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ceph: use separate class for ceph sockets' sk_lock 

Use a separate class for ceph sockets to prevent lockdep confusion.
Because ceph sockets only get passed kernel pointers, there is no
dependency from sk_lock -> mmap_sem.  If we share the same class as other
sockets, lockdep detects a circular dependency from

	mmap_sem (page fault) -> fs mutex -> sk_lock -> mmap_sem

because dependencies are noted from both ceph and user contexts.  Using
a separate class prevents the sk_lock(ceph) -> mmap_sem dependency and
makes lockdep happy.

Signed-off-by: Sage Weil <sage@newdream.net>
This commit is contained in:
Sage Weil 2010-04-13 14:07:07 -07:00
parent e1e4dd0caa
commit a6a5349d17
1 changed files with 8 additions and 0 deletions
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8
fs/ceph/messenger.c
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@ -29,6 +29,10 @@ static char tag_msg = CEPH_MSGR_TAG_MSG;
static char tag_ack = CEPH_MSGR_TAG_ACK;
static char tag_keepalive = CEPH_MSGR_TAG_KEEPALIVE;
#ifdef CONFIG_LOCKDEP
static struct lock_class_key socket_class;
#endif
static void queue_con(struct ceph_connection *con);
static void con_work(struct work_struct *);
@ -227,6 +231,10 @@ static struct socket *ceph_tcp_connect(struct ceph_connection *con)
con->sock = sock;
sock->sk->sk_allocation = GFP_NOFS;
#ifdef CONFIG_LOCKDEP
lockdep_set_class(&sock->sk->sk_lock, &socket_class);
#endif
set_sock_callbacks(sock, con);
dout("connect %s\n", pr_addr(&con->peer_addr.in_addr));