hi,
There is a small defect in this patch.
I am sending a v2to this patch.
On Tue, Mar 20, 2012 at 9:45 AM, Kautuk Consul <consul.kau...@gmail.com> 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 um.
>
> Signed-off-by: Kautuk Consul <consul.kau...@gmail.com>
> ---
> arch/um/kernel/trap.c | 24 +++++++++++++++++++-----
> 1 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
> index dafc947..76adb61 100644
> --- a/arch/um/kernel/trap.c
> +++ b/arch/um/kernel/trap.c
> @@ -30,6 +30,8 @@ int handle_page_fault(unsigned long address, unsigned long
> ip,
> pmd_t *pmd;
> pte_t *pte;
> int err = -EFAULT;
> + unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
> + (is_write ? FAULT_FLAG_WRITE : 0);
>
> *code_out = SEGV_MAPERR;
>
> @@ -40,6 +42,7 @@ int handle_page_fault(unsigned long address, unsigned long
> ip,
> if (in_atomic())
> goto out_nosemaphore;
>
> +retry:
> down_read(&mm->mmap_sem);
> vma = find_vma(mm, address);
> if (!vma)
> @@ -65,7 +68,11 @@ good_area:
> do {
> int 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))
> + goto out;
The out: label will do an up_read which is not required here.
So, in v2 of this patch I am now doing a goto out_nosmaphore.
> +
> if (unlikely(fault & VM_FAULT_ERROR)) {
> if (fault & VM_FAULT_OOM) {
> goto out_of_memory;
> @@ -75,10 +82,17 @@ good_area:
> }
> BUG();
> }
> - if (fault & VM_FAULT_MAJOR)
> - current->maj_flt++;
> - else
> - current->min_flt++;
> + if (flags & FAULT_FLAG_ALLOW_RETRY) {
> + if (fault & VM_FAULT_MAJOR)
> + current->maj_flt++;
> + else
> + current->min_flt++;
> + if (fault & VM_FAULT_RETRY) {
> + flags &= ~FAULT_FLAG_ALLOW_RETRY;
> +
> + goto retry;
> + }
> + }
>
> pgd = pgd_offset(mm, address);
> pud = pud_offset(pgd, address);
> --
> 1.7.5.4
>
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