[PATCH v6 04/16] x86/mm: Use helper fault_signal_pending()

From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Peter Xu <peterx@redhat.com>, Martin Cracauer <cracauer@cons.org>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Hugh Dickins <hughd@google.com>,
	Jerome Glisse <jglisse@redhat.com>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	Matthew Wilcox <willy@infradead.org>,
	Pavel Emelyanov <xemul@virtuozzo.com>,
	Brian Geffon <bgeffon@google.com>,
	Maya Gokhale <gokhale2@llnl.gov>,
	Denis Plotnikov <dplotnikov@virtuozzo.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Marty McFadden <mcfadden8@llnl.gov>,
	David Hildenbrand <david@redhat.com>,
	Bobby Powers <bobbypowers@gmail.com>,
	Mel Gorman <mgorman@suse.de>
Subject: [PATCH v6 04/16] x86/mm: Use helper fault_signal_pending()
Date: Thu, 20 Feb 2020 10:02:08 -0500	[thread overview]
Message-ID: <20200220150208.5159-1-peterx@redhat.com> (raw)
In-Reply-To: <20200220145432.4561-1-peterx@redhat.com>

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@redhat.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 fa4ea09593ab..6a00bc8d047f 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1442,27 +1442,25 @@ void do_user_addr_fault(struct pt_regs *regs,
 	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, hw_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, hw_error_code, address, SIGBUS, BUS_ADRERR);
-		return;
+		flags &= ~FAULT_FLAG_ALLOW_RETRY;
+		flags |= FAULT_FLAG_TRIED;
+		goto retry;
 	}
 
 	up_read(&mm->mmap_sem);
-- 
2.24.1

