From: Christoph Hellwig <hch@infradead.org>
To: "J. Bruce Fields" <bfields@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Trond Myklebust <trondmy@hammerspace.com>,
Anna Schumaker <schumakeranna@gmail.com>,
Chuck Lever <chuck.lever@oracle.com>
Subject: Re: [PATCH 2/3] nfsd: move change attribute generation to filesystem
Date: Fri, 22 Jan 2021 08:20:59 +0000 [thread overview]
Message-ID: <20210122082059.GA119852@infradead.org> (raw)
In-Reply-To: <20210121202756.GA13298@pick.fieldses.org>
On Thu, Jan 21, 2021 at 03:27:56PM -0500, J. Bruce Fields wrote:
> > Another indirect call just to fetch the change attribute (which happens
> > a lot IIRC) does not seem very optimal to me.
>
> In the next patch we're removing an fh_getattr (vfs_getattr) in the case
> we call the new op, so that's typically a net decrease in indirect
> calls.
>
> Though maybe we could use a flag here and do without either.
>
> > And the fact that we need three duplicate implementations also is not
> > very nice.
>
> Ext4 and xfs are identical, btrfs is a little different since it doesn't
> consult I_VERSION. (And then there's nfs, which uses the origin
> server's i_version if it can.)
I'd much prefer to just keep consulting the I_VERSION flag and only
add the new op as an override for the NFS export.
>
> I also have a vague idea that some filesystem-specific improvements
> might be possible. (E.g., if a filesystem had some kind of boot count
> in the superblock, maybe that would be a better way to prevent the
> change attribute from going backwards on reboot than the thing
> generic_fetch_iversion is currently doing with ctime. But I have no
> concrete plan there, maybe I'm dreaming.)
Even without the ctime i_version never goes backward, what is the
problem here?
next prev parent reply other threads:[~2021-01-22 8:22 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 19:24 [PATCH 0/3] NFS change attribute patches J. Bruce Fields
2021-01-19 19:24 ` [PATCH 1/3] nfs: use change attribute for NFS re-exports J. Bruce Fields
2021-01-19 19:24 ` [PATCH 2/3] nfsd: move change attribute generation to filesystem J. Bruce Fields
2021-01-20 8:46 ` Christoph Hellwig
2021-01-21 20:27 ` J. Bruce Fields
2021-01-22 8:20 ` Christoph Hellwig [this message]
2021-01-22 14:47 ` J. Bruce Fields
2021-01-22 17:32 ` Christoph Hellwig
2021-01-22 18:46 ` J. Bruce Fields
2021-01-29 19:25 ` J. Bruce Fields
2021-01-29 19:26 ` [PATCH 1/2 v2] nfs: use change attribute for NFS re-exports J. Bruce Fields
2021-01-29 19:27 ` [PATCH 2/2 v2] nfsd: skip some unnecessary stats in the v4 case J. Bruce Fields
2021-01-30 6:02 ` Christoph Hellwig
2021-01-29 20:43 ` [PATCH 1/2 v2] nfs: use change attribute for NFS re-exports Chuck Lever
2021-01-30 6:02 ` Christoph Hellwig
2021-01-19 19:24 ` [PATCH 3/3] nfsd: skip some unnecessary stats in the v4 case J. Bruce Fields
2021-01-22 17:34 ` [PATCH 0/3] NFS change attribute patches Christoph Hellwig
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