[PATCH 2/4] fs: drop_caches: fix skipping over shadow cache inodes

Johannes Weiner
2021-06-14T21:19:12Z

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.

Reported-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
fs/drop_caches.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index f00fcc4a4f72..e619c31b6bd9 100644
--- 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;
}
--
2.32.0