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From:   Matthew Wilcox <willy@infradead.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Matthew Wilcox <mawilcox@microsoft.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org
Subject: [PATCH v7 51/61] shmem: Convert shmem_free_swap to XArray
Date:   Mon, 19 Feb 2018 11:45:46 -0800
Message-Id: <20180219194556.6575-52-willy@infradead.org>
In-Reply-To: <20180219194556.6575-1-willy@infradead.org>
References: <20180219194556.6575-1-willy@infradead.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Matthew Wilcox <mawilcox@microsoft.com>

This is a perfect use for xa_cmpxchg().  Note the use of 0 for GFP
flags; we won't be allocating memory.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
 mm/shmem.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 50f068f59c82..a7931660897d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -635,16 +635,13 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
 }
 
 /*
- * Remove swap entry from radix tree, free the swap and its page cache.
+ * Remove swap entry from page cache, free the swap and its page cache.
  */
 static int shmem_free_swap(struct address_space *mapping,
 			   pgoff_t index, void *radswap)
 {
-	void *old;
+	void *old = xa_cmpxchg(&mapping->pages, index, radswap, NULL, 0);
 
-	xa_lock_irq(&mapping->pages);
-	old = radix_tree_delete_item(&mapping->pages, index, radswap);
-	xa_unlock_irq(&mapping->pages);
 	if (old != radswap)
 		return -ENOENT;
 	free_swap_and_cache(radix_to_swp_entry(radswap));
-- 
2.16.1