Ocfs2 devel - Apr 2015 - [patch 2/9] ocfs2: flush inode data to disk and free inode when i_count becomes zero

From: Xue jiufei <xuejiufei at huawei.com>
Subject: ocfs2: flush inode data to disk and free inode when i_count becomes
zero

Disk inode deletion may be heavily delayed when one node unlink a file
after the same dentry is freed on another node(say N1) because of memory
shrink but inode is left in memory.  This inode can only be freed while N1
doing the orphan scan work.

However, N1 may skip orphan scan for several times because other nodes may
do the work earlier.  In our tests, it may take 1 hour on 4 nodes cluster
and it hurts the user experience.  So we think the inode should be freed
after the data flushed to disk when i_count becomes zero to avoid such
circumstances.

Signed-off-by: Joyce.xue <xuejiufei at huawei.com>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: Mark Fasheh <mfasheh at suse.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---

 fs/ocfs2/inode.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff -puN
fs/ocfs2/inode.c~ocfs2-flush-inode-data-to-disk-and-free-inode-when-i_count-becomes-zero
fs/ocfs2/inode.c
---
a/fs/ocfs2/inode.c~ocfs2-flush-inode-data-to-disk-and-free-inode-when-i_count-becomes-zero
+++ a/fs/ocfs2/inode.c
@@ -1191,17 +1191,19 @@ void ocfs2_evict_inode(struct inode *ino
 int ocfs2_drop_inode(struct inode *inode)
 {
 	struct ocfs2_inode_info *oi = OCFS2_I(inode);
-	int res;
 
 	trace_ocfs2_drop_inode((unsigned long long)oi->ip_blkno,
 				inode->i_nlink, oi->ip_flags);
 
-	if (oi->ip_flags & OCFS2_INODE_MAYBE_ORPHANED)
-		res = 1;
-	else
-		res = generic_drop_inode(inode);
+	assert_spin_locked(&inode->i_lock);
+	inode->i_state |= I_WILL_FREE;
+	spin_unlock(&inode->i_lock);
+	write_inode_now(inode, 1);
+	spin_lock(&inode->i_lock);
+	WARN_ON(inode->i_state & I_NEW);
+	inode->i_state &= ~I_WILL_FREE;
 
-	return res;
+	return 1;
 }
 
 /*
_