linux-ext4 - Re: [RFCv2 0/4] ext4: bmap & fiemap conversion to use iomap

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Message-ID: <20200221114709.GB27165@quack2.suse.cz>
Date:   Fri, 21 Feb 2020 12:47:09 +0100
From:   Jan Kara <jack@...e.cz>
To:     Ritesh Harjani <riteshh@...ux.ibm.com>
Cc:     Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
        tytso@....edu, "Darrick J. Wong" <darrick.wong@...cle.com>,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, cmaiolino@...hat.com
Subject: Re: [RFCv2 0/4] ext4: bmap & fiemap conversion to use iomap

On Fri 21-02-20 09:46:43, Ritesh Harjani wrote:
> 
> 
> On 2/20/20 10:39 PM, Christoph Hellwig wrote:
> > On Thu, Feb 20, 2020 at 10:33:03PM +0530, Ritesh Harjani wrote:
> > > So I was making some changes along the above lines and I think we can take
> > > below approach for filesystem which could determine the
> > > _EXTENT_LAST relatively easily and for cases if it cannot
> > > as Jan also mentioned we could keep the current behavior as is and let
> > > iomap core decide the last disk extent.
> > 
> > Well, given that _EXTENT_LAST never worked properly on any file system
> > since it was added this actually changes behavior and could break
> > existing users.  I'd rather update the documentation to match reality
> > rather than writing a lot of code for a feature no one obviously cared
> > about for years.
> 
> Well I agree to this. Since either ways the _EXTENT_LAST has never worked
> properly or in the same manner across different filesystems.
> In ext4 itself it works differently for extent v/s non-extent based FS.
> So updating the documentation would be a right way to go from here.
> 
> Ted/Jan - do you agree here:-
> Shall we move ahead with this patch series in converting ext4_fiemap to
> use iomap APIs, without worrying about how _EXTENT_LAST is being set via
> iomap core code?

Yes, I'd go ahead with the conversion and don't really bother with backward
compatibility here. In the unlikely case someone comes with a real breakage
this causes, we can always think about how to fix this.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR