On Mon, May 20, 2019 at 04:19:34PM +1000, Alexey Kardashevskiy wrote:
> On 04/05/2019 06:16, Daniel Jordan wrote:
> > locked_vm accounting is done roughly the same way in five places, so
> > unify them in a helper. Standardize the debug prints, which vary
> > slightly.
>
> And I rather liked that prints were different and tell precisely which
> one of three each printk is.
I'm not following. One of three...callsites? But there were five callsites.
Anyway, I added a _RET_IP_ to the debug print so you can differentiate.
> I commented below but in general this seems working.
>
> Tested-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
Thanks! And for the review as well.
> > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> > index 6b64e45a5269..d39a1b830d82 100644
> > --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> > @@ -34,49 +35,13 @@
> > static void tce_iommu_detach_group(void *iommu_data,
> > struct iommu_group *iommu_group);
> >
> > -static long try_increment_locked_vm(struct mm_struct *mm, long npages)
> > +static int tce_account_locked_vm(struct mm_struct *mm, unsigned long npages,
> > + bool inc)
> > {
> > - long ret = 0, locked, lock_limit;
> > -
> > if (WARN_ON_ONCE(!mm))
> > return -EPERM;
>
>
> If this WARN_ON is the only reason for having tce_account_locked_vm()
> instead of calling account_locked_vm() directly, you can then ditch the
> check as I have never ever seen this triggered.
Great, will do.
> > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> > index d0f731c9920a..15ac76171ccd 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -273,25 +273,14 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
> > return -ESRCH; /* process exited */
> >
> > ret = down_write_killable(&mm->mmap_sem);
> > - if (!ret) {
> > - if (npage > 0) {
> > - if (!dma->lock_cap) {
> > - unsigned long limit;
> > -
> > - limit = task_rlimit(dma->task,
> > - RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> > -
> > - if (mm->locked_vm + npage > limit)
> > - ret = -ENOMEM;
> > - }
> > - }
> > + if (ret)
> > + goto out;
>
>
> A single "goto" to jump just 3 lines below seems unnecessary.
No strong preference here, I'll take out the goto.
> > +int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
> > + struct task_struct *task, bool bypass_rlim)
> > +{
> > + unsigned long locked_vm, limit;
> > + int ret = 0;
> > +
> > + locked_vm = mm->locked_vm;
> > + if (inc) {
> > + if (!bypass_rlim) {
> > + limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> > + if (locked_vm + pages > limit) {
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > + }
>
> Nit:
>
> if (!ret)
>
> and then you don't need "goto out".
Ok, sure.
> > + mm->locked_vm = locked_vm + pages;
> > + } else {
> > + WARN_ON_ONCE(pages > locked_vm);
> > + mm->locked_vm = locked_vm - pages;
>
>
> Can go negative here. Not a huge deal but inaccurate imo.
I hear you, but setting a negative value to zero, as we had done previously,
doesn't make much sense to me.
