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Subject[PATCH RESEND v6 16/16] mm/userfaultfd: Honor FAULT_FLAG_KILLABLE in fault path
Date
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.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
fs/userfaultfd.c | 36 ++++++++++++++++++++++++++++--------
1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index c076d3295958..703c1c3faa6e 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -334,6 +334,30 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
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_fault *vmf, unsigned long reason)
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_fault *vmf, unsigned long reason)
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_fault *vmf, unsigned long reason)
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_fault *vmf, unsigned long reason)
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();
}
--
2.24.1
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