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

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Message-Id: <20200221041644.53A9852052@d06av21.portsmouth.uk.ibm.com>
Date:   Fri, 21 Feb 2020 09:46:43 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
        tytso@....edu
Cc:     "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 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?



-ritesh