[101/155] mm/userfaultfd: honor FAULT_FLAG_KILLABLE in fault path

Commit Message

Andrew Morton April 2, 2020, 4:09 a.m. UTC

From: Peter Xu <[e-mail]>
Subject: mm/userfaultfd: honor FAULT_FLAG_KILLABLE in fault path

Userfaultfd fault path was by default killable even if the caller does not
have FAULT_FLAG_KILLABLE.  That makes sense before in that when with gup
we don't have FAULT_FLAG_KILLABLE properly set before.  Now after previous
patch we've got FAULT_FLAG_KILLABLE applied even for gup code so it should
also make sense to let userfaultfd to honor the FAULT_FLAG_KILLABLE.

Because we're unconditionally setting FAULT_FLAG_KILLABLE in gup code
right now, this patch should have no functional change.  It also cleaned
the code a little bit by introducing some helpers.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Peter Xu <[e-mail]>
Tested-by: Brian Geffon <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Bobby Powers <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: Denis Plotnikov <[e-mail]>
Cc: "Dr . David Alan Gilbert" <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Jerome Glisse <[e-mail]>
Cc: Johannes Weiner <[e-mail]>
Cc: "Kirill A . Shutemov" <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Martin Cracauer <[e-mail]>
Cc: Marty McFadden <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Maya Gokhale <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Pavel Emelyanov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 fs/userfaultfd.c |   36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

Patch

--- a/fs/userfaultfd.c~mm-userfaultfd-honor-fault_flag_killable-in-fault-path
+++ a/fs/userfaultfd.c
@@ -334,6 +334,30 @@  out:
 	return ret;
 }
 
+/* Should pair with userfaultfd_signal_pending() */
+static inline long userfaultfd_get_blocking_state(unsigned int flags)
+{
+	if (flags & FAULT_FLAG_INTERRUPTIBLE)
+		return TASK_INTERRUPTIBLE;
+
+	if (flags & FAULT_FLAG_KILLABLE)
+		return TASK_KILLABLE;
+
+	return TASK_UNINTERRUPTIBLE;
+}
+
+/* Should pair with userfaultfd_get_blocking_state() */
+static inline bool userfaultfd_signal_pending(unsigned int flags)
+{
+	if (flags & FAULT_FLAG_INTERRUPTIBLE)
+		return signal_pending(current);
+
+	if (flags & FAULT_FLAG_KILLABLE)
+		return fatal_signal_pending(current);
+
+	return false;
+}
+
 /*
  * The locking rules involved in returning VM_FAULT_RETRY depending on
  * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and
@@ -355,7 +379,7 @@  vm_fault_t handle_userfault(struct vm_fa
 	struct userfaultfd_ctx *ctx;
 	struct userfaultfd_wait_queue uwq;
 	vm_fault_t ret = VM_FAULT_SIGBUS;
-	bool must_wait, return_to_userland;
+	bool must_wait;
 	long blocking_state;
 
 	/*
@@ -462,9 +486,7 @@  vm_fault_t handle_userfault(struct vm_fa
 	uwq.ctx = ctx;
 	uwq.waken = false;
 
-	return_to_userland = vmf->flags & FAULT_FLAG_INTERRUPTIBLE;
-	blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
-			 TASK_KILLABLE;
+	blocking_state = userfaultfd_get_blocking_state(vmf->flags);
 
 	spin_lock_irq(&ctx->fault_pending_wqh.lock);
 	/*
@@ -490,8 +512,7 @@  vm_fault_t handle_userfault(struct vm_fa
 	up_read(&mm->mmap_sem);
 
 	if (likely(must_wait && !READ_ONCE(ctx->released) &&
-		   (return_to_userland ? !signal_pending(current) :
-		    !fatal_signal_pending(current)))) {
+		   !userfaultfd_signal_pending(vmf->flags))) {
 		wake_up_poll(&ctx->fd_wqh, EPOLLIN);
 		schedule();
 		ret |= VM_FAULT_MAJOR;
@@ -513,8 +534,7 @@  vm_fault_t handle_userfault(struct vm_fa
 			set_current_state(blocking_state);
 			if (READ_ONCE(uwq.waken) ||
 			    READ_ONCE(ctx->released) ||
-			    (return_to_userland ? signal_pending(current) :
-			     fatal_signal_pending(current)))
+			    userfaultfd_signal_pending(vmf->flags))
 				break;
 			schedule();
 		}