[PATCH 36/62] page cache: Convert find_get_entry to xarray

Matthew Wilcox
2017-11-22T21:14:34Z

Slightly simpler and shorter code.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
mm/filemap.c | 56 +++++++++++++++++++++-----------------------------------
1 file changed, 21 insertions(+), 35 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index f60f22867a1a..2172c9f9efb9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1391,51 +1391,37 @@ EXPORT_SYMBOL(page_cache_prev_hole);
*/
struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
{
- void **pagep;
+ XA_STATE(xas, offset);
struct page *head, *page;

rcu_read_lock();
repeat:
- page = NULL;
- pagep = radix_tree_lookup_slot(&mapping->pages, offset);
- if (pagep) {
- page = radix_tree_deref_slot(pagep);
- if (unlikely(!page))
- goto out;
- if (radix_tree_exception(page)) {
- if (radix_tree_deref_retry(page))
- goto repeat;
- /*
- * A shadow entry of a recently evicted page,
- * or a swap entry from shmem/tmpfs. Return
- * it without attempting to raise page count.
- */
- goto out;
- }
+ page = xas_load(&mapping->pages, &xas);
+ if (!page || xa_is_value(page))
+ goto out;

- head = compound_head(page);
- if (!page_cache_get_speculative(head))
- goto repeat;
+ head = compound_head(page);
+ if (!page_cache_get_speculative(head))
+ goto repeat;

- /* The page was split under us? */
- if (compound_head(page) != head) {
- put_page(head);
- goto repeat;
- }
+ /* The page was split under us? */
+ if (compound_head(page) != head) {
+ put_page(head);
+ goto repeat;
+ }

- /*
- * Has the page moved?
- * This is part of the lockless pagecache protocol. See
- * include/linux/pagemap.h for details.
- */
- if (unlikely(page != *pagep)) {
- put_page(head);
- goto repeat;
- }
+ /*
+ * Has the page moved?
+ * This is part of the lockless pagecache protocol. See
+ * include/linux/pagemap.h for details.
+ */
+ if (unlikely(page != xas_reload(&mapping->pages, &xas))) {
+ put_page(head);
+ goto repeat;
}
+
out:
rcu_read_unlock();
-
return page;
}
EXPORT_SYMBOL(find_get_entry);
--
2.15.0