shmem: set a_ops earlier in shmem_symlink

Set the a_ops in shmem_symlink before reading a folio from the mapping
to prepare for asserting that shmem_get_folio is only called on shmem
mappings.
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>

mm/shmem.c

@@ -3506,10 +3506,10 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
 		inode->i_op = &shmem_short_symlink_operations;
 	} else {
 		inode_nohighmem(inode);
+		inode->i_mapping->a_ops = &shmem_aops;
 		error = shmem_get_folio(inode, 0, &folio, SGP_WRITE);
 		if (error)
 			goto out_remove_offset;
-		inode->i_mapping->a_ops = &shmem_aops;
 		inode->i_op = &shmem_symlink_inode_operations;
 		memcpy(folio_address(folio), symname, len);
 		folio_mark_uptodate(folio);