linux-kernel - [PATCH v4 15/35] mm, slub: restore irqs around calling new

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Date:   Thu,  5 Aug 2021 17:19:40 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Mike Galbraith <efault@....de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Jann Horn <jannh@...gle.com>, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v4 15/35] mm, slub: restore irqs around calling new_slab()

allocate_slab() currently re-enables irqs before calling to the page allocator.
It depends on gfpflags_allow_blocking() to determine if it's safe to do so.
Now we can instead simply restore irq before calling it through new_slab().
The other caller early_kmem_cache_node_alloc() is unaffected by this.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 868a782b6f62..9350ff5110a0 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1792,9 +1792,6 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 
 	flags &= gfp_allowed_mask;
 
-	if (gfpflags_allow_blocking(flags))
-		local_irq_enable();
-
 	flags |= s->allocflags;
 
 	/*
@@ -1853,8 +1850,6 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	page->frozen = 1;
 
 out:
-	if (gfpflags_allow_blocking(flags))
-		local_irq_disable();
 	if (!page)
 		return NULL;
 
@@ -2782,16 +2777,17 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 		goto check_new_page;
 	}
 
+	local_irq_restore(flags);
 	put_cpu_ptr(s->cpu_slab);
 	page = new_slab(s, gfpflags, node);
 	c = get_cpu_ptr(s->cpu_slab);
 
 	if (unlikely(!page)) {
-		local_irq_restore(flags);
 		slab_out_of_memory(s, gfpflags, node);
 		return NULL;
 	}
 
+	local_irq_save(flags);
 	if (c->page)
 		flush_slab(s, c);
 
-- 
2.32.0