From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-erofs@lists.ozlabs.org
Subject: Re: [PATCH 2/2] iomap: Support inline data with block size < page size
Date: Sat, 24 Jul 2021 13:11:09 +0800 [thread overview]
Message-ID: <YPug7VUMZboQu4QW@B-P7TQMD6M-0146.local> (raw)
In-Reply-To: <YPubNbDS0KgUALtt@B-P7TQMD6M-0146.local>
On Sat, Jul 24, 2021 at 12:46:45PM +0800, Gao Xiang wrote:
> Hi Matthew,
>
> On Sat, Jul 24, 2021 at 04:44:35AM +0100, Matthew Wilcox (Oracle) wrote:
> > Remove the restriction that inline data must start on a page boundary
> > in a file. This allows, for example, the first 2KiB to be stored out
> > of line and the trailing 30 bytes to be stored inline.
> >
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > ---
> > fs/iomap/buffered-io.c | 18 ++++++++----------
> > 1 file changed, 8 insertions(+), 10 deletions(-)
> >
> > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> > index 7bd8e5de996d..d7d6af29af7f 100644
> > --- a/fs/iomap/buffered-io.c
> > +++ b/fs/iomap/buffered-io.c
> > @@ -209,25 +209,23 @@ static int iomap_read_inline_data(struct inode *inode, struct page *page,
> > struct iomap *iomap, loff_t pos)
> > {
> > size_t size = iomap->length + iomap->offset - pos;
> > + size_t poff = offset_in_page(pos);
> > void *addr;
> >
> > if (PageUptodate(page))
> > - return PAGE_SIZE;
> > + return PAGE_SIZE - poff;
> >
> > - /* inline data must start page aligned in the file */
> > - if (WARN_ON_ONCE(offset_in_page(pos)))
> > - return -EIO;
> > if (WARN_ON_ONCE(!iomap_inline_data_size_valid(iomap)))
> > return -EIO;
> > - if (WARN_ON_ONCE(page_has_private(page)))
> > - return -EIO;
> > + if (poff > 0)
> > + iomap_page_create(inode, page);
>
> Thanks for the patch!
>
> Previously I'd like to skip the leading uptodate blocks and update the
> extent it covers that is due to already exist iop. If we get rid of the
> offset_in_page(pos) restriction like this, I'm not sure if we (or some
> other fs users) could face something like below (due to somewhat buggy
> fs users likewise):
>
> [0 - 4096) plain block
>
> [4096 - 4608) tail INLINE 1 (e.g. by mistake or just splitted
> .iomap_begin() report.)
> [4608 - 5120] tail INLINE 2
>
(cont.)
So I think without the !offset_in_page(pos) restriction, at least we
may need to add something like:
if (WARN_ON_ONCE(size != i_size_read(inode) - iomap->offset))
return -EIO;
to the approach to detect such cases at least but that is no need with
page-sized and !offset_in_page(pos) restriction.
> with this code iomap_set_range_uptodate() wouldn't behave correctly.
>
> In addition, currently EROFS cannot test such path (since EROFS is
> page-sized block only for now) as Darrick said in the previous reply,
> so I think it would be better together with the folio patchset and
> targeted for the corresponding merge window, so I can test iomap
> supported EROFS with the new folio support together (That also give
> me some time to support sub-pagesized uncompressed blocks...)
>
> >
> > - addr = kmap_atomic(page);
> > + addr = kmap_atomic(page) + poff;
> > memcpy(addr, iomap_inline_buf(iomap, pos), size);
> > - memset(addr + size, 0, PAGE_SIZE - size);
> > + memset(addr + size, 0, PAGE_SIZE - poff - size);
> > kunmap_atomic(addr);
>
> As my limited understanding, this may need to be fixed, since it
> doesn't match kmap_atomic(page)...
>
> Thanks,
> Gao Xiang
>
> > - SetPageUptodate(page);
> > - return PAGE_SIZE;
> > + iomap_set_range_uptodate(page, poff, PAGE_SIZE - poff);
> > + return PAGE_SIZE - poff;
> > }
> >
> > static inline bool iomap_block_needs_zeroing(struct inode *inode,
> > --
> > 2.30.2
> >
next prev parent reply other threads:[~2021-07-24 5:11 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-24 3:44 [PATCH 0/2] iomap: make inline data support more flexible Matthew Wilcox (Oracle)
2021-07-24 3:44 ` [PATCH 1/2] iomap: Support file tail packing Matthew Wilcox (Oracle)
2021-07-24 3:44 ` [PATCH 2/2] iomap: Support inline data with block size < page size Matthew Wilcox (Oracle)
2021-07-24 4:46 ` Gao Xiang
2021-07-24 5:11 ` Gao Xiang [this message]
2021-07-24 7:52 ` Gao Xiang
2021-07-24 14:03 ` Matthew Wilcox
2021-07-24 15:14 ` Gao Xiang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YPug7VUMZboQu4QW@B-P7TQMD6M-0146.local \
--to=hsiangkao@linux.alibaba.com \
--cc=linux-erofs@lists.ozlabs.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-xfs@vger.kernel.org \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).