linux-ext4 - Re: [PATCH v6 00/11] ext4: port direct I/O to iomap infrastructure

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Date:   Wed, 30 Oct 2019 12:39:18 +0100
From:   Jan Kara <jack@...e.cz>
To:     Matthew Bobrowski <mbobrowski@...browski.org>
Cc:     "Theodore Y. Ts'o" <tytso@....edu>, jack@...e.cz,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, hch@...radead.org,
        david@...morbit.com, darrick.wong@...cle.com
Subject: Re: [PATCH v6 00/11] ext4: port direct I/O to iomap infrastructure

On Wed 30-10-19 12:26:52, Jan Kara wrote:
> On Wed 30-10-19 13:00:24, Matthew Bobrowski wrote:
> > On Tue, Oct 29, 2019 at 07:34:01PM -0400, Theodore Y. Ts'o wrote:
> > > On Tue, Oct 29, 2019 at 07:31:59PM -0400, Theodore Y. Ts'o wrote:
> > > > Hi Matthew, it looks like there are a number of problems with this
> > > > patch series when using the ext3 backwards compatibility mode (e.g.,
> > > > no extents enabled).
> > > > 
> > > > So the following configurations are failing:
> > > > 
> > > > kvm-xfstests -c ext3   generic/091 generic/240 generic/263
> > 
> > This is one mode that I didn't get around to testing. Let me take a
> > look at the above and get back to you.
> 
> If I should guess, I'd start looking at what that -ENOTBLK fallback from
> direct IO ends up doing as we seem to be hitting that path...

Hum, actually no. This write from fsx output:

24( 24 mod 256): WRITE    0x23000 thru 0x285ff  (0x5600 bytes)

should have allocated blocks to where the failed write was going (0x24000).
But still I'd expect some interaction between how buffered writes to holes
interact with following direct IO writes... One of the subtle differences
we have introduced with iomap conversion is that the old code in
__generic_file_write_iter() did fsync & invalidate written range after
buffered write fallback and we don't seem to do that now (probably should
be fixed regardless of relation to this bug).

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