linux-kernel - [PATCH v7 35/61] mm: Convert truncate to XArray

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Message-Id: <20180219194556.6575-36-willy@infradead.org>
Date:   Mon, 19 Feb 2018 11:45:30 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH v7 35/61] mm: Convert truncate to XArray

From: Matthew Wilcox <mawilcox@...rosoft.com>

This is essentially xa_cmpxchg() with the locking handled above us,
and it doesn't have to handle replacing a NULL entry.

Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
 mm/truncate.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index 3fe1e7461684..9267c1a12a31 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -33,15 +33,12 @@
 static inline void __clear_shadow_entry(struct address_space *mapping,
 				pgoff_t index, void *entry)
 {
-	struct radix_tree_node *node;
-	void **slot;
+	XA_STATE(xas, &mapping->pages, index);
 
-	if (!__radix_tree_lookup(&mapping->pages, index, &node, &slot))
+	xas_set_update(&xas, workingset_update_node);
+	if (xas_load(&xas) != entry)
 		return;
-	if (*slot != entry)
-		return;
-	__radix_tree_replace(&mapping->pages, node, slot, NULL,
-			     workingset_update_node);
+	xas_store(&xas, NULL);
 	mapping->nrexceptional--;
 }
 
@@ -738,10 +735,10 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 		index++;
 	}
 	/*
-	 * For DAX we invalidate page tables after invalidating radix tree.  We
+	 * For DAX we invalidate page tables after invalidating page cache.  We
 	 * could invalidate page tables while invalidating each entry however
 	 * that would be expensive. And doing range unmapping before doesn't
-	 * work as we have no cheap way to find whether radix tree entry didn't
+	 * work as we have no cheap way to find whether page cache entry didn't
 	 * get remapped later.
 	 */
 	if (dax_mapping(mapping)) {
-- 
2.16.1