linux-kernel - [PATCH 03/26] mm/arc: Use general page fault accounting

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Date:   Fri, 26 Jun 2020 18:31:07 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Will Deacon <will@...nel.org>, peterx@...hat.com,
        Michael Ellerman <mpe@...erman.id.au>,
        Vineet Gupta <vgupta@...opsys.com>,
        linux-snps-arc@...ts.infradead.org
Subject: [PATCH 03/26] mm/arc: 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.

Fix PERF_COUNT_SW_PAGE_FAULTS perf event manually for page fault retries, by
moving it before taking mmap_sem.

CC: Vineet Gupta <vgupta@...opsys.com>
CC: linux-snps-arc@...ts.infradead.org
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 arch/arc/mm/fault.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index 34380139e7a2..68e6849cf086 100644
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -106,6 +106,7 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 	if (write)
 		flags |= FAULT_FLAG_WRITE;
 
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
 	down_read(&mm->mmap_sem);
 
@@ -131,7 +132,7 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 		goto bad_area;
 	}
 
-	fault = handle_mm_fault(vma, address, flags, NULL);
+	fault = handle_mm_fault(vma, address, flags, regs);
 
 	/* Quick path to respond to signals */
 	if (fault_signal_pending(fault, regs)) {
@@ -156,22 +157,9 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
 	 * Major/minor page fault accounting
 	 * (in case of retry we only land here once)
 	 */
-	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
-
-	if (likely(!(fault & VM_FAULT_ERROR))) {
-		if (fault & VM_FAULT_MAJOR) {
-			tsk->maj_flt++;
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-				      regs, address);
-		} else {
-			tsk->min_flt++;
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-				      regs, address);
-		}
-
+	if (likely(!(fault & VM_FAULT_ERROR)))
 		/* Normal return path: fault Handled Gracefully */
 		return;
-	}
 
 	if (!user_mode(regs))
 		goto no_context;
-- 
2.26.2