Re: [PATCH -next] IB/qib: Remove unused variable 'locked'

[Davidlohr Bueso <dave@xxxxxxxxxxxx>]

On Sun, 17 Feb 2019, H?kon Bugge wrote:

> > On 16 Feb 2019, at 13:15, Davidlohr Bueso <dave@xxxxxxxxxxxx> wrote:
> >
> > On Fri, 15 Feb 2019, Jason Gunthorpe wrote:
> >
> > > On Sat, Feb 16, 2019 at 03:36:18AM +0000, YueHaibing wrote:
> > > > Fixes gcc '-Wunused-but-set-variable' warning:
> > > >
> > > > drivers/infiniband/hw/qib/qib_user_pages.c: In function 'qib_get_user_pages':
> > > > drivers/infiniband/hw/qib/qib_user_pages.c:103:16: warning:
> > > > variable 'locked' set but not used [-Wunused-but-set-variable]
> > > >
> > > > It's never used since introduction.
> > > >
> > > > Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
> > > > drivers/infiniband/hw/qib/qib_user_pages.c | 4 ++--
> > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/infiniband/hw/qib/qib_user_pages.c b/drivers/infiniband/hw/qib/qib_user_pages.c
> > > > index ef8bcf366ddc..a5be36c07451 100644
> > > > +++ b/drivers/infiniband/hw/qib/qib_user_pages.c
> > > > @@ -100,12 +100,12 @@ int qib_map_page(struct pci_dev *hwdev, struct page *page, dma_addr_t *daddr)
> > > > int qib_get_user_pages(unsigned long start_page, size_t num_pages,
> > > > 		       struct page **p)
> > > > {
> > > > -	unsigned long locked, lock_limit;
> > > > +	unsigned long lock_limit;
> > > > 	size_t got;
> > > > 	int ret;
> > > >
> > > > 	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> > > > -	locked = atomic64_add_return(num_pages, &current->mm->pinned_vm);
> > > > +	atomic64_add_return(num_pages, &current->mm->pinned_vm);
> > > >
> > > > 	if (num_pages > lock_limit && !capable(CAP_IPC_LOCK)) {
> > > > 		ret = -ENOMEM;
> > >
> > > This looks just wrong... The algorithm should look like the one in umem
> >
> > Indeed, but the current check also looks wrong; we wanna check against the
> > new value after the addition of num_pages.
> >
> > Thanks,
> > Davidlohr
> >
> > -----------8<------------------------------------------------------------
> > [PATCH] drivers/IB,qib: Fix pinned/locked limit check in qib_get_user_pages()
> >
> > The current check does not take into account the previous value of
> > pinned_vm; thus it is quite bogus as is. Fix this by checking the
> > new value after the (optimistic) atomic inc.
> >
> > Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx <mailto:dbueso@xxxxxxx>>
> > ---
> > drivers/infiniband/hw/qib/qib_user_pages.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/infiniband/hw/qib/qib_user_pages.c b/drivers/infiniband/hw/qib/qib_user_pages.c
> > index ef8bcf366ddc..123ca8f64f75 100644
> > --- a/drivers/infiniband/hw/qib/qib_user_pages.c
> > +++ b/drivers/infiniband/hw/qib/qib_user_pages.c
> > @@ -107,7 +107,7 @@ int qib_get_user_pages(unsigned long start_page, size_t num_pages,
> > 	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> > 	locked = atomic64_add_return(num_pages, &current->mm->pinned_vm);
> > -	if (num_pages > lock_limit && !capable(CAP_IPC_LOCK)) {
> > +	if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
> > 		ret = -ENOMEM;
> > 		goto bail;
>
> But you have still added num_pages to current->mm->pinned_vm. Need to subtract them.

bail:
	atomic64_sub(num_pages, &current->mm->pinned_vm);
	return ret;