linux-kernel - [RFC 12/26] mm, slub: restore irqs around calling new

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Message-Id: <20210524233946.20352-13-vbabka@suse.cz>
Date:   Tue, 25 May 2021 01:39:32 +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 12/26] 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

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 16f3cbb81627..47a3438d6a35 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1763,9 +1763,6 @@ 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;
 
 	/*
@@ -1824,8 +1821,6 @@ 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;
 
@@ -2753,17 +2748,18 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
 		goto check_new_page;
 	}
 
+	local_irq_restore(flags);
 	migrate_enable();
 	page = new_slab(s, gfpflags, node);
 	migrate_disable();
 	c = this_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);
 
-- 
2.31.1