From: Vlastimil Babka <vbabka@suse.cz>
Date: Mon, 23 Aug 2021 23:58:59 +0000 (+1000)
Subject: mm, slub: call deactivate_slab() without disabling irqs
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=a7d52f9726e76a8f0f40f1b6d3798414f2f71e2b;p=users%2Fjedix%2Flinux-maple.git

mm, slub: call deactivate_slab() without disabling irqs

The function is now safe to be called with irqs enabled, so move the calls
outside of irq disabled sections.

When called from ___slab_alloc() -> flush_slab() we have irqs disabled, so
to reenable them before deactivate_slab() we need to open-code
flush_slab() in ___slab_alloc() and reenable irqs after modifying the
kmem_cache_cpu fields.  But that means a IRQ handler meanwhile might have
assigned a new page to kmem_cache_cpu.page so we have to retry the whole
check.

The remaining callers of flush_slab() are the IPI handler which has
disabled irqs anyway, and slub_cpu_dead() which will be dealt with in the
following patch.

Link: https://lkml.kernel.org/r/20210805152000.12817-22-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---

diff --git a/mm/slub.c b/mm/slub.c
index 00a96e9030e5..44c4de4b3755 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2765,8 +2765,8 @@ deactivate_slab:
 	freelist = c->freelist;
 	c->page = NULL;
 	c->freelist = NULL;
-	deactivate_slab(s, page, freelist);
 	local_irq_restore(flags);
+	deactivate_slab(s, page, freelist);
 
 new_slab:
 
@@ -2834,18 +2834,32 @@ check_new_page:
 		 */
 		goto return_single;
 
+retry_load_page:
+
 	local_irq_save(flags);
-	if (unlikely(c->page))
-		flush_slab(s, c);
+	if (unlikely(c->page)) {
+		void *flush_freelist = c->freelist;
+		struct page *flush_page = c->page;
+
+		c->page = NULL;
+		c->freelist = NULL;
+		c->tid = next_tid(c->tid);
+
+		local_irq_restore(flags);
+
+		deactivate_slab(s, flush_page, flush_freelist);
+
+		stat(s, CPUSLAB_FLUSH);
+
+		goto retry_load_page;
+	}
 	c->page = page;
 
 	goto load_freelist;
 
 return_single:
 
-	local_irq_save(flags);
 	deactivate_slab(s, page, get_freepointer(s, freelist));
-	local_irq_restore(flags);
 	return freelist;
 }