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    Subject[PATCH 01/19 v2] avr32/mm/fault.c: Port OOM changes to do_page_fault
    Date
    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 AVR32.

    Signed-off-by: Mohd. Faris <mohdfarisq2010@gmail.com>
    Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
    ---
    arch/avr32/mm/fault.c | 30 +++++++++++++++++++++++++-----
    1 files changed, 25 insertions(+), 5 deletions(-)

    diff --git a/arch/avr32/mm/fault.c b/arch/avr32/mm/fault.c
    index f7040a1..0362d03 100644
    --- a/arch/avr32/mm/fault.c
    +++ b/arch/avr32/mm/fault.c
    @@ -65,6 +65,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
    long signr;
    int code;
    int fault;
    + unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

    if (notify_page_fault(regs, ecr))
    return;
    @@ -86,6 +87,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)

    local_irq_enable();

    +retry:
    down_read(&mm->mmap_sem);

    vma = find_vma(mm, address);
    @@ -122,6 +124,7 @@ good_area:
    if (!(vma->vm_flags & VM_WRITE))
    goto bad_area;
    writeaccess = 1;
    + flags |= FAULT_FLAG_WRITE;
    break;
    default:
    panic("Unhandled case %lu in do_page_fault!", ecr);
    @@ -132,7 +135,11 @@ good_area:
    * sure we exit gracefully rather than endlessly redo the
    * fault.
    */
    - fault = handle_mm_fault(mm, vma, address, writeaccess ? FAULT_FLAG_WRITE : 0);
    + 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;
    @@ -140,10 +147,23 @@ good_area:
    goto do_sigbus;
    BUG();
    }
    - if (fault & VM_FAULT_MAJOR)
    - tsk->maj_flt++;
    - else
    - tsk->min_flt++;
    +
    + if (flags & FAULT_FLAG_ALLOW_RETRY) {
    + if (fault & VM_FAULT_MAJOR)
    + tsk->maj_flt++;
    + else
    + tsk->min_flt++;
    + 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;
    + }
    + }

    up_read(&mm->mmap_sem);
    return;
    --
    1.7.5.4


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