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

[Davidlohr Bueso <dave@xxxxxxxxxxxx>]

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>
---
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;
	}
--
2.16.4