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

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Message-Id: <20210614211904.14420-2-hannes@cmpxchg.org>
Date:   Mon, 14 Jun 2021 17:19:02 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Roman Gushchin <guro@...com>, Tejun Heo <tj@...nel.org>,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: [PATCH 2/4] 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.

Reported-by: Roman Gushchin <guro@...com>
Signed-off-by: Johannes Weiner <hannes@...xchg.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