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    Subject[PATCH 07/20] microblaze/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 microblaze.

    Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
    ---
    arch/microblaze/mm/fault.c | 33 ++++++++++++++++++++++++++++-----
    1 files changed, 28 insertions(+), 5 deletions(-)

    diff --git a/arch/microblaze/mm/fault.c b/arch/microblaze/mm/fault.c
    index ae97d2c..60e19e6 100644
    --- a/arch/microblaze/mm/fault.c
    +++ b/arch/microblaze/mm/fault.c
    @@ -93,6 +93,8 @@ void do_page_fault(struct pt_regs *regs, unsigned long address,
    int code = SEGV_MAPERR;
    int is_write = error_code & ESR_S;
    int fault;
    + unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
    + (is_write ? FAULT_FLAG_WRITE : 0);

    regs->ear = address;
    regs->esr = error_code;
    @@ -139,6 +141,7 @@ void do_page_fault(struct pt_regs *regs, unsigned long address,
    if (kernel_mode(regs) && !search_exception_tables(regs->pc))
    goto bad_area_nosemaphore;

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

    @@ -211,7 +214,11 @@ good_area:
    * make sure we exit gracefully rather than endlessly redo
    * the fault.
    */
    - fault = handle_mm_fault(mm, vma, address, is_write ? 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;
    @@ -219,11 +226,27 @@ good_area:
    goto do_sigbus;
    BUG();
    }
    - if (unlikely(fault & VM_FAULT_MAJOR))
    - current->maj_flt++;
    - else
    - current->min_flt++;
    +
    + if (flags & FAULT_FLAG_ALLOW_RETRY) {
    + if (unlikely(fault & VM_FAULT_MAJOR))
    + current->maj_flt++;
    + else
    + current->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);
    +
    /*
    * keep track of tlb+htab misses that are good addrs but
    * just need pte's created via handle_mm_fault()
    --
    1.7.5.4


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