linux-kernel - [PATCH 05/25] mm/arm: Use mm_fault

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Date:   Mon, 15 Jun 2020 18:15:47 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>, peterx@...hat.com,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 05/25] mm/arm: Use mm_fault_accounting()

Use the new mm_fault_accounting() helper for page fault accounting.

Avoid doing page fault accounting multiple times if the page fault is retried.
Meanwhile, take the page fault as a major fault as long as any of the retried
page fault is a major fault.

CC: Russell King <linux@...linux.org.uk>
CC: Will Deacon <will@...nel.org>
CC: linux-arm-kernel@...ts.infradead.org
Signed-off-by: Peter Xu <peterx@...hat.com>
---
 arch/arm/mm/fault.c | 21 ++++-----------------
 1 file changed, 4 insertions(+), 17 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 2dd5c41cbb8d..92d4436e74da 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -240,7 +240,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	struct task_struct *tsk;
 	struct mm_struct *mm;
 	int sig, code;
-	vm_fault_t fault;
+	vm_fault_t fault, major = 0;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
 
 	if (kprobe_page_fault(regs, fsr))
@@ -290,6 +290,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	}
 
 	fault = __do_page_fault(mm, addr, fsr, flags, tsk);
+	major |= fault & VM_FAULT_MAJOR;
 
 	/* If we need to retry but a fatal signal is pending, handle the
 	 * signal first. We do not need to release the mmap_sem because
@@ -301,23 +302,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 		return 0;
 	}
 
-	/*
-	 * 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.
-	 */
-
-	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 	if (!(fault & VM_FAULT_ERROR) && flags & FAULT_FLAG_ALLOW_RETRY) {
-		if (fault & VM_FAULT_MAJOR) {
-			tsk->maj_flt++;
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-					regs, addr);
-		} else {
-			tsk->min_flt++;
-			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-					regs, addr);
-		}
 		if (fault & VM_FAULT_RETRY) {
 			flags |= FAULT_FLAG_TRIED;
 			goto retry;
@@ -326,6 +311,8 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 
 	up_read(&mm->mmap_sem);
 
+	mm_fault_accounting(tsk, regs, addr, major);
+
 	/*
 	 * Handle the "normal" case first - VM_FAULT_MAJOR
 	 */
-- 
2.26.2