fs: drop_caches: fix skipping over shadow cache inodes

When drop_caches truncates the page cache in an inode it also includes any
shadow entries for evicted pages.  However, there is a preliminary check
on whether the inode has pages: if it has *only* shadow entries, it will
skip running truncation on the inode and leave it behind.

Fix the check to mapping_empty(), such that it runs truncation on any
inode that has cache entries at all.

Link: https://lkml.kernel.org/r/20210614211904.14420-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Roman Gushchin <guro@fb.com>
Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index f00fcc4a4f7215dbfa2ab657299cf706fdd92efd..e619c31b6bd92a4f570127b91a37253126ca9e3a 100644 (file)
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -3,6 +3,7 @@
  * Implement the manual drop-all-pagecache function
  */
 
+#include <linux/pagemap.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
@@ -27,7 +28,7 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
                 * we need to reschedule to avoid softlockups.
                 */
                if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
-                   (inode->i_mapping->nrpages == 0 && !need_resched())) {
+                   (mapping_empty(inode->i_mapping) && !need_resched())) {
                        spin_unlock(&inode->i_lock);
                        continue;
                }