diff options
| -rw-r--r-- | fs/mount.h | 6 | ||||
| -rw-r--r-- | fs/namespace.c | 29 | ||||
| -rw-r--r-- | include/linux/mount.h | 2 |
3 files changed, 37 insertions, 0 deletions
diff --git a/fs/mount.h b/fs/mount.h index d2e25d7b64b3..2c856fc47ae3 100644 --- a/fs/mount.h +++ b/fs/mount.h @@ -94,6 +94,12 @@ extern struct mount *__lookup_mnt_last(struct vfsmount *, struct dentry *); extern int __legitimize_mnt(struct vfsmount *, unsigned); extern bool legitimize_mnt(struct vfsmount *, unsigned); +static inline bool __path_is_mountpoint(const struct path *path) +{ + struct mount *m = __lookup_mnt(path->mnt, path->dentry); + return m && likely(!(m->mnt.mnt_flags & MNT_SYNC_UMOUNT)); +} + extern void __detach_mounts(struct dentry *dentry); static inline void detach_mounts(struct dentry *dentry) diff --git a/fs/namespace.c b/fs/namespace.c index e6c234b1a645..7a73383e8365 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1159,6 +1159,35 @@ struct vfsmount *mntget(struct vfsmount *mnt) } EXPORT_SYMBOL(mntget); +/* path_is_mountpoint() - Check if path is a mount in the current + * namespace. + * + * d_mountpoint() can only be used reliably to establish if a dentry is + * not mounted in any namespace and that common case is handled inline. + * d_mountpoint() isn't aware of the possibility there may be multiple + * mounts using a given dentry in a different namespace. This function + * checks if the passed in path is a mountpoint rather than the dentry + * alone. + */ +bool path_is_mountpoint(const struct path *path) +{ + unsigned seq; + bool res; + + if (!d_mountpoint(path->dentry)) + return false; + + rcu_read_lock(); + do { + seq = read_seqbegin(&mount_lock); + res = __path_is_mountpoint(path); + } while (read_seqretry(&mount_lock, seq)); + rcu_read_unlock(); + + return res; +} +EXPORT_SYMBOL(path_is_mountpoint); + struct vfsmount *mnt_clone_internal(struct path *path) { struct mount *p; diff --git a/include/linux/mount.h b/include/linux/mount.h index 1172cce949a4..5b6dd004bfdc 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -98,4 +98,6 @@ extern dev_t name_to_dev_t(const char *name); extern unsigned int sysctl_mount_max; +extern bool path_is_mountpoint(const struct path *path); + #endif /* _LINUX_MOUNT_H */ |