[Devel] [PATCH RHEL8 COMMIT] x86/mm: use helper fault_signal_pending()

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-80.1.2.vz8.3.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-80.1.2.vz8.3.6
------>
commit a315aaaa267819595e4eb0d20140774efcb9b337
Author: Peter Xu <peterx at redhat.com>
Date:   Mon Apr 20 10:34:10 2020 +0300

    x86/mm: use helper fault_signal_pending()
    
    Let's move the fatal signal check even earlier so that we can directly use
    the new fault_signal_pending() in x86 mm code.
    
    Signed-off-by: Peter Xu <peterx at redhat.com>
    Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
    Tested-by: Brian Geffon <bgeffon at google.com>
    Cc: Andrea Arcangeli <aarcange at redhat.com>
    Cc: Bobby Powers <bobbypowers at gmail.com>
    Cc: David Hildenbrand <david at redhat.com>
    Cc: Denis Plotnikov <dplotnikov at virtuozzo.com>
    Cc: "Dr . David Alan Gilbert" <dgilbert at redhat.com>
    Cc: Hugh Dickins <hughd at google.com>
    Cc: Jerome Glisse <jglisse at redhat.com>
    Cc: Johannes Weiner <hannes at cmpxchg.org>
    Cc: "Kirill A . Shutemov" <kirill at shutemov.name>
    Cc: Martin Cracauer <cracauer at cons.org>
    Cc: Marty McFadden <mcfadden8 at llnl.gov>
    Cc: Matthew Wilcox <willy at infradead.org>
    Cc: Maya Gokhale <gokhale2 at llnl.gov>
    Cc: Mel Gorman <mgorman at suse.de>
    Cc: Mike Kravetz <mike.kravetz at oracle.com>
    Cc: Mike Rapoport <rppt at linux.vnet.ibm.com>
    Cc: Pavel Emelyanov <xemul at openvz.org>
    Link: http://lkml.kernel.org/r/20200220155353.8676-5-peterx@redhat.com
    Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
    
    https://jira.sw.ru/browse/PSBM-102938
    (cherry picked from commit 39678191cd8988c811813baf4c97b43bf46094e4)
    Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 arch/x86/mm/fault.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index cdafd5fa6d0a..8e71ebad64a1 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1405,27 +1405,25 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
 	fault = handle_mm_fault(vma, address, flags);
 	major |= fault & VM_FAULT_MAJOR;
 
+	/* Quick path to respond to signals */
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
+			no_context(regs, error_code, address, SIGBUS,
+				   BUS_ADRERR);
+		return;
+	}
+
 	/*
 	 * If we need to retry the mmap_sem has already been released,
 	 * and if there is a fatal signal pending there is no guarantee
 	 * that we made any progress. Handle this case first.
 	 */
-	if (unlikely(fault & VM_FAULT_RETRY)) {
+	if (unlikely((fault & VM_FAULT_RETRY) &&
+		     (flags & FAULT_FLAG_ALLOW_RETRY))) {
 		/* Retry at most once */
-		if (flags & FAULT_FLAG_ALLOW_RETRY) {
-			flags &= ~FAULT_FLAG_ALLOW_RETRY;
-			flags |= FAULT_FLAG_TRIED;
-			if (!fatal_signal_pending(tsk))
-				goto retry;
-		}
-
-		/* User mode? Just return to handle the fatal exception */
-		if (flags & FAULT_FLAG_USER)
-			return;
-
-		/* Not returning to user mode? Handle exceptions or die: */
-		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
-		return;
+		flags &= ~FAULT_FLAG_ALLOW_RETRY;
+		flags |= FAULT_FLAG_TRIED;
+		goto retry;
 	}
 
 	up_read(&mm->mmap_sem);