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From: Andreas Gruenbacher <agruenba@redhat.com>
To: "Andreas Grünbacher" <andreas.gruenbacher@gmail.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Andreas Gruenbacher" <agruenba@redhat.com>,
	"Darrick J . Wong" <djwong@kernel.org>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Huang Jianan" <huangjianan@oppo.com>,
	linux-erofs@lists.ozlabs.org,
	"Linux FS-devel Mailing List" <linux-fsdevel@vger.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7] iomap: make inline data support more flexible
Date: Mon, 26 Jul 2021 15:10:51 +0200	[thread overview]
Message-ID: <CAHc6FU6t84w-RoV7jyQmVAdvjEk6AcVVL6YkhBr10rNKs8DOrQ@mail.gmail.com> (raw)
In-Reply-To: <YP6vs180ThT1A2dO@B-P7TQMD6M-0146.local>

On Mon, Jul 26, 2021 at 2:51 PM Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> Hi Andreas, Christoph,
>
> On Mon, Jul 26, 2021 at 02:27:12PM +0200, Andreas Grünbacher wrote:
> > Am Mo., 26. Juli 2021 um 14:17 Uhr schrieb Christoph Hellwig <hch@lst.de>:
> > >
> > > > Subject: iomap: Support tail packing
> > >
> > > I can't say I like this "tail packing" language here when we have the
> > > perfectly fine inline wording.  Same for various comments in the actual
> > > code.
> > >
> > > > +     /* inline and tail-packed data must start page aligned in the file */
> > > > +     if (WARN_ON_ONCE(offset_in_page(iomap->offset)))
> > > > +             return -EIO;
> > > > +     if (WARN_ON_ONCE(size > PAGE_SIZE - offset_in_page(iomap->inline_data)))
> > > > +             return -EIO;
> > >
> > > Why can't we use iomap_inline_data_size_valid here?
> >
> > We can now. Gao, can you change that?
>
> Thank you all taking so much time on this! much appreciated.
>
> I'm fine to update that.
>
> >
> > > That is how can size be different from iomap->length?
> >
> > Quoting from my previous reply,
> >
> > "In the iomap_readpage case (iomap_begin with flags == 0),
> > iomap->length will be the amount of data up to the end of the inode.
>
> For tail-packing cases, iomap->length is just the length of tail-packing
> inline extent.
>
> > In the iomap_file_buffered_write case (iomap_begin with flags ==
> > IOMAP_WRITE), iomap->length will be the size of iomap->inline_data.
> > (For extending writes, we need to write beyond the current end of
> > inode.) So iomap->length isn't all that useful for
> > iomap_read_inline_data."
>
> Ok, now it seems I get your point. For the current gfs2 inline cases:
>   iomap_write_begin
>     iomap_write_begin_inline
>       iomap_read_inline_data
>
> here, gfs2 passes a buffer instead with "iomap->length", maybe it
> could be larger than i_size_read(inode) for gfs2. Is that correct?
>
>         loff_t max_size = gfs2_max_stuffed_size(ip);
>
>         iomap->length = max_size;
>
> If that is what gfs2 currently does, I think it makes sense to
> temporarily use as this, but IMO, iomap->inline_bufsize is not
> iomap->length. These are 2 different concepts.
>
> >
> > > Shouldn't the offset_in_page also go into iomap_inline_data_size_valid,
> > > which should probably be called iomap_inline_data_valid then?
> >
> > Hmm, not sure what you mean: iomap_inline_data_size_valid does take
> > offset_in_page(iomap->inline_data) into account.
> >
> > > >       if (iomap->type == IOMAP_INLINE) {
> > > > +             int ret = iomap_read_inline_data(inode, page, iomap);
> > > > +             return ret ?: PAGE_SIZE;
> >
> > > The ?: expression without the first leg is really confuing.  Especially
> > > if a good old if is much more readable here.
> >
> > I'm sure Gao can change this.
> >
> > >                 int ret = iomap_read_inline_data(inode, page, iomap);
> > >
> > >                 if (ret)
> > >                         return ret;
> > >                 return PAGE_SIZE;
>
> I'm fine to update it if no strong opinion.
>
> > >
> > > > +             copied = copy_from_iter(iomap_inline_data(iomap, pos), length, iter);
> > >
> > >
> > > > +             copied = copy_to_iter(iomap_inline_data(iomap, pos), length, iter);
> > >
> > > Pleae avoid the overly long lines.
> >
> > I thought people were okay with 80 character long lines?
>
> Christoph mentioned before as below:
> https://lore.kernel.org/linux-fsdevel/YPVe41YqpfGLNsBS@infradead.org/
>
> We also need to take the offset into account for the write side.
> I guess it would be nice to have a local variable for the inline
> address to not duplicate that calculation multiple times.

Fair enough, we could add a local variable:

  void *inline_data = iomap_inline_data(iomap, pos);

and use that in the copy_from_iter and copy_to_iter. Why not.

Thanks,
Andreas


  reply	other threads:[~2021-07-26 13:11 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-23 17:41 [PATCH v7] iomap: make inline data support more flexible Gao Xiang
2021-07-23 17:41 ` Gao Xiang
2021-07-23 19:40 ` Matthew Wilcox
2021-07-23 19:40   ` Matthew Wilcox
2021-07-24  0:54   ` Gao Xiang
2021-07-24  0:54     ` Gao Xiang
2021-07-25 21:39 ` Andreas Grünbacher
2021-07-25 21:39   ` Andreas Grünbacher
2021-07-25 22:16 ` Andreas Gruenbacher
2021-07-25 22:16   ` Andreas Gruenbacher
2021-07-26  2:36   ` Gao Xiang
2021-07-26  2:36     ` Gao Xiang
2021-07-26  7:22     ` Andreas Gruenbacher
2021-07-26  7:22       ` Andreas Gruenbacher
2021-07-26  7:38       ` Gao Xiang
2021-07-26  7:38         ` Gao Xiang
2021-07-26 21:36       ` Darrick J. Wong
2021-07-26 21:36         ` Darrick J. Wong
2021-07-26 22:20         ` Andreas Grünbacher
2021-07-26 22:20           ` Andreas Grünbacher
2021-07-26  3:06   ` Matthew Wilcox
2021-07-26  3:06     ` Matthew Wilcox
2021-07-26  6:56     ` Andreas Gruenbacher
2021-07-26  6:56       ` Andreas Gruenbacher
2021-07-26  4:00   ` Gao Xiang
2021-07-26  4:00     ` Gao Xiang
2021-07-26  8:08     ` Andreas Grünbacher
2021-07-26  8:08       ` Andreas Grünbacher
2021-07-26  8:17       ` Gao Xiang
2021-07-26  8:17         ` Gao Xiang
2021-07-26 11:06     ` Andreas Gruenbacher
2021-07-26 11:06       ` Andreas Gruenbacher
2021-07-26 12:17       ` Christoph Hellwig
2021-07-26 12:17         ` Christoph Hellwig
2021-07-26 12:27         ` Andreas Grünbacher
2021-07-26 12:27           ` Andreas Grünbacher
2021-07-26 12:50           ` Gao Xiang
2021-07-26 12:50             ` Gao Xiang
2021-07-26 13:10             ` Andreas Gruenbacher [this message]
2021-07-26 13:27           ` Christoph Hellwig
2021-07-26 13:27             ` Christoph Hellwig
2021-07-27  8:20         ` David Sterba
2021-07-27  8:20           ` David Sterba
2021-07-27 13:35           ` Matthew Wilcox
2021-07-27 15:04             ` Gao Xiang
2021-07-27 15:04               ` Gao Xiang
2021-07-27 16:53             ` David Sterba
2021-07-27 16:53               ` David Sterba
2021-07-26 12:32       ` Matthew Wilcox
2021-07-26 12:32         ` Matthew Wilcox
2021-07-26 13:03         ` Andreas Gruenbacher
2021-07-26 13:03           ` Andreas Gruenbacher
2021-07-26 13:12           ` Gao Xiang
2021-07-26 13:12             ` Gao Xiang
2021-07-26 13:30             ` Christoph Hellwig
2021-07-26  8:08 ` Joseph Qi
2021-07-26  8:08   ` Joseph Qi
2021-08-01 10:29 Andreas Gruenbacher
2021-08-01 10:29 ` Andreas Gruenbacher

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