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qemu/tools/virtiofsd/fuse_lowlevel.h

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/*
* FUSE: Filesystem in Userspace
* Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
*
* This program can be distributed under the terms of the GNU LGPLv2.
* See the file COPYING.LIB.
*/
#ifndef FUSE_LOWLEVEL_H_
#define FUSE_LOWLEVEL_H_
/**
* @file
*
* Low level API
*
* IMPORTANT: you should define FUSE_USE_VERSION before including this
* header. To use the newest API define it to 31 (recommended for any
* new application).
*/
#ifndef FUSE_USE_VERSION
#error FUSE_USE_VERSION not defined
#endif
#include "fuse_common.h"
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <utime.h>
/*
* Miscellaneous definitions
*/
/** The node ID of the root inode */
#define FUSE_ROOT_ID 1
/** Inode number type */
typedef uint64_t fuse_ino_t;
/** Request pointer type */
typedef struct fuse_req *fuse_req_t;
/**
* Session
*
* This provides hooks for processing requests, and exiting
*/
struct fuse_session;
/** Directory entry parameters supplied to fuse_reply_entry() */
struct fuse_entry_param {
/**
* Unique inode number
*
* In lookup, zero means negative entry (from version 2.5)
* Returning ENOENT also means negative entry, but by setting zero
* ino the kernel may cache negative entries for entry_timeout
* seconds.
*/
fuse_ino_t ino;
/**
* Generation number for this entry.
*
* If the file system will be exported over NFS, the
* ino/generation pairs need to be unique over the file
* system's lifetime (rather than just the mount time). So if
* the file system reuses an inode after it has been deleted,
* it must assign a new, previously unused generation number
* to the inode at the same time.
*
*/
uint64_t generation;
/**
* Inode attributes.
*
* Even if attr_timeout == 0, attr must be correct. For example,
* for open(), FUSE uses attr.st_size from lookup() to determine
* how many bytes to request. If this value is not correct,
* incorrect data will be returned.
*/
struct stat attr;
/**
* Validity timeout (in seconds) for inode attributes. If
* attributes only change as a result of requests that come
* through the kernel, this should be set to a very large
* value.
*/
double attr_timeout;
/**
* Validity timeout (in seconds) for the name. If directory
* entries are changed/deleted only as a result of requests
* that come through the kernel, this should be set to a very
* large value.
*/
double entry_timeout;
};
/**
* Additional context associated with requests.
*
* Note that the reported client uid, gid and pid may be zero in some
* situations. For example, if the FUSE file system is running in a
* PID or user namespace but then accessed from outside the namespace,
* there is no valid uid/pid/gid that could be reported.
*/
struct fuse_ctx {
/** User ID of the calling process */
uid_t uid;
/** Group ID of the calling process */
gid_t gid;
/** Thread ID of the calling process */
pid_t pid;
/** Umask of the calling process */
mode_t umask;
};
struct fuse_forget_data {
fuse_ino_t ino;
uint64_t nlookup;
};
/* 'to_set' flags in setattr */
#define FUSE_SET_ATTR_MODE (1 << 0)
#define FUSE_SET_ATTR_UID (1 << 1)
#define FUSE_SET_ATTR_GID (1 << 2)
#define FUSE_SET_ATTR_SIZE (1 << 3)
#define FUSE_SET_ATTR_ATIME (1 << 4)
#define FUSE_SET_ATTR_MTIME (1 << 5)
#define FUSE_SET_ATTR_ATIME_NOW (1 << 7)
#define FUSE_SET_ATTR_MTIME_NOW (1 << 8)
#define FUSE_SET_ATTR_CTIME (1 << 10)
/*
* Request methods and replies
*/
/**
* Low level filesystem operations
*
* Most of the methods (with the exception of init and destroy)
* receive a request handle (fuse_req_t) as their first argument.
* This handle must be passed to one of the specified reply functions.
*
* This may be done inside the method invocation, or after the call
* has returned. The request handle is valid until one of the reply
* functions is called.
*
* Other pointer arguments (name, fuse_file_info, etc) are not valid
* after the call has returned, so if they are needed later, their
* contents have to be copied.
*
* In general, all methods are expected to perform any necessary
* permission checking. However, a filesystem may delegate this task
* to the kernel by passing the `default_permissions` mount option to
* `fuse_session_new()`. In this case, methods will only be called if
* the kernel's permission check has succeeded.
*
* The filesystem sometimes needs to handle a return value of -ENOENT
* from the reply function, which means, that the request was
* interrupted, and the reply discarded. For example if
* fuse_reply_open() return -ENOENT means, that the release method for
* this file will not be called.
*/
struct fuse_lowlevel_ops {
/**
* Initialize filesystem
*
* This function is called when libfuse establishes
* communication with the FUSE kernel module. The file system
* should use this module to inspect and/or modify the
* connection parameters provided in the `conn` structure.
*
* Note that some parameters may be overwritten by options
* passed to fuse_session_new() which take precedence over the
* values set in this handler.
*
* There's no reply to this function
*
* @param userdata the user data passed to fuse_session_new()
*/
void (*init)(void *userdata, struct fuse_conn_info *conn);
/**
* Clean up filesystem.
*
* Called on filesystem exit. When this method is called, the
* connection to the kernel may be gone already, so that eg. calls
* to fuse_lowlevel_notify_* will fail.
*
* There's no reply to this function
*
* @param userdata the user data passed to fuse_session_new()
*/
void (*destroy)(void *userdata);
/**
* Look up a directory entry by name and get its attributes.
*
* Valid replies:
* fuse_reply_entry
* fuse_reply_err
*
* @param req request handle
* @param parent inode number of the parent directory
* @param name the name to look up
*/
void (*lookup)(fuse_req_t req, fuse_ino_t parent, const char *name);
/**
* Forget about an inode
*
* This function is called when the kernel removes an inode
* from its internal caches.
*
* The inode's lookup count increases by one for every call to
* fuse_reply_entry and fuse_reply_create. The nlookup parameter
* indicates by how much the lookup count should be decreased.
*
* Inodes with a non-zero lookup count may receive request from
* the kernel even after calls to unlink, rmdir or (when
* overwriting an existing file) rename. Filesystems must handle
* such requests properly and it is recommended to defer removal
* of the inode until the lookup count reaches zero. Calls to
* unlink, rmdir or rename will be followed closely by forget
* unless the file or directory is open, in which case the
* kernel issues forget only after the release or releasedir
* calls.
*
* Note that if a file system will be exported over NFS the
* inodes lifetime must extend even beyond forget. See the
* generation field in struct fuse_entry_param above.
*
* On unmount the lookup count for all inodes implicitly drops
* to zero. It is not guaranteed that the file system will
* receive corresponding forget messages for the affected
* inodes.
*
* Valid replies:
* fuse_reply_none
*
* @param req request handle
* @param ino the inode number
* @param nlookup the number of lookups to forget
*/
void (*forget)(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup);
/**
* Get file attributes.
*
* If writeback caching is enabled, the kernel may have a
* better idea of a file's length than the FUSE file system
* (eg if there has been a write that extended the file size,
* but that has not yet been passed to the filesystem.n
*
* In this case, the st_size value provided by the file system
* will be ignored.
*
* Valid replies:
* fuse_reply_attr
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi for future use, currently always NULL
*/
void (*getattr)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);
/**
* Set file attributes
*
* In the 'attr' argument only members indicated by the 'to_set'
* bitmask contain valid values. Other members contain undefined
* values.
*
* Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is
* expected to reset the setuid and setgid bits if the file
* size or owner is being changed.
*
* If the setattr was invoked from the ftruncate() system call
* under Linux kernel versions 2.6.15 or later, the fi->fh will
* contain the value set by the open method or will be undefined
* if the open method didn't set any value. Otherwise (not
* ftruncate call, or kernel version earlier than 2.6.15) the fi
* parameter will be NULL.
*
* Valid replies:
* fuse_reply_attr
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param attr the attributes
* @param to_set bit mask of attributes which should be set
* @param fi file information, or NULL
*/
void (*setattr)(fuse_req_t req, fuse_ino_t ino, struct stat *attr,
int to_set, struct fuse_file_info *fi);
/**
* Read symbolic link
*
* Valid replies:
* fuse_reply_readlink
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
*/
void (*readlink)(fuse_req_t req, fuse_ino_t ino);
/**
* Create file node
*
* Create a regular file, character device, block device, fifo or
* socket node.
*
* Valid replies:
* fuse_reply_entry
* fuse_reply_err
*
* @param req request handle
* @param parent inode number of the parent directory
* @param name to create
* @param mode file type and mode with which to create the new file
* @param rdev the device number (only valid if created file is a device)
*/
void (*mknod)(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode, dev_t rdev);
/**
* Create a directory
*
* Valid replies:
* fuse_reply_entry
* fuse_reply_err
*
* @param req request handle
* @param parent inode number of the parent directory
* @param name to create
* @param mode with which to create the new file
*/
void (*mkdir)(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode);
/**
* Remove a file
*
* If the file's inode's lookup count is non-zero, the file
* system is expected to postpone any removal of the inode
* until the lookup count reaches zero (see description of the
* forget function).
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param parent inode number of the parent directory
* @param name to remove
*/
void (*unlink)(fuse_req_t req, fuse_ino_t parent, const char *name);
/**
* Remove a directory
*
* If the directory's inode's lookup count is non-zero, the
* file system is expected to postpone any removal of the
* inode until the lookup count reaches zero (see description
* of the forget function).
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param parent inode number of the parent directory
* @param name to remove
*/
void (*rmdir)(fuse_req_t req, fuse_ino_t parent, const char *name);
/**
* Create a symbolic link
*
* Valid replies:
* fuse_reply_entry
* fuse_reply_err
*
* @param req request handle
* @param link the contents of the symbolic link
* @param parent inode number of the parent directory
* @param name to create
*/
void (*symlink)(fuse_req_t req, const char *link, fuse_ino_t parent,
const char *name);
/**
* Rename a file
*
* If the target exists it should be atomically replaced. If
* the target's inode's lookup count is non-zero, the file
* system is expected to postpone any removal of the inode
* until the lookup count reaches zero (see description of the
* forget function).
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure with error code EINVAL, i.e. all
* future bmap requests will fail with EINVAL without being
* send to the filesystem process.
*
* *flags* may be `RENAME_EXCHANGE` or `RENAME_NOREPLACE`. If
* RENAME_NOREPLACE is specified, the filesystem must not
* overwrite *newname* if it exists and return an error
* instead. If `RENAME_EXCHANGE` is specified, the filesystem
* must atomically exchange the two files, i.e. both must
* exist and neither may be deleted.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param parent inode number of the old parent directory
* @param name old name
* @param newparent inode number of the new parent directory
* @param newname new name
*/
void (*rename)(fuse_req_t req, fuse_ino_t parent, const char *name,
fuse_ino_t newparent, const char *newname,
unsigned int flags);
/**
* Create a hard link
*
* Valid replies:
* fuse_reply_entry
* fuse_reply_err
*
* @param req request handle
* @param ino the old inode number
* @param newparent inode number of the new parent directory
* @param newname new name to create
*/
void (*link)(fuse_req_t req, fuse_ino_t ino, fuse_ino_t newparent,
const char *newname);
/**
* Open a file
*
* Open flags are available in fi->flags. The following rules
* apply.
*
* - Creation (O_CREAT, O_EXCL, O_NOCTTY) flags will be
* filtered out / handled by the kernel.
*
* - Access modes (O_RDONLY, O_WRONLY, O_RDWR) should be used
* by the filesystem to check if the operation is
* permitted. If the ``-o default_permissions`` mount
* option is given, this check is already done by the
* kernel before calling open() and may thus be omitted by
* the filesystem.
*
* - When writeback caching is enabled, the kernel may send
* read requests even for files opened with O_WRONLY. The
* filesystem should be prepared to handle this.
*
* - When writeback caching is disabled, the filesystem is
* expected to properly handle the O_APPEND flag and ensure
* that each write is appending to the end of the file.
*
* - When writeback caching is enabled, the kernel will
* handle O_APPEND. However, unless all changes to the file
* come through the kernel this will not work reliably. The
* filesystem should thus either ignore the O_APPEND flag
* (and let the kernel handle it), or return an error
* (indicating that reliably O_APPEND is not available).
*
* Filesystem may store an arbitrary file handle (pointer,
* index, etc) in fi->fh, and use this in other all other file
* operations (read, write, flush, release, fsync).
*
* Filesystem may also implement stateless file I/O and not store
* anything in fi->fh.
*
* There are also some flags (direct_io, keep_cache) which the
* filesystem may set in fi, to change the way the file is opened.
* See fuse_file_info structure in <fuse_common.h> for more details.
*
* If this request is answered with an error code of ENOSYS
* and FUSE_CAP_NO_OPEN_SUPPORT is set in
* `fuse_conn_info.capable`, this is treated as success and
* future calls to open and release will also succeed without being
* sent to the filesystem process.
*
* Valid replies:
* fuse_reply_open
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
*/
void (*open)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);
/**
* Read data
*
* Read should send exactly the number of bytes requested except
* on EOF or error, otherwise the rest of the data will be
* substituted with zeroes. An exception to this is when the file
* has been opened in 'direct_io' mode, in which case the return
* value of the read system call will reflect the return value of
* this operation.
*
* fi->fh will contain the value set by the open method, or will
* be undefined if the open method didn't set any value.
*
* Valid replies:
* fuse_reply_buf
* fuse_reply_iov
* fuse_reply_data
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param size number of bytes to read
* @param off offset to read from
* @param fi file information
*/
void (*read)(fuse_req_t req, fuse_ino_t ino, size_t size, off_t off,
struct fuse_file_info *fi);
/**
* Write data
*
* Write should return exactly the number of bytes requested
* except on error. An exception to this is when the file has
* been opened in 'direct_io' mode, in which case the return value
* of the write system call will reflect the return value of this
* operation.
*
* Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is
* expected to reset the setuid and setgid bits.
*
* fi->fh will contain the value set by the open method, or will
* be undefined if the open method didn't set any value.
*
* Valid replies:
* fuse_reply_write
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param buf data to write
* @param size number of bytes to write
* @param off offset to write to
* @param fi file information
*/
void (*write)(fuse_req_t req, fuse_ino_t ino, const char *buf, size_t size,
off_t off, struct fuse_file_info *fi);
/**
* Flush method
*
* This is called on each close() of the opened file.
*
* Since file descriptors can be duplicated (dup, dup2, fork), for
* one open call there may be many flush calls.
*
* Filesystems shouldn't assume that flush will always be called
* after some writes, or that if will be called at all.
*
* fi->fh will contain the value set by the open method, or will
* be undefined if the open method didn't set any value.
*
* NOTE: the name of the method is misleading, since (unlike
* fsync) the filesystem is not forced to flush pending writes.
* One reason to flush data is if the filesystem wants to return
* write errors during close. However, such use is non-portable
* because POSIX does not require [close] to wait for delayed I/O to
* complete.
*
* If the filesystem supports file locking operations (setlk,
* getlk) it should remove all locks belonging to 'fi->owner'.
*
* If this request is answered with an error code of ENOSYS,
* this is treated as success and future calls to flush() will
* succeed automatically without being send to the filesystem
* process.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
*
* [close]:
* http://pubs.opengroup.org/onlinepubs/9699919799/functions/close.html
*/
void (*flush)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);
/**
* Release an open file
*
* Release is called when there are no more references to an open
* file: all file descriptors are closed and all memory mappings
* are unmapped.
*
* For every open call there will be exactly one release call (unless
* the filesystem is force-unmounted).
*
* The filesystem may reply with an error, but error values are
* not returned to close() or munmap() which triggered the
* release.
*
* fi->fh will contain the value set by the open method, or will
* be undefined if the open method didn't set any value.
* fi->flags will contain the same flags as for open.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
*/
void (*release)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);
/**
* Synchronize file contents
*
* If the datasync parameter is non-zero, then only the user data
* should be flushed, not the meta data.
*
* If this request is answered with an error code of ENOSYS,
* this is treated as success and future calls to fsync() will
* succeed automatically without being send to the filesystem
* process.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param datasync flag indicating if only data should be flushed
* @param fi file information
*/
void (*fsync)(fuse_req_t req, fuse_ino_t ino, int datasync,
struct fuse_file_info *fi);
/**
* Open a directory
*
* Filesystem may store an arbitrary file handle (pointer, index,
* etc) in fi->fh, and use this in other all other directory
* stream operations (readdir, releasedir, fsyncdir).
*
* If this request is answered with an error code of ENOSYS and
* FUSE_CAP_NO_OPENDIR_SUPPORT is set in `fuse_conn_info.capable`,
* this is treated as success and future calls to opendir and
* releasedir will also succeed without being sent to the filesystem
* process. In addition, the kernel will cache readdir results
* as if opendir returned FOPEN_KEEP_CACHE | FOPEN_CACHE_DIR.
*
* Valid replies:
* fuse_reply_open
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
*/
void (*opendir)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi);
/**
* Read directory
*
* Send a buffer filled using fuse_add_direntry(), with size not
* exceeding the requested size. Send an empty buffer on end of
* stream.
*
* fi->fh will contain the value set by the opendir method, or
* will be undefined if the opendir method didn't set any value.
*
* Returning a directory entry from readdir() does not affect
* its lookup count.
*
* If off_t is non-zero, then it will correspond to one of the off_t
* values that was previously returned by readdir() for the same
* directory handle. In this case, readdir() should skip over entries
* coming before the position defined by the off_t value. If entries
* are added or removed while the directory handle is open, they filesystem
* may still include the entries that have been removed, and may not
* report the entries that have been created. However, addition or
* removal of entries must never cause readdir() to skip over unrelated
* entries or to report them more than once. This means
* that off_t can not be a simple index that enumerates the entries
* that have been returned but must contain sufficient information to
* uniquely determine the next directory entry to return even when the
* set of entries is changing.
*
* The function does not have to report the '.' and '..'
* entries, but is allowed to do so. Note that, if readdir does
* not return '.' or '..', they will not be implicitly returned,
* and this behavior is observable by the caller.
*
* Valid replies:
* fuse_reply_buf
* fuse_reply_data
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param size maximum number of bytes to send
* @param off offset to continue reading the directory stream
* @param fi file information
*/
void (*readdir)(fuse_req_t req, fuse_ino_t ino, size_t size, off_t off,
struct fuse_file_info *fi);
/**
* Release an open directory
*
* For every opendir call there will be exactly one releasedir
* call (unless the filesystem is force-unmounted).
*
* fi->fh will contain the value set by the opendir method, or
* will be undefined if the opendir method didn't set any value.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
*/
void (*releasedir)(fuse_req_t req, fuse_ino_t ino,
struct fuse_file_info *fi);
/**
* Synchronize directory contents
*
* If the datasync parameter is non-zero, then only the directory
* contents should be flushed, not the meta data.
*
* fi->fh will contain the value set by the opendir method, or
* will be undefined if the opendir method didn't set any value.
*
* If this request is answered with an error code of ENOSYS,
* this is treated as success and future calls to fsyncdir() will
* succeed automatically without being send to the filesystem
* process.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param datasync flag indicating if only data should be flushed
* @param fi file information
*/
void (*fsyncdir)(fuse_req_t req, fuse_ino_t ino, int datasync,
struct fuse_file_info *fi);
/**
* Get file system statistics
*
* Valid replies:
* fuse_reply_statfs
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number, zero means "undefined"
*/
void (*statfs)(fuse_req_t req, fuse_ino_t ino);
/**
* Set an extended attribute
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure with error code EOPNOTSUPP, i.e. all
* future setxattr() requests will fail with EOPNOTSUPP without being
* send to the filesystem process.
*
* Valid replies:
* fuse_reply_err
*/
void (*setxattr)(fuse_req_t req, fuse_ino_t ino, const char *name,
const char *value, size_t size, int flags);
/**
* Get an extended attribute
*
* If size is zero, the size of the value should be sent with
* fuse_reply_xattr.
*
* If the size is non-zero, and the value fits in the buffer, the
* value should be sent with fuse_reply_buf.
*
* If the size is too small for the value, the ERANGE error should
* be sent.
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure with error code EOPNOTSUPP, i.e. all
* future getxattr() requests will fail with EOPNOTSUPP without being
* send to the filesystem process.
*
* Valid replies:
* fuse_reply_buf
* fuse_reply_data
* fuse_reply_xattr
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param name of the extended attribute
* @param size maximum size of the value to send
*/
void (*getxattr)(fuse_req_t req, fuse_ino_t ino, const char *name,
size_t size);
/**
* List extended attribute names
*
* If size is zero, the total size of the attribute list should be
* sent with fuse_reply_xattr.
*
* If the size is non-zero, and the null character separated
* attribute list fits in the buffer, the list should be sent with
* fuse_reply_buf.
*
* If the size is too small for the list, the ERANGE error should
* be sent.
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure with error code EOPNOTSUPP, i.e. all
* future listxattr() requests will fail with EOPNOTSUPP without being
* send to the filesystem process.
*
* Valid replies:
* fuse_reply_buf
* fuse_reply_data
* fuse_reply_xattr
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param size maximum size of the list to send
*/
void (*listxattr)(fuse_req_t req, fuse_ino_t ino, size_t size);
/**
* Remove an extended attribute
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure with error code EOPNOTSUPP, i.e. all
* future removexattr() requests will fail with EOPNOTSUPP without being
* send to the filesystem process.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param name of the extended attribute
*/
void (*removexattr)(fuse_req_t req, fuse_ino_t ino, const char *name);
/**
* Check file access permissions
*
* This will be called for the access() and chdir() system
* calls. If the 'default_permissions' mount option is given,
* this method is not called.
*
* This method is not called under Linux kernel versions 2.4.x
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent success, i.e. this and all future access()
* requests will succeed without being send to the filesystem process.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param mask requested access mode
*/
void (*access)(fuse_req_t req, fuse_ino_t ino, int mask);
/**
* Create and open a file
*
* If the file does not exist, first create it with the specified
* mode, and then open it.
*
* See the description of the open handler for more
* information.
*
* If this method is not implemented or under Linux kernel
* versions earlier than 2.6.15, the mknod() and open() methods
* will be called instead.
*
* If this request is answered with an error code of ENOSYS, the handler
* is treated as not implemented (i.e., for this and future requests the
* mknod() and open() handlers will be called instead).
*
* Valid replies:
* fuse_reply_create
* fuse_reply_err
*
* @param req request handle
* @param parent inode number of the parent directory
* @param name to create
* @param mode file type and mode with which to create the new file
* @param fi file information
*/
void (*create)(fuse_req_t req, fuse_ino_t parent, const char *name,
mode_t mode, struct fuse_file_info *fi);
/**
* Test for a POSIX file lock
*
* Valid replies:
* fuse_reply_lock
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
* @param lock the region/type to test
*/
void (*getlk)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
struct flock *lock);
/**
* Acquire, modify or release a POSIX file lock
*
* For POSIX threads (NPTL) there's a 1-1 relation between pid and
* owner, but otherwise this is not always the case. For checking
* lock ownership, 'fi->owner' must be used. The l_pid field in
* 'struct flock' should only be used to fill in this field in
* getlk().
*
* Note: if the locking methods are not implemented, the kernel
* will still allow file locking to work locally. Hence these are
* only interesting for network filesystems and similar.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
* @param lock the region/type to set
* @param sleep locking operation may sleep
*/
void (*setlk)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
struct flock *lock, int sleep);
/**
* Map block index within file to block index within device
*
* Note: This makes sense only for block device backed filesystems
* mounted with the 'blkdev' option
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure, i.e. all future bmap() requests will
* fail with the same error code without being send to the filesystem
* process.
*
* Valid replies:
* fuse_reply_bmap
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param blocksize unit of block index
* @param idx block index within file
*/
void (*bmap)(fuse_req_t req, fuse_ino_t ino, size_t blocksize,
uint64_t idx);
/**
* Ioctl
*
* Note: For unrestricted ioctls (not allowed for FUSE
* servers), data in and out areas can be discovered by giving
* iovs and setting FUSE_IOCTL_RETRY in *flags*. For
* restricted ioctls, kernel prepares in/out data area
* according to the information encoded in cmd.
*
* Valid replies:
* fuse_reply_ioctl_retry
* fuse_reply_ioctl
* fuse_reply_ioctl_iov
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param cmd ioctl command
* @param arg ioctl argument
* @param fi file information
* @param flags for FUSE_IOCTL_* flags
* @param in_buf data fetched from the caller
* @param in_bufsz number of fetched bytes
* @param out_bufsz maximum size of output data
*
* Note : the unsigned long request submitted by the application
* is truncated to 32 bits.
*/
void (*ioctl)(fuse_req_t req, fuse_ino_t ino, unsigned int cmd, void *arg,
struct fuse_file_info *fi, unsigned flags, const void *in_buf,
size_t in_bufsz, size_t out_bufsz);
/**
* Poll for IO readiness
*
* Note: If ph is non-NULL, the client should notify
* when IO readiness events occur by calling
* fuse_lowlevel_notify_poll() with the specified ph.
*
* Regardless of the number of times poll with a non-NULL ph
* is received, single notification is enough to clear all.
* Notifying more times incurs overhead but doesn't harm
* correctness.
*
* The callee is responsible for destroying ph with
* fuse_pollhandle_destroy() when no longer in use.
*
* If this request is answered with an error code of ENOSYS, this is
* treated as success (with a kernel-defined default poll-mask) and
* future calls to pull() will succeed the same way without being send
* to the filesystem process.
*
* Valid replies:
* fuse_reply_poll
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
* @param ph poll handle to be used for notification
*/
void (*poll)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
struct fuse_pollhandle *ph);
/**
* Write data made available in a buffer
*
* This is a more generic version of the ->write() method. If
* FUSE_CAP_SPLICE_READ is set in fuse_conn_info.want and the
* kernel supports splicing from the fuse device, then the
* data will be made available in pipe for supporting zero
* copy data transfer.
*
* buf->count is guaranteed to be one (and thus buf->idx is
* always zero). The write_buf handler must ensure that
* bufv->off is correctly updated (reflecting the number of
* bytes read from bufv->buf[0]).
*
* Unless FUSE_CAP_HANDLE_KILLPRIV is disabled, this method is
* expected to reset the setuid and setgid bits.
*
* Valid replies:
* fuse_reply_write
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param bufv buffer containing the data
* @param off offset to write to
* @param fi file information
*/
void (*write_buf)(fuse_req_t req, fuse_ino_t ino, struct fuse_bufvec *bufv,
off_t off, struct fuse_file_info *fi);
/**
* Forget about multiple inodes
*
* See description of the forget function for more
* information.
*
* Valid replies:
* fuse_reply_none
*
* @param req request handle
*/
void (*forget_multi)(fuse_req_t req, size_t count,
struct fuse_forget_data *forgets);
/**
* Acquire, modify or release a BSD file lock
*
* Note: if the locking methods are not implemented, the kernel
* will still allow file locking to work locally. Hence these are
* only interesting for network filesystems and similar.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param fi file information
* @param op the locking operation, see flock(2)
*/
void (*flock)(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
int op);
/**
* Allocate requested space. If this function returns success then
* subsequent writes to the specified range shall not fail due to the lack
* of free space on the file system storage media.
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure with error code EOPNOTSUPP, i.e. all
* future fallocate() requests will fail with EOPNOTSUPP without being
* send to the filesystem process.
*
* Valid replies:
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param offset starting point for allocated region
* @param length size of allocated region
* @param mode determines the operation to be performed on the given range,
* see fallocate(2)
*/
void (*fallocate)(fuse_req_t req, fuse_ino_t ino, int mode, off_t offset,
off_t length, struct fuse_file_info *fi);
/**
* Read directory with attributes
*
* Send a buffer filled using fuse_add_direntry_plus(), with size not
* exceeding the requested size. Send an empty buffer on end of
* stream.
*
* fi->fh will contain the value set by the opendir method, or
* will be undefined if the opendir method didn't set any value.
*
* In contrast to readdir() (which does not affect the lookup counts),
* the lookup count of every entry returned by readdirplus(), except "."
* and "..", is incremented by one.
*
* Valid replies:
* fuse_reply_buf
* fuse_reply_data
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param size maximum number of bytes to send
* @param off offset to continue reading the directory stream
* @param fi file information
*/
void (*readdirplus)(fuse_req_t req, fuse_ino_t ino, size_t size, off_t off,
struct fuse_file_info *fi);
/**
* Copy a range of data from one file to another
*
* Performs an optimized copy between two file descriptors without the
* additional cost of transferring data through the FUSE kernel module
* to user space (glibc) and then back into the FUSE filesystem again.
*
* In case this method is not implemented, glibc falls back to reading
* data from the source and writing to the destination. Effectively
* doing an inefficient copy of the data.
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure with error code EOPNOTSUPP, i.e. all
* future copy_file_range() requests will fail with EOPNOTSUPP without
* being send to the filesystem process.
*
* Valid replies:
* fuse_reply_write
* fuse_reply_err
*
* @param req request handle
* @param ino_in the inode number or the source file
* @param off_in starting point from were the data should be read
* @param fi_in file information of the source file
* @param ino_out the inode number or the destination file
* @param off_out starting point where the data should be written
* @param fi_out file information of the destination file
* @param len maximum size of the data to copy
* @param flags passed along with the copy_file_range() syscall
*/
void (*copy_file_range)(fuse_req_t req, fuse_ino_t ino_in, off_t off_in,
struct fuse_file_info *fi_in, fuse_ino_t ino_out,
off_t off_out, struct fuse_file_info *fi_out,
size_t len, int flags);
/**
* Find next data or hole after the specified offset
*
* If this request is answered with an error code of ENOSYS, this is
* treated as a permanent failure, i.e. all future lseek() requests will
* fail with the same error code without being send to the filesystem
* process.
*
* Valid replies:
* fuse_reply_lseek
* fuse_reply_err
*
* @param req request handle
* @param ino the inode number
* @param off offset to start search from
* @param whence either SEEK_DATA or SEEK_HOLE
* @param fi file information
*/
void (*lseek)(fuse_req_t req, fuse_ino_t ino, off_t off, int whence,
struct fuse_file_info *fi);
};
/**
* Reply with an error code or success.
*
* Possible requests:
* all except forget
*
* Whereever possible, error codes should be chosen from the list of
* documented error conditions in the corresponding system calls
* manpage.
*
* An error code of ENOSYS is sometimes treated specially. This is
* indicated in the documentation of the affected handler functions.
*
* The following requests may be answered with a zero error code:
* unlink, rmdir, rename, flush, release, fsync, fsyncdir, setxattr,
* removexattr, setlk.
*
* @param req request handle
* @param err the positive error value, or zero for success
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_err(fuse_req_t req, int err);
/**
* Don't send reply
*
* Possible requests:
* forget
* forget_multi
* retrieve_reply
*
* @param req request handle
*/
void fuse_reply_none(fuse_req_t req);
/**
* Reply with a directory entry
*
* Possible requests:
* lookup, mknod, mkdir, symlink, link
*
* Side effects:
* increments the lookup count on success
*
* @param req request handle
* @param e the entry parameters
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e);
/**
* Reply with a directory entry and open parameters
*
* currently the following members of 'fi' are used:
* fh, direct_io, keep_cache
*
* Possible requests:
* create
*
* Side effects:
* increments the lookup count on success
*
* @param req request handle
* @param e the entry parameters
* @param fi file information
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
const struct fuse_file_info *fi);
/**
* Reply with attributes
*
* Possible requests:
* getattr, setattr
*
* @param req request handle
* @param attr the attributes
* @param attr_timeout validity timeout (in seconds) for the attributes
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_attr(fuse_req_t req, const struct stat *attr,
double attr_timeout);
/**
* Reply with the contents of a symbolic link
*
* Possible requests:
* readlink
*
* @param req request handle
* @param link symbolic link contents
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_readlink(fuse_req_t req, const char *link);
/**
* Reply with open parameters
*
* currently the following members of 'fi' are used:
* fh, direct_io, keep_cache
*
* Possible requests:
* open, opendir
*
* @param req request handle
* @param fi file information
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_open(fuse_req_t req, const struct fuse_file_info *fi);
/**
* Reply with number of bytes written
*
* Possible requests:
* write
*
* @param req request handle
* @param count the number of bytes written
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_write(fuse_req_t req, size_t count);
/**
* Reply with data
*
* Possible requests:
* read, readdir, getxattr, listxattr
*
* @param req request handle
* @param buf buffer containing data
* @param size the size of data in bytes
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_buf(fuse_req_t req, const char *buf, size_t size);
/**
* Reply with data copied/moved from buffer(s)
*
* Possible requests:
* read, readdir, getxattr, listxattr
*
* Side effects:
* when used to return data from a readdirplus() (but not readdir())
* call, increments the lookup count of each returned entry by one
* on success.
*
* @param req request handle
* @param bufv buffer vector
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_data(fuse_req_t req, struct fuse_bufvec *bufv);
/**
* Reply with data vector
*
* Possible requests:
* read, readdir, getxattr, listxattr
*
* @param req request handle
* @param iov the vector containing the data
* @param count the size of vector
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_iov(fuse_req_t req, const struct iovec *iov, int count);
/**
* Reply with filesystem statistics
*
* Possible requests:
* statfs
*
* @param req request handle
* @param stbuf filesystem statistics
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_statfs(fuse_req_t req, const struct statvfs *stbuf);
/**
* Reply with needed buffer size
*
* Possible requests:
* getxattr, listxattr
*
* @param req request handle
* @param count the buffer size needed in bytes
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_xattr(fuse_req_t req, size_t count);
/**
* Reply with file lock information
*
* Possible requests:
* getlk
*
* @param req request handle
* @param lock the lock information
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_lock(fuse_req_t req, const struct flock *lock);
/**
* Reply with block index
*
* Possible requests:
* bmap
*
* @param req request handle
* @param idx block index within device
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_bmap(fuse_req_t req, uint64_t idx);
/*
* Filling a buffer in readdir
*/
/**
* Add a directory entry to the buffer
*
* Buffer needs to be large enough to hold the entry. If it's not,
* then the entry is not filled in but the size of the entry is still
* returned. The caller can check this by comparing the bufsize
* parameter with the returned entry size. If the entry size is
* larger than the buffer size, the operation failed.
*
* From the 'stbuf' argument the st_ino field and bits 12-15 of the
* st_mode field are used. The other fields are ignored.
*
* *off* should be any non-zero value that the filesystem can use to
* identify the current point in the directory stream. It does not
* need to be the actual physical position. A value of zero is
* reserved to mean "from the beginning", and should therefore never
* be used (the first call to fuse_add_direntry should be passed the
* offset of the second directory entry).
*
* @param req request handle
* @param buf the point where the new entry will be added to the buffer
* @param bufsize remaining size of the buffer
* @param name the name of the entry
* @param stbuf the file attributes
* @param off the offset of the next entry
* @return the space needed for the entry
*/
size_t fuse_add_direntry(fuse_req_t req, char *buf, size_t bufsize,
const char *name, const struct stat *stbuf, off_t off);
/**
* Add a directory entry to the buffer with the attributes
*
* See documentation of `fuse_add_direntry()` for more details.
*
* @param req request handle
* @param buf the point where the new entry will be added to the buffer
* @param bufsize remaining size of the buffer
* @param name the name of the entry
* @param e the directory entry
* @param off the offset of the next entry
* @return the space needed for the entry
*/
size_t fuse_add_direntry_plus(fuse_req_t req, char *buf, size_t bufsize,
const char *name,
const struct fuse_entry_param *e, off_t off);
/**
* Reply to ask for data fetch and output buffer preparation. ioctl
* will be retried with the specified input data fetched and output
* buffer prepared.
*
* Possible requests:
* ioctl
*
* @param req request handle
* @param in_iov iovec specifying data to fetch from the caller
* @param in_count number of entries in in_iov
* @param out_iov iovec specifying addresses to write output to
* @param out_count number of entries in out_iov
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_ioctl_retry(fuse_req_t req, const struct iovec *in_iov,
size_t in_count, const struct iovec *out_iov,
size_t out_count);
/**
* Reply to finish ioctl
*
* Possible requests:
* ioctl
*
* @param req request handle
* @param result result to be passed to the caller
* @param buf buffer containing output data
* @param size length of output data
*/
int fuse_reply_ioctl(fuse_req_t req, int result, const void *buf, size_t size);
/**
* Reply to finish ioctl with iov buffer
*
* Possible requests:
* ioctl
*
* @param req request handle
* @param result result to be passed to the caller
* @param iov the vector containing the data
* @param count the size of vector
*/
int fuse_reply_ioctl_iov(fuse_req_t req, int result, const struct iovec *iov,
int count);
/**
* Reply with poll result event mask
*
* @param req request handle
* @param revents poll result event mask
*/
int fuse_reply_poll(fuse_req_t req, unsigned revents);
/**
* Reply with offset
*
* Possible requests:
* lseek
*
* @param req request handle
* @param off offset of next data or hole
* @return zero for success, -errno for failure to send reply
*/
int fuse_reply_lseek(fuse_req_t req, off_t off);
/*
* Notification
*/
/**
* Notify IO readiness event
*
* For more information, please read comment for poll operation.
*
* @param ph poll handle to notify IO readiness event for
*/
int fuse_lowlevel_notify_poll(struct fuse_pollhandle *ph);
/**
* Notify to invalidate cache for an inode.
*
* Added in FUSE protocol version 7.12. If the kernel does not support
* this (or a newer) version, the function will return -ENOSYS and do
* nothing.
*
* If the filesystem has writeback caching enabled, invalidating an
* inode will first trigger a writeback of all dirty pages. The call
* will block until all writeback requests have completed and the
* inode has been invalidated. It will, however, not wait for
* completion of pending writeback requests that have been issued
* before.
*
* If there are no dirty pages, this function will never block.
*
* @param se the session object
* @param ino the inode number
* @param off the offset in the inode where to start invalidating
* or negative to invalidate attributes only
* @param len the amount of cache to invalidate or 0 for all
* @return zero for success, -errno for failure
*/
int fuse_lowlevel_notify_inval_inode(struct fuse_session *se, fuse_ino_t ino,
off_t off, off_t len);
/**
* Notify to invalidate parent attributes and the dentry matching
* parent/name
*
* To avoid a deadlock this function must not be called in the
* execution path of a related filesytem operation or within any code
* that could hold a lock that could be needed to execute such an
* operation. As of kernel 4.18, a "related operation" is a lookup(),
* symlink(), mknod(), mkdir(), unlink(), rename(), link() or create()
* request for the parent, and a setattr(), unlink(), rmdir(),
* rename(), setxattr(), removexattr(), readdir() or readdirplus()
* request for the inode itself.
*
* When called correctly, this function will never block.
*
* Added in FUSE protocol version 7.12. If the kernel does not support
* this (or a newer) version, the function will return -ENOSYS and do
* nothing.
*
* @param se the session object
* @param parent inode number
* @param name file name
* @param namelen strlen() of file name
* @return zero for success, -errno for failure
*/
int fuse_lowlevel_notify_inval_entry(struct fuse_session *se, fuse_ino_t parent,
const char *name, size_t namelen);
/**
* This function behaves like fuse_lowlevel_notify_inval_entry() with
* the following additional effect (at least as of Linux kernel 4.8):
*
* If the provided *child* inode matches the inode that is currently
* associated with the cached dentry, and if there are any inotify
* watches registered for the dentry, then the watchers are informed
* that the dentry has been deleted.
*
* To avoid a deadlock this function must not be called while
* executing a related filesytem operation or while holding a lock
* that could be needed to execute such an operation (see the
* description of fuse_lowlevel_notify_inval_entry() for more
* details).
*
* When called correctly, this function will never block.
*
* Added in FUSE protocol version 7.18. If the kernel does not support
* this (or a newer) version, the function will return -ENOSYS and do
* nothing.
*
* @param se the session object
* @param parent inode number
* @param child inode number
* @param name file name
* @param namelen strlen() of file name
* @return zero for success, -errno for failure
*/
int fuse_lowlevel_notify_delete(struct fuse_session *se, fuse_ino_t parent,
fuse_ino_t child, const char *name,
size_t namelen);
/**
* Store data to the kernel buffers
*
* Synchronously store data in the kernel buffers belonging to the
* given inode. The stored data is marked up-to-date (no read will be
* performed against it, unless it's invalidated or evicted from the
* cache).
*
* If the stored data overflows the current file size, then the size
* is extended, similarly to a write(2) on the filesystem.
*
* If this function returns an error, then the store wasn't fully
* completed, but it may have been partially completed.
*
* Added in FUSE protocol version 7.15. If the kernel does not support
* this (or a newer) version, the function will return -ENOSYS and do
* nothing.
*
* @param se the session object
* @param ino the inode number
* @param offset the starting offset into the file to store to
* @param bufv buffer vector
* @return zero for success, -errno for failure
*/
int fuse_lowlevel_notify_store(struct fuse_session *se, fuse_ino_t ino,
off_t offset, struct fuse_bufvec *bufv);
/*
* Utility functions
*/
/**
* Get the userdata from the request
*
* @param req request handle
* @return the user data passed to fuse_session_new()
*/
void *fuse_req_userdata(fuse_req_t req);
/**
* Get the context from the request
*
* The pointer returned by this function will only be valid for the
* request's lifetime
*
* @param req request handle
* @return the context structure
*/
const struct fuse_ctx *fuse_req_ctx(fuse_req_t req);
/**
* Get the current supplementary group IDs for the specified request
*
* Similar to the getgroups(2) system call, except the return value is
* always the total number of group IDs, even if it is larger than the
* specified size.
*
* The current fuse kernel module in linux (as of 2.6.30) doesn't pass
* the group list to userspace, hence this function needs to parse
* "/proc/$TID/task/$TID/status" to get the group IDs.
*
* This feature may not be supported on all operating systems. In
* such a case this function will return -ENOSYS.
*
* @param req request handle
* @param size size of given array
* @param list array of group IDs to be filled in
* @return the total number of supplementary group IDs or -errno on failure
*/
int fuse_req_getgroups(fuse_req_t req, int size, gid_t list[]);
/**
* Callback function for an interrupt
*
* @param req interrupted request
* @param data user data
*/
typedef void (*fuse_interrupt_func_t)(fuse_req_t req, void *data);
/**
* Register/unregister callback for an interrupt
*
* If an interrupt has already happened, then the callback function is
* called from within this function, hence it's not possible for
* interrupts to be lost.
*
* @param req request handle
* @param func the callback function or NULL for unregister
* @param data user data passed to the callback function
*/
void fuse_req_interrupt_func(fuse_req_t req, fuse_interrupt_func_t func,
void *data);
/**
* Check if a request has already been interrupted
*
* @param req request handle
* @return 1 if the request has been interrupted, 0 otherwise
*/
int fuse_req_interrupted(fuse_req_t req);
/*
* Inquiry functions
*/
/**
* Print low-level version information to stdout.
*/
void fuse_lowlevel_version(void);
/**
* Print available low-level options to stdout. This is not an
* exhaustive list, but includes only those options that may be of
* interest to an end-user of a file system.
*/
void fuse_lowlevel_help(void);
/**
* Print available options for `fuse_parse_cmdline()`.
*/
void fuse_cmdline_help(void);
/*
* Filesystem setup & teardown
*/
struct fuse_cmdline_opts {
int foreground;
int debug;
int nodefault_subtype;
int show_version;
int show_help;
unsigned int max_idle_threads;
};
/**
* Utility function to parse common options for simple file systems
* using the low-level API. A help text that describes the available
* options can be printed with `fuse_cmdline_help`. A single
* non-option argument is treated as the mountpoint. Multiple
* non-option arguments will result in an error.
*
* If neither -o subtype= or -o fsname= options are given, a new
* subtype option will be added and set to the basename of the program
* (the fsname will remain unset, and then defaults to "fuse").
*
* Known options will be removed from *args*, unknown options will
* remain.
*
* @param args argument vector (input+output)
* @param opts output argument for parsed options
* @return 0 on success, -1 on failure
*/
int fuse_parse_cmdline(struct fuse_args *args, struct fuse_cmdline_opts *opts);
/**
* Create a low level session.
*
* Returns a session structure suitable for passing to
* fuse_session_mount() and fuse_session_loop().
*
* This function accepts most file-system independent mount options
* (like context, nodev, ro - see mount(8)), as well as the general
* fuse mount options listed in mount.fuse(8) (e.g. -o allow_root and
* -o default_permissions, but not ``-o use_ino``). Instead of `-o
* debug`, debugging may also enabled with `-d` or `--debug`.
*
* If not all options are known, an error message is written to stderr
* and the function returns NULL.
*
* Option parsing skips argv[0], which is assumed to contain the
* program name. To prevent accidentally passing an option in
* argv[0], this element must always be present (even if no options
* are specified). It may be set to the empty string ('\0') if no
* reasonable value can be provided.
*
* @param args argument vector
* @param op the (low-level) filesystem operations
* @param op_size sizeof(struct fuse_lowlevel_ops)
* @param userdata user data
*
* @return the fuse session on success, NULL on failure
**/
struct fuse_session *fuse_session_new(struct fuse_args *args,
const struct fuse_lowlevel_ops *op,
size_t op_size, void *userdata);
/**
* Mount a FUSE file system.
*
* @param se session object
*
* @return 0 on success, -1 on failure.
**/
int fuse_session_mount(struct fuse_session *se);
/**
* Enter a single threaded, blocking event loop.
*
* When the event loop terminates because the connection to the FUSE
* kernel module has been closed, this function returns zero. This
* happens when the filesystem is unmounted regularly (by the
* filesystem owner or root running the umount(8) or fusermount(1)
* command), or if connection is explicitly severed by writing ``1``
* to the``abort`` file in ``/sys/fs/fuse/connections/NNN``. The only
* way to distinguish between these two conditions is to check if the
* filesystem is still mounted after the session loop returns.
*
* When some error occurs during request processing, the function
* returns a negated errno(3) value.
*
* If the loop has been terminated because of a signal handler
* installed by fuse_set_signal_handlers(), this function returns the
* (positive) signal value that triggered the exit.
*
* @param se the session
* @return 0, -errno, or a signal value
*/
int fuse_session_loop(struct fuse_session *se);
/**
* Flag a session as terminated.
*
* This function is invoked by the POSIX signal handlers, when
* registered using fuse_set_signal_handlers(). It will cause any
* running event loops to terminate on the next opportunity.
*
* @param se the session
*/
void fuse_session_exit(struct fuse_session *se);
/**
* Reset the terminated flag of a session
*
* @param se the session
*/
void fuse_session_reset(struct fuse_session *se);
/**
* Query the terminated flag of a session
*
* @param se the session
* @return 1 if exited, 0 if not exited
*/
int fuse_session_exited(struct fuse_session *se);
/**
* Ensure that file system is unmounted.
*
* In regular operation, the file system is typically unmounted by the
* user calling umount(8) or fusermount(1), which then terminates the
* FUSE session loop. However, the session loop may also terminate as
* a result of an explicit call to fuse_session_exit() (e.g. by a
* signal handler installed by fuse_set_signal_handler()). In this
* case the filesystem remains mounted, but any attempt to access it
* will block (while the filesystem process is still running) or give
* an ESHUTDOWN error (after the filesystem process has terminated).
*
* If the communication channel with the FUSE kernel module is still
* open (i.e., if the session loop was terminated by an explicit call
* to fuse_session_exit()), this function will close it and unmount
* the filesystem. If the communication channel has been closed by the
* kernel, this method will do (almost) nothing.
*
* NOTE: The above semantics mean that if the connection to the kernel
* is terminated via the ``/sys/fs/fuse/connections/NNN/abort`` file,
* this method will *not* unmount the filesystem.
*
* @param se the session
*/
void fuse_session_unmount(struct fuse_session *se);
/**
* Destroy a session
*
* @param se the session
*/
void fuse_session_destroy(struct fuse_session *se);
/*
* Custom event loop support
*/
/**
* Return file descriptor for communication with kernel.
*
* The file selector can be used to integrate FUSE with a custom event
* loop. Whenever data is available for reading on the provided fd,
* the event loop should call `fuse_session_receive_buf` followed by
* `fuse_session_process_buf` to process the request.
*
* The returned file descriptor is valid until `fuse_session_unmount`
* is called.
*
* @param se the session
* @return a file descriptor
*/
int fuse_session_fd(struct fuse_session *se);
/**
* Process a raw request supplied in a generic buffer
*
* The fuse_buf may contain a memory buffer or a pipe file descriptor.
*
* @param se the session
* @param buf the fuse_buf containing the request
*/
void fuse_session_process_buf(struct fuse_session *se,
const struct fuse_buf *buf);
/**
* Read a raw request from the kernel into the supplied buffer.
*
* Depending on file system options, system capabilities, and request
* size the request is either read into a memory buffer or spliced
* into a temporary pipe.
*
* @param se the session
* @param buf the fuse_buf to store the request in
* @return the actual size of the raw request, or -errno on error
*/
int fuse_session_receive_buf(struct fuse_session *se, struct fuse_buf *buf);
#endif /* FUSE_LOWLEVEL_H_ */
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