v4.19.13 snapshot.
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
new file mode 100644
index 0000000..0d30374
--- /dev/null
+++ b/include/linux/exportfs.h
@@ -0,0 +1,231 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_EXPORTFS_H
+#define LINUX_EXPORTFS_H 1
+
+#include <linux/types.h>
+
+struct dentry;
+struct iattr;
+struct inode;
+struct iomap;
+struct super_block;
+struct vfsmount;
+
+/* limit the handle size to NFSv4 handle size now */
+#define MAX_HANDLE_SZ 128
+
+/*
+ * The fileid_type identifies how the file within the filesystem is encoded.
+ * In theory this is freely set and parsed by the filesystem, but we try to
+ * stick to conventions so we can share some generic code and don't confuse
+ * sniffers like ethereal/wireshark.
+ *
+ * The filesystem must not use the value '0' or '0xff'.
+ */
+enum fid_type {
+ /*
+ * The root, or export point, of the filesystem.
+ * (Never actually passed down to the filesystem.
+ */
+ FILEID_ROOT = 0,
+
+ /*
+ * 32bit inode number, 32 bit generation number.
+ */
+ FILEID_INO32_GEN = 1,
+
+ /*
+ * 32bit inode number, 32 bit generation number,
+ * 32 bit parent directory inode number.
+ */
+ FILEID_INO32_GEN_PARENT = 2,
+
+ /*
+ * 64 bit object ID, 64 bit root object ID,
+ * 32 bit generation number.
+ */
+ FILEID_BTRFS_WITHOUT_PARENT = 0x4d,
+
+ /*
+ * 64 bit object ID, 64 bit root object ID,
+ * 32 bit generation number,
+ * 64 bit parent object ID, 32 bit parent generation.
+ */
+ FILEID_BTRFS_WITH_PARENT = 0x4e,
+
+ /*
+ * 64 bit object ID, 64 bit root object ID,
+ * 32 bit generation number,
+ * 64 bit parent object ID, 32 bit parent generation,
+ * 64 bit parent root object ID.
+ */
+ FILEID_BTRFS_WITH_PARENT_ROOT = 0x4f,
+
+ /*
+ * 32 bit block number, 16 bit partition reference,
+ * 16 bit unused, 32 bit generation number.
+ */
+ FILEID_UDF_WITHOUT_PARENT = 0x51,
+
+ /*
+ * 32 bit block number, 16 bit partition reference,
+ * 16 bit unused, 32 bit generation number,
+ * 32 bit parent block number, 32 bit parent generation number
+ */
+ FILEID_UDF_WITH_PARENT = 0x52,
+
+ /*
+ * 64 bit checkpoint number, 64 bit inode number,
+ * 32 bit generation number.
+ */
+ FILEID_NILFS_WITHOUT_PARENT = 0x61,
+
+ /*
+ * 64 bit checkpoint number, 64 bit inode number,
+ * 32 bit generation number, 32 bit parent generation.
+ * 64 bit parent inode number.
+ */
+ FILEID_NILFS_WITH_PARENT = 0x62,
+
+ /*
+ * 32 bit generation number, 40 bit i_pos.
+ */
+ FILEID_FAT_WITHOUT_PARENT = 0x71,
+
+ /*
+ * 32 bit generation number, 40 bit i_pos,
+ * 32 bit parent generation number, 40 bit parent i_pos
+ */
+ FILEID_FAT_WITH_PARENT = 0x72,
+
+ /*
+ * 128 bit child FID (struct lu_fid)
+ * 128 bit parent FID (struct lu_fid)
+ */
+ FILEID_LUSTRE = 0x97,
+
+ /*
+ * Filesystems must not use 0xff file ID.
+ */
+ FILEID_INVALID = 0xff,
+};
+
+struct fid {
+ union {
+ struct {
+ u32 ino;
+ u32 gen;
+ u32 parent_ino;
+ u32 parent_gen;
+ } i32;
+ struct {
+ u32 block;
+ u16 partref;
+ u16 parent_partref;
+ u32 generation;
+ u32 parent_block;
+ u32 parent_generation;
+ } udf;
+ __u32 raw[0];
+ };
+};
+
+/**
+ * struct export_operations - for nfsd to communicate with file systems
+ * @encode_fh: encode a file handle fragment from a dentry
+ * @fh_to_dentry: find the implied object and get a dentry for it
+ * @fh_to_parent: find the implied object's parent and get a dentry for it
+ * @get_name: find the name for a given inode in a given directory
+ * @get_parent: find the parent of a given directory
+ * @commit_metadata: commit metadata changes to stable storage
+ *
+ * See Documentation/filesystems/nfs/Exporting for details on how to use
+ * this interface correctly.
+ *
+ * encode_fh:
+ * @encode_fh should store in the file handle fragment @fh (using at most
+ * @max_len bytes) information that can be used by @decode_fh to recover the
+ * file referred to by the &struct dentry @de. If the @connectable flag is
+ * set, the encode_fh() should store sufficient information so that a good
+ * attempt can be made to find not only the file but also it's place in the
+ * filesystem. This typically means storing a reference to de->d_parent in
+ * the filehandle fragment. encode_fh() should return the fileid_type on
+ * success and on error returns 255 (if the space needed to encode fh is
+ * greater than @max_len*4 bytes). On error @max_len contains the minimum
+ * size(in 4 byte unit) needed to encode the file handle.
+ *
+ * fh_to_dentry:
+ * @fh_to_dentry is given a &struct super_block (@sb) and a file handle
+ * fragment (@fh, @fh_len). It should return a &struct dentry which refers
+ * to the same file that the file handle fragment refers to. If it cannot,
+ * it should return a %NULL pointer if the file cannot be found, or an
+ * %ERR_PTR error code of %ENOMEM if a memory allocation failure occurred.
+ * Any other error code is treated like %NULL, and will cause an %ESTALE error
+ * for callers of exportfs_decode_fh().
+ * Any suitable dentry can be returned including, if necessary, a new dentry
+ * created with d_alloc_root. The caller can then find any other extant
+ * dentries by following the d_alias links.
+ *
+ * fh_to_parent:
+ * Same as @fh_to_dentry, except that it returns a pointer to the parent
+ * dentry if it was encoded into the filehandle fragment by @encode_fh.
+ *
+ * get_name:
+ * @get_name should find a name for the given @child in the given @parent
+ * directory. The name should be stored in the @name (with the
+ * understanding that it is already pointing to a a %NAME_MAX+1 sized
+ * buffer. get_name() should return %0 on success, a negative error code
+ * or error. @get_name will be called without @parent->i_mutex held.
+ *
+ * get_parent:
+ * @get_parent should find the parent directory for the given @child which
+ * is also a directory. In the event that it cannot be found, or storage
+ * space cannot be allocated, a %ERR_PTR should be returned.
+ *
+ * commit_metadata:
+ * @commit_metadata should commit metadata changes to stable storage.
+ *
+ * Locking rules:
+ * get_parent is called with child->d_inode->i_mutex down
+ * get_name is not (which is possibly inconsistent)
+ */
+
+struct export_operations {
+ int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
+ struct inode *parent);
+ struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type);
+ struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type);
+ int (*get_name)(struct dentry *parent, char *name,
+ struct dentry *child);
+ struct dentry * (*get_parent)(struct dentry *child);
+ int (*commit_metadata)(struct inode *inode);
+
+ int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
+ int (*map_blocks)(struct inode *inode, loff_t offset,
+ u64 len, struct iomap *iomap,
+ bool write, u32 *device_generation);
+ int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
+ int nr_iomaps, struct iattr *iattr);
+};
+
+extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
+ int *max_len, struct inode *parent);
+extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
+ int *max_len, int connectable);
+extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
+ int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
+ void *context);
+
+/*
+ * Generic helpers for filesystems.
+ */
+extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
+ struct fid *fid, int fh_len, int fh_type,
+ struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
+extern struct dentry *generic_fh_to_parent(struct super_block *sb,
+ struct fid *fid, int fh_len, int fh_type,
+ struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
+
+#endif /* LINUX_EXPORTFS_H */