linux-kernel - [PATCH v2 02/33] maple_tree: Detect dead nodes in mas

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Message-ID: <20230127194110.533103-3-surenb@google.com>
Date:   Fri, 27 Jan 2023 11:40:39 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     michel@...pinasse.org, jglisse@...gle.com, mhocko@...e.com,
        vbabka@...e.cz, hannes@...xchg.org, mgorman@...hsingularity.net,
        dave@...olabs.net, willy@...radead.org, liam.howlett@...cle.com,
        peterz@...radead.org, ldufour@...ux.ibm.com, paulmck@...nel.org,
        mingo@...hat.com, will@...nel.org, luto@...nel.org,
        songliubraving@...com, peterx@...hat.com, david@...hat.com,
        dhowells@...hat.com, hughd@...gle.com, bigeasy@...utronix.de,
        kent.overstreet@...ux.dev, punit.agrawal@...edance.com,
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        axelrasmussen@...gle.com, joelaf@...gle.com, minchan@...gle.com,
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        gurua@...gle.com, arjunroy@...gle.com, soheil@...gle.com,
        leewalsh@...gle.com, posk@...gle.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        surenb@...gle.com, Liam Howlett <Liam.Howlett@...cle.com>
Subject: [PATCH v2 02/33] maple_tree: Detect dead nodes in mas_start()

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

When initially starting a search, the root node may already be in the
process of being replaced in RCU mode.  Detect and restart the walk if
this is the case.  This is necessary for RCU mode of the maple tree.

Fixes: 54a611b60590 ("Maple Tree: add new data structure")
Signed-off-by: Liam Howlett <Liam.Howlett@...cle.com>
Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 lib/maple_tree.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index e5eeecd14eee..482e17a460cb 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -1353,12 +1353,16 @@ static inline struct maple_enode *mas_start(struct ma_state *mas)
 		mas->max = ULONG_MAX;
 		mas->depth = 0;
 
+retry:
 		root = mas_root(mas);
 		/* Tree with nodes */
 		if (likely(xa_is_node(root))) {
 			mas->depth = 1;
 			mas->node = mte_safe_root(root);
 			mas->offset = 0;
+			if (mte_dead_node(mas->node))
+				goto retry;
+
 			return NULL;
 		}
 
-- 
2.39.1