linux-kernel - [PATCH v4 25/73] page cache: Convert page deletion to XArray

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Message-Id: <20171206004159.3755-26-willy@infradead.org>
Date:   Tue,  5 Dec 2017 16:41:11 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Matthew Wilcox <mawilcox@...rosoft.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Jens Axboe <axboe@...nel.dk>,
        Rehas Sachdeva <aquannie@...il.com>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-nilfs@...r.kernel.org, linux-btrfs@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 25/73] page cache: Convert page deletion to XArray

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

The code is slightly shorter and simpler.

Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
 mm/filemap.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 2439747a0a17..6e2808fd3c06 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -115,27 +115,25 @@
 static void page_cache_tree_delete(struct address_space *mapping,
 				   struct page *page, void *shadow)
 {
-	int i, nr;
+	XA_STATE(xas, &mapping->pages, page->index);
+	unsigned int i, nr;
 
-	/* hugetlb pages are represented by one entry in the radix tree */
+	xas_set_update(&xas, workingset_lookup_update(mapping));
+
+	/* hugetlb pages are represented by a single entry in the xarray */
 	nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	VM_BUG_ON_PAGE(PageTail(page), page);
 	VM_BUG_ON_PAGE(nr != 1 && shadow, page);
 
-	for (i = 0; i < nr; i++) {
-		struct radix_tree_node *node;
-		void **slot;
-
-		__radix_tree_lookup(&mapping->pages, page->index + i,
-				    &node, &slot);
-
-		VM_BUG_ON_PAGE(!node && nr != 1, page);
-
-		radix_tree_clear_tags(&mapping->pages, node, slot);
-		__radix_tree_replace(&mapping->pages, node, slot, shadow,
-				workingset_lookup_update(mapping));
+	i = nr;
+repeat:
+	xas_store(&xas, shadow);
+	xas_init_tags(&xas);
+	if (--i) {
+		xas_next(&xas);
+		goto repeat;
 	}
 
 	page->mapping = NULL;
-- 
2.15.0