On Tue, Jun 12, 2018 at 03:29:26AM +0100, Al Viro wrote:
> It might (or might not) work for the filesystems you'd been testing
> on, but it's a lot of trouble waiting to happen. Hell, try and use
> ecryptfs as lower layer, see how fast it'll blow up. Sure, it's
> a dumb testcase, but I don't see how to check if something more
> realistic is trouble-free.
>
> I'd been trying to come up with some way to salvage that kludge of yours,
> but I don't see any solutions. We don't have good proxies for "this
> filesystem might be unsafe as lower layer" ;-/
Note that anything that uses file_dentry() anywhere near ->open(),
->read_iter() or ->write_iter() is an instant trouble with your scheme.
Such as
int nfs_open(struct inode *inode, struct file *filp)
{
struct nfs_open_context *ctx;
ctx = alloc_nfs_open_context(file_dentry(filp), filp->f_mode, filp);
if (IS_ERR(ctx))
return PTR_ERR(ctx);
nfs_file_set_open_context(filp, ctx);
put_nfs_open_context(ctx);
nfs_fscache_open_file(inode, filp);
return 0;
}
You do want to support NFS for lower layers, right?
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