From: Boaz Harrosh <bharrosh@panasas.com>
Date: Thu, 10 Feb 2011 23:01:20 +0000 (-0800)
Subject: vfs: call rcu_barrier after ->kill_sb()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d863b50ab01333659314c2034890cb76d9fdc3c7;p=linux-beck.git

vfs: call rcu_barrier after ->kill_sb()

In commit fa0d7e3de6d6 ("fs: icache RCU free inodes"), we use rcu free
inode instead of freeing the inode directly.  It causes a crash when we
rmmod immediately after we umount the volume[1].

So we need to call rcu_barrier after we kill_sb so that the inode is
freed before we do rmmod.  The idea is inspired by Aneesh Kumar.
rcu_barrier will wait for all callbacks to end before preceding.  The
original patch was done by Tao Ma, but synchronize_rcu() is not enough
here.

1. http://marc.info/?l=linux-fsdevel&m=129680863330185&w=2

Tested-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/fs/super.c b/fs/super.c
index 74e149efed81..7e9dd4cc2c01 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -177,6 +177,11 @@ void deactivate_locked_super(struct super_block *s)
 	struct file_system_type *fs = s->s_type;
 	if (atomic_dec_and_test(&s->s_active)) {
 		fs->kill_sb(s);
+		/*
+		 * We need to call rcu_barrier so all the delayed rcu free
+		 * inodes are flushed before we release the fs module.
+		 */
+		rcu_barrier();
 		put_filesystem(fs);
 		put_super(s);
 	} else {