linux-kernel - [PATCH RFC v3 9/9] maple_tree: replace preallocation with slub percpu array prefill

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Date:   Wed, 29 Nov 2023 10:53:34 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, maple-tree@...ts.infradead.org,
        kasan-dev@...glegroups.com
Subject: [PATCH RFC v3 9/9] maple_tree: replace preallocation with slub
 percpu array prefill

With the percpu array we can try not doing the preallocations in maple
tree, and instead make sure the percpu array is prefilled, and using
GFP_ATOMIC in places that relied on the preallocation (in case we miss
or fail trylock on the array), i.e. mas_store_prealloc(). For now simply
add __GFP_NOFAIL there as well.
---
 lib/maple_tree.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index f5c0bca2c5d7..d84a0c0fe83b 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -5452,7 +5452,12 @@ void mas_store_prealloc(struct ma_state *mas, void *entry)
 
 	mas_wr_store_setup(&wr_mas);
 	trace_ma_write(__func__, mas, 0, entry);
+
+retry:
 	mas_wr_store_entry(&wr_mas);
+	if (unlikely(mas_nomem(mas, GFP_ATOMIC | __GFP_NOFAIL)))
+		goto retry;
+
 	MAS_WR_BUG_ON(&wr_mas, mas_is_err(mas));
 	mas_destroy(mas);
 }
@@ -5471,8 +5476,6 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
 	MA_WR_STATE(wr_mas, mas, entry);
 	unsigned char node_size;
 	int request = 1;
-	int ret;
-
 
 	if (unlikely(!mas->index && mas->last == ULONG_MAX))
 		goto ask_now;
@@ -5512,16 +5515,8 @@ int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp)
 
 	/* node store, slot store needs one node */
 ask_now:
-	mas_node_count_gfp(mas, request, gfp);
-	if (likely(!mas_is_err(mas)))
-		return 0;
+	return kmem_cache_prefill_percpu_array(maple_node_cache, request, gfp);
 
-	mas_set_alloc_req(mas, 0);
-	ret = xa_err(mas->node);
-	mas_reset(mas);
-	mas_destroy(mas);
-	mas_reset(mas);
-	return ret;
 }
 EXPORT_SYMBOL_GPL(mas_preallocate);
 

-- 
2.43.0