From: Christoph Hellwig <hch@lst.de>
To: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@lst.de>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
avi@scylladb.com
Subject: Re: [PATCH 09/10] iomap: add a IOMAP_DIO_NOALLOC flag
Date: Thu, 14 Jan 2021 18:26:50 +0100 [thread overview]
Message-ID: <20210114172650.GA30826@lst.de> (raw)
In-Reply-To: <20210112232923.GD331610@dread.disaster.area>
On Wed, Jan 13, 2021 at 10:29:23AM +1100, Dave Chinner wrote:
> On Tue, Jan 12, 2021 at 05:26:15PM +0100, Christoph Hellwig wrote:
> > Add a flag to request that the iomap instances do not allocate blocks
> > by translating it to another new IOMAP_NOALLOC flag.
>
> Except "no allocation" that is not what XFS needs for concurrent
> sub-block DIO.
Well, this is just a quick draft. I could not come up with a better
name, so I picked on that explains most but not all of what is going
on.
> If we're going to use a flag for this specific functionality, let's
> call it what it is: IOMAP_DIO_UNALIGNED/IOMAP_UNALIGNED and do two
> things with it.
Sounds fine with me.
>
> 1. Make unaligned IO a formal part of the iomap_dio_rw()
> behaviour so it can do the common checks to for things that
> need exclusive serialisation for unaligned IO (i.e. avoid IO
> spanning EOF, abort if there are cached pages over the
> range, etc).
Note that these all writes already fall back to buffered I/O if
invalidate_inode_pages2_range fails, so there must never be cached
pages for direct I/O these days. This is different from NOWAIT
I/O where we simply give up if there are any cached pages and don't
even try to invalidate them.
> 2. require the filesystem mapping callback do only allow
> unaligned IO into ranges that are contiguous and don't
> require mapping state changes or sub-block zeroing to be
> performed during the sub-block IO.
Yeah.
next prev parent reply other threads:[~2021-01-14 17:27 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 16:26 [RFC] another attempt to reduce sub-block DIO serialisation Christoph Hellwig
2021-01-12 16:26 ` [PATCH 01/10] xfs: factor out a xfs_ilock_iocb helper Christoph Hellwig
2021-01-12 22:41 ` Dave Chinner
2021-01-12 16:26 ` [PATCH 02/10] xfs: make xfs_file_aio_write_checks IOCB_NOWAIT-aware Christoph Hellwig
2021-01-12 22:42 ` Dave Chinner
2021-01-12 16:26 ` [PATCH 03/10] xfs: cleanup the read/write helper naming Christoph Hellwig
2021-01-12 22:43 ` Dave Chinner
2021-01-12 16:26 ` [PATCH 04/10] xfs: remove the buffered I/O fallback assert Christoph Hellwig
2021-01-12 22:44 ` Dave Chinner
2021-01-12 16:26 ` [PATCH 05/10] xfs: simplify the read/write tracepoints Christoph Hellwig
2021-01-12 22:54 ` Dave Chinner
2021-01-12 16:26 ` [PATCH 06/10] xfs: improve the reflink_bounce_dio_write tracepoint Christoph Hellwig
2021-01-12 22:56 ` Dave Chinner
2021-01-12 16:26 ` [PATCH 07/10] xfs: split unaligned DIO write code out Christoph Hellwig
2021-01-12 23:00 ` Dave Chinner
2021-01-12 16:26 ` [PATCH 08/10] iomap: pass a flags argument to iomap_dio_rw Christoph Hellwig
2021-01-12 16:26 ` [PATCH 09/10] iomap: add a IOMAP_DIO_NOALLOC flag Christoph Hellwig
2021-01-12 23:29 ` Dave Chinner
2021-01-13 15:32 ` Brian Foster
2021-01-13 22:49 ` Dave Chinner
2021-01-14 10:23 ` Brian Foster
2021-01-14 10:43 ` Avi Kivity
2021-01-14 17:29 ` Christoph Hellwig
2021-01-14 17:26 ` Christoph Hellwig [this message]
2021-01-12 16:26 ` [PATCH 10/10] xfs: reduce exclusive locking on unaligned dio Christoph Hellwig
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