linux-kernel - [PATCH 1/5] mm/slub: move struct track init out of set

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Date:   Fri, 25 Feb 2022 19:03:14 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Pekka Enberg <penberg@...nel.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        patches@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Oliver Glitta <glittao@...il.com>,
        Faiyaz Mohammed <faiyazm@...eaurora.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 1/5] mm/slub: move struct track init out of set_track()

set_track() either zeroes out the struct track or fills it, depending on
the addr parameter. This is unnecessary as there's only one place that
calls it for the initialization - init_tracking(). We can simply do the
zeroing there, with a single memset() that covers both TRACK_ALLOC and
TRACK_FREE as they are adjacent.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 261474092e43..1fc451f4fe62 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -729,34 +729,32 @@ static void set_track(struct kmem_cache *s, void *object,
 {
 	struct track *p = get_track(s, object, alloc);
 
-	if (addr) {
 #ifdef CONFIG_STACKTRACE
-		unsigned int nr_entries;
+	unsigned int nr_entries;
 
-		metadata_access_enable();
-		nr_entries = stack_trace_save(kasan_reset_tag(p->addrs),
-					      TRACK_ADDRS_COUNT, 3);
-		metadata_access_disable();
+	metadata_access_enable();
+	nr_entries = stack_trace_save(kasan_reset_tag(p->addrs),
+				      TRACK_ADDRS_COUNT, 3);
+	metadata_access_disable();
 
-		if (nr_entries < TRACK_ADDRS_COUNT)
-			p->addrs[nr_entries] = 0;
+	if (nr_entries < TRACK_ADDRS_COUNT)
+		p->addrs[nr_entries] = 0;
 #endif
-		p->addr = addr;
-		p->cpu = smp_processor_id();
-		p->pid = current->pid;
-		p->when = jiffies;
-	} else {
-		memset(p, 0, sizeof(struct track));
-	}
+	p->addr = addr;
+	p->cpu = smp_processor_id();
+	p->pid = current->pid;
+	p->when = jiffies;
 }
 
 static void init_tracking(struct kmem_cache *s, void *object)
 {
+	struct track *p;
+
 	if (!(s->flags & SLAB_STORE_USER))
 		return;
 
-	set_track(s, object, TRACK_FREE, 0UL);
-	set_track(s, object, TRACK_ALLOC, 0UL);
+	p = get_track(s, object, TRACK_ALLOC);
+	memset(p, 0, 2*sizeof(struct track));
 }
 
 static void print_track(const char *s, struct track *t, unsigned long pr_time)
-- 
2.35.1