[PATCH kernel 2/4] powerpc/mm/iommu/vfio_spapr_tce: Change mm_iommu_get to reference a region

[Alexey Kardashevskiy]

We are going to add another helper to preregister device memory so
instead of having mm_iommu_new() which pre-registers the normal memory
and references the region, we need separate helpers for pre-registerign
and referencing.

To make the mm_iommu_get name reflect what it is supposed to do, this
changes mm_iommu_get() to reference the region so from now on for every
mm_iommu_get() we need a matching mm_iommu_put().

Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
---
 arch/powerpc/mm/mmu_context_iommu.c |  5 +++++
 drivers/vfio/vfio_iommu_spapr_tce.c | 33 ++++++++++++++++++++++-----------
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/mm/mmu_context_iommu.c 
b/arch/powerpc/mm/mmu_context_iommu.c
index 8eeb99d..a8c4a3c 100644
--- a/arch/powerpc/mm/mmu_context_iommu.c
+++ b/arch/powerpc/mm/mmu_context_iommu.c
@@ -373,13 +373,18 @@ struct mm_iommu_table_group_mem_t *mm_iommu_get(struct 
mm_struct *mm,
 {
        struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
 
+       mutex_lock(&mem_list_mutex);
+
        list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
                if ((mem->ua == ua) && (mem->entries == entries)) {
                        ret = mem;
+                       ++mem->used;
                        break;
                }
        }
 
+       mutex_unlock(&mem_list_mutex);
+
        return ret;
 }
 EXPORT_SYMBOL_GPL(mm_iommu_get);
diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c 
b/drivers/vfio/vfio_iommu_spapr_tce.c
index 1701798..56db071 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -151,7 +151,8 @@ static long tce_iommu_unregister_pages(struct tce_container 
*container,
 {
        struct mm_iommu_table_group_mem_t *mem;
        struct tce_iommu_prereg *tcemem;
-       bool found = false;
+       bool found;
+       long ret;
 
        if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK))
                return -EINVAL;
@@ -168,9 +169,13 @@ static long tce_iommu_unregister_pages(struct 
tce_container *container,
        }
 
        if (!found)
-               return -ENOENT;
+               ret = -ENOENT;
+       else
+               ret = tce_iommu_prereg_free(container, tcemem);
 
-       return tce_iommu_prereg_free(container, tcemem);
+       mm_iommu_put(container->mm, mem);
+
+       return ret;
 }
 
 static long tce_iommu_register_pages(struct tce_container *container,
@@ -188,19 +193,21 @@ static long tce_iommu_register_pages(struct tce_container 
*container,
        mem = mm_iommu_get(container->mm, vaddr, entries);
        if (mem) {
                list_for_each_entry(tcemem, &container->prereg_list, next) {
-                       if (tcemem->mem == mem)
-                               return -EBUSY;
+                       if (tcemem->mem == mem) {
+                               ret = -EBUSY;
+                               goto put_exit;
+                       }
                }
+       } else {
+               ret = mm_iommu_new(container->mm, vaddr, entries, &mem);
+               if (ret)
+                       return ret;
        }
 
-       ret = mm_iommu_new(container->mm, vaddr, entries, &mem);
-       if (ret)
-               return ret;
-
        tcemem = kzalloc(sizeof(*tcemem), GFP_KERNEL);
        if (!tcemem) {
-               mm_iommu_put(container->mm, mem);
-               return -ENOMEM;
+               ret = -ENOMEM;
+               goto put_exit;
        }
 
        tcemem->mem = mem;
@@ -209,6 +216,10 @@ static long tce_iommu_register_pages(struct tce_container 
*container,
        container->enabled = true;
 
        return 0;
+
+put_exit:
+       mm_iommu_put(container->mm, mem);
+       return ret;
 }
 
 static bool tce_page_is_contained(struct page *page, unsigned page_shift)
-- 
2.11.0