On Tue, Oct 10, 2017 at 6:09 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> On Tue, Oct 10, 2017 at 07:49:30AM -0700, Dan Williams wrote:
>> @@ -1009,6 +1019,22 @@ xfs_file_llseek(
>> }
>>
>> /*
>> + * MAP_DIRECT faults can only be serviced while the FL_LAYOUT lease is
>> + * valid. See map_direct_invalidate.
>> + */
>> +static int
>> +xfs_can_fault_direct(
>> + struct vm_area_struct *vma)
>> +{
>> + if (!xfs_vma_is_direct(vma))
>> + return 0;
>> +
>> + if (!test_map_direct_valid(vma->vm_private_data))
>> + return VM_FAULT_SIGBUS;
>> + return 0;
>> +}
>
> Better, but I'm going to be an annoying pedant here: a "can
> <something>" check should return a boolean true/false.
>
> Also, it's a bit jarring to see that a non-direct VMA that /can't/
> do direct faults returns the same thing as a direct-vma that /can/
> do direct faults, so a couple of extra comments for people who will
> quickly forget how this code works (i.e. me) will be helpful. Say
> something like this:
>
> /*
> * MAP_DIRECT faults can only be serviced while the FL_LAYOUT lease is
> * valid. See map_direct_invalidate.
> */
> static bool
> xfs_vma_has_direct_lease(
> struct vm_area_struct *vma)
> {
> /* Non MAP_DIRECT vmas do not require layout leases */
> if (!xfs_vma_is_direct(vma))
> return true;
>
> if (!test_map_direct_valid(vma->vm_private_data))
> return false;
>
> /* We have a valid lease */
> return true;
> }
>
> .....
> if (!xfs_vma_has_direct_lease(vma)) {
> ret = VM_FAULT_SIGBUS;
> goto out_unlock;
> }
> ....
Looks good to me.
