[PATCH v2 11/20] mm: add and use unmap_page_range vm_ops hook

[Anthony Yznaga <anthony.yznaga@oracle.com>]

Special handling is needed when unmapping a hugetlb vma and will
be needed when unmapping an msharefs vma once support is added for
handling faults in an mshare region.

Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
---
 include/linux/mm.h | 10 ++++++++++
 ipc/shm.c          | 17 +++++++++++++++++
 mm/hugetlb.c       | 25 +++++++++++++++++++++++++
 mm/memory.c        | 36 +++++++++++++-----------------------
 4 files changed, 65 insertions(+), 23 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f2f9d15213ab..d6cac2cca4da 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -40,6 +40,7 @@ struct anon_vma_chain;
 struct user_struct;
 struct pt_regs;
 struct folio_batch;
+struct zap_details;
 
 void arch_mm_preinit(void);
 void mm_core_init(void);
@@ -661,8 +662,17 @@ struct vm_operations_struct {
 	 */
 	struct page *(*find_special_page)(struct vm_area_struct *vma,
 					  unsigned long addr);
+	void (*unmap_page_range)(struct mmu_gather *tlb,
+				 struct vm_area_struct *vma,
+				 unsigned long addr, unsigned long end,
+				 struct zap_details *details);
 };
 
+void __unmap_page_range(struct mmu_gather *tlb,
+			struct vm_area_struct *vma,
+			unsigned long addr, unsigned long end,
+			struct zap_details *details);
+
 #ifdef CONFIG_NUMA_BALANCING
 static inline void vma_numab_state_init(struct vm_area_struct *vma)
 {
diff --git a/ipc/shm.c b/ipc/shm.c
index 99564c870084..cadd551e60b9 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -585,6 +585,22 @@ static struct mempolicy *shm_get_policy(struct vm_area_struct *vma,
 }
 #endif
 
+static void shm_unmap_page_range(struct mmu_gather *tlb,
+				 struct vm_area_struct *vma,
+				 unsigned long addr, unsigned long end,
+				 struct zap_details *details)
+{
+	struct file *file = vma->vm_file;
+	struct shm_file_data *sfd = shm_file_data(file);
+
+	if (sfd->vm_ops->unmap_page_range) {
+		sfd->vm_ops->unmap_page_range(tlb, vma, addr, end, details);
+		return;
+	}
+
+	__unmap_page_range(tlb, vma, addr, end, details);
+}
+
 static int shm_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct shm_file_data *sfd = shm_file_data(file);
@@ -685,6 +701,7 @@ static const struct vm_operations_struct shm_vm_ops = {
 	.set_policy = shm_set_policy,
 	.get_policy = shm_get_policy,
 #endif
+	.unmap_page_range = shm_unmap_page_range,
 };
 
 /**
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 39f92aad7bd1..e4a516f458a0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5426,6 +5426,30 @@ static vm_fault_t hugetlb_vm_op_fault(struct vm_fault *vmf)
 	return 0;
 }
 
+static void hugetlb_vm_op_unmap_page_range(struct mmu_gather *tlb,
+				struct vm_area_struct *vma,
+				unsigned long addr, unsigned long end,
+				struct zap_details *details)
+{
+	zap_flags_t zap_flags = details ?  details->zap_flags : 0;
+
+	/*
+	 * It is undesirable to test vma->vm_file as it
+	 * should be non-null for valid hugetlb area.
+	 * However, vm_file will be NULL in the error
+	 * cleanup path of mmap_region. When
+	 * hugetlbfs ->mmap method fails,
+	 * mmap_region() nullifies vma->vm_file
+	 * before calling this function to clean up.
+	 * Since no pte has actually been setup, it is
+	 * safe to do nothing in this case.
+	 */
+	if (!vma->vm_file)
+		return;
+
+	__unmap_hugepage_range(tlb, vma, addr, end, NULL, zap_flags);
+}
+
 /*
  * When a new function is introduced to vm_operations_struct and added
  * to hugetlb_vm_ops, please consider adding the function to shm_vm_ops.
@@ -5439,6 +5463,7 @@ const struct vm_operations_struct hugetlb_vm_ops = {
 	.close = hugetlb_vm_op_close,
 	.may_split = hugetlb_vm_op_split,
 	.pagesize = hugetlb_vm_op_pagesize,
+	.unmap_page_range = hugetlb_vm_op_unmap_page_range,
 };
 
 static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
diff --git a/mm/memory.c b/mm/memory.c
index 6ea3551eb2df..db558fe43088 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1876,7 +1876,7 @@ static inline unsigned long zap_p4d_range(struct mmu_gather *tlb,
 	return addr;
 }
 
-void unmap_page_range(struct mmu_gather *tlb,
+void __unmap_page_range(struct mmu_gather *tlb,
 			     struct vm_area_struct *vma,
 			     unsigned long addr, unsigned long end,
 			     struct zap_details *details)
@@ -1896,6 +1896,16 @@ void unmap_page_range(struct mmu_gather *tlb,
 	tlb_end_vma(tlb, vma);
 }
 
+void unmap_page_range(struct mmu_gather *tlb,
+			     struct vm_area_struct *vma,
+			     unsigned long addr, unsigned long end,
+			     struct zap_details *details)
+{
+	if (vma->vm_ops && vma->vm_ops->unmap_page_range)
+		vma->vm_ops->unmap_page_range(tlb, vma, addr, end, details);
+	else
+		__unmap_page_range(tlb, vma, addr, end, details);
+}
 
 static void unmap_single_vma(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, unsigned long start_addr,
@@ -1917,28 +1927,8 @@ static void unmap_single_vma(struct mmu_gather *tlb,
 	if (unlikely(vma->vm_flags & VM_PFNMAP))
 		untrack_pfn(vma, 0, 0, mm_wr_locked);
 
-	if (start != end) {
-		if (unlikely(is_vm_hugetlb_page(vma))) {
-			/*
-			 * It is undesirable to test vma->vm_file as it
-			 * should be non-null for valid hugetlb area.
-			 * However, vm_file will be NULL in the error
-			 * cleanup path of mmap_region. When
-			 * hugetlbfs ->mmap method fails,
-			 * mmap_region() nullifies vma->vm_file
-			 * before calling this function to clean up.
-			 * Since no pte has actually been setup, it is
-			 * safe to do nothing in this case.
-			 */
-			if (vma->vm_file) {
-				zap_flags_t zap_flags = details ?
-				    details->zap_flags : 0;
-				__unmap_hugepage_range(tlb, vma, start, end,
-							     NULL, zap_flags);
-			}
-		} else
-			unmap_page_range(tlb, vma, start, end, details);
-	}
+	if (start != end)
+		unmap_page_range(tlb, vma, start, end, details);
 }
 
 /**
-- 
2.43.5