mm/nios2: use general page fault accounting

Use the general page fault accounting by passing regs into
handle_mm_fault().  It naturally solve the issue of multiple page fault
accounting when page fault retry happened.

Add the missing PERF_COUNT_SW_PAGE_FAULTS perf events too.  Note, the
other two perf events (PERF_COUNT_SW_PAGE_FAULTS_[MAJ|MIN]) were done in
handle_mm_fault().
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Link: http://lkml.kernel.org/r/20200707225021.200906-14-peterx@redhat.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/nios2/mm/fault.c

@@ -24,6 +24,7 @@
 #include <linux/mm.h>
 #include <linux/extable.h>
 #include <linux/uaccess.h>
+#include <linux/perf_event.h>
 
 #include <asm/mmu_context.h>
 #include <asm/traps.h>
@@ -83,6 +84,8 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
 
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
 	if (!mmap_read_trylock(mm)) {
 		if (!user_mode(regs) && !search_exception_tables(regs->ea))
 			goto bad_area_nosemaphore;
@@ -131,7 +134,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 	 * make sure we exit gracefully rather than endlessly redo
 	 * the fault.
 	 */
-	fault = handle_mm_fault(vma, address, flags, NULL);
+	fault = handle_mm_fault(vma, address, flags, regs);
 
 	if (fault_signal_pending(fault, regs))
 		return;
@@ -146,16 +149,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
 		BUG();
 	}
 
-	/*
-	 * Major/minor page fault accounting is only done on the
-	 * initial attempt. If we go through a retry, it is extremely
-	 * likely that the page will be found in page cache at that point.
-	 */
 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
-		if (fault & VM_FAULT_MAJOR)
-			current->maj_flt++;
-		else
-			current->min_flt++;
 		if (fault & VM_FAULT_RETRY) {
 			flags |= FAULT_FLAG_TRIED;