ICFS/sources/main.c

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>
  Copyright (C) 2011       Sebastian Pipping <sebastian@pipping.org>

  This program can be distributed under the terms of the GNU GPLv2.
  See the file COPYING.
*/

/** @file
 *
 * This file system mirrors the existing file system hierarchy of the
 * system, starting at the root file system. This is implemented by
 * just "passing through" all requests to the corresponding user-space
 * libc functions. This implementation is a little more sophisticated
 * than the one in passthrough.c, so performance is not quite as bad.
 *
 * Compile with:
 *
 *     gcc -Wall passthrough_fh.c `pkg-config fuse3 --cflags --libs` -lulockmgr
 * -o passthrough_fh
 *
 * ## Source code ##
 * \include passthrough_fh.c
 */

#define FUSE_USE_VERSION 31

#define _GNU_SOURCE

#include <fuse3/fuse.h>

#ifdef HAVE_LIBULOCKMGR
#include <ulockmgr.h>
#endif

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <unistd.h>
#ifdef HAVE_SETXATTR
#include <sys/xattr.h>
#endif
#include <sys/file.h> /* flock(2) */

#include "sourcefs.h"

const char *mountpoint = NULL;

static void *xmp_init(struct fuse_conn_info *conn, struct fuse_config *cfg) {
  (void)conn;
  cfg->use_ino = 1;
  cfg->nullpath_ok = 1;

  /* parallel_direct_writes feature depends on direct_io features.
     To make parallel_direct_writes valid, need either set cfg->direct_io
     in current function (recommended in high level API) or set fi->direct_io
     in xmp_create() or xmp_open(). */
  // cfg->direct_io = 1;
  // cfg->parallel_direct_writes = 1;

  /* Pick up changes from lower filesystem right away. This is
     also necessary for better hardlink support. When the kernel
     calls the unlink() handler, it does not know the inode of
     the to-be-removed entry and can therefore not invalidate
     the cache of the associated inode - resulting in an
     incorrect st_nlink value being reported for any remaining
     hardlinks to this inode. */
  cfg->entry_timeout = 0;
  cfg->attr_timeout = 0;
  cfg->negative_timeout = 0;

  return NULL;
}

static int xmp_getattr(const char *path, struct stat *stbuf,
                       struct fuse_file_info *fi) {
  int res;

  (void)path;

  if (fi)
    res = fstat(fi->fh, stbuf);
  else
    res = source_stat(path, stbuf);
  if (res == -1) {
    perror("Stat failed");
    return -errno;
  }

  return 0;
}

static int xmp_access(const char *path, int mask) {
  int res;

  res = access(path, mask);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_readlink(const char *path, char *buf, size_t size) {
  int res;

  res = readlink(path, buf, size - 1);
  if (res == -1)
    return -errno;

  buf[res] = '\0';
  return 0;
}

struct xmp_dirp {
  DIR *dp;
  struct dirent *entry;
  off_t offset;
};

static int xmp_opendir(const char *path, struct fuse_file_info *fi) {
  int res;
  struct xmp_dirp *d = malloc(sizeof(struct xmp_dirp));
  if (d == NULL)
    return -ENOMEM;

  d->dp = source_opendir(path);
  if (d->dp == NULL) {
    perror("Opendir failed");
    res = -errno;
    free(d);
    return res;
  }
  d->offset = 0;
  d->entry = NULL;

  fi->fh = (unsigned long)d;
  return 0;
}

static inline struct xmp_dirp *get_dirp(struct fuse_file_info *fi) {
  return (struct xmp_dirp *)(uintptr_t)fi->fh;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
                       off_t offset, struct fuse_file_info *fi,
                       enum fuse_readdir_flags flags) {
  struct xmp_dirp *d = get_dirp(fi);

  (void)path;
  if (offset != d->offset) {
#ifndef __FreeBSD__
    seekdir(d->dp, offset);
#else
    /* Subtract the one that we add when calling
       telldir() below */
    seekdir(d->dp, offset - 1);
#endif
    d->entry = NULL;
    d->offset = offset;
  }
  while (1) {
    struct stat st;
    off_t nextoff;
    // enum fuse_fill_dir_flags fill_flags = FUSE_FILL_DIR_DEFAULTS;
    enum fuse_fill_dir_flags fill_flags = 0;

    if (!d->entry) {
      d->entry = readdir(d->dp);
      if (!d->entry)
        break;
    }
#ifdef HAVE_FSTATAT
    if (flags & FUSE_READDIR_PLUS) {
      int res;

      res = fstatat(dirfd(d->dp), d->entry->d_name, &st, AT_SYMLINK_NOFOLLOW);
      if (res != -1)
        fill_flags |= FUSE_FILL_DIR_PLUS;
    }
#endif
    if (!(fill_flags & FUSE_FILL_DIR_PLUS)) {
      memset(&st, 0, sizeof(st));
      st.st_ino = d->entry->d_ino;
      st.st_mode = d->entry->d_type << 12;
    }
    nextoff = telldir(d->dp);
#ifdef __FreeBSD__
    /* Under FreeBSD, telldir() may return 0 the first time
       it is called. But for libfuse, an offset of zero
       means that offsets are not supported, so we shift
       everything by one. */
    nextoff++;
#endif
    if (filler(buf, d->entry->d_name, &st, nextoff, fill_flags))
      break;

    d->entry = NULL;
    d->offset = nextoff;
  }

  return 0;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_releasedir(const char *path, struct fuse_file_info *fi) {
  struct xmp_dirp *d = get_dirp(fi);
  (void)path;
  closedir(d->dp);
  free(d);
  return 0;
}

/*
// TODO: make this work
static int xmp_mknod(const char *path, mode_t mode, dev_t rdev) {
  int res;

  if (S_ISFIFO(mode))
    res = mkfifo(path, mode);
  else
    res = mknod(path, mode, rdev);
  if (res == -1)
    return -errno;

  return 0;
}
*/

static int xmp_mkdir(const char *path, mode_t mode) {
  int res;

  res = source_mkdir(path, mode);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_unlink(const char *path) {
  int res;

  res = source_unlink(path);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_rmdir(const char *path) {
  int res;

  res = source_rmdir(path);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_symlink(const char *from, const char *to) {
  int res;

  res = source_symlink(from, to);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_rename(const char *from, const char *to, unsigned int flags) {
  int res;

  /* When we have renameat2() in libc, then we can implement flags */
  if (flags)
    return -EINVAL;

  res = source_rename(from, to);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_link(const char *from, const char *to) {
  int res;

  res = source_link(from, to);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_chmod(const char *path, mode_t mode, struct fuse_file_info *fi) {
  int res;

  if (fi)
    res = fchmod(fi->fh, mode);
  else
    res = source_chmod(path, mode);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_chown(const char *path, uid_t uid, gid_t gid,
                     struct fuse_file_info *fi) {
  int res;

  if (fi)
    res = fchown(fi->fh, uid, gid);
  else
    res = source_chown(path, uid, gid);
  if (res == -1)
    return -errno;

  return 0;
}

static int xmp_truncate(const char *path, off_t size,
                        struct fuse_file_info *fi) {
  int res;

  if (fi)
    res = ftruncate(fi->fh, size);
  else
    res = source_truncate(path, size);

  if (res == -1)
    return -errno;

  return 0;
}

#ifdef HAVE_UTIMENSAT
static int xmp_utimens(const char *path, const struct timespec ts[2],
                       struct fuse_file_info *fi) {
  int res;

  /* don't use utime/utimes since they follow symlinks */
  if (fi)
    res = futimens(fi->fh, ts);
  else
    res = utimensat(0, path, ts, AT_SYMLINK_NOFOLLOW);
  if (res == -1)
    return -errno;

  return 0;
}
#endif

static int xmp_create(const char *path, mode_t mode,
                      struct fuse_file_info *fi) {
  int fd;

  fd = source_create(path, fi->flags, mode);
  if (fd == -1)
    return -errno;

  fi->fh = fd;
  return 0;
}

static int xmp_open(const char *path, struct fuse_file_info *fi) {
  int fd;

  fd = source_open(path, fi->flags);
  if (fd == -1)
    return -errno;

  /* Enable direct_io when open has flags O_DIRECT to enjoy the feature
     parallel_direct_writes (i.e., to get a shared lock, not exclusive lock,
     for writes to the same file).
  if (fi->flags & O_DIRECT) {
    fi->direct_io = 1;
    fi->parallel_direct_writes = 1;
  }
  */

  fi->fh = fd;
  return 0;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_read(const char *path, char *buf, size_t size, off_t offset,
                    struct fuse_file_info *fi) {
  int res;

  (void)path;
  res = pread(fi->fh, buf, size, offset);
  if (res == -1)
    res = -errno;

  return res;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_read_buf(const char *path, struct fuse_bufvec **bufp,
                        size_t size, off_t offset, struct fuse_file_info *fi) {
  struct fuse_bufvec *src;

  (void)path;

  src = malloc(sizeof(struct fuse_bufvec));
  if (src == NULL)
    return -ENOMEM;

  *src = FUSE_BUFVEC_INIT(size);

  src->buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK;
  src->buf[0].fd = fi->fh;
  src->buf[0].pos = offset;

  *bufp = src;

  return 0;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_write(const char *path, const char *buf, size_t size,
                     off_t offset, struct fuse_file_info *fi) {
  int res;

  (void)path;
  res = pwrite(fi->fh, buf, size, offset);
  if (res == -1)
    res = -errno;

  return res;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_write_buf(const char *path, struct fuse_bufvec *buf,
                         off_t offset, struct fuse_file_info *fi) {
  struct fuse_bufvec dst = FUSE_BUFVEC_INIT(fuse_buf_size(buf));

  (void)path;

  dst.buf[0].flags = FUSE_BUF_IS_FD | FUSE_BUF_FD_SEEK;
  dst.buf[0].fd = fi->fh;
  dst.buf[0].pos = offset;

  return fuse_buf_copy(&dst, buf, FUSE_BUF_SPLICE_NONBLOCK);
}

static int xmp_statfs(const char *path, struct statvfs *stbuf) {
  int res;

  res = statvfs(path, stbuf);
  if (res == -1)
    return -errno;

  return 0;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_flush(const char *path, struct fuse_file_info *fi) {
  int res;

  (void)path;
  /* This is called from every close on an open file, so call the
     close on the underlying filesystem.	But since flush may be
     called multiple times for an open file, this must not really
     close the file.  This is important if used on a network
     filesystem like NFS which flush the data/metadata on close() */
  res = close(dup(fi->fh));
  if (res == -1)
    return -errno;

  return 0;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_release(const char *path, struct fuse_file_info *fi) {
  (void)path;
  close(fi->fh);

  return 0;
}

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_fsync(const char *path, int isdatasync,
                     struct fuse_file_info *fi) {
  int res;
  (void)path;

#ifndef HAVE_FDATASYNC
  (void)isdatasync;
#else
  if (isdatasync)
    res = fdatasync(fi->fh);
  else
#endif
  res = fsync(fi->fh);
  if (res == -1)
    return -errno;

  return 0;
}

#ifdef HAVE_POSIX_FALLOCATE
static int xmp_fallocate(const char *path, int mode, off_t offset, off_t length,
                         struct fuse_file_info *fi) {
  (void)path;

  if (mode)
    return -EOPNOTSUPP;

  return -posix_fallocate(fi->fh, offset, length);
}
#endif

#ifdef HAVE_SETXATTR
/* xattr operations are optional and can safely be left unimplemented */
static int xmp_setxattr(const char *path, const char *name, const char *value,
                        size_t size, int flags) {
  int res = lsetxattr(path, name, value, size, flags);
  if (res == -1)
    return -errno;
  return 0;
}

static int xmp_getxattr(const char *path, const char *name, char *value,
                        size_t size) {
  int res = lgetxattr(path, name, value, size);
  if (res == -1)
    return -errno;
  return res;
}

static int xmp_listxattr(const char *path, char *list, size_t size) {
  int res = llistxattr(path, list, size);
  if (res == -1)
    return -errno;
  return res;
}

static int xmp_removexattr(const char *path, const char *name) {
  int res = lremovexattr(path, name);
  if (res == -1)
    return -errno;
  return 0;
}
#endif /* HAVE_SETXATTR */

#ifdef HAVE_LIBULOCKMGR
static int xmp_lock(const char *path, struct fuse_file_info *fi, int cmd,
                    struct flock *lock) {
  (void)path;

  return ulockmgr_op(fi->fh, cmd, lock, &fi->lock_owner,
                     sizeof(fi->lock_owner));
}
#endif

/* Complete copy of the example method(no need to modify anything so far) */
static int xmp_flock(const char *path, struct fuse_file_info *fi, int op) {
  int res;
  (void)path;

  res = flock(fi->fh, op);
  if (res == -1)
    return -errno;

  return 0;
}

#ifdef HAVE_COPY_FILE_RANGE
static ssize_t xmp_copy_file_range(const char *path_in,
                                   struct fuse_file_info *fi_in, off_t off_in,
                                   const char *path_out,
                                   struct fuse_file_info *fi_out, off_t off_out,
                                   size_t len, int flags) {
  ssize_t res;
  (void)path_in;
  (void)path_out;

  res = copy_file_range(fi_in->fh, &off_in, fi_out->fh, &off_out, len, flags);
  if (res == -1)
    return -errno;

  return res;
}
#endif

/* Complete copy of the example method(no need to modify anything so far) */
static off_t xmp_lseek(const char *path, off_t off, int whence,
                       struct fuse_file_info *fi) {
  off_t res;
  (void)path;

  res = lseek(fi->fh, off, whence);
  if (res == -1)
    return -errno;

  return res;
}

// TODO: look trough "optional"(commented out) operations.
static const struct fuse_operations xmp_oper = {
    .init = xmp_init,
    .getattr = xmp_getattr,
    // .access = xmp_access,
    .readlink = xmp_readlink,
    .opendir = xmp_opendir,
    .readdir = xmp_readdir,
    .releasedir = xmp_releasedir,
    //    .mknod = xmp_mknod,
    .mkdir = xmp_mkdir,
    .symlink = xmp_symlink,
    .unlink = xmp_unlink,
    .rmdir = xmp_rmdir,
    .rename = xmp_rename,
    .link = xmp_link,
    .chmod = xmp_chmod,
    .chown = xmp_chown,
    .truncate = xmp_truncate,
#ifdef HAVE_UTIMENSAT
// .utimens = xmp_utimens,
#endif
    .create = xmp_create,
    .open = xmp_open,
    .read = xmp_read,
    .read_buf = xmp_read_buf,
    .write = xmp_write,
    .write_buf = xmp_write_buf,
    .statfs = xmp_statfs,
    .flush = xmp_flush,
    .release = xmp_release,
    .fsync = xmp_fsync,
#ifdef HAVE_POSIX_FALLOCATE
// .fallocate = xmp_fallocate,
#endif
#ifdef HAVE_SETXATTR
// .setxattr = xmp_setxattr,
// .getxattr = xmp_getxattr,
// .listxattr = xmp_listxattr,
// .removexattr = xmp_removexattr,
#endif
#ifdef HAVE_LIBULOCKMGR
// .lock = xmp_lock,
#endif
    .flock = xmp_flock,
#ifdef HAVE_COPY_FILE_RANGE
// .copy_file_range = xmp_copy_file_range,
#endif
    .lseek = xmp_lseek,
};

int main(int argc, char *argv[]) {
  umask(0);

  // FUSE won't tell us the mountpoint on it's own, so we need to extract it
  // ourselves.
  mountpoint = realpath(argv[argc - 1], NULL);

  int ret = source_init(mountpoint);
  if (ret != 0) {
    perror("Failed to initialize filesystem.");
    exit(EXIT_FAILURE);
  }

  return fuse_main(argc, argv, &xmp_oper, NULL);
}