mm: page_alloc: __GFP_FS lockdep annotation for direct compaction

Patch series "mm: fix reclaim storms in defrag_mode", v2.

As we deployed vm.defrag_mode=1 in Meta production, some workloads
regressed with recurring pressure spikes and swap storms (which in turn
triggered userspace OOM rules on pressure and swap utilization levels).

Tracing pinned this to non-movable requests spinning and reclaiming
unproductively when kswapd/kcompactd are overwhelmed.  Direct reclaim
predominantly frees up pages in movable blocks, but those requests cannot
use that space under defrag_mode rules; and it is unlikely to free up
whole blocks incidentally for __rmqueue_claim() to work.

This series fixes it by making non-movable requests participate in
pageblock production in the allocator slowpath - meaning, they will invoke
direct reclaim and direct compaction with pageblock_order.

That requires some small-ish adjustments up front in the allocator and the
compaction code: three prep patches and the fix last.

The series has been in production against one of the affected workloads
for several weeks and restores the OOM kill rate to !defrag_mode baseline.


This patch (of 4):

A subsequent patch will have some order-0 allocations participate in
compaction under defrag_mode, to stave off extfrag events.

Since this is a sprawling expansion of entry points, and compaction can
enter filesystem paths, add lockdep annotations that catches __GFP_FS
passing errors.

Direct reclaim has had this annotation for a while, and since reclaim and
compaction are usually used in conjunction, this is unlikely to unearth
old bugs.  It's more about future proofing and peace of mind.

Link: https://lore.kernel.org/20260722150006.3848560-1-hannes@cmpxchg.org
Link: https://lore.kernel.org/20260722150006.3848560-2-hannes@cmpxchg.org
Fixes: e3aa7df331bc ("mm: page_alloc: defrag_mode")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Gregory Price <gourry@gourry.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f93a6bb9a872..36cdec9c5c73 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4149,12 +4149,14 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
 
 	psi_memstall_enter(&pflags);
 	delayacct_compact_start();
+	fs_reclaim_acquire(gfp_mask);
 	noreclaim_flag = memalloc_noreclaim_save();
 
 	*compact_result = try_to_compact_pages(gfp_mask, order, alloc_flags, ac,
 								prio, &page);
 
 	memalloc_noreclaim_restore(noreclaim_flag);
+	fs_reclaim_release(gfp_mask);
 	psi_memstall_leave(&pflags);
 	delayacct_compact_end();