linux-kernel - [PATCH v2 04/10] mm/vmalloc: Avoid cond_resched() when blocking is not permitted

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Message-ID: <20250915134041.151462-5-urezki@gmail.com>
Date: Mon, 15 Sep 2025 15:40:34 +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>
Subject: [PATCH v2 04/10] mm/vmalloc: Avoid cond_resched() when blocking is not permitted

vm_area_alloc_pages() contains the only voluntary reschedule points
along vmalloc() allocation path. They are needed to ensure forward
progress on PREEMPT_NONE kernels under contention for vmap metadata
(e.g. alloc_vmap_area()).

However, yielding should only be done if the given GFP flags allow
blocking. This patch avoids calling cond_resched() when allocation
context is non-blocking(GFP_ATOMIC, GFP_NOWAIT).

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 mm/vmalloc.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 49a0f81930a8..b77e8be75f10 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3633,7 +3633,9 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 							pages + nr_allocated);
 
 			nr_allocated += nr;
-			cond_resched();
+
+			if (gfpflags_allow_blocking(gfp))
+				cond_resched();
 
 			/*
 			 * If zero or pages were obtained partly,
@@ -3675,7 +3677,9 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 		for (i = 0; i < (1U << order); i++)
 			pages[nr_allocated + i] = page + i;
 
-		cond_resched();
+		if (gfpflags_allow_blocking(gfp))
+			cond_resched();
+
 		nr_allocated += 1U << order;
 	}
 
-- 
2.47.3