[PATCH 2/4] mm: Stop accounting shadow entries

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

We no longer need to keep track of how many shadow entries are
present in a mapping.  This saves a few writes to the inode and
memory barriers.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/filemap.c    | 12 ------------
 mm/truncate.c   |  1 -
 mm/workingset.c |  1 -
 3 files changed, 14 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 76383d558b7c..7c3f97bd6dcd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -139,17 +139,6 @@ static void page_cache_delete(struct address_space *mapping,
 
 	page->mapping = NULL;
 	/* Leave page->index set: truncation lookup relies upon it */
-
-	if (shadow) {
-		mapping->nrexceptional += nr;
-		/*
-		 * Make sure the nrexceptional update is committed before
-		 * the nrpages update so that final truncate racing
-		 * with reclaim does not see both counters 0 at the
-		 * same time and miss a shadow entry.
-		 */
-		smp_wmb();
-	}
 	mapping->nrpages -= nr;
 }
 
@@ -860,7 +849,6 @@ static int __add_to_page_cache_locked(struct page *page,
 			goto unlock;
 
 		if (xa_is_value(old)) {
-			mapping->nrexceptional--;
 			if (shadowp)
 				*shadowp = old;
 		}
diff --git a/mm/truncate.c b/mm/truncate.c
index 7c4c8ac140be..a59184793607 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -40,7 +40,6 @@ static inline void __clear_shadow_entry(struct address_space *mapping,
 	if (xas_load(&xas) != entry)
 		return;
 	xas_store(&xas, NULL);
-	mapping->nrexceptional--;
 }
 
 static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
diff --git a/mm/workingset.c b/mm/workingset.c
index fdeabea54e77..0649bfb1ca33 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -547,7 +547,6 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
 		goto out_invalid;
 	if (WARN_ON_ONCE(node->count != node->nr_values))
 		goto out_invalid;
-	mapping->nrexceptional -= node->nr_values;
 	xas.xa_node = xa_parent_locked(&mapping->i_pages, node);
 	xas.xa_offset = node->offset;
 	xas.xa_shift = node->shift + XA_CHUNK_SHIFT;
-- 
2.27.0