Coda: add spin lock to protect accesses to struct coda_inode_info.

We mostly need it to protect cached user permissions. The c_flags field
is advisory, reading the wrong value is harmless and in the worst case
we hit a slow path where we have to make an extra upcall to the
userspace cache manager when revalidating a dentry or inode.

Signed-off-by: Yoshihisa Abe <yoshiabe@cs.cmu.edu>
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/coda/inode.c

@@ -16,6 +16,7 @@
 #include <linux/errno.h>
 #include <linux/unistd.h>
 #include <linux/smp_lock.h>
+#include <linux/spinlock.h>
 #include <linux/file.h>
 #include <linux/vfs.h>
 #include <linux/slab.h>
@@ -51,6 +52,7 @@ static struct inode *coda_alloc_inode(struct super_block *sb)
 	ei->c_flags = 0;
 	ei->c_uid = 0;
 	ei->c_cached_perm = 0;
+	spin_lock_init(&ei->c_lock);
 	return &ei->vfs_inode;
 }