linux-kernel - [RFC PATCH v2 2/6] slub: Prepare __slab_free() for unfrozen partial slab out of node partial list

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Message-Id: <20231021144317.3400916-3-chengming.zhou@linux.dev>
Date:   Sat, 21 Oct 2023 14:43:13 +0000
From:   chengming.zhou@...ux.dev
To:     cl@...ux.com, penberg@...nel.org
Cc:     rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, 42.hyeyoo@...il.com, willy@...radead.org,
        pcc@...gle.com, tytso@....edu, maz@...nel.org,
        ruansy.fnst@...itsu.com, vishal.moola@...il.com,
        lrh2000@....edu.cn, hughd@...gle.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, chengming.zhou@...ux.dev,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: [RFC PATCH v2 2/6] slub: Prepare __slab_free() for unfrozen partial slab out of node partial list

From: Chengming Zhou <zhouchengming@...edance.com>

Now the partial slub will be frozen when taken out of node partial list,
so the __slab_free() will know from "was_frozen" that the partial slab
is not on node partial list and is used by one kmem_cache_cpu.

But we will change this, make partial slabs leave the node partial list
with unfrozen state, so we need to change __slab_free() to use the new
slab_test_node_partial() we just introduced.

Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
---
 mm/slub.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mm/slub.c b/mm/slub.c
index 3fad4edca34b..adeff8df85ec 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3610,6 +3610,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
 	unsigned long counters;
 	struct kmem_cache_node *n = NULL;
 	unsigned long flags;
+	bool on_node_partial;
 
 	stat(s, FREE_SLOWPATH);
 
@@ -3657,6 +3658,7 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
 				 */
 				spin_lock_irqsave(&n->list_lock, flags);
 
+				on_node_partial = slab_test_node_partial(slab);
 			}
 		}
 
@@ -3685,6 +3687,15 @@ static void __slab_free(struct kmem_cache *s, struct slab *slab,
 		return;
 	}
 
+	/*
+	 * This slab was not full and not on the per-node partial list either,
+	 * in which case we shouldn't manipulate its list, just early return.
+	 */
+	if (prior && !on_node_partial) {
+		spin_unlock_irqrestore(&n->list_lock, flags);
+		return;
+	}
+
 	if (unlikely(!new.inuse && n->nr_partial >= s->min_partial))
 		goto slab_empty;
 
-- 
2.20.1