The patch titled
Subject: mm: return faster for non-fatal signals in user mode faults
has been added to the -mm tree. Its filename is
mm-return-faster-for-non-fatal-signals-in-user-mode-faults.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-return-faster-for-non-fatal-signals-in-user-mode-faults.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-return-faster-for-non-fatal-signals-in-user-mode-faults.patch
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------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm: return faster for non-fatal signals in user mode faults
The idea comes from the upstream discussion between Linus and Andrea:
https://lore.kernel.org/lkml/20171102193644.GB22686@xxxxxxxxxx/
A summary to the issue: there was a special path in handle_userfault() in
the past that we'll return a VM_FAULT_NOPAGE when we detected non-fatal
signals when waiting for userfault handling. We did that by reacquiring
the mmap_sem before returning. However that brings a risk in that the
vmas might have changed when we retake the mmap_sem and even we could be
holding an invalid vma structure.
This patch is a preparation of removing that special path by allowing the
page fault to return even faster if we were interrupted by a non-fatal
signal during a user-mode page fault handling routine.
Link: http://lkml.kernel.org/r/20200220160230.9598-1-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Suggested-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Bobby Powers <bobbypowers@xxxxxxxxx>
Cc: Brian Geffon <bgeffon@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx>
Cc: "Dr . David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jerome Glisse <jglisse@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Martin Cracauer <cracauer@xxxxxxxx>
Cc: Marty McFadden <mcfadden8@xxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Maya Gokhale <gokhale2@xxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched/signal.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/include/linux/sched/signal.h~mm-return-faster-for-non-fatal-signals-in-user-mode-faults
+++ a/include/linux/sched/signal.h
@@ -379,7 +379,8 @@ static inline bool fault_signal_pending(
struct pt_regs *regs)
{
return unlikely((fault_flags & VM_FAULT_RETRY) &&
- fatal_signal_pending(current));
+ (fatal_signal_pending(current) ||
+ (user_mode(regs) && signal_pending(current))));
}
/*
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-gup-rename-nonblocking-to-locked-where-proper.patch
mm-gup-fix-__get_user_pages-on-fault-retry-of-hugetlb.patch
mm-introduce-fault_signal_pending.patch
x86-mm-use-helper-fault_signal_pending.patch
arc-mm-use-helper-fault_signal_pending.patch
arm64-mm-use-helper-fault_signal_pending.patch
powerpc-mm-use-helper-fault_signal_pending.patch
sh-mm-use-helper-fault_signal_pending.patch
mm-return-faster-for-non-fatal-signals-in-user-mode-faults.patch
userfaultfd-dont-retake-mmap_sem-to-emulate-nopage.patch
mm-introduce-fault_flag_default.patch
mm-introduce-fault_flag_interruptible.patch
mm-allow-vm_fault_retry-for-multiple-times.patch
mm-gup-allow-vm_fault_retry-for-multiple-times.patch
mm-gup-allow-to-react-to-fatal-signals.patch
mm-userfaultfd-honor-fault_flag_killable-in-fault-path.patch
mm-merge-parameters-for-change_protection.patch
userfaultfd-wp-apply-_page_uffd_wp-bit.patch
userfaultfd-wp-drop-_page_uffd_wp-properly-when-fork.patch
userfaultfd-wp-add-pmd_swp_uffd_wp-helpers.patch
userfaultfd-wp-support-swap-and-page-migration.patch
khugepaged-skip-collapse-if-uffd-wp-detected.patch
userfaultfd-wp-dont-wake-up-when-doing-write-protect.patch
userfaultfd-wp-declare-_uffdio_writeprotect-conditionally.patch
userfaultfd-selftests-refactor-statistics.patch
userfaultfd-selftests-add-write-protect-test.patch
