From: "Darrick J. Wong" <djwong@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v2 20/28] iomap: Convert iomap_write_begin() and iomap_write_end() to folios
Date: Wed, 17 Nov 2021 09:10:54 -0800 [thread overview]
Message-ID: <20211117171054.GX24307@magnolia> (raw)
In-Reply-To: <YZUSPga7V797gY4Z@casper.infradead.org>
On Wed, Nov 17, 2021 at 02:31:26PM +0000, Matthew Wilcox wrote:
> On Tue, Nov 16, 2021 at 08:31:27PM -0800, Darrick J. Wong wrote:
> > > @@ -764,16 +761,17 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
> > > break;
> > > }
> > >
> > > - status = iomap_write_begin(iter, pos, bytes, &page);
> > > + status = iomap_write_begin(iter, pos, bytes, &folio);
> > > if (unlikely(status))
> > > break;
> > >
> > > + page = folio_file_page(folio, pos >> PAGE_SHIFT);
> > > if (mapping_writably_mapped(iter->inode->i_mapping))
> > > flush_dcache_page(page);
> > >
> > > copied = copy_page_from_iter_atomic(page, offset, bytes, i);
> >
> > Hrmm. In principle (or I guess even a subsequent patch), if we had
> > multi-page folios, could we simply loop the pages in the folio instead
> > of doing a single page and then calling back into iomap_write_begin to
> > get (probably) the same folio?
> >
> > This looks like a fairly straightforward conversion, but I was wondering
> > about that one little point...
>
> Theoretically, yes, we should be able to do that. But all of this code
> is pretty subtle ("What if we hit a page fault? What if we're writing
> to part of this folio from an mmap of a different part of this folio?
> What if it's !Uptodate? What if we hit this weird ARM super-mprotect
> memory tag thing? What if ...") and, frankly, I got scared. So I've
> left that as future work; someone else can try to wrap their brain around
> all of this.
<nod> That's roughly the same conclusion I came to -- conceptually we
could keep walking pages until we hit /any/ problem or other difference
with the first page that we don't feel like dealing with, and pass that
count to iomap_end... but no need to try that right this second.
Just checking that I grokked what's going on in this series. :)
--D
next prev parent reply other threads:[~2021-11-17 17:10 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-08 4:05 [PATCH v2 00/28] iomap/xfs folio patches Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 01/28] csky,sparc: Declare flush_dcache_folio() Matthew Wilcox (Oracle)
2021-11-09 8:36 ` Christoph Hellwig
2021-11-15 15:54 ` Matthew Wilcox
2021-11-16 6:33 ` Christoph Hellwig
2021-11-16 21:49 ` Matthew Wilcox
2021-11-17 9:52 ` Geert Uytterhoeven
2021-11-08 4:05 ` [PATCH v2 02/28] mm: Add functions to zero portions of a folio Matthew Wilcox (Oracle)
2021-11-09 8:40 ` Christoph Hellwig
2021-11-17 4:45 ` Darrick J. Wong
2021-11-17 14:07 ` Matthew Wilcox
2021-11-17 17:07 ` Darrick J. Wong
2021-11-18 15:55 ` Matthew Wilcox
2021-11-18 17:26 ` Darrick J. Wong
2021-11-18 20:08 ` Matthew Wilcox
2021-11-08 4:05 ` [PATCH v2 03/28] fs: Remove FS_THP_SUPPORT Matthew Wilcox (Oracle)
2021-11-17 4:36 ` Darrick J. Wong
2021-11-08 4:05 ` [PATCH v2 04/28] fs: Rename AS_THP_SUPPORT and mapping_thp_support Matthew Wilcox (Oracle)
2021-11-09 8:41 ` Christoph Hellwig
2021-11-15 16:03 ` Matthew Wilcox
2021-11-16 6:33 ` Christoph Hellwig
2021-11-08 4:05 ` [PATCH v2 05/28] block: Add bio_add_folio() Matthew Wilcox (Oracle)
2021-11-17 4:48 ` Darrick J. Wong
2021-11-08 4:05 ` [PATCH v2 06/28] block: Add bio_for_each_folio_all() Matthew Wilcox (Oracle)
2021-11-17 4:48 ` Darrick J. Wong
2021-11-08 4:05 ` [PATCH v2 07/28] fs/buffer: Convert __block_write_begin_int() to take a folio Matthew Wilcox (Oracle)
2021-11-09 8:42 ` Christoph Hellwig
2021-11-17 4:35 ` Darrick J. Wong
2021-11-08 4:05 ` [PATCH v2 08/28] iomap: Convert to_iomap_page " Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 09/28] iomap: Convert iomap_page_create " Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 10/28] iomap: Convert iomap_page_release " Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 11/28] iomap: Convert iomap_releasepage to use " Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 12/28] iomap: Add iomap_invalidate_folio Matthew Wilcox (Oracle)
2021-11-17 2:20 ` Darrick J. Wong
2021-11-08 4:05 ` [PATCH v2 13/28] iomap: Pass the iomap_page into iomap_set_range_uptodate Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 14/28] iomap: Convert bio completions to use folios Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 15/28] iomap: Use folio offsets instead of page offsets Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 16/28] iomap: Convert iomap_read_inline_data to take a folio Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 17/28] iomap: Convert readahead and readpage to use " Matthew Wilcox (Oracle)
2021-11-09 8:43 ` Christoph Hellwig
2021-11-08 4:05 ` [PATCH v2 18/28] iomap: Convert iomap_page_mkwrite " Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 19/28] iomap: Convert __iomap_zero_iter " Matthew Wilcox (Oracle)
2021-11-09 8:47 ` Christoph Hellwig
2021-11-17 2:24 ` Darrick J. Wong
2021-11-17 14:20 ` Matthew Wilcox
2021-12-09 21:38 ` Matthew Wilcox
2021-12-10 16:19 ` Matthew Wilcox
2021-12-13 7:34 ` Christoph Hellwig
2021-12-13 18:08 ` Matthew Wilcox
2021-12-16 19:36 ` Darrick J. Wong
2021-12-16 20:43 ` Matthew Wilcox
2021-11-08 4:05 ` [PATCH v2 20/28] iomap: Convert iomap_write_begin() and iomap_write_end() to folios Matthew Wilcox (Oracle)
2021-11-17 4:31 ` Darrick J. Wong
2021-11-17 14:31 ` Matthew Wilcox
2021-11-17 17:10 ` Darrick J. Wong [this message]
2021-11-08 4:05 ` [PATCH v2 21/28] iomap: Convert iomap_write_end_inline to take a folio Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 22/28] iomap,xfs: Convert ->discard_page to ->discard_folio Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 23/28] iomap: Simplify iomap_writepage_map() Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 24/28] iomap: Simplify iomap_do_writepage() Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 25/28] iomap: Convert iomap_add_to_ioend() to take a folio Matthew Wilcox (Oracle)
2021-11-17 4:34 ` Darrick J. Wong
2021-11-08 4:05 ` [PATCH v2 26/28] iomap: Convert iomap_migrate_page() to use folios Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 27/28] iomap: Support multi-page folios in invalidatepage Matthew Wilcox (Oracle)
2021-11-08 4:05 ` [PATCH v2 28/28] xfs: Support multi-page folios Matthew Wilcox (Oracle)
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