On 2025/12/22 15:46, Gao Xiang wrote:
Users can use the new `--disconnect` option to forcibly disconnect or
abort NBD block devices.

Signed-off-by: Gao Xiang <[email protected]>

Hi Xiang,

It seems

    mount.erofs -u /dev/nbdX

serving the same purpose of --disconnect? Why do we need a separate --disconnect subcommand?


Thanks,

Yifan

---
  mount/main.c | 55 +++++++++++++++++++++++++++++++++++++++++++++-------
  1 file changed, 48 insertions(+), 7 deletions(-)

diff --git a/mount/main.c b/mount/main.c
index b3b2e0fc33e0..693dba2dc78d 100644
--- a/mount/main.c
+++ b/mount/main.c
@@ -51,6 +51,7 @@ enum erofs_backend_drv {
  enum erofsmount_mode {
        EROFSMOUNT_MODE_MOUNT,
        EROFSMOUNT_MODE_UMOUNT,
+       EROFSMOUNT_MODE_DISCONNECT,
        EROFSMOUNT_MODE_REATTACH,
  };
@@ -88,13 +89,14 @@ static void usage(int argc, char **argv)
                "Manage EROFS filesystem.\n"
                "\n"
                "General options:\n"
-               " -V, --version            print the version number of mount.erofs 
and exit\n"
-               " -h, --help               display this help and exit\n"
-               " -o options               comma-separated list of mount 
options\n"
-               " -t type[.subtype]        filesystem type (and optional 
subtype)\n"
-               "                  subtypes: fuse, local, nbd\n"
-               " -u                       unmount the filesystem\n"
-               "    --reattach            reattach to an existing NBD device\n"
+               " -V, --version         print the version number of mount.erofs and 
exit\n"
+               " -h, --help            display this help and exit\n"
+               " -o options            comma-separated list of mount options\n"
+               " -t type[.subtype]     filesystem type (and optional 
subtype)\n"
+               "                       subtypes: fuse, local, nbd\n"
+               " -u                    unmount the filesystem\n"
+               "    --disconnect       abort an existing NBD device forcibly\n"
+               "    --reattach         reattach to an existing NBD device\n"
  #ifdef OCIEROFS_ENABLED
                "\n"
                "OCI-specific options (with -o):\n"
@@ -271,6 +273,7 @@ static int erofsmount_parse_options(int argc, char **argv)
                {"help", no_argument, 0, 'h'},
                {"version", no_argument, 0, 'V'},
                {"reattach", no_argument, 0, 512},
+               {"disconnect", no_argument, 0, 513},
                {0, 0, 0, 0},
        };
        char *dot;
@@ -316,6 +319,9 @@ static int erofsmount_parse_options(int argc, char **argv)
                case 512:
                        mountcfg.mountmode = EROFSMOUNT_MODE_REATTACH;
                        break;
+               case 513:
+                       mountcfg.mountmode = EROFSMOUNT_MODE_DISCONNECT;
+                       break;
                default:
                        return -EINVAL;
                }
@@ -1415,6 +1421,33 @@ err_out:
        return err < 0 ? err : 0;
  }
+static int erofsmount_disconnect(const char *target)
+{
+       int nbdnum, err, fd;
+       struct stat st;
+
+       err = lstat(target, &st);
+       if (err < 0)
+               return -errno;
+
+       if (!S_ISBLK(st.st_mode) || major(st.st_rdev) != EROFS_NBD_MAJOR)
+               return -ENOTBLK;
+
+       nbdnum = erofs_nbd_get_index_from_minor(minor(st.st_rdev));
+       err = erofs_nbd_nl_disconnect(nbdnum);
+       if (err == -EOPNOTSUPP) {
+               fd = open(target, O_RDWR);
+               if (fd < 0) {
+                       err = -errno;
+                       goto err_out;
+               }
+               err = erofs_nbd_disconnect(fd);
+               close(fd);
+       }
+err_out:
+       return err < 0 ? err : 0;
+}
+
  int main(int argc, char *argv[])
  {
        int err;
@@ -1443,6 +1476,14 @@ int main(int argc, char *argv[])
                return err ? EXIT_FAILURE : EXIT_SUCCESS;
        }
+ if (mountcfg.mountmode == EROFSMOUNT_MODE_DISCONNECT) {
+               err = erofsmount_disconnect(mountcfg.target);
+               if (err < 0)
+                       fprintf(stderr, "Failed to disconnect %s: %s\n",
+                               mountcfg.target, erofs_strerror(err));
+               return err ? EXIT_FAILURE : EXIT_SUCCESS;
+       }
+
        if (mountcfg.backend == EROFSFUSE) {
                err = erofsmount_fuse(mountcfg.device, mountcfg.target,
                                      mountcfg.fstype, mountcfg.full_options);

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