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Subject[PATCH 1/5] vfio/type1: use pinned_vm instead of locked_vm to account pinned pages
Date
Beginning with bc3e53f682d9 ("mm: distinguish between mlocked and pinned
pages"), locked and pinned pages are accounted separately. Type1
accounts pinned pages to locked_vm; use pinned_vm instead.

pinned_vm recently became atomic and so no longer relies on mmap_sem
held as writer: delete.

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
---
drivers/vfio/vfio_iommu_type1.c | 31 ++++++++++++-------------------
1 file changed, 12 insertions(+), 19 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 73652e21efec..a56cc341813f 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -257,7 +257,8 @@ static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
{
struct mm_struct *mm;
- int ret;
+ s64 pinned_vm;
+ int ret = 0;

if (!npage)
return 0;
@@ -266,24 +267,15 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
if (!mm)
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;
+ pinned_vm = atomic64_add_return(npage, &mm->pinned_vm);

- if (mm->locked_vm + npage > limit)
- ret = -ENOMEM;
- }
+ if (npage > 0 && !dma->lock_cap) {
+ unsigned long limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >>
+ PAGE_SHIFT;
+ if (pinned_vm > limit) {
+ atomic64_sub(npage, &mm->pinned_vm);
+ ret = -ENOMEM;
}
-
- if (!ret)
- mm->locked_vm += npage;
-
- up_write(&mm->mmap_sem);
}

if (async)
@@ -401,6 +393,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
long ret, pinned = 0, lock_acct = 0;
bool rsvd;
dma_addr_t iova = vaddr - dma->vaddr + dma->iova;
+ atomic64_t *pinned_vm = &current->mm->pinned_vm;

/* This code path is only user initiated */
if (!current->mm)
@@ -418,7 +411,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
* pages are already counted against the user.
*/
if (!rsvd && !vfio_find_vpfn(dma, iova)) {
- if (!dma->lock_cap && current->mm->locked_vm + 1 > limit) {
+ if (!dma->lock_cap && atomic64_read(pinned_vm) + 1 > limit) {
put_pfn(*pfn_base, dma->prot);
pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
limit << PAGE_SHIFT);
@@ -445,7 +438,7 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,

if (!rsvd && !vfio_find_vpfn(dma, iova)) {
if (!dma->lock_cap &&
- current->mm->locked_vm + lock_acct + 1 > limit) {
+ atomic64_read(pinned_vm) + lock_acct + 1 > limit) {
put_pfn(pfn, dma->prot);
pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
__func__, limit << PAGE_SHIFT);
--
2.20.1
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