linux-kernel - [PATCH RFC v3 8/9] maple_tree: Remove MA_STATE

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Message-Id: <20231129-slub-percpu-caches-v3-8-6bcf536772bc@suse.cz>
Date:   Wed, 29 Nov 2023 10:53:33 +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, Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH RFC v3 8/9] maple_tree: Remove MA_STATE_PREALLOC

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

MA_SATE_PREALLOC was added to catch any writes that try to allocate when
the maple state is being used in preallocation mode.  This can safely be
removed in favour of the percpu array of nodes.

Note that mas_expected_entries() still expects no allocations during
operation and so MA_STATE_BULK can be used in place of preallocations
for this case, which is primarily used for forking.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 lib/maple_tree.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index d9e7088fd9a7..f5c0bca2c5d7 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -68,11 +68,9 @@
  * Maple state flags
  * * MA_STATE_BULK		- Bulk insert mode
  * * MA_STATE_REBALANCE		- Indicate a rebalance during bulk insert
- * * MA_STATE_PREALLOC		- Preallocated nodes, WARN_ON allocation
  */
 #define MA_STATE_BULK		1
 #define MA_STATE_REBALANCE	2
-#define MA_STATE_PREALLOC	4
 
 #define ma_parent_ptr(x) ((struct maple_pnode *)(x))
 #define mas_tree_parent(x) ((unsigned long)(x->tree) | MA_ROOT_PARENT)
@@ -1255,11 +1253,8 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
 		return;
 
 	mas_set_alloc_req(mas, 0);
-	if (mas->mas_flags & MA_STATE_PREALLOC) {
-		if (allocated)
-			return;
-		WARN_ON(!allocated);
-	}
+	if (mas->mas_flags & MA_STATE_BULK)
+		return;
 
 	if (!allocated || mas->alloc->node_count == MAPLE_ALLOC_SLOTS) {
 		node = (struct maple_alloc *)mt_alloc_one(gfp);
@@ -5518,7 +5513,6 @@ 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);
-	mas->mas_flags |= MA_STATE_PREALLOC;
 	if (likely(!mas_is_err(mas)))
 		return 0;
 
@@ -5561,7 +5555,7 @@ void mas_destroy(struct ma_state *mas)
 
 		mas->mas_flags &= ~MA_STATE_REBALANCE;
 	}
-	mas->mas_flags &= ~(MA_STATE_BULK|MA_STATE_PREALLOC);
+	mas->mas_flags &= ~MA_STATE_BULK;
 
 	total = mas_allocated(mas);
 	while (total) {
@@ -5610,9 +5604,6 @@ int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries)
 	 * of nodes during the operation.
 	 */
 
-	/* Optimize splitting for bulk insert in-order */
-	mas->mas_flags |= MA_STATE_BULK;
-
 	/*
 	 * Avoid overflow, assume a gap between each entry and a trailing null.
 	 * If this is wrong, it just means allocation can happen during
@@ -5629,8 +5620,9 @@ int mas_expected_entries(struct ma_state *mas, unsigned long nr_entries)
 	/* Add working room for split (2 nodes) + new parents */
 	mas_node_count_gfp(mas, nr_nodes + 3, GFP_KERNEL);
 
-	/* Detect if allocations run out */
-	mas->mas_flags |= MA_STATE_PREALLOC;
+	/* Optimize splitting for bulk insert in-order */
+	mas->mas_flags |= MA_STATE_BULK;
+
 
 	if (!mas_is_err(mas))
 		return 0;

-- 
2.43.0