c66f77f9dbebf88e36bbe402e9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -417,6 +417,10 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
void set_pageblock_migratetype(struct page *page, int migratetype)
{
+ lockdep_assert_once(system_state == SYSTEM_BOOTING ||
+ in_mem_hotplug() ||
+ lockdep_is_held(&page_zone(page)->lock));
+
I assume the call chain on the memory hotplug path is mostly
move_pfn_range_to_zone()->memmap_init_range()->set_pageblock_migratetype()
either when onlining a memory block, or from pagemap_range() while
holding the hotplug lock.
But there is also the
memmap_init_zone_device()->memmap_init_compound()->__init_zone_device_page()->set_pageblock_migratetype()
one, called from pagemap_range() *without* holding the hotplug lock, and
you assertion would be missing that.
I'm not too happy about that assertion in general.
--
Cheers,
David / dhildenb
