diff options
| -rw-r--r-- | libmount/src/hook_subdir.c | 21 | ||||
| -rw-r--r-- | sys-utils/mount.8.adoc | 4 |
2 files changed, 19 insertions, 6 deletions
diff --git a/libmount/src/hook_subdir.c b/libmount/src/hook_subdir.c index 1e5d79958a..7cbb2c88d4 100644 --- a/libmount/src/hook_subdir.c +++ b/libmount/src/hook_subdir.c @@ -313,6 +313,7 @@ static int is_subdir_required(struct libmnt_context *cxt, int *rc, char **subdir struct libmnt_optlist *ol; struct libmnt_opt *opt; const char *dir = NULL; + unsigned long flags = 0; assert(cxt); assert(rc); @@ -328,16 +329,26 @@ static int is_subdir_required(struct libmnt_context *cxt, int *rc, char **subdir return 0; dir = mnt_opt_get_value(opt); - if (!dir || !*dir) { DBG(HOOK, ul_debug("failed to parse X-mount.subdir '%s'", dir)); *rc = -MNT_ERR_MOUNTOPT; - } else { - *subdir = strdup(dir); - if (!*subdir) - *rc = -ENOMEM; + return 0; + } + + *rc = mnt_optlist_get_flags(ol, &flags, cxt->map_linux, 0); + if (*rc) + return 0; + + if (flags & MS_REMOUNT || flags & MS_BIND || flags & MS_MOVE + || mnt_context_propagation_only(cxt)) { + DBG(HOOK, ul_debug("ignore subdir= (bind/move/remount/..)")); + return 0; } + *subdir = strdup(dir); + if (!*subdir) + *rc = -ENOMEM; + return *rc == 0; } diff --git a/sys-utils/mount.8.adoc b/sys-utils/mount.8.adoc index bb4151225a..95998ce2ad 100644 --- a/sys-utils/mount.8.adoc +++ b/sys-utils/mount.8.adoc @@ -767,7 +767,9 @@ Note that *mount*(8) still sanitizes and canonicalizes the source and target pat Do not create and mount a loop device, even if the source of the mount is a regular file. **X-mount.subdir=**_directory_:: -Allow mounting a sub-directory of a filesystem instead of the root directory. For now, this feature is implemented by a temporary filesystem root-directory mount in an unshared namespace and then binding the sub-directory to the final mount point and unmounting the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple *mount*(2) syscalls. +Allow mounting a subdirectory of a filesystem instead of the root directory. This is effective only when a new instance of a filesystem is attached to the system. The option is silently ignored for operations like remount, bind mount, or move. ++ +For now, this feature is implemented by a temporary filesystem root-directory mount in an unshared namespace and then binding the sub-directory to the final mount point and unmounting the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple *mount*(2) syscalls. + Note that this feature will not work in session with an unshared private mount namespace (after *unshare --mount*) on old kernels or with *mount*(8) without support for file-descriptors-based mount kernel API. In this case, you need *unshare --mount --propagation shared*. + |