shmem: move shmem_mapping out of line

shmem_aops really should not be exported to the world.  Move
shmem_mapping and export it as internal for the one semi-legitimate
modular user in udmabuf.

This effectively reverts commit 30e6a51d ("mm/shmem.c: make
shmem_mapping() inline"). which added a bogus shmem_aops non-GPL export
for no reason whatsoever as there as no shmem_mapping call outside of
core MM code at that point.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

include/linux/shmem_fs.h

@@ -97,11 +97,7 @@ extern unsigned long shmem_get_unmapped_area(struct file *, unsigned long addr,
 		unsigned long len, unsigned long pgoff, unsigned long flags);
 extern int shmem_lock(struct file *file, int lock, struct ucounts *ucounts);
 #ifdef CONFIG_SHMEM
-extern const struct address_space_operations shmem_aops;
-static inline bool shmem_mapping(struct address_space *mapping)
-{
-	return mapping->a_ops == &shmem_aops;
-}
+bool shmem_mapping(struct address_space *mapping);
 #else
 static inline bool shmem_mapping(struct address_space *mapping)
 {

mm/shmem.c

@@ -254,7 +254,7 @@ static void shmem_inode_unacct_blocks(struct inode *inode, long pages)
 }
 
 static const struct super_operations shmem_ops;
-const struct address_space_operations shmem_aops;
+static const struct address_space_operations shmem_aops;
 static const struct file_operations shmem_file_operations;
 static const struct inode_operations shmem_inode_operations;
 static const struct inode_operations shmem_dir_inode_operations;
@@ -263,6 +263,12 @@ static const struct vm_operations_struct shmem_vm_ops;
 static const struct vm_operations_struct shmem_anon_vm_ops;
 static struct file_system_type shmem_fs_type;
 
+bool shmem_mapping(struct address_space *mapping)
+{
+	return mapping->a_ops == &shmem_aops;
+}
+EXPORT_SYMBOL_GPL(shmem_mapping);
+
 bool vma_is_anon_shmem(struct vm_area_struct *vma)
 {
 	return vma->vm_ops == &shmem_anon_vm_ops;
@@ -4466,7 +4472,7 @@ static int shmem_error_remove_folio(struct address_space *mapping,
 	return 0;
 }
 
-const struct address_space_operations shmem_aops = {
+static const struct address_space_operations shmem_aops = {
 	.writepage	= shmem_writepage,
 	.dirty_folio	= noop_dirty_folio,
 #ifdef CONFIG_TMPFS
@@ -4478,7 +4484,6 @@ const struct address_space_operations shmem_aops = {
 #endif
 	.error_remove_folio = shmem_error_remove_folio,
 };
-EXPORT_SYMBOL(shmem_aops);
 
 static const struct file_operations shmem_file_operations = {
 	.mmap		= shmem_mmap,