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Subject[PATCH v9 27/61] page cache: Convert page deletion to XArray
Date
From: Matthew Wilcox <mawilcox@microsoft.com>

The code is slightly shorter and simpler.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
mm/filemap.c | 30 ++++++++++++++----------------
1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 0e19ea454cba..bdda1beda932 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -111,30 +111,28 @@
* ->tasklist_lock (memory_failure, collect_procs_ao)
*/

-static void page_cache_tree_delete(struct address_space *mapping,
+static void page_cache_delete(struct address_space *mapping,
struct page *page, void *shadow)
{
- int i, nr;
+ XA_STATE(xas, &mapping->i_pages, page->index);
+ unsigned int i, nr;

- /* hugetlb pages are represented by one entry in the radix tree */
+ mapping_set_update(&xas, 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->i_pages, page->index + i,
- &node, &slot);
-
- VM_BUG_ON_PAGE(!node && nr != 1, page);
-
- radix_tree_clear_tags(&mapping->i_pages, node, slot);
- __radix_tree_replace(&mapping->i_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;
@@ -234,7 +232,7 @@ void __delete_from_page_cache(struct page *page, void *shadow)
trace_mm_filemap_delete_from_page_cache(page);

unaccount_page_cache_page(mapping, page);
- page_cache_tree_delete(mapping, page, shadow);
+ page_cache_delete(mapping, page, shadow);
}

static void page_cache_free_page(struct address_space *mapping,
--
2.16.1
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