The existing FIXME comment notes that memory hotplug doesn't invoke shrink_slab() directly. This patch adds context explaining that this is an intentional design choice to avoid recursion or deadlocks in the memory reclaim path, as slab shrinking is handled by vmscan. Signed-off-by: Manish Kumar --- mm/page_isolation.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/page_isolation.c b/mm/page_isolation.c index b2fc5266e3d2..2ca20c3f0a97 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -176,10 +176,16 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ /* * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. - * We just check MOVABLE pages. + * + * This is an intentional limitation: invoking shrink_slab() from a + * hotplug path can cause reclaim recursion or deadlock if the normal + * memory reclaim (vmscan) path is already active. Slab shrinking is + * handled by the vmscan reclaim code under normal operation, so hotplug + * avoids direct calls into shrink_slab() to prevent reentrancy issues. + * + * We therefore only check MOVABLE pages here. * * Pass the intersection of [start_pfn, end_pfn) and the page's pageblock - * to avoid redundant checks. */ check_unmovable_start = max(page_to_pfn(page), start_pfn); check_unmovable_end = min(pageblock_end_pfn(page_to_pfn(page)), -- 2.43.0