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Commit 96f3a5cc authored by Ley Foon Tan's avatar Ley Foon Tan
Browse files

nios2: Port OOM changes to do_page_fault() 



Commit d065bd81 ("mm: retry page fault when blocking on disk transfer") and
and commit 37b23e05 ("x86,mm: make pagefault killable")

The above commits introduced changes into the nios2 pagefault handler
for making the page fault handler retryable as well as killable.

These changes reduce the mmap_sem hold time, which is crucial
during OOM killer invocation.

Signed-off-by: default avatarLey Foon Tan <lftan@altera.com>
parent ad7ef26d

arch/nios2/mm/fault.c

+32 −5
Original line number Diff line number Diff line
@@ -47,7 +47,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause, 
	struct mm_struct *mm = tsk->mm;

	int code = SEGV_MAPERR;

	int fault;

	unsigned int flags = 0;

	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;



	cause >>= 2;
@@ -86,6 +86,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause, 
	if (!down_read_trylock(&mm->mmap_sem)) {

		if (!user_mode(regs) && !search_exception_tables(regs->ea))

			goto bad_area_nosemaphore;

retry:

		down_read(&mm->mmap_sem);

	}
@@ -132,6 +133,10 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause, 
	 * the fault.

	 */

	fault = handle_mm_fault(mm, vma, address, flags);



	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))

		return;



	if (unlikely(fault & VM_FAULT_ERROR)) {

		if (fault & VM_FAULT_OOM)

			goto out_of_memory;
@@ -141,10 +146,32 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause, 
			goto do_sigbus;

		BUG();

	}



	/*

	 * 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.

	 */

	if (flags & FAULT_FLAG_ALLOW_RETRY) {

		if (fault & VM_FAULT_MAJOR)

		tsk->maj_flt++;

			current->maj_flt++;

		else

		tsk->min_flt++;

			current->min_flt++;

		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;



			/*

			 * No need to up_read(&mm->mmap_sem) as we would

			 * have already released it in __lock_page_or_retry

			 * in mm/filemap.c.

			 */



			goto retry;

		}

	}



	up_read(&mm->mmap_sem);

	return;