From: David Howells <dhowe...@redhat.com> Date: Thu, 09 Mar 2017 08:09:05 +0000
> Lockdep issues a circular dependency warning when AFS issues an operation > through AF_RXRPC from a context in which the VFS/VM holds the mmap_sem. > > The theory lockdep comes up with is as follows: ... > However, lockdep's theory is wrong in this instance because it deals only > with lock classes and not individual locks. The AF_INET lock in (2) isn't > really equivalent to the AF_INET lock in (3) as the former deals with a > socket entirely internal to the kernel that never sees userspace. This is > a limitation in the design of lockdep. > > Fix the general case by: > > (1) Double up all the locking keys used in sockets so that one set are > used if the socket is created by userspace and the other set is used > if the socket is created by the kernel. > > (2) Store the kern parameter passed to sk_alloc() in a variable in the > sock struct (sk_kern_sock). This informs sock_lock_init(), > sock_init_data() and sk_clone_lock() as to the lock keys to be used. > > Note that the child created by sk_clone_lock() inherits the parent's > kern setting. > > (3) Add a 'kern' parameter to ->accept() that is analogous to the one > passed in to ->create() that distinguishes whether kernel_accept() or > sys_accept4() was the caller and can be passed to sk_alloc(). > > Note that a lot of accept functions merely dequeue an already > allocated socket. I haven't touched these as the new socket already > exists before we get the parameter. > > Note also that there are a couple of places where I've made the accepted > socket unconditionally kernel-based: > > irda_accept() > rds_rcp_accept_one() > tcp_accept_from_sock() > > because they follow a sock_create_kern() and accept off of that. > > Whilst creating this, I noticed that lustre and ocfs don't create sockets > through sock_create_kern() and thus they aren't marked as for-kernel, > though they appear to be internal. I wonder if these should do that so > that they use the new set of lock keys. > > Signed-off-by: David Howells <dhowe...@redhat.com> Applied, thanks David.
