Commit 79fea6c6 authored by Peter Xu's avatar Peter Xu Committed by Linus Torvalds
Browse files

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: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 52e3f8d0

arch/arm/mm/fault.c

+6 −19
Original line number Diff line number Diff line
@@ -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;

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