From c6609c0a1c34fc097152b28b496236625673924f Mon Sep 17 00:00:00 2001 From: Ian Kent Date: Thu, 24 Nov 2016 08:03:41 +1100 Subject: 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 Cc: Al Viro Cc: Eric W. Biederman Cc: Omar Sandoval Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- fs/namespace.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'fs/namespace.c') 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; -- cgit v1.2.3 From 640eb7e7b5242af53c456552a526d0080e6333f8 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Date: Mon, 14 Nov 2016 22:14:35 +0100 Subject: fs: Constify path_is_under()'s arguments MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The function path_is_under() doesn't modify the paths pointed by its arguments but only browse them. Constifying this pointers make a cleaner interface to be used by (future) code which may only have access to const struct path pointers (e.g. LSM hooks). Signed-off-by: Mickaël Salaün Cc: Alexander Viro Signed-off-by: Al Viro --- fs/namespace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index e6c234b1a645..4d80a5066a1f 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2997,7 +2997,7 @@ bool is_path_reachable(struct mount *mnt, struct dentry *dentry, return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); } -bool path_is_under(struct path *path1, struct path *path2) +bool path_is_under(const struct path *path1, const struct path *path2) { bool res; read_seqlock_excl(&mount_lock); -- cgit v1.2.3 From ca71cf71eeda04dc9ad18271504e499013af5415 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 20 Nov 2016 19:45:28 -0500 Subject: namespace.c: constify struct path passed to a bunch of primitives Signed-off-by: Al Viro --- fs/namespace.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index 4d80a5066a1f..9ad88a45b3e3 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -678,7 +678,7 @@ out: * * lookup_mnt takes a reference to the found vfsmount. */ -struct vfsmount *lookup_mnt(struct path *path) +struct vfsmount *lookup_mnt(const struct path *path) { struct mount *child_mnt; struct vfsmount *m; @@ -1159,7 +1159,7 @@ struct vfsmount *mntget(struct vfsmount *mnt) } EXPORT_SYMBOL(mntget); -struct vfsmount *mnt_clone_internal(struct path *path) +struct vfsmount *mnt_clone_internal(const struct path *path) { struct mount *p; p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); @@ -1758,7 +1758,7 @@ out: /* Caller should check returned pointer for errors */ -struct vfsmount *collect_mounts(struct path *path) +struct vfsmount *collect_mounts(const struct path *path) { struct mount *tree; namespace_lock(); @@ -1791,7 +1791,7 @@ void drop_collected_mounts(struct vfsmount *mnt) * * Release with mntput(). */ -struct vfsmount *clone_private_mount(struct path *path) +struct vfsmount *clone_private_mount(const struct path *path) { struct mount *old_mnt = real_mount(path->mnt); struct mount *new_mnt; -- cgit v1.2.3