[lustre-devel] [PATCH 04/22] ext4: export inode management

[Oleg Drokin]

> On Jul 22, 2019, at 12:34 AM, NeilBrown <neilb at suse.com> wrote:
> 
> On Sun, Jul 21 2019, James Simmons wrote:
> 
>> Make ext4_delete_entry() exportable for osd-ldiskfs. Also add
>> exportable ext4_create_inode().
> 
> Why can't lustre use vfs_unlink like everyone else?  And vfs_mknod()?
> My hope is that what we land upstream will use generic interfaces only.
> If there is something that osd needs to do that the generic interfaces
> cannot support, then we need to look at how to add that to the generic
> interface.

That’s probably going to be a tough thing to do. At times we need certain things
that are bad from vfs standpoint in general sense, but because we have various
outside guarantees from locking and such - we can still do them.

nothing precise comes to mind now, but I remember various games with
nlink count/moving and resurrecting such files.

We also have wider “transaction boundaries”. Where say normal via-vfs transaction
is metadata only, we can request certain data (from ext4 perspective, but metadata
from Lustre) to be part of a particular transaction.