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| author | Ian Kent <ikent@redhat.com> | 2016-11-24 08:03:41 +1100 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2016-12-03 20:51:35 -0500 |
| commit | c6609c0a1c34fc097152b28b496236625673924f (patch) | |
| tree | 864cfb55fd8727e2a475ca44dd8d7df5a8488005 | |
| parent | fb5f51c7425ebc808d91329257cbc963e2421368 (diff) | |
| download | linux-c6609c0a1c34fc097152b28b496236625673924f.tar.gz | |
vfs: add path_is_mountpoint() helper
d_mountpoint() can only be used reliably to establish if a dentry is not mounted in any namespace. It isn't aware of the possibility there may be multiple mounts using a given dentry that may be in a different namespace. Add helper functions, path_is_mountpoint(), that checks if a struct path is a mountpoint for this case. Link: http://lkml.kernel.org/r/20161011053358.27645.9729.stgit@pluto.themaw.net Signed-off-by: Ian Kent <raven@themaw.net> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Omar Sandoval <osandov@osandov.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -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 */ |