mm/arm: 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.  To do this, we need to pass
the pt_regs pointer into __do_page_fault().

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

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Link: http://lkml.kernel.org/r/20200707225021.200906-5-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 01a8e0f..efa4020 100644 (file)
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -202,7 +202,8 @@ static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 
 static vm_fault_t __kprobes
 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
-               unsigned int flags, struct task_struct *tsk)
+               unsigned int flags, struct task_struct *tsk,
+               struct pt_regs *regs)
 {
        struct vm_area_struct *vma;
        vm_fault_t fault;
@@ -224,7 +225,7 @@ good_area:
                goto out;
        }
 
-       return handle_mm_fault(vma, addr & PAGE_MASK, flags, NULL);
+       return handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
 
 check_stack:
        /* Don't allow expansion below FIRST_USER_ADDRESS */
@@ -266,6 +267,8 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
        if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
                flags |= FAULT_FLAG_WRITE;
 
+       perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
+
        /*
         * As per x86, we may deadlock here.  However, since the kernel only
         * validly references user space from well defined areas of the code,
@@ -290,7 +293,7 @@ retry:
 #endif
        }
 
-       fault = __do_page_fault(mm, addr, fsr, flags, tsk);
+       fault = __do_page_fault(mm, addr, fsr, flags, tsk, regs);
 
        /* If we need to retry but a fatal signal is pending, handle the
         * signal first. We do not need to release the mmap_lock because
@@ -302,23 +305,7 @@ retry:
                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;