Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Hao Li <lihao2018.fnst@cn.fujitsu.com>
To:     <viro@zeniv.linux.org.uk>
CC:     <david@fromorbit.com>, <ira.weiny@intel.com>,
        <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-xfs@vger.kernel.org>, <lihao2018.fnst@cn.fujitsu.com>,
        <y-goto@fujitsu.com>
Subject: [PATCH] fs: Handle I_DONTCACHE in iput_final() instead of generic_drop_inode()
Date:   Mon, 31 Aug 2020 18:13:13 +0800
Message-ID: <20200831101313.168889-1-lihao2018.fnst@cn.fujitsu.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7BIT
Content-Type:   text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

If generic_drop_inode() returns true, it means iput_final() can evict
this inode regardless of whether it is dirty or not. If we check
I_DONTCACHE in generic_drop_inode(), any inode with this bit set will be
evicted unconditionally. This is not the desired behavior because
I_DONTCACHE only means the inode shouldn't be cached on the LRU list.
As for whether we need to evict this inode, this is what
generic_drop_inode() should do. This patch corrects the usage of
I_DONTCACHE.

This patch was proposed in [1].

[1]: https://lore.kernel.org/linux-fsdevel/20200831003407.GE12096@dread.disaster.area/

Signed-off-by: Hao Li <lihao2018.fnst@cn.fujitsu.com>
---
 fs/inode.c         | 3 ++-
 include/linux/fs.h | 3 +--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 72c4c347afb7..4e45d5ea3d0f 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1625,7 +1625,8 @@ static void iput_final(struct inode *inode)
 	else
 		drop = generic_drop_inode(inode);
 
-	if (!drop && (sb->s_flags & SB_ACTIVE)) {
+	if (!drop && !(inode->i_state & I_DONTCACHE) &&
+			(sb->s_flags & SB_ACTIVE)) {
 		inode_add_lru(inode);
 		spin_unlock(&inode->i_lock);
 		return;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e019ea2f1347..93caee80ce47 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2922,8 +2922,7 @@ extern int inode_needs_sync(struct inode *inode);
 extern int generic_delete_inode(struct inode *inode);
 static inline int generic_drop_inode(struct inode *inode)
 {
-	return !inode->i_nlink || inode_unhashed(inode) ||
-		(inode->i_state & I_DONTCACHE);
+	return !inode->i_nlink || inode_unhashed(inode);
 }
 extern void d_mark_dontcache(struct inode *inode);
 
-- 
2.28.0