linux-kernel - [PATCH 1/2] maple_tree: fix alloc node fail issue

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Date: Wed, 26 Jun 2024 12:06:30 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc: Jiazi Li <jqqlijiazi@...il.com>, linux-kernel@...r.kernel.org,
        maple-tree@...ts.infradead.org,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH 1/2] maple_tree: fix alloc node fail issue

From: Jiazi Li <jqqlijiazi@...il.com>

In the following code, the second call to the mas_node_count will
return -ENOMEM:

	mas_node_count(mas, MAPLE_ALLOC_SLOTS + 1);
	mas_node_count(mas, MAPLE_ALLOC_SLOTS * 2 + 2);

This is because there may be some full maple_alloc node in current
maple state. Use full maple_alloc node will make max_req equal to 0.
And it leads to mt_alloc_bulk return 0.
As a result, mas_node_count set mas.node to MA_ERROR(-ENOMEM).

Find a non-full maple_alloc node, and if necessary, use this non-full
node in the next while loop.

Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Suggested-by: Liam R. Howlett <Liam.Howlett@...cle.com>
Signed-off-by: Jiazi Li <jqqlijiazi@...il.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 lib/maple_tree.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index 634d49e39a02..fe5c6fab26c3 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1272,7 +1272,10 @@ static inline void mas_alloc_nodes(struct ma_state *mas, gfp_t gfp)
 
 		node->node_count += count;
 		allocated += count;
-		node = node->slot[0];
+		/* find a non-full node*/
+		do {
+			node = node->slot[0];
+		} while (unlikely(node->node_count == MAPLE_ALLOC_SLOTS));
 		requested -= count;
 	}
 	mas->alloc->total = allocated;
-- 
2.43.0