(replying from a different ID as you didn't copy me on reply)
On 6/20/07, Jan Blunck <jblunck@xxxxxxx> wrote:
On Wed, 20 Jun 2007 11:22:41 +0530, Bharata B Rao wrote:
> +/*
> + * When propagating mount events to peer group, this is called under
> + * vfsmount_lock. Hence using GFP_ATOMIC for kmalloc here.
> + * TODO: Can we use a separate kmem cache for union_mount ?
> + */
> +struct union_mount *alloc_union_mount(struct vfsmount *src_mnt,
> + struct dentry *src_dentry, struct vfsmount *dst_mnt,
> + struct dentry *dst_dentry)
> +{
> + struct union_mount *u;
> + u = kmalloc(sizeof(struct union_mount), GFP_ATOMIC);
> + if (!u)
> + return u;
> + u->dst_mnt = mntget(dst_mnt);
> + u->dst_dentry = dget(dst_dentry);
> + u->src_mnt = src_mnt;
> + u->src_dentry = dget(src_dentry);
> + INIT_LIST_HEAD(&u->hash);
> + INIT_LIST_HEAD(&u->list);
> + return u;
> +}
Hmm, you pin the dentries in memory until umount. This isn't good. Besides
that this doesn't work with file systems that do invalidate their
dentries. The file system must have a chance to replace the dentry in the
union structure.
Yes, both top level and next level dentries are pinned until umount of
the upper layer. I was thinking if we could prune these from
prune_dcache(). What do you think ?
Ok, I haven't thought about filesystem invalidating the dentries. Yet
to understand the dentry invalidation, but would filesystem invalidate
an inuse dentry ?
Regards,
Bharata.
--
"Men come and go but mountains remain" -- Ruskin Bond.
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