[PATCH 3/5] mm, shmem: Add shmem_vma() helper

["Jerome Marchand" <jmarchan@redhat.com>]

Add a simple helper to check if a vm area belongs to shmem.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
---
 include/linux/mm.h | 6 ++++++
 mm/shmem.c         | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 34099fa..04a58d1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1074,11 +1074,17 @@ int shmem_zero_setup(struct vm_area_struct *);
 
 extern int shmem_locate(struct vm_area_struct *vma, pgoff_t pgoff, int *count);
 bool shmem_mapping(struct address_space *mapping);
+bool shmem_vma(struct vm_area_struct *vma);
+
 #else
 static inline bool shmem_mapping(struct address_space *mapping)
 {
 	return false;
 }
+static inline bool shmem_vma(struct vm_area_struct *vma)
+{
+	return false;
+}
 #endif
 
 extern int can_do_mlock(void);
diff --git a/mm/shmem.c b/mm/shmem.c
index 11b37a7..be87a20 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1447,6 +1447,14 @@ bool shmem_mapping(struct address_space *mapping)
 	return mapping->backing_dev_info == &shmem_backing_dev_info;
 }
 
+bool shmem_vma(struct vm_area_struct *vma)
+{
+	return (vma->vm_file &&
+		vma->vm_file->f_dentry->d_inode->i_mapping->backing_dev_info
+		== &shmem_backing_dev_info);
+
+}
+
 #ifdef CONFIG_TMPFS
 static const struct inode_operations shmem_symlink_inode_operations;
 static const struct inode_operations shmem_short_symlink_operations;
-- 
1.9.3

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