On Mon, May 20, 2019 at 04:19:34PM +1000, Alexey Kardashevskiy wrote:

On 04/05/2019 06:16, Daniel Jordan wrote:

quoted

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 <redacted>

Thanks!  And for the review as well.

quoted

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.

quoted

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.

quoted

+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.

quoted

+		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.