On Thu, 19 Nov 2015 00:49:58 +0100
Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx> wrote:
> The userfaultfd does need FAULT_FLAG_ALLOW_RETRY to not return
> VM_FAULT_SIGBUS. So we improve the gmap code to handle one
> VM_FAULT_RETRY.
>
> Signed-off-by: Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx>
> ---
> arch/s390/mm/pgtable.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
> index 54ef3bc..8a0025d 100644
> --- a/arch/s390/mm/pgtable.c
> +++ b/arch/s390/mm/pgtable.c
> @@ -577,15 +577,22 @@ int gmap_fault(struct gmap *gmap, unsigned long gaddr,
> unsigned int fault_flags)
> {
> unsigned long vmaddr;
> - int rc;
> + int rc, fault;
>
> + fault_flags |= FAULT_FLAG_ALLOW_RETRY;
> +retry:
> down_read(&gmap->mm->mmap_sem);
> vmaddr = __gmap_translate(gmap, gaddr);
> if (IS_ERR_VALUE(vmaddr)) {
> rc = vmaddr;
> goto out_up;
> }
> - if (fixup_user_fault(current, gmap->mm, vmaddr, fault_flags)) {
> + fault = fixup_user_fault(current, gmap->mm, vmaddr, fault_flags);
> + if (fault & VM_FAULT_RETRY) {
> + fault_flags &= ~FAULT_FLAG_ALLOW_RETRY;
> + fault_flags |= FAULT_FLAG_TRIED;
> + goto retry;
> + } else if (fault) {
> rc = -EFAULT;
> goto out_up;
> }
Me thinks that you want to add the retry code into fixup_user_fault itself.
You basically have the same code around the three calls to fixup_user_fault.
Yes, it will be a common code patch but I guess that it will be acceptable
given userfaultfd as a reason.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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