linux-kernel - [PATCH-next 4/5] mm/vmalloc: refactor the preloading loagic

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Message-Id: <20210402202237.20334-4-urezki@gmail.com>
Date:   Fri,  2 Apr 2021 22:22:36 +0200
From:   "Uladzislau Rezki (Sony)" <urezki@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Hillf Danton <hdanton@...a.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH-next 4/5] mm/vmalloc: refactor the preloading loagic

Instead of keeping open-coded style, move the code related to
preloading into a separate function. Therefore introduce the
preload_this_cpu_lock() routine that prelaods a current CPU
with one extra vmap_area object.

There is no functional change as a result of this patch.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 mm/vmalloc.c | 60 +++++++++++++++++++++++-----------------------------
 1 file changed, 27 insertions(+), 33 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8b564f91a610..093c7e034ca2 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1430,6 +1430,29 @@ static void free_vmap_area(struct vmap_area *va)
 	spin_unlock(&free_vmap_area_lock);
 }
 
+static inline void
+preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
+{
+	struct vmap_area *va = NULL;
+
+	/*
+	 * Preload this CPU with one extra vmap_area object. It is used
+	 * when fit type of free area is NE_FIT_TYPE. It guarantees that
+	 * a CPU that does an allocation is preloaded.
+	 *
+	 * We do it in non-atomic context, thus it allows us to use more
+	 * permissive allocation masks to be more stable under low memory
+	 * condition and high memory pressure.
+	 */
+	if (!this_cpu_read(ne_fit_preload_node))
+		va = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);
+
+	spin_lock(lock);
+
+	if (va && __this_cpu_cmpxchg(ne_fit_preload_node, NULL, va))
+		kmem_cache_free(vmap_area_cachep, va);
+}
+
 /*
  * Allocate a region of KVA of the specified size and alignment, within the
  * vstart and vend.
@@ -1439,7 +1462,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 				unsigned long vstart, unsigned long vend,
 				int node, gfp_t gfp_mask)
 {
-	struct vmap_area *va, *pva;
+	struct vmap_area *va;
 	unsigned long addr;
 	int purged = 0;
 	int ret;
@@ -1465,43 +1488,14 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 	kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask);
 
 retry:
-	/*
-	 * Preload this CPU with one extra vmap_area object. It is used
-	 * when fit type of free area is NE_FIT_TYPE. Please note, it
-	 * does not guarantee that an allocation occurs on a CPU that
-	 * is preloaded, instead we minimize the case when it is not.
-	 * It can happen because of cpu migration, because there is a
-	 * race until the below spinlock is taken.
-	 *
-	 * The preload is done in non-atomic context, thus it allows us
-	 * to use more permissive allocation masks to be more stable under
-	 * low memory condition and high memory pressure. In rare case,
-	 * if not preloaded, GFP_NOWAIT is used.
-	 *
-	 * Set "pva" to NULL here, because of "retry" path.
-	 */
-	pva = NULL;
-
-	if (!this_cpu_read(ne_fit_preload_node))
-		/*
-		 * Even if it fails we do not really care about that.
-		 * Just proceed as it is. If needed "overflow" path
-		 * will refill the cache we allocate from.
-		 */
-		pva = kmem_cache_alloc_node(vmap_area_cachep, gfp_mask, node);
-
-	spin_lock(&free_vmap_area_lock);
-
-	if (pva && __this_cpu_cmpxchg(ne_fit_preload_node, NULL, pva))
-		kmem_cache_free(vmap_area_cachep, pva);
+	preload_this_cpu_lock(&free_vmap_area_lock, gfp_mask, node);
+	addr = __alloc_vmap_area(size, align, vstart, vend);
+	spin_unlock(&free_vmap_area_lock);
 
 	/*
 	 * If an allocation fails, the "vend" address is
 	 * returned. Therefore trigger the overflow path.
 	 */
-	addr = __alloc_vmap_area(size, align, vstart, vend);
-	spin_unlock(&free_vmap_area_lock);
-
 	if (unlikely(addr == vend))
 		goto overflow;
 
-- 
2.20.1