From 80b5dce8c59b0de1ed6e403b8298e02dcb4db64b Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 3 Oct 2013 01:31:18 -0700 Subject: vfs: Add a function to lazily unmount all mounts from any dentry. The new function detach_mounts comes in two pieces. The first piece is a static inline test of d_mounpoint that returns immediately without taking any locks if d_mounpoint is not set. In the common case when mountpoints are absent this allows the vfs to continue running with it's same cacheline foot print. The second piece of detach_mounts __detach_mounts actually does the work and it assumes that a mountpoint is present so it is slow and takes namespace_sem for write, and then locks the mount hash (aka mount_lock) after a struct mountpoint has been found. With those two locks held each entry on the list of mounts on a mountpoint is selected and lazily unmounted until all of the mount have been lazily unmounted. v7: Wrote a proper change description and removed the changelog documenting deleted wrong turns. Signed-off-by: Eric W. Biederman Signed-off-by: Al Viro --- fs/mount.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'fs/mount.h') diff --git a/fs/mount.h b/fs/mount.h index 68bb03ed7f1..f82c6284090 100644 --- a/fs/mount.h +++ b/fs/mount.h @@ -87,6 +87,15 @@ extern struct mount *__lookup_mnt_last(struct vfsmount *, struct dentry *); extern bool legitimize_mnt(struct vfsmount *, unsigned); +extern void __detach_mounts(struct dentry *dentry); + +static inline void detach_mounts(struct dentry *dentry) +{ + if (!d_mountpoint(dentry)) + return; + __detach_mounts(dentry); +} + static inline void get_mnt_ns(struct mnt_namespace *ns) { atomic_inc(&ns->count); -- cgit v1.2.3-70-g09d2