From 01619491a5f0766014fe863c5ae480665436e7a2 Mon Sep 17 00:00:00 2001 From: Ian Kent Date: Thu, 24 Nov 2016 08:03:41 +1100 Subject: vfs: add path_has_submounts() 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 the given dentry, possibly in a different namespace. Add function, path_has_submounts(), that checks is a struct path contains mounts (or is a mountpoint itself) to handle this case. Link: http://lkml.kernel.org/r/20161011053403.27645.55242.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/dcache.c | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) (limited to 'fs/dcache.c') diff --git a/fs/dcache.c b/fs/dcache.c index 5c7cc953ac81..8515875854b6 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1306,6 +1306,45 @@ int have_submounts(struct dentry *parent) } EXPORT_SYMBOL(have_submounts); +struct check_mount { + struct vfsmount *mnt; + unsigned int mounted; +}; + +static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry) +{ + struct check_mount *info = data; + struct path path = { .mnt = info->mnt, .dentry = dentry }; + + if (likely(!d_mountpoint(dentry))) + return D_WALK_CONTINUE; + if (__path_is_mountpoint(&path)) { + info->mounted = 1; + return D_WALK_QUIT; + } + return D_WALK_CONTINUE; +} + +/** + * path_has_submounts - check for mounts over a dentry in the + * current namespace. + * @parent: path to check. + * + * Return true if the parent or its subdirectories contain + * a mount point in the current namespace. + */ +int path_has_submounts(const struct path *parent) +{ + struct check_mount data = { .mnt = parent->mnt, .mounted = 0 }; + + read_seqlock_excl(&mount_lock); + d_walk(parent->dentry, &data, path_check_mount, NULL); + read_sequnlock_excl(&mount_lock); + + return data.mounted; +} +EXPORT_SYMBOL(path_has_submounts); + /* * Called by mount code to set a mountpoint and check if the mountpoint is * reachable (e.g. NFS can unhash a directory dentry and then the complete -- cgit