mm: document is_page_cache_freeable()

Enlighten the reader of this code about what reference count makes a page cache page freeable. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux-foundation.org> Reviewed-by: Christoph Lameter <cl@linux-foundation.org> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: document is_page_cache_freeable()
Enlighten the reader of this code about what reference count makes a page cache page freeable. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux-foundation.org> Reviewed-by: Christoph Lameter <cl@linux-foundation.org> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Johannes Weiner · Linus Torvalds
1 parent edcf4748cd
Showing 1 changed file with 5 additions and 0 deletions Side-by-side Diff
mm/vmscan.c
@@ -286,6 +286,11 @@
  
 static inline int is_page_cache_freeable(struct page *page)
 {
+	/*
+	 * A freeable page cache page is referenced only by the caller
+	 * that isolated the page, the page cache radix tree and
+	 * optional buffer heads at page->private.
+	 */
 	return page_count(page) - page_has_private(page) == 2;
 }
...	...	@@ -286,6 +286,11 @@
286	286
287	287	static inline int is_page_cache_freeable(struct page *page)
288	288	{
	289	+ /*
	290	+ * A freeable page cache page is referenced only by the caller
	291	+ * that isolated the page, the page cache radix tree and
	292	+ * optional buffer heads at page->private.
	293	+ */
289	294	return page_count(page) - page_has_private(page) == 2;
290	295	}
291	296