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Diffstat (limited to 'tools/virtiofsd/fuse_lowlevel.h')
| -rw-r--r-- | tools/virtiofsd/fuse_lowlevel.h | 2089 |
1 files changed, 2089 insertions, 0 deletions
diff --git a/tools/virtiofsd/fuse_lowlevel.h b/tools/virtiofsd/fuse_lowlevel.h new file mode 100644 index 0000000000..18c6363f07 --- /dev/null +++ b/tools/virtiofsd/fuse_lowlevel.h @@ -0,0 +1,2089 @@ +/* + 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 <utime.h> +#include <fcntl.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/statvfs.h> +#include <sys/uio.h> + +#ifdef __cplusplus +extern "C" { +#endif + +/* ----------------------------------------------------------- * + * 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); + + /** + * Callback function for the retrieve request + * + * Valid replies: + * fuse_reply_none + * + * @param req request handle + * @param cookie user data supplied to fuse_lowlevel_notify_retrieve() + * @param ino the inode number supplied to fuse_lowlevel_notify_retrieve() + * @param offset the offset supplied to fuse_lowlevel_notify_retrieve() + * @param bufv the buffer containing the returned data + */ + void (*retrieve_reply) (fuse_req_t req, void *cookie, fuse_ino_t ino, + off_t offset, struct fuse_bufvec *bufv); + + /** + * 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) + * + * Zero copy data transfer ("splicing") will be used under + * the following circumstances: + * + * 1. FUSE_CAP_SPLICE_WRITE is set in fuse_conn_info.want, and + * 2. the kernel supports splicing from the fuse device + * (FUSE_CAP_SPLICE_WRITE is set in fuse_conn_info.capable), and + * 3. *flags* does not contain FUSE_BUF_NO_SPLICE + * 4. The amount of data that is provided in file-descriptor backed + * buffers (i.e., buffers for which bufv[n].flags == FUSE_BUF_FD) + * is at least twice the page size. + * + * In order for SPLICE_F_MOVE to be used, the following additional + * conditions have to be fulfilled: + * + * 1. FUSE_CAP_SPLICE_MOVE is set in fuse_conn_info.want, and + * 2. the kernel supports it (i.e, FUSE_CAP_SPLICE_MOVE is set in + fuse_conn_info.capable), and + * 3. *flags* contains FUSE_BUF_SPLICE_MOVE + * + * Note that, if splice is used, the data is actually spliced twice: + * once into a temporary pipe (to prepend header data), and then again + * into the kernel. If some of the provided buffers are memory-backed, + * the data in them is copied in step one and spliced in step two. + * + * The FUSE_BUF_SPLICE_FORCE_SPLICE and FUSE_BUF_SPLICE_NONBLOCK flags + * are silently ignored. + * + * 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 + * @param flags flags controlling the copy + * @return zero for success, -errno for failure to send reply + */ +int fuse_reply_data(fuse_req_t req, struct fuse_bufvec *bufv, + enum fuse_buf_copy_flags flags); + +/** + * 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 + * @param flags flags controlling the copy + * @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, + enum fuse_buf_copy_flags flags); +/** + * Retrieve data from the kernel buffers + * + * Retrieve data in the kernel buffers belonging to the given inode. + * If successful then the retrieve_reply() method will be called with + * the returned data. + * + * Only present pages are returned in the retrieve reply. Retrieving + * stops when it finds a non-present page and only data prior to that + * is returned. + * + * If this function returns an error, then the retrieve will not be + * completed and no reply will be sent. + * + * This function doesn't change the dirty state of pages in the kernel + * buffer. For dirty pages the write() method will be called + * regardless of having been retrieved previously. + * + * 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 size the number of bytes to retrieve + * @param offset the starting offset into the file to retrieve from + * @param cookie user data to supply to the reply callback + * @return zero for success, -errno for failure + */ +int fuse_lowlevel_notify_retrieve(struct fuse_session *se, fuse_ino_t ino, + size_t size, off_t offset, void *cookie); + + +/* ----------------------------------------------------------- * + * 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 singlethread; + int foreground; + int debug; + int nodefault_subtype; + char *mountpoint; + int show_version; + int show_help; + int clone_fd; + 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 mountpoint the mount point path + * @param se session object + * + * @return 0 on success, -1 on failure. + **/ +int fuse_session_mount(struct fuse_session *se, const char *mountpoint); + +/** + * 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); + +/** + * Enter a multi-threaded event loop. + * + * For a description of the return value and the conditions when the + * event loop exits, refer to the documentation of + * fuse_session_loop(). + * + * @param se the session + * @param config session loop configuration + * @return see fuse_session_loop() + */ +#if FUSE_USE_VERSION < 32 +int fuse_session_loop_mt_31(struct fuse_session *se, int clone_fd); +#define fuse_session_loop_mt(se, clone_fd) fuse_session_loop_mt_31(se, clone_fd) +#else +int fuse_session_loop_mt(struct fuse_session *se, struct fuse_loop_config *config); +#endif + +/** + * 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); + +#ifdef __cplusplus +} +#endif + +#endif /* FUSE_LOWLEVEL_H_ */ |