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Commit 14c02e41 authored by Laurent Dufour's avatar Laurent Dufour Committed by Michael Ellerman
Browse files

powerpc/mm: Handle VM_FAULT_RETRY earlier 



In do_page_fault() if handle_mm_fault() returns VM_FAULT_RETRY, retry
the page fault handling before anything else.

This would simplify the handling of the mmap_sem lock in this part of
the code.

Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarLaurent Dufour <ldufour@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent c2294e0f

arch/powerpc/mm/fault.c

+38 −29
Original line number Diff line number Diff line
@@ -458,6 +458,26 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, 
	 * the fault.

	 */

	fault = handle_mm_fault(vma, address, flags);



	/*

	 * Handle the retry right now, the mmap_sem has been released in that

	 * case.

	 */

	if (unlikely(fault & VM_FAULT_RETRY)) {

		/* We retry only once */

		if (flags & FAULT_FLAG_ALLOW_RETRY) {

			/*

			 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk

			 * of starvation.

			 */

			flags &= ~FAULT_FLAG_ALLOW_RETRY;

			flags |= FAULT_FLAG_TRIED;

			if (!fatal_signal_pending(current))

				goto retry;

		}

		/* We will enter mm_fault_error() below */

	}



	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {

		if (fault & VM_FAULT_SIGSEGV)

			goto bad_area;
@@ -469,11 +489,8 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, 
	}



	/*

	 * 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.

	 * Major/minor page fault accounting.

	 */

	if (flags & FAULT_FLAG_ALLOW_RETRY) {

	if (fault & VM_FAULT_MAJOR) {

		current->maj_flt++;

		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
@@ -494,14 +511,6 @@ int do_page_fault(struct pt_regs *regs, unsigned long address, 
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,

			      regs, address);

	}

		if (fault & VM_FAULT_RETRY) {

			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk

			 * of starvation. */

			flags &= ~FAULT_FLAG_ALLOW_RETRY;

			flags |= FAULT_FLAG_TRIED;

			goto retry;

		}

	}



	up_read(&mm->mmap_sem);

	goto bail;