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From: Gao Xiang <>
To: "Andreas Grünbacher" <>
Cc: "Darrick J. Wong" <>,
	Matthew Wilcox <>,,
	Linux FS-devel Mailing List <>,
	LKML <>,
	Christoph Hellwig <>
Subject: Re: [PATCH v4] iomap: support tail packing inline read
Date: Wed, 21 Jul 2021 10:53:58 +0800	[thread overview]
Message-ID: <YPeMRsJwELjoWLFs@B-P7TQMD6M-0146.local> (raw)
In-Reply-To: <>

Hi Andreas,

On Wed, Jul 21, 2021 at 04:26:47AM +0200, Andreas Grünbacher wrote:
> Am Mi., 21. Juli 2021 um 02:33 Uhr schrieb Gao Xiang
> <>:
> > > And since you can only kmap one page at a time, an inline read grabs the
> > > first part of the data in "page one" and then we have to call
> > > iomap_begin a second time get a new address so that we can read the rest
> > > from "page two"?
> >
> > Nope, currently EROFS inline data won't cross page like this.
> >
> > But in principle, yes, I don't want to limit it to the current
> > EROFS or gfs2 usage. I think we could make this iomap function
> > more generally (I mean, I'd like to make the INLINE extent
> > functionity as general as possible,
> Nono. Can we please limit this patch what we actually need right now,
> and worry about extending it later?

Can you elaborate what it will benefit us if we only support one tail
block for iomap_read_inline_data()? (I mean it has similar LOC changes,
similar implementation / complexity.) The only concern I think is if
it causes gfs2 regression, so that is what I'd like to confirm.

In contrast, I'd like to avoid iomap_write_begin() tail-packing because
it's complex and no fs user interests in it for now. So I leave it
untouched for now.

Another concern I really like to convert EROFS to iomap is I'd like to
support sub-page blocksize for EROFS after converting. I don't want to
touch iomap inline code again like this since it interacts 2 directories
thus cause too much coupling.

Gao Xiang

> > my v1 original approach
> > in principle can support any inline extent in the middle of
> > file rather than just tail blocks, but zeroing out post-EOF
> > needs another iteration) and I don't see it add more code and
> > complexity.
> Thanks,
> Andreas

  reply	other threads:[~2021-07-21  2:55 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-20 13:35 Gao Xiang
2021-07-20 20:42 ` Darrick J. Wong
2021-07-20 21:18   ` Matthew Wilcox
2021-07-21  0:03     ` Gao Xiang
2021-07-21  0:17       ` Darrick J. Wong
2021-07-21  0:33         ` Gao Xiang
2021-07-21  2:26           ` Andreas Grünbacher
2021-07-21  2:53             ` Gao Xiang [this message]
2021-07-21  6:43               ` Andreas Grünbacher
2021-07-21  7:28                 ` Gao Xiang
2021-07-21  6:33     ` Andreas Grünbacher
2021-07-20 23:46   ` Gao Xiang

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