[064/212] fs: drop_caches: fix skipping over shadow cache inodes

Commit Message

Andrew Morton Sept. 2, 2021, 9:53 p.m. UTC

From: Johannes Weiner <[e-mail]>
Subject: 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/[e-mail]
Signed-off-by: Johannes Weiner <[e-mail]>
Reported-by: Roman Gushchin <[e-mail]>
Acked-by: Roman Gushchin <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 fs/drop_caches.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch

--- a/fs/drop_caches.c~fs-drop_caches-fix-skipping-over-shadow-cache-inodes
+++ a/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 sup
 		 * 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;
 		}