[RFC PATCH v2 4/5] 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/shmem_fs.h | 1 +
 mm/shmem.c               | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 99992cf..b1fd7c1 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -59,6 +59,7 @@ extern struct file *shmem_kernel_file_setup(const char *name, loff_t size,
 extern int shmem_zero_setup(struct vm_area_struct *);
 extern int shmem_lock(struct file *file, int lock, struct user_struct *user);
 extern bool shmem_mapping(struct address_space *mapping);
+extern bool shmem_vma(struct vm_area_struct *vma);
 extern void shmem_unlock_mapping(struct address_space *mapping);
 extern struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 					pgoff_t index, gfp_t gfp_mask);
diff --git a/mm/shmem.c b/mm/shmem.c
index 134a422..e2d7be6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1493,6 +1493,12 @@ 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 &&
+		shmem_mapping(file_inode(vma->vm_file)->i_mapping);
+}
+
 #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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