linux-kernel - [PATCH v8 49/63] shmem: Convert shmem_alloc

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Date:   Tue,  6 Mar 2018 11:23:59 -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,
        Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
        linux-nilfs@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: [PATCH v8 49/63] shmem: Convert shmem_alloc_hugepage to XArray

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

xa_find() is a slightly easier API to use than
radix_tree_gang_lookup_slot() because it contains its own RCU locking.

Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
 mm/shmem.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index fb06fb3e644a..a0a354a87f3b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1416,23 +1416,17 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 		struct shmem_inode_info *info, pgoff_t index)
 {
 	struct vm_area_struct pvma;
-	struct inode *inode = &info->vfs_inode;
-	struct address_space *mapping = inode->i_mapping;
-	pgoff_t idx, hindex;
-	void __rcu **results;
+	struct address_space *mapping = info->vfs_inode.i_mapping;
+	pgoff_t hindex;
 	struct page *page;
 
 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
 		return NULL;
 
 	hindex = round_down(index, HPAGE_PMD_NR);
-	rcu_read_lock();
-	if (radix_tree_gang_lookup_slot(&mapping->i_pages, &results, &idx,
-				hindex, 1) && idx < hindex + HPAGE_PMD_NR) {
-		rcu_read_unlock();
+	if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
+								XA_PRESENT))
 		return NULL;
-	}
-	rcu_read_unlock();
 
 	shmem_pseudo_vma_init(&pvma, info, hindex);
 	page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
-- 
2.16.1