lkml.org 
[lkml]   [2012]   [Aug]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 4/8] fs, exportfs: Add export_encode_inode_fh helper
On Thu, Aug 16, 2012 at 01:02:37AM +0400, Cyrill Gorcunov wrote:
> On Wed, Aug 15, 2012 at 04:45:46PM -0400, J. Bruce Fields wrote:
> > On Wed, Aug 15, 2012 at 01:21:20PM +0400, Cyrill Gorcunov wrote:
> > > To provide fsnotify object inodes being watched without
> > > binding to alphabetical path we need to encode them with
> > > exportfs help. This patch adds a helper which operates
> > > with plain inodes directly.
> >
> > I don't get it--this seems like a really roundabout way to get inode and
> > generation number, if that's all you want.
>
> We can re-open the targets via filehandle on restore, this was the idea.
> All this series aimed to achieve the way to restore objects after checkpoit,
> thus we need to provide additional information which would be enough.

For this to work it'll need to be something you can pass to
open_by_handle_at, won't it?

> > On the other hand, if you want a real filehandle then wouldn't you want
> > to e.g. call the filesystem's ->encode_fh() if necessary, as
> > exportfs_encode_fh() does?
>
> Well, one of the problem I hit when I've been trying to use encode_fh
> is that every new implementation of encode_fh will require some size
> (even unknown) in buffer where encoded data pushed. Correct me please
> if I'm wrong. But with export_encode_inode_fh there is a small buffer
> with pretty known size needed on stack needed for printing data in
> fdinfo.

You can just give encode_fh a too-small data and let it fail if it's not
big enough.

(In practice I think everyone supports NFSv3 filehandles which have a
maximum size of 64 bytes.)

--b.


\
 
 \ /
  Last update: 2012-08-16 00:43    [W:0.101 / U:0.172 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site