overlayfs: make mcoverlayfs compile for 4.14.0-115 (el7 arm64)

Use the 4.18 module as a base

Change-Id: I6c9ef66399800828e1932573da5a97573545c5da

executer/kernel/mcoverlayfs/linux-4.18.14/dir.c

@@ -17,6 +17,7 @@
 #include <linux/posix_acl_xattr.h>
 #include <linux/atomic.h>
 #include <linux/ratelimit.h>
+#include <linux/version.h>
 #include "overlayfs.h"
 
 static unsigned short ovl_redirect_max = 256;
@@ -601,9 +602,12 @@ static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 	if (!inode)
 		goto out_drop_write;
 
+//normally added in 4.19, but rhel backported so lazy choice
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 18, 0)
 	spin_lock(&inode->i_lock);
 	inode->i_state |= I_CREATING;
 	spin_unlock(&inode->i_lock);
+#endif
 
 	inode_init_owner(inode, dentry->d_parent->d_inode, mode);
 	attr.mode = inode->i_mode;

executer/kernel/mcoverlayfs/linux-4.18.14/export.c

@@ -17,6 +17,7 @@
 #include <linux/xattr.h>
 #include <linux/exportfs.h>
 #include <linux/ratelimit.h>
+#include <linux/version.h>
 #include "overlayfs.h"
 
 static int ovl_encode_maybe_copy_up(struct dentry *dentry)
@@ -287,6 +288,7 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
 	return type;
 }
 
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 16, 0)
 /*
  * Find or instantiate an overlay dentry from real dentries and index.
  */
@@ -838,11 +840,14 @@ static struct dentry *ovl_get_parent(struct dentry *dentry)
 	WARN_ON_ONCE(1);
 	return ERR_PTR(-EIO);
 }
+#endif
 
 const struct export_operations ovl_export_operations = {
 	.encode_fh	= ovl_encode_fh,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 16, 0)
 	.fh_to_dentry	= ovl_fh_to_dentry,
 	.fh_to_parent	= ovl_fh_to_parent,
 	.get_name	= ovl_get_name,
 	.get_parent	= ovl_get_parent,
+#endif
 };

executer/kernel/mcoverlayfs/linux-4.18.14/inode.c

@@ -13,6 +13,7 @@
 #include <linux/xattr.h>
 #include <linux/posix_acl.h>
 #include <linux/ratelimit.h>
+#include <linux/version.h>
 #include "overlayfs.h"
 
 
@@ -778,8 +779,12 @@ static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
 static struct inode *ovl_iget5(struct super_block *sb, struct inode *newinode,
 			       struct inode *key)
 {
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 18, 0)
 	return newinode ? inode_insert5(newinode, (unsigned long) key,
 					 ovl_inode_test, ovl_inode_set, key) :
+#else
+	return
+#endif
 			  iget5_locked(sb, (unsigned long) key,
 				       ovl_inode_test, ovl_inode_set, key);
 }

executer/kernel/mcoverlayfs/linux-4.18.14/namei.c

@@ -15,6 +15,8 @@
 #include <linux/ratelimit.h>
 #include <linux/mount.h>
 #include <linux/exportfs.h>
+#include <linux/version.h>
+#include <linux/kallsyms.h>
 #include "overlayfs.h"
 
 struct ovl_lookup_data {
@@ -94,6 +96,10 @@ invalid:
 
 static int ovl_acceptable(void *ctx, struct dentry *dentry)
 {
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 16, 0)
+	static bool (*is_subdir)(struct dentry *new_dentry, struct dentry *old_dentry);
+#endif
+
 	/*
 	 * A non-dir origin may be disconnected, which is fine, because
 	 * we only need it for its unique inode number.
@@ -105,6 +111,13 @@ static int ovl_acceptable(void *ctx, struct dentry *dentry)
 	if (d_unhashed(dentry))
 		return 0;
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 16, 0)
+	if (!is_subdir) {
+		is_subdir = (void *)kallsyms_lookup_name("is_subdir");
+		WARN_ON(!is_subdir);
+	}
+#endif
+
 	/* Check if directory belongs to the layer we are decoding from */
 	return is_subdir(dentry, ((struct vfsmount *)ctx)->mnt_root);
 }

executer/kernel/mcoverlayfs/linux-4.18.14/super.c

@@ -18,6 +18,7 @@
 #include <linux/seq_file.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/exportfs.h>
+#include <linux/version.h>
 #include "overlayfs.h"
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -726,7 +727,11 @@ static int ovl_mount_dir_noesc(const char *name, struct path *path)
 	return 0;
 
 out_put:
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 15, 0)
 	path_put_init(path);
+#else
+	path_put(path);
+#endif
 out:
 	return err;
 }
@@ -744,7 +749,11 @@ static int ovl_mount_dir(const char *name, struct path *path)
 			if (ovl_dentry_remote(path->dentry)) {
 				pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
 				       tmp);
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 15, 0)
 				path_put_init(path);
+#else
+				path_put(path);
+#endif
 				err = -EINVAL;
 			}
 		kfree(tmp);
@@ -805,7 +814,11 @@ static int ovl_lower_dir(const char *name, struct path *path,
 	return 0;
 
 out_put:
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 15, 0)
 	path_put_init(path);
+#else
+	path_put(path);
+#endif
 out:
 	return err;
 }