mm: thp: support "THPeligible" semantics for mTHP with anonymous shmem

After the commit 7fb1b25 ("mm: shmem: add mTHP support for anonymous
shmem"), we can configure different policies through the multi-size THP
sysfs interface for anonymous shmem.  But currently "THPeligible"
indicates only whether the mapping is eligible for allocating THP-pages as
well as the THP is PMD mappable or not for anonymous shmem, we need to
support semantics for mTHP with anonymous shmem similar to those for mTHP
with anonymous memory.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Bang Li <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Kefeng Wang <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Bang Li

include/linux/shmem_fs.h

@@ -113,12 +113,21 @@ int shmem_unuse(unsigned int type);
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 extern bool shmem_is_huge(struct inode *inode, pgoff_t index, bool shmem_huge_force,
 			  struct mm_struct *mm, unsigned long vm_flags);
+unsigned long shmem_allowable_huge_orders(struct inode *inode,
+				struct vm_area_struct *vma, pgoff_t index,
+				bool global_huge);
 #else
 static __always_inline bool shmem_is_huge(struct inode *inode, pgoff_t index, bool shmem_huge_force,
 					  struct mm_struct *mm, unsigned long vm_flags)
 {
 	return false;
 }
+static inline unsigned long shmem_allowable_huge_orders(struct inode *inode,
+				struct vm_area_struct *vma, pgoff_t index,
+				bool global_huge)
+{
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_SHMEM

mm/huge_memory.c

@@ -151,10 +151,15 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 	 * Must be done before hugepage flags check since shmem has its
 	 * own flags.
 	 */
-	if (!in_pf && shmem_file(vma->vm_file))
-		return shmem_is_huge(file_inode(vma->vm_file), vma->vm_pgoff,
-				     !enforce_sysfs, vma->vm_mm, vm_flags)
-			? orders : 0;
+	if (!in_pf && shmem_file(vma->vm_file)) {
+		bool global_huge = shmem_is_huge(file_inode(vma->vm_file), vma->vm_pgoff,
+							!enforce_sysfs, vma->vm_mm, vm_flags);
+
+		if (!vma_is_anon_shmem(vma))
+			return global_huge ? orders : 0;
+		return shmem_allowable_huge_orders(file_inode(vma->vm_file),
+							vma, vma->vm_pgoff, global_huge);
+	}
 
 	if (!vma_is_anonymous(vma)) {
 		/*

mm/shmem.c

@@ -1622,7 +1622,7 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static unsigned long shmem_allowable_huge_orders(struct inode *inode,
+unsigned long shmem_allowable_huge_orders(struct inode *inode,
 				struct vm_area_struct *vma, pgoff_t index,
 				bool global_huge)
 {
@@ -1707,13 +1707,6 @@ static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault
 	return orders;
 }
 #else
-static unsigned long shmem_allowable_huge_orders(struct inode *inode,
-				struct vm_area_struct *vma, pgoff_t index,
-				bool global_huge)
-{
-	return 0;
-}
-
 static unsigned long shmem_suitable_orders(struct inode *inode, struct vm_fault *vmf,
 					   struct address_space *mapping, pgoff_t index,
 					   unsigned long orders)