Unexport do_add_mount() and add in follow_automount(), not ->d_automount()
Unexport do_add_mount() and make ->d_automount() return the vfsmount to be
added rather than calling do_add_mount() itself. follow_automount() will then
do the addition.
This slightly complicates things as ->d_automount() normally wants to add the
new vfsmount to an expiration list and start an expiration timer. The problem
with that is that the vfsmount will be deleted if it has a refcount of 1 and
the timer will not repeat if the expiration list is empty.
To this end, we require the vfsmount to be returned from d_automount() with a
refcount of (at least) 2. One of these refs will be dropped unconditionally.
In addition, follow_automount() must get a 3rd ref around the call to
do_add_mount() lest it eat a ref and return an error, leaving the mount we
have open to being expired as we would otherwise have only 1 ref on it.
d_automount() should also add the the vfsmount to the expiration list (by
calling mnt_set_expiry()) and start the expiration timer before returning, if
this mechanism is to be used. The vfsmount will be unlinked from the
expiration list by follow_automount() if do_add_mount() fails.
This patch also fixes the call to do_add_mount() for AFS to propagate the mount
flags from the parent vfsmount.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index d23b2e3..aa59184 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -241,7 +241,6 @@
struct vfsmount *afs_d_automount(struct path *path)
{
struct vfsmount *newmnt;
- int err;
_enter("{%s,%s}", path->mnt->mnt_devname, path->dentry->d_name.name);
@@ -249,24 +248,12 @@
if (IS_ERR(newmnt))
return newmnt;
- mntget(newmnt);
- err = do_add_mount(newmnt, path, MNT_SHRINKABLE, &afs_vfsmounts);
- switch (err) {
- case 0:
- queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
- afs_mntpt_expiry_timeout * HZ);
- _leave(" = %p {%s}", newmnt, newmnt->mnt_devname);
- return newmnt;
- case -EBUSY:
- /* someone else made a mount here whilst we were busy */
- mntput(newmnt);
- _leave(" = NULL [EBUSY]");
- return NULL;
- default:
- mntput(newmnt);
- _leave(" = %d", err);
- return ERR_PTR(err);
- }
+ mntget(newmnt); /* prevent immediate expiration */
+ mnt_set_expiry(newmnt, &afs_vfsmounts);
+ queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
+ afs_mntpt_expiry_timeout * HZ);
+ _leave(" = %p {%s}", newmnt, newmnt->mnt_devname);
+ return newmnt;
}
/*