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SubjectRe: [PATCH 04/20 v3] powerpc/mm/fault.c: Port OOM changes to do_page_fault
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On Wed, 2012-03-21 at 08:28 +1100, Benjamin Herrenschmidt wrote:
> On Tue, 2012-03-20 at 12:01 -0400, Kautuk Consul wrote:
> > Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
> > (mm: retry page fault when blocking on disk transfer) and
> > commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
> > (x86,mm: make pagefault killable)
> >
> > The above commits introduced changes into the x86 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.
> >
> > Port these changes to powerpc.
>
> I have done that port already :-) It's in powerpc-next which I will send
> to Linus to pull today or tomorrow....

BTW. Feel free to review what I've done, it's quite possible that I have
screwed something up ...

Cheers,
Ben.

> Cheers,
> Ben.
>
> > Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
> > Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
> > ---
> > arch/powerpc/mm/fault.c | 51 +++++++++++++++++++++++++++++++++-------------
> > 1 files changed, 36 insertions(+), 15 deletions(-)
> >
> > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> > index 2f0d1b0..a3b1176 100644
> > --- a/arch/powerpc/mm/fault.c
> > +++ b/arch/powerpc/mm/fault.c
> > @@ -129,6 +129,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
> > int is_write = 0, ret;
> > int trap = TRAP(regs);
> > int is_exec = trap == 0x400;
> > + unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
> >
> > #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
> > /*
> > @@ -212,6 +213,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
> > if (!user_mode(regs) && !search_exception_tables(regs->nip))
> > goto bad_area_nosemaphore;
> >
> > +retry:
> > down_read(&mm->mmap_sem);
> > }
> >
> > @@ -313,6 +315,7 @@ good_area:
> > } else if (is_write) {
> > if (!(vma->vm_flags & VM_WRITE))
> > goto bad_area;
> > + flags |= FAULT_FLAG_WRITE;
> > /* a read */
> > } else {
> > /* protection fault */
> > @@ -327,7 +330,11 @@ good_area:
> > * make sure we exit gracefully rather than endlessly redo
> > * the fault.
> > */
> > - ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
> > + ret = handle_mm_fault(mm, vma, address, flags);
> > +
> > + if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
> > + return 0;
> > +
> > if (unlikely(ret & VM_FAULT_ERROR)) {
> > if (ret & VM_FAULT_OOM)
> > goto out_of_memory;
> > @@ -335,22 +342,36 @@ good_area:
> > goto do_sigbus;
> > BUG();
> > }
> > - if (ret & VM_FAULT_MAJOR) {
> > - current->maj_flt++;
> > - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
> > - regs, address);
> > -#ifdef CONFIG_PPC_SMLPAR
> > - if (firmware_has_feature(FW_FEATURE_CMO)) {
> > - preempt_disable();
> > - get_lppaca()->page_ins += (1 << PAGE_FACTOR);
> > - preempt_enable();
> > + if (flags & FAULT_FLAG_ALLOW_RETRY) {
> > + if (ret & VM_FAULT_MAJOR) {
> > + current->maj_flt++;
> > + perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
> > + regs, address);
> > +#ifdef CONFIG_PPC_SMLPAR
> > + if (firmware_has_feature(FW_FEATURE_CMO)) {
> > + preempt_disable();
> > + get_lppaca()->page_ins += (1 << PAGE_FACTOR);
> > + preempt_enable();
> > + }
> > +#endif
> > + } else {
> > + current->min_flt++;
> > + perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
> > + regs, address);
> > + }
> > + if (fault & VM_FAULT_RETRY) {
> > + flags &= ~FAULT_FLAG_ALLOW_RETRY;
> > +
> > + /*
> > + * 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;
> > }
> > -#endif
> > - } else {
> > - current->min_flt++;
> > - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
> > - regs, address);
> > }
> > +
> > up_read(&mm->mmap_sem);
> > return 0;
> >
>




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