Re: [PATCH 3/3] powerpc/mm: move mmap_sem unlocking in do_page_fault()

Aneesh Kumar K.V
2017-03-21T09:12:36Z

Laurent Dufour <ldufour@linux.vnet.ibm.com> writes:

> Since the fault retry is now handled earlier, we can release the
> mmap_sem lock earlier too and remove later unlocking previously done in
> mm_fault_error().
>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
> ---
> arch/powerpc/mm/fault.c | 19 ++++---------------
> 1 file changed, 4 insertions(+), 15 deletions(-)
>
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index 2a6bc7e6e69a..21e06cce8984 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -151,13 +151,6 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
> * continue the pagefault.
> */
> if (fatal_signal_pending(current)) {
> - /*
> - * If we have retry set, the mmap semaphore will have
> - * alrady been released in __lock_page_or_retry(). Else
> - * we release it now.
> - */
> - if (!(fault & VM_FAULT_RETRY))
> - up_read(&current->mm->mmap_sem);
> /* Coming from kernel, we need to deal with uaccess fixups */
> if (user_mode(regs))
> return MM_FAULT_RETURN;
> @@ -170,8 +163,6 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
>
> /* Out of memory */
> if (fault & VM_FAULT_OOM) {
> - up_read(&current->mm->mmap_sem);
> -
> /*
> * We ran out of memory, or some other thing happened to us that
> * made us unable to handle the page fault gracefully.
> @@ -182,10 +173,8 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
> return MM_FAULT_RETURN;
> }
>
> - if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
> - up_read(&current->mm->mmap_sem);
> + if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
> return do_sigbus(regs, addr, fault);
> - }
>
> /* We don't understand the fault code, this is fatal */
> BUG();
> @@ -452,11 +441,12 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
> goto retry;
> }
> /* We will enter mm_fault_error() below */
> - }
> + } else
> + up_read(&current->mm->mmap_sem);
>
> if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
> if (fault & VM_FAULT_SIGSEGV)
> - goto bad_area;
> + goto bad_area_nosemaphore;
> rc = mm_fault_error(regs, address, fault);
> if (rc >= MM_FAULT_RETURN)
> goto bail;
> @@ -488,7 +478,6 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
> regs, address);
> }
>
> - up_read(&mm->mmap_sem);
> goto bail;
>
> bad_area:
> --
> 2.7.4