linux-kernel - Re: [PATCH v3 2/5] fat: allocate persistent inode numbers

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Date:	Mon, 24 Sep 2012 12:22:25 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	Namjae Jeon <linkinjeon@...il.com>, akpm@...ux-foundation.org,
	viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Ravishankar N <ravi.n1@...sung.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH v3 2/5] fat: allocate persistent inode numbers

On Tue, Sep 25, 2012 at 01:16:45AM +0900, OGAWA Hirofumi wrote:
> "J. Bruce Fields" <bfields@...ldses.org> writes:
> 
> >> > There is some unclear thing.
> >> > When I see first mail, I think maybe you don't want to use i_pos for inode->ino.
> >> > FAT allocate inode->ino from i_unique on server side and If NFS client
> >> > use i_pos for inode->ino in fat_get_attr, inode numbers on each
> >> > client/server will still be mismatched.
> >> >
> >> > Would you plz give me hint ?
> >> 
> >> ->i_ino is long. It can't hold i_pos fully on 32bit arch, so we can't
> >> use ->i_no to store i_pos, and changing ->i_ino is unnecessary. If
> >> getattr() returned i_pos as ino, nobody see ->i_ino anymore except
> >> internal of kernel.
> >
> > The NFS server must always return the same inode number for the same
> > filehandle.  To do otherwise is a bug.
> >
> >> Furthermore I think there is no issue even if server and client didn't
> >> have same ino. Because client just uses FH (nfs4 seems to be using
> >> stat.ino though).
> >
> > The client may expose a different inode number to userspace, but it's
> > probably the server-provided inode number that it's checking.
> >
> > (And even if the Linux client didn't currently happen to do that check,
> > this would still be a bug.)
> 
> In this context, inode number != inode->i_ino, right? It should be
> kstat.ino, and in FAT case, it will return i_pos always. Otherwise 64bit
> inode number would not work.
> 
> So, I think we are doing right thing for now.

Oh, OK.  On a quick check, yes, the numbers the server returns to
clients are taken from either kstat.ino or the ino argument of the
filldir function.

--b.
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