include/linux/exportfs.h

Source file repositories/reference/linux-study-clean/include/linux/exportfs.h

File Facts

System
Linux kernel
Corpus path
include/linux/exportfs.h
Extension
.h
Size
12791 bytes
Lines
399
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct fid {
	union {
		struct {
			u32 ino;
			u32 gen;
			u32 parent_ino;
			u32 parent_gen;
		} i32;
		struct {
			u64 ino;
			u32 gen;
		} __packed i64;
		struct {
 			u32 block;
 			u16 partref;
 			u16 parent_partref;
 			u32 generation;
 			u32 parent_block;
 			u32 parent_generation;
 		} udf;
		DECLARE_FLEX_ARRAY(__u32, raw);
	};
};

enum handle_to_path_flags {
	HANDLE_CHECK_PERMS   = (1 << 0),
	HANDLE_CHECK_SUBTREE = (1 << 1),
};

struct handle_to_path_ctx {
	struct path root;
	enum handle_to_path_flags flags;
	unsigned int fh_flags;
};

#define EXPORT_FH_CONNECTABLE	0x1 /* Encode file handle with parent */
#define EXPORT_FH_FID		0x2 /* File handle may be non-decodeable */
#define EXPORT_FH_DIR_ONLY	0x4 /* Only decode file handle for a directory */

/*
 * Filesystems use only lower 8 bits of file_handle type for fid_type.
 * name_to_handle_at() uses upper 16 bits of type as user flags to be
 * interpreted by open_by_handle_at().
 */
#define FILEID_USER_FLAGS_MASK	0xffff0000
#define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK)

/* Flags supported in encoded handle_type that is exported to user */
#define FILEID_IS_CONNECTABLE	0x10000
#define FILEID_IS_DIR		0x20000
#define FILEID_VALID_USER_FLAGS	(FILEID_IS_CONNECTABLE | FILEID_IS_DIR)

/**
 * 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
 *
 * Methods for open_by_handle(2) syscall with special kernel file systems:
 * @permission:     custom permission for opening a file by handle
 * @open:           custom open routine for opening file by handle
 *
 * See Documentation/filesystems/nfs/exporting.rst for details on how to use
 * this interface correctly and the definition of the flags.
 *
 * @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 @flag has CONNECTABLE bit
 *    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

Annotation

Implementation Notes