qemu

fuse.c (23174B)

---

 /*
  * Present a block device as a raw image through FUSE
  *
  * Copyright (c) 2020 Max Reitz <mreitz@redhat.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; under version 2 or later of the License.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
 #define FUSE_USE_VERSION 31
 
 #include "qemu/osdep.h"
 #include "qemu/memalign.h"
 #include "block/aio.h"
 #include "block/block.h"
 #include "block/export.h"
 #include "block/fuse.h"
 #include "block/qapi.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-block.h"
 #include "sysemu/block-backend.h"
 
 #include <fuse.h>
 #include <fuse_lowlevel.h>
 
 #if defined(CONFIG_FALLOCATE_ZERO_RANGE)
 #include <linux/falloc.h>
 #endif
 
 #ifdef __linux__
 #include <linux/fs.h>
 #endif
 
 /* Prevent overly long bounce buffer allocations */
 #define FUSE_MAX_BOUNCE_BYTES (MIN(BDRV_REQUEST_MAX_BYTES, 64 * 1024 * 1024))
 
 
 typedef struct FuseExport {
     BlockExport common;
 
     struct fuse_session *fuse_session;
     struct fuse_buf fuse_buf;
     bool mounted, fd_handler_set_up;
 
     char *mountpoint;
     bool writable;
     bool growable;
     /* Whether allow_other was used as a mount option or not */
     bool allow_other;
 
     mode_t st_mode;
     uid_t st_uid;
     gid_t st_gid;
 } FuseExport;
 
 static GHashTable *exports;
 static const struct fuse_lowlevel_ops fuse_ops;
 
 static void fuse_export_shutdown(BlockExport *exp);
 static void fuse_export_delete(BlockExport *exp);
 
 static void init_exports_table(void);
 
 static int setup_fuse_export(FuseExport *exp, const char *mountpoint,
                              bool allow_other, Error **errp);
 static void read_from_fuse_export(void *opaque);
 
 static bool is_regular_file(const char *path, Error **errp);
 
 
 static int fuse_export_create(BlockExport *blk_exp,
                               BlockExportOptions *blk_exp_args,
                               Error **errp)
 {
     FuseExport *exp = container_of(blk_exp, FuseExport, common);
     BlockExportOptionsFuse *args = &blk_exp_args->u.fuse;
     int ret;
 
     assert(blk_exp_args->type == BLOCK_EXPORT_TYPE_FUSE);
 
     /* For growable and writable exports, take the RESIZE permission */
     if (args->growable || blk_exp_args->writable) {
         uint64_t blk_perm, blk_shared_perm;
 
         blk_get_perm(exp->common.blk, &blk_perm, &blk_shared_perm);
 
         ret = blk_set_perm(exp->common.blk, blk_perm | BLK_PERM_RESIZE,
                            blk_shared_perm, errp);
         if (ret < 0) {
             return ret;
         }
     }
 
     init_exports_table();
 
     /*
      * It is important to do this check before calling is_regular_file() --
      * that function will do a stat(), which we would have to handle if we
      * already exported something on @mountpoint.  But we cannot, because
      * we are currently caught up here.
      * (Note that ideally we would want to resolve relative paths here,
      * but bdrv_make_absolute_filename() might do the wrong thing for
      * paths that contain colons, and realpath() would resolve symlinks,
      * which we do not want: The mount point is not going to be the
      * symlink's destination, but the link itself.)
      * So this will not catch all potential clashes, but hopefully at
      * least the most common one of specifying exactly the same path
      * string twice.
      */
     if (g_hash_table_contains(exports, args->mountpoint)) {
         error_setg(errp, "There already is a FUSE export on '%s'",
                    args->mountpoint);
         ret = -EEXIST;
         goto fail;
     }
 
     if (!is_regular_file(args->mountpoint, errp)) {
         ret = -EINVAL;
         goto fail;
     }
 
     exp->mountpoint = g_strdup(args->mountpoint);
     exp->writable = blk_exp_args->writable;
     exp->growable = args->growable;
 
     /* set default */
     if (!args->has_allow_other) {
         args->allow_other = FUSE_EXPORT_ALLOW_OTHER_AUTO;
     }
 
     exp->st_mode = S_IFREG | S_IRUSR;
     if (exp->writable) {
         exp->st_mode |= S_IWUSR;
     }
     exp->st_uid = getuid();
     exp->st_gid = getgid();
 
     if (args->allow_other == FUSE_EXPORT_ALLOW_OTHER_AUTO) {
         /* Ignore errors on our first attempt */
         ret = setup_fuse_export(exp, args->mountpoint, true, NULL);
         exp->allow_other = ret == 0;
         if (ret < 0) {
             ret = setup_fuse_export(exp, args->mountpoint, false, errp);
         }
     } else {
         exp->allow_other = args->allow_other == FUSE_EXPORT_ALLOW_OTHER_ON;
         ret = setup_fuse_export(exp, args->mountpoint, exp->allow_other, errp);
     }
     if (ret < 0) {
         goto fail;
     }
 
     return 0;
 
 fail:
     fuse_export_delete(blk_exp);
     return ret;
 }
 
 /**
  * Allocates the global @exports hash table.
  */
 static void init_exports_table(void)
 {
     if (exports) {
         return;
     }
 
     exports = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, NULL);
 }
 
 /**
  * Create exp->fuse_session and mount it.
  */
 static int setup_fuse_export(FuseExport *exp, const char *mountpoint,
                              bool allow_other, Error **errp)
 {
     const char *fuse_argv[4];
     char *mount_opts;
     struct fuse_args fuse_args;
     int ret;
 
     /*
      * max_read needs to match what fuse_init() sets.
      * max_write need not be supplied.
      */
     mount_opts = g_strdup_printf("max_read=%zu,default_permissions%s",
                                  FUSE_MAX_BOUNCE_BYTES,
                                  allow_other ? ",allow_other" : "");
 
     fuse_argv[0] = ""; /* Dummy program name */
     fuse_argv[1] = "-o";
     fuse_argv[2] = mount_opts;
     fuse_argv[3] = NULL;
     fuse_args = (struct fuse_args)FUSE_ARGS_INIT(3, (char **)fuse_argv);
 
     exp->fuse_session = fuse_session_new(&fuse_args, &fuse_ops,
                                          sizeof(fuse_ops), exp);
     g_free(mount_opts);
     if (!exp->fuse_session) {
         error_setg(errp, "Failed to set up FUSE session");
         ret = -EIO;
         goto fail;
     }
 
     ret = fuse_session_mount(exp->fuse_session, mountpoint);
     if (ret < 0) {
         error_setg(errp, "Failed to mount FUSE session to export");
         ret = -EIO;
         goto fail;
     }
     exp->mounted = true;
 
     g_hash_table_insert(exports, g_strdup(mountpoint), NULL);
 
     aio_set_fd_handler(exp->common.ctx,
                        fuse_session_fd(exp->fuse_session), true,
                        read_from_fuse_export, NULL, NULL, NULL, exp);
     exp->fd_handler_set_up = true;
 
     return 0;
 
 fail:
     fuse_export_shutdown(&exp->common);
     return ret;
 }
 
 /**
  * Callback to be invoked when the FUSE session FD can be read from.
  * (This is basically the FUSE event loop.)
  */
 static void read_from_fuse_export(void *opaque)
 {
     FuseExport *exp = opaque;
     int ret;
 
     blk_exp_ref(&exp->common);
 
     do {
         ret = fuse_session_receive_buf(exp->fuse_session, &exp->fuse_buf);
     } while (ret == -EINTR);
     if (ret < 0) {
         goto out;
     }
 
     fuse_session_process_buf(exp->fuse_session, &exp->fuse_buf);
 
 out:
     blk_exp_unref(&exp->common);
 }
 
 static void fuse_export_shutdown(BlockExport *blk_exp)
 {
     FuseExport *exp = container_of(blk_exp, FuseExport, common);
 
     if (exp->fuse_session) {
         fuse_session_exit(exp->fuse_session);
 
         if (exp->fd_handler_set_up) {
             aio_set_fd_handler(exp->common.ctx,
                                fuse_session_fd(exp->fuse_session), true,
                                NULL, NULL, NULL, NULL, NULL);
             exp->fd_handler_set_up = false;
         }
     }
 
     if (exp->mountpoint) {
         /*
          * Safe to drop now, because we will not handle any requests
          * for this export anymore anyway.
          */
         g_hash_table_remove(exports, exp->mountpoint);
     }
 }
 
 static void fuse_export_delete(BlockExport *blk_exp)
 {
     FuseExport *exp = container_of(blk_exp, FuseExport, common);
 
     if (exp->fuse_session) {
         if (exp->mounted) {
             fuse_session_unmount(exp->fuse_session);
         }
 
         fuse_session_destroy(exp->fuse_session);
     }
 
     free(exp->fuse_buf.mem);
     g_free(exp->mountpoint);
 }
 
 /**
  * Check whether @path points to a regular file.  If not, put an
  * appropriate message into *errp.
  */
 static bool is_regular_file(const char *path, Error **errp)
 {
     struct stat statbuf;
     int ret;
 
     ret = stat(path, &statbuf);
     if (ret < 0) {
         error_setg_errno(errp, errno, "Failed to stat '%s'", path);
         return false;
     }
 
     if (!S_ISREG(statbuf.st_mode)) {
         error_setg(errp, "'%s' is not a regular file", path);
         return false;
     }
 
     return true;
 }
 
 /**
  * A chance to set change some parameters supplied to FUSE_INIT.
  */
 static void fuse_init(void *userdata, struct fuse_conn_info *conn)
 {
     /*
      * MIN_NON_ZERO() would not be wrong here, but what we set here
      * must equal what has been passed to fuse_session_new().
      * Therefore, as long as max_read must be passed as a mount option
      * (which libfuse claims will be changed at some point), we have
      * to set max_read to a fixed value here.
      */
     conn->max_read = FUSE_MAX_BOUNCE_BYTES;
 
     conn->max_write = MIN_NON_ZERO(BDRV_REQUEST_MAX_BYTES, conn->max_write);
 }
 
 /**
  * Let clients look up files.  Always return ENOENT because we only
  * care about the mountpoint itself.
  */
 static void fuse_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
 {
     fuse_reply_err(req, ENOENT);
 }
 
 /**
  * Let clients get file attributes (i.e., stat() the file).
  */
 static void fuse_getattr(fuse_req_t req, fuse_ino_t inode,
                          struct fuse_file_info *fi)
 {
     struct stat statbuf;
     int64_t length, allocated_blocks;
     time_t now = time(NULL);
     FuseExport *exp = fuse_req_userdata(req);
 
     length = blk_getlength(exp->common.blk);
     if (length < 0) {
         fuse_reply_err(req, -length);
         return;
     }
 
     allocated_blocks = bdrv_get_allocated_file_size(blk_bs(exp->common.blk));
     if (allocated_blocks <= 0) {
         allocated_blocks = DIV_ROUND_UP(length, 512);
     } else {
         allocated_blocks = DIV_ROUND_UP(allocated_blocks, 512);
     }
 
     statbuf = (struct stat) {
         .st_ino     = inode,
         .st_mode    = exp->st_mode,
         .st_nlink   = 1,
         .st_uid     = exp->st_uid,
         .st_gid     = exp->st_gid,
         .st_size    = length,
         .st_blksize = blk_bs(exp->common.blk)->bl.request_alignment,
         .st_blocks  = allocated_blocks,
         .st_atime   = now,
         .st_mtime   = now,
         .st_ctime   = now,
     };
 
     fuse_reply_attr(req, &statbuf, 1.);
 }
 
 static int fuse_do_truncate(const FuseExport *exp, int64_t size,
                             bool req_zero_write, PreallocMode prealloc)
 {
     uint64_t blk_perm, blk_shared_perm;
     BdrvRequestFlags truncate_flags = 0;
     bool add_resize_perm;
     int ret, ret_check;
 
     /* Growable and writable exports have a permanent RESIZE permission */
     add_resize_perm = !exp->growable && !exp->writable;
 
     if (req_zero_write) {
         truncate_flags |= BDRV_REQ_ZERO_WRITE;
     }
 
     if (add_resize_perm) {
 
         if (!qemu_in_main_thread()) {
             /* Changing permissions like below only works in the main thread */
             return -EPERM;
         }
 
         blk_get_perm(exp->common.blk, &blk_perm, &blk_shared_perm);
 
         ret = blk_set_perm(exp->common.blk, blk_perm | BLK_PERM_RESIZE,
                            blk_shared_perm, NULL);
         if (ret < 0) {
             return ret;
         }
     }
 
     ret = blk_truncate(exp->common.blk, size, true, prealloc,
                        truncate_flags, NULL);
 
     if (add_resize_perm) {
         /* Must succeed, because we are only giving up the RESIZE permission */
         ret_check = blk_set_perm(exp->common.blk, blk_perm,
                                  blk_shared_perm, &error_abort);
         assert(ret_check == 0);
     }
 
     return ret;
 }
 
 /**
  * Let clients set file attributes.  Only resizing and changing
  * permissions (st_mode, st_uid, st_gid) is allowed.
  * Changing permissions is only allowed as far as it will actually
  * permit access: Read-only exports cannot be given +w, and exports
  * without allow_other cannot be given a different UID or GID, and
  * they cannot be given non-owner access.
  */
 static void fuse_setattr(fuse_req_t req, fuse_ino_t inode, struct stat *statbuf,
                          int to_set, struct fuse_file_info *fi)
 {
     FuseExport *exp = fuse_req_userdata(req);
     int supported_attrs;
     int ret;
 
     supported_attrs = FUSE_SET_ATTR_SIZE | FUSE_SET_ATTR_MODE;
     if (exp->allow_other) {
         supported_attrs |= FUSE_SET_ATTR_UID | FUSE_SET_ATTR_GID;
     }
 
     if (to_set & ~supported_attrs) {
         fuse_reply_err(req, ENOTSUP);
         return;
     }
 
     /* Do some argument checks first before committing to anything */
     if (to_set & FUSE_SET_ATTR_MODE) {
         /*
          * Without allow_other, non-owners can never access the export, so do
          * not allow setting permissions for them
          */
         if (!exp->allow_other &&
             (statbuf->st_mode & (S_IRWXG | S_IRWXO)) != 0)
         {
             fuse_reply_err(req, EPERM);
             return;
         }
 
         /* +w for read-only exports makes no sense, disallow it */
         if (!exp->writable &&
             (statbuf->st_mode & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
         {
             fuse_reply_err(req, EROFS);
             return;
         }
     }
 
     if (to_set & FUSE_SET_ATTR_SIZE) {
         if (!exp->writable) {
             fuse_reply_err(req, EACCES);
             return;
         }
 
         ret = fuse_do_truncate(exp, statbuf->st_size, true, PREALLOC_MODE_OFF);
         if (ret < 0) {
             fuse_reply_err(req, -ret);
             return;
         }
     }
 
     if (to_set & FUSE_SET_ATTR_MODE) {
         /* Ignore FUSE-supplied file type, only change the mode */
         exp->st_mode = (statbuf->st_mode & 07777) | S_IFREG;
     }
 
     if (to_set & FUSE_SET_ATTR_UID) {
         exp->st_uid = statbuf->st_uid;
     }
 
     if (to_set & FUSE_SET_ATTR_GID) {
         exp->st_gid = statbuf->st_gid;
     }
 
     fuse_getattr(req, inode, fi);
 }
 
 /**
  * Let clients open a file (i.e., the exported image).
  */
 static void fuse_open(fuse_req_t req, fuse_ino_t inode,
                       struct fuse_file_info *fi)
 {
     fuse_reply_open(req, fi);
 }
 
 /**
  * Handle client reads from the exported image.
  */
 static void fuse_read(fuse_req_t req, fuse_ino_t inode,
                       size_t size, off_t offset, struct fuse_file_info *fi)
 {
     FuseExport *exp = fuse_req_userdata(req);
     int64_t length;
     void *buf;
     int ret;
 
     /* Limited by max_read, should not happen */
     if (size > FUSE_MAX_BOUNCE_BYTES) {
         fuse_reply_err(req, EINVAL);
         return;
     }
 
     /**
      * Clients will expect short reads at EOF, so we have to limit
      * offset+size to the image length.
      */
     length = blk_getlength(exp->common.blk);
     if (length < 0) {
         fuse_reply_err(req, -length);
         return;
     }
 
     if (offset + size > length) {
         size = length - offset;
     }
 
     buf = qemu_try_blockalign(blk_bs(exp->common.blk), size);
     if (!buf) {
         fuse_reply_err(req, ENOMEM);
         return;
     }
 
     ret = blk_pread(exp->common.blk, offset, size, buf, 0);
     if (ret >= 0) {
         fuse_reply_buf(req, buf, size);
     } else {
         fuse_reply_err(req, -ret);
     }
 
     qemu_vfree(buf);
 }
 
 /**
  * Handle client writes to the exported image.
  */
 static void fuse_write(fuse_req_t req, fuse_ino_t inode, const char *buf,
                        size_t size, off_t offset, struct fuse_file_info *fi)
 {
     FuseExport *exp = fuse_req_userdata(req);
     int64_t length;
     int ret;
 
     /* Limited by max_write, should not happen */
     if (size > BDRV_REQUEST_MAX_BYTES) {
         fuse_reply_err(req, EINVAL);
         return;
     }
 
     if (!exp->writable) {
         fuse_reply_err(req, EACCES);
         return;
     }
 
     /**
      * Clients will expect short writes at EOF, so we have to limit
      * offset+size to the image length.
      */
     length = blk_getlength(exp->common.blk);
     if (length < 0) {
         fuse_reply_err(req, -length);
         return;
     }
 
     if (offset + size > length) {
         if (exp->growable) {
             ret = fuse_do_truncate(exp, offset + size, true, PREALLOC_MODE_OFF);
             if (ret < 0) {
                 fuse_reply_err(req, -ret);
                 return;
             }
         } else {
             size = length - offset;
         }
     }
 
     ret = blk_pwrite(exp->common.blk, offset, size, buf, 0);
     if (ret >= 0) {
         fuse_reply_write(req, size);
     } else {
         fuse_reply_err(req, -ret);
     }
 }
 
 /**
  * Let clients perform various fallocate() operations.
  */
 static void fuse_fallocate(fuse_req_t req, fuse_ino_t inode, int mode,
                            off_t offset, off_t length,
                            struct fuse_file_info *fi)
 {
     FuseExport *exp = fuse_req_userdata(req);
     int64_t blk_len;
     int ret;
 
     if (!exp->writable) {
         fuse_reply_err(req, EACCES);
         return;
     }
 
     blk_len = blk_getlength(exp->common.blk);
     if (blk_len < 0) {
         fuse_reply_err(req, -blk_len);
         return;
     }
 
 #ifdef CONFIG_FALLOCATE_PUNCH_HOLE
     if (mode & FALLOC_FL_KEEP_SIZE) {
         length = MIN(length, blk_len - offset);
     }
 #endif /* CONFIG_FALLOCATE_PUNCH_HOLE */
 
     if (!mode) {
         /* We can only fallocate at the EOF with a truncate */
         if (offset < blk_len) {
             fuse_reply_err(req, EOPNOTSUPP);
             return;
         }
 
         if (offset > blk_len) {
             /* No preallocation needed here */
             ret = fuse_do_truncate(exp, offset, true, PREALLOC_MODE_OFF);
             if (ret < 0) {
                 fuse_reply_err(req, -ret);
                 return;
             }
         }
 
         ret = fuse_do_truncate(exp, offset + length, true,
                                PREALLOC_MODE_FALLOC);
     }
 #ifdef CONFIG_FALLOCATE_PUNCH_HOLE
     else if (mode & FALLOC_FL_PUNCH_HOLE) {
         if (!(mode & FALLOC_FL_KEEP_SIZE)) {
             fuse_reply_err(req, EINVAL);
             return;
         }
 
         do {
             int size = MIN(length, BDRV_REQUEST_MAX_BYTES);
 
             ret = blk_pdiscard(exp->common.blk, offset, size);
             offset += size;
             length -= size;
         } while (ret == 0 && length > 0);
     }
 #endif /* CONFIG_FALLOCATE_PUNCH_HOLE */
 #ifdef CONFIG_FALLOCATE_ZERO_RANGE
     else if (mode & FALLOC_FL_ZERO_RANGE) {
         if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + length > blk_len) {
             /* No need for zeroes, we are going to write them ourselves */
             ret = fuse_do_truncate(exp, offset + length, false,
                                    PREALLOC_MODE_OFF);
             if (ret < 0) {
                 fuse_reply_err(req, -ret);
                 return;
             }
         }
 
         do {
             int size = MIN(length, BDRV_REQUEST_MAX_BYTES);
 
             ret = blk_pwrite_zeroes(exp->common.blk,
                                     offset, size, 0);
             offset += size;
             length -= size;
         } while (ret == 0 && length > 0);
     }
 #endif /* CONFIG_FALLOCATE_ZERO_RANGE */
     else {
         ret = -EOPNOTSUPP;
     }
 
     fuse_reply_err(req, ret < 0 ? -ret : 0);
 }
 
 /**
  * Let clients fsync the exported image.
  */
 static void fuse_fsync(fuse_req_t req, fuse_ino_t inode, int datasync,
                        struct fuse_file_info *fi)
 {
     FuseExport *exp = fuse_req_userdata(req);
     int ret;
 
     ret = blk_flush(exp->common.blk);
     fuse_reply_err(req, ret < 0 ? -ret : 0);
 }
 
 /**
  * Called before an FD to the exported image is closed.  (libfuse
  * notes this to be a way to return last-minute errors.)
  */
 static void fuse_flush(fuse_req_t req, fuse_ino_t inode,
                         struct fuse_file_info *fi)
 {
     fuse_fsync(req, inode, 1, fi);
 }
 
 #ifdef CONFIG_FUSE_LSEEK
 /**
  * Let clients inquire allocation status.
  */
 static void fuse_lseek(fuse_req_t req, fuse_ino_t inode, off_t offset,
                        int whence, struct fuse_file_info *fi)
 {
     FuseExport *exp = fuse_req_userdata(req);
 
     if (whence != SEEK_HOLE && whence != SEEK_DATA) {
         fuse_reply_err(req, EINVAL);
         return;
     }
 
     while (true) {
         int64_t pnum;
         int ret;
 
         ret = bdrv_block_status_above(blk_bs(exp->common.blk), NULL,
                                       offset, INT64_MAX, &pnum, NULL, NULL);
         if (ret < 0) {
             fuse_reply_err(req, -ret);
             return;
         }
 
         if (!pnum && (ret & BDRV_BLOCK_EOF)) {
             int64_t blk_len;
 
             /*
              * If blk_getlength() rounds (e.g. by sectors), then the
              * export length will be rounded, too.  However,
              * bdrv_block_status_above() may return EOF at unaligned
              * offsets.  We must not let this become visible and thus
              * always simulate a hole between @offset (the real EOF)
              * and @blk_len (the client-visible EOF).
              */
 
             blk_len = blk_getlength(exp->common.blk);
             if (blk_len < 0) {
                 fuse_reply_err(req, -blk_len);
                 return;
             }
 
             if (offset > blk_len || whence == SEEK_DATA) {
                 fuse_reply_err(req, ENXIO);
             } else {
                 fuse_reply_lseek(req, offset);
             }
             return;
         }
 
         if (ret & BDRV_BLOCK_DATA) {
             if (whence == SEEK_DATA) {
                 fuse_reply_lseek(req, offset);
                 return;
             }
         } else {
             if (whence == SEEK_HOLE) {
                 fuse_reply_lseek(req, offset);
                 return;
             }
         }
 
         /* Safety check against infinite loops */
         if (!pnum) {
             fuse_reply_err(req, ENXIO);
             return;
         }
 
         offset += pnum;
     }
 }
 #endif
 
 static const struct fuse_lowlevel_ops fuse_ops = {
     .init       = fuse_init,
     .lookup     = fuse_lookup,
     .getattr    = fuse_getattr,
     .setattr    = fuse_setattr,
     .open       = fuse_open,
     .read       = fuse_read,
     .write      = fuse_write,
     .fallocate  = fuse_fallocate,
     .flush      = fuse_flush,
     .fsync      = fuse_fsync,
 #ifdef CONFIG_FUSE_LSEEK
     .lseek      = fuse_lseek,
 #endif
 };
 
 const BlockExportDriver blk_exp_fuse = {
     .type               = BLOCK_EXPORT_TYPE_FUSE,
     .instance_size      = sizeof(FuseExport),
     .create             = fuse_export_create,
     .delete             = fuse_export_delete,
     .request_shutdown   = fuse_export_shutdown,
 };