linux-kernel - [PATCH] fs: synchronize_rcu when unregister

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Message-Id: <fs-unreg-rcu@mdm.bga.com>
Date:	Thu, 14 Apr 2011 10:41:24 -0500
From:	Milton Miller <miltonm@....com>
To:	Nick Piggin <npiggin@...nel.dk>,
	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dipankar Sarma <dipankar@...ibm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] fs: synchronize_rcu when unregister_filesystem success not failure

While checking unregister_filesystem for saftey vs extra calls for
"ext4: register ext2 and ext3 alias after ext4" I realized that
the synchronize_rcu() was called on the error path but not on
the success path.

Should we call it in both?
Cc: stable (2.6.38)
Signed-off-by: Milton Miller <miltonm@....com>

Index: work.git/fs/filesystems.c
===================================================================
--- work.git.orig/fs/filesystems.c	2011-04-14 10:06:44.360068116 -0500
+++ work.git/fs/filesystems.c	2011-04-14 10:08:41.880061794 -0500
@@ -110,14 +110,13 @@ int unregister_filesystem(struct file_sy
 			*tmp = fs->next;
 			fs->next = NULL;
 			write_unlock(&file_systems_lock);
+			synchronize_rcu();
 			return 0;
 		}
 		tmp = &(*tmp)->next;
 	}
 	write_unlock(&file_systems_lock);
 
-	synchronize_rcu();
-
 	return -EINVAL;
 }
--
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