From: Matthew Wilcox <willy@infradead.org>
To: John Hubbard <jhubbard@nvidia.com>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 18/25] btrfs: Use readahead_batch_length
Date: Thu, 17 Dec 2020 12:12:46 +0000 [thread overview]
Message-ID: <20201217121246.GD15600@casper.infradead.org> (raw)
In-Reply-To: <a5b979d7-1086-fe6c-6e82-f20ecb56d24c@nvidia.com>
On Thu, Dec 17, 2020 at 01:15:10AM -0800, John Hubbard wrote:
> On 12/16/20 10:23 AM, Matthew Wilcox (Oracle) wrote:
> > Implement readahead_batch_length() to determine the number of bytes in
> > the current batch of readahead pages and use it in btrfs.
> >
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > ---
> > fs/btrfs/extent_io.c | 6 ++----
> > include/linux/pagemap.h | 9 +++++++++
> > 2 files changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> > index 6e3b72e63e42..42936a83a91b 100644
> > --- a/fs/btrfs/extent_io.c
> > +++ b/fs/btrfs/extent_io.c
> > @@ -4436,10 +4436,8 @@ void extent_readahead(struct readahead_control *rac)
> > int nr;
> > while ((nr = readahead_page_batch(rac, pagepool))) {
> > - u64 contig_start = page_offset(pagepool[0]);
> > - u64 contig_end = page_offset(pagepool[nr - 1]) + PAGE_SIZE - 1;
> > -
> > - ASSERT(contig_start + nr * PAGE_SIZE - 1 == contig_end);
> > + u64 contig_start = readahead_pos(rac);
> > + u64 contig_end = contig_start + readahead_batch_length(rac);
>
> Something in this tiny change is breaking btrfs: it hangs my Fedora 33 test
> system (which changed over to btrfs) on boot. I haven't quite figured out
> what's really wrong, but git bisect lands here, *and* turning the whole
> extent_readahead() function into a no-op (on top of the whole series)
> allows everything to work once again.
>
> Sorry for not actually solving the root cause, but I figured you'd be able
> to jump straight to the answer, with the above information, so I'm sending
> it out early.
ehh ... probably an off-by-one. Does subtracting 1 from contig_end fix it?
I'll spool up a test VM shortly and try it out.
next prev parent reply other threads:[~2020-12-17 12:13 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-16 18:23 [PATCH 00/25] Page folios Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 01/25] mm: Introduce struct folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 02/25] mm: Add put_folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 03/25] mm: Add get_folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 04/25] mm: Create FolioFlags Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 05/25] mm: Add unlock_folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 06/25] mm: Add lock_folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 07/25] mm: Add lock_folio_killable Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 08/25] mm: Add __alloc_folio_node and alloc_folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 09/25] mm: Convert __page_cache_alloc to return a folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 10/25] mm/filemap: Convert end_page_writeback to use " Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 11/25] mm: Convert mapping_get_entry to return " Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 12/25] mm: Add mark_folio_accessed Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 13/25] mm: Add filemap_get_folio and find_get_folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 14/25] mm/filemap: Add folio_add_to_page_cache Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 15/25] mm/swap: Convert rotate_reclaimable_page to folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 16/25] mm: Add folio_mapping Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 17/25] mm: Rename THP_SUPPORT to MULTI_PAGE_FOLIOS Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 18/25] btrfs: Use readahead_batch_length Matthew Wilcox (Oracle)
2020-12-17 9:15 ` John Hubbard
2020-12-17 12:12 ` Matthew Wilcox [this message]
2020-12-17 13:42 ` Matthew Wilcox
2020-12-17 19:36 ` John Hubbard
2020-12-16 18:23 ` [PATCH 19/25] fs: Change page refcount rules for readahead Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 20/25] fs: Change readpage to take a folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 21/25] mm: Convert wait_on_page_bit to wait_on_folio_bit Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 22/25] mm: Add wait_on_folio_locked & wait_on_folio_locked_killable Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 23/25] mm: Add flush_dcache_folio Matthew Wilcox (Oracle)
2020-12-16 20:59 ` kernel test robot
2020-12-16 22:01 ` Matthew Wilcox
2020-12-16 18:23 ` [PATCH 24/25] mm: Add read_cache_folio and read_mapping_folio Matthew Wilcox (Oracle)
2020-12-16 18:23 ` [PATCH 25/25] fs: Convert vfs_dedupe_file_range_compare to folios Matthew Wilcox (Oracle)
2020-12-17 12:47 ` [PATCH 00/25] Page folios David Hildenbrand
2020-12-17 13:55 ` Matthew Wilcox
2020-12-17 14:35 ` David Hildenbrand
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=20201217121246.GD15600@casper.infradead.org \
--to=willy@infradead.org \
--cc=jhubbard@nvidia.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.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).