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

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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;



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