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authorEric W. Biederman <ebiederman@twitter.com>2013-10-03 01:31:18 -0700
committerAl Viro <viro@zeniv.linux.org.uk>2014-10-09 02:38:55 -0400
commit80b5dce8c59b0de1ed6e403b8298e02dcb4db64b (patch)
tree90b7a4f30c050d37f7ec436b63c8f9d7816199f0 /fs/mount.h
parente2dfa935464272395b4f35f4cc74ffcc87418b84 (diff)
downloadlwn-80b5dce8c59b0de1ed6e403b8298e02dcb4db64b.tar.gz
lwn-80b5dce8c59b0de1ed6e403b8298e02dcb4db64b.zip
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 <ebiederman@twitter.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/mount.h')
-rw-r--r--fs/mount.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/mount.h b/fs/mount.h
index 68bb03ed7f19..f82c62840905 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);