linux-kernel - [RFC v2 28/34] mm, slab: make flush_slab() possible to call with irqs enabled

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Date:   Wed,  9 Jun 2021 13:38:57 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jann Horn <jannh@...gle.com>, Vlastimil Babka <vbabka@...e.cz>
Subject: [RFC v2 28/34] mm, slab: make flush_slab() possible to call with irqs enabled

Currently flush_slab() is always called with disabled IRQs if it's needed, but
the following patches will change that, so add a parameter to control IRQ
disabling within the function, which only protects the kmem_cache_cpu
manipulation and not the call to deactivate_slab() which doesn't need it.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 12d35d6a6eaa..5c70fc17e9be 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2438,16 +2438,28 @@ static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
 #endif	/* CONFIG_SLUB_CPU_PARTIAL */
 }
 
-static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
+static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c,
+			      bool lock)
 {
-	void *freelist = c->freelist;
-	struct page *page = c->page;
+	unsigned long flags;
+	void *freelist;
+	struct page *page;
+
+	if (lock)
+		local_irq_save(flags);
+
+	freelist = c->freelist;
+	page = c->page;
 
 	c->page = NULL;
 	c->freelist = NULL;
 	c->tid = next_tid(c->tid);
 
-	deactivate_slab(s, page, freelist);
+	if (lock)
+		local_irq_restore(flags);
+
+	if (page)
+		deactivate_slab(s, page, freelist);
 
 	stat(s, CPUSLAB_FLUSH);
 }
@@ -2457,7 +2469,7 @@ static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
 	struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
 
 	if (c->page)
-		flush_slab(s, c);
+		flush_slab(s, c, false);
 
 	unfreeze_partials_cpu(s, c);
 }
@@ -2473,7 +2485,7 @@ static void flush_cpu_slab(void *d)
 	struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
 
 	if (c->page)
-		flush_slab(s, c);
+		flush_slab(s, c, false);
 
 	unfreeze_partials(s);
 }
-- 
2.31.1