linux-kernel - [PATCH v3 08/10] mm: Skip might_alloc() warnings when PF

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Message-ID: <20251001192647.195204-9-urezki@gmail.com>
Date: Wed,  1 Oct 2025 21:26:44 +0200
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
To: linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...nel.org>,
	Baoquan He <bhe@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Michal Hocko <mhocko@...e.com>
Subject: [PATCH v3 08/10] mm: Skip might_alloc() warnings when PF_MEMALLOC is set

might_alloc() catches invalid blocking allocations in contexts
where sleeping is not allowed.

However when PF_MEMALLOC is set, the page allocator already skips
reclaim and other blocking paths. In such cases, a blocking gfp_mask
does not actually lead to blocking, so triggering might_alloc() splats
is misleading.

Adjust might_alloc() to skip warnings when the current task has
PF_MEMALLOC set, matching the allocator's actual blocking behaviour.

Acked-by: Michal Hocko <mhocko@...e.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 include/linux/sched/mm.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 0232d983b715..a74582aed747 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -318,6 +318,9 @@ static inline void might_alloc(gfp_t gfp_mask)
 	fs_reclaim_acquire(gfp_mask);
 	fs_reclaim_release(gfp_mask);
 
+	if (current->flags & PF_MEMALLOC)
+		return;
+
 	might_sleep_if(gfpflags_allow_blocking(gfp_mask));
 }
 
-- 
2.47.3