userfaultfd: use fault_wqh lock
authorMatthew Wilcox <mawilcox@microsoft.com>
Wed, 22 Aug 2018 04:56:30 +0000 (21:56 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 22 Aug 2018 17:52:47 +0000 (10:52 -0700)
commitc430d1e848ff1240d126e79780f3c26208b8aed9
treeaa2c5cd32056e24e075310d950f4385203c7cc87
parentee8ef0a4b167c1f2605bc9b5701c603224673d53
userfaultfd: use fault_wqh lock

The userfaultfd code currently uses the unlocked waitqueue helpers for
managing fault_wqh, but instead of holding the waitqueue lock for this
waitqueue around these calls, it the waitqueue lock of
fault_pending_wq, which is a different waitqueue instance.  Given that
the waitqueue is not exposed to the rest of the kernel this actually
works ok at the moment, but prevents the userfaultfd locking rules from
being enforced using lockdep.

Switch to the internally locked waitqueue helpers instead.  This means
that the lock inside fault_wqh now nests inside the fault_pending_wqh
lock, but that's not a problem since it was entirely unused before.

[hch@lst.de: slight changelog updates]
[rppt@linux.vnet.ibm.com: spotted changelog spellos]
Link: http://lkml.kernel.org/r/20171214152344.6880-3-hch@lst.de
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/userfaultfd.c