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| author | Eric W. Biederman <ebiederman@twitter.com> | 2013-10-03 10:31:18 +0200 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2014-10-09 08:38:55 +0200 |
| commit | 80b5dce8c59b0de1ed6e403b8298e02dcb4db64b (patch) | |
| tree | 90b7a4f30c050d37f7ec436b63c8f9d7816199f0 | |
| parent | vfs: factor out lookup_mountpoint from new_mountpoint (diff) | |
| download | linux-80b5dce8c59b0de1ed6e403b8298e02dcb4db64b.tar.xz linux-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>
| -rw-r--r-- | fs/mount.h | 9 | ||||
| -rw-r--r-- | fs/namespace.c | 31 |
2 files changed, 40 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); diff --git a/fs/namespace.c b/fs/namespace.c index 88fc3f4d77ed..00e5b1efa591 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1468,6 +1468,37 @@ static int do_umount(struct mount *mnt, int flags) return retval; } +/* + * __detach_mounts - lazily unmount all mounts on the specified dentry + * + * During unlink, rmdir, and d_drop it is possible to loose the path + * to an existing mountpoint, and wind up leaking the mount. + * detach_mounts allows lazily unmounting those mounts instead of + * leaking them. + * + * The caller may hold dentry->d_inode->i_mutex. + */ +void __detach_mounts(struct dentry *dentry) +{ + struct mountpoint *mp; + struct mount *mnt; + + namespace_lock(); + mp = lookup_mountpoint(dentry); + if (!mp) + goto out_unlock; + + lock_mount_hash(); + while (!hlist_empty(&mp->m_list)) { + mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); + umount_tree(mnt, 2); + } + unlock_mount_hash(); + put_mountpoint(mp); +out_unlock: + namespace_unlock(); +} + /* * Is the caller allowed to modify his namespace? */ |