[PATCH 03/19] drivers/vdpa: Convert vdpa to use the new vm_structure

[Alistair Popple]

Convert vdpa to use the new vm_structure and associated
account_pinned_vm() functions. This also fixes a bug where
vduse_dev_reg_umem() could exceed the rlimit due to non-atomically
checking and updating mm->pinned_vm which could lead to a race.

Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 drivers/vdpa/vdpa_user/vduse_dev.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 0c3b486..bc300e2 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -23,6 +23,7 @@
 #include <linux/nospec.h>
 #include <linux/vmalloc.h>
 #include <linux/sched/mm.h>
+#include <linux/vm_account.h>
 #include <uapi/linux/vduse.h>
 #include <uapi/linux/vdpa.h>
 #include <uapi/linux/virtio_config.h>
@@ -70,7 +71,7 @@ struct vduse_umem {
 	unsigned long iova;
 	unsigned long npages;
 	struct page **pages;
-	struct mm_struct *mm;
+	struct vm_account vm_account;
 };
 
 struct vduse_dev {
@@ -950,8 +951,7 @@ static int vduse_dev_dereg_umem(struct vduse_dev *dev,
 	vduse_domain_remove_user_bounce_pages(dev->domain);
 	unpin_user_pages_dirty_lock(dev->umem->pages,
 				    dev->umem->npages, true);
-	atomic64_sub(dev->umem->npages, &dev->umem->mm->pinned_vm);
-	mmdrop(dev->umem->mm);
+	vm_unaccount_pinned(&dev->umem->vm_account, dev->umem->npages);
 	vfree(dev->umem->pages);
 	kfree(dev->umem);
 	dev->umem = NULL;
@@ -967,7 +967,7 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
 	struct page **page_list = NULL;
 	struct vduse_umem *umem = NULL;
 	long pinned = 0;
-	unsigned long npages, lock_limit;
+	unsigned long npages;
 	int ret;
 
 	if (!dev->domain->bounce_map ||
@@ -990,8 +990,8 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
 
 	mmap_read_lock(current->mm);
 
-	lock_limit = PFN_DOWN(rlimit(RLIMIT_MEMLOCK));
-	if (npages + atomic64_read(&current->mm->pinned_vm) > lock_limit)
+	vm_account_init_current(&umem->vm_account);
+	if (vm_account_pinned(&umem->vm_account, npages))
 		goto out;
 
 	pinned = pin_user_pages(uaddr, npages, FOLL_LONGTERM | FOLL_WRITE,
@@ -1006,22 +1006,21 @@ static int vduse_dev_reg_umem(struct vduse_dev *dev,
 	if (ret)
 		goto out;
 
-	atomic64_add(npages, &current->mm->pinned_vm);
-
 	umem->pages = page_list;
 	umem->npages = pinned;
 	umem->iova = iova;
-	umem->mm = current->mm;
-	mmgrab(current->mm);
 
 	dev->umem = umem;
 out:
-	if (ret && pinned > 0)
+	if (ret && pinned > 0) {
 		unpin_user_pages(page_list, pinned);
+		vm_unaccount_pinned(&umem->vm_account, npages);
+	}
 
 	mmap_read_unlock(current->mm);
 unlock:
 	if (ret) {
+		vm_account_release(&umem->vm_account);
 		vfree(page_list);
 		kfree(umem);
 	}
-- 
git-series 0.9.1