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From: "Andreas Grünbacher" <andreas.gruenbacher@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
	Dave Chinner <david@fromorbit.com>,
	cluster-devel <cluster-devel@redhat.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Dave Chinner <dchinner@redhat.com>
Subject: Re: [PATCH v4 06/11] iomap: Add write_{begin,end} iomap operations
Date: Fri, 25 May 2018 19:58:14 +0200	[thread overview]
Message-ID: <CAHpGcM+m=Ar=_WO31J3OqdvGPHq3Ozq-QtAYKt0y8WL6+ybWtQ@mail.gmail.com> (raw)
In-Reply-To: <20180518160458.GA3503@lst.de>

2018-05-18 18:04 GMT+02:00 Christoph Hellwig <hch@lst.de>:
> On Tue, May 15, 2018 at 10:16:52AM +0200, Andreas Gruenbacher wrote:
>> > Yes.  And from a quick look we can easily handle "stuffed" aka inline
>> > data with the existing architecture.  We just need a new IOMAP_INLINE
>> > flag for the extent type. Details will need to be worked out how to
>> > pass that data, either a struct page or virtual address should probably
>> > do it.
>>
>> This is about data journaling, it has nothing to do with "stuffed"
>> files per se. With journaled data writes, we need to do some special
>> processing for each page so that the page ends up in the journal
>> before it gets written back to its proper on-disk location. It just
>> happens that since we need these per-page operations anyway, the
>> "unstuffing" and "re-stuffing" nicely fits in those operations as
>> well.
>
> Your series makes two uses of the callbacks - one use case is to
> deal with inline data.

Yes, it's not perfect.

> The right way to deal with that is to make
> inline data an explicit iomap type (done in my next posting of the
> buffer head removal series), and then have iomap_begin find the data,
> kmap it and return it in the iomap, with iomap_end doing any fixups.

I see what you mean. How would iomap_write_actor deal with
IOMAP_INLINE -- just skip iomap_write_begin and iomap_write_end and
grab the page from the iomap? I'm a bit worried about reintroducing
the deadlock that iomap_write_actor so carefully tries to avoid.

> For the data journaing I agree that we need a post-write per page
> callout, but I think this should be just a simple optional callout
> just for data journaling, which doesn't override the remaining
> write_end handling.
>
>> Been there. An earlier version of the patches did have a separate
>> stuffed write path and the unstuffing and re-stuffing didn't happen in
>> those per-page operations. The result was much messier overall.
>
> Pointer, please.

It's in this patch:

  https://patchwork.kernel.org/patch/10191007/

from this posting:

https://www.spinics.net/lists/linux-fsdevel/msg121318.html

Thanks,
Andreas

  reply	other threads:[~2018-05-25 17:58 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-14 15:36 [PATCH v4 00/11] gfs2 iomap write support Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 01/11] gfs2: Update find_metapath comment Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 02/11] gfs2: hole_size improvement Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 03/11] gfs2: gfs2_stuffed_write_end cleanup Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 04/11] gfs2: Remove ordered write mode handling from gfs2_trans_add_data Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 05/11] gfs2: Iomap cleanups and improvements Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 06/11] iomap: Add write_{begin,end} iomap operations Andreas Gruenbacher
2018-05-15  1:11   ` Dave Chinner
2018-05-15  7:22     ` Christoph Hellwig
2018-05-15  8:16       ` Andreas Gruenbacher
2018-05-18 16:04         ` Christoph Hellwig
2018-05-25 17:58           ` Andreas Grünbacher [this message]
2018-05-28 13:02             ` Christoph Hellwig
2018-05-14 15:36 ` [PATCH v4 07/11] gfs2: iomap buffered write support Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 08/11] gfs2: gfs2_extent_length cleanup Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 09/11] gfs2: iomap direct I/O support Andreas Gruenbacher
2018-05-15  7:31   ` Christoph Hellwig
2018-05-16 20:36     ` Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 10/11] gfs2: Remove gfs2_write_{begin,end} Andreas Gruenbacher
2018-05-14 15:36 ` [PATCH v4 11/11] iomap: Complete partial direct I/O writes synchronously Andreas Gruenbacher
2018-05-15  7:24   ` Christoph Hellwig
2018-05-16 20:27     ` Andreas Gruenbacher
2018-05-18 15:56       ` Christoph Hellwig
2018-05-18 18:35         ` Andreas Grünbacher

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