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From: Matthew Wilcox <willy@infradead.org>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Jan Kara <jack@suse.cz>,
	William Kucharski <william.kucharski@oracle.com>,
	Linux-FSDevel <linux-fsdevel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>, Christoph Hellwig <hch@lst.de>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Yang Shi <yang.shi@linux.alibaba.com>,
	dchinner@redhat.com, linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 00/16] Overhaul multi-page lookups for THP
Date: Thu, 26 Nov 2020 12:15:46 +0000	[thread overview]
Message-ID: <20201126121546.GN4327@casper.infradead.org> (raw)
In-Reply-To: <CANsGZ6a95WK7+2H4Zyg5FwDxhdJQqR8nKND1Cn6r6e3QxWeW4Q@mail.gmail.com>

On Wed, Nov 25, 2020 at 04:11:57PM -0800, Hugh Dickins wrote:
> The little fix definitely needed was shown by generic/083: each
> fsstress waiting for page lock, happens even without forcing huge
> pages. See below...

Huh ... I need to look into why my xfstests run is skipping generic/083:

0006 generic/083 3s ... run fstests generic/083 at 2020-11-26 12:11:52
0006 [not run] this test requires a valid $SCRATCH_MNT and unique 
0006 Ran: generic/083
0006 Not run: generic/083

> >                         if (!unfalloc || !PageUptodate(page)) {
> >                                 if (page_mapping(page) != mapping) {
> >                                         /* Page was replaced by swap: retry */
> >                                         unlock_page(page);
> > -                                       index--;
> > +                                       put_page(page);
> >                                         break;
> >                                 }
> >                                 VM_BUG_ON_PAGE(PageWriteback(page), page);
> > -                               if (shmem_punch_compound(page, start, end))
> > -                                       truncate_inode_page(mapping, page);
> > -                               else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
> > -                                       /* Wipe the page and don't get stuck */
> > -                                       clear_highpage(page);
> > -                                       flush_dcache_page(page);
> > -                                       set_page_dirty(page);
> > -                                       if (index <
> > -                                           round_up(start, HPAGE_PMD_NR))
> > -                                               start = index + 1;
> > -                               }
> > +                               index = truncate_inode_partial_page(mapping,
> > +                                               page, lstart, lend);
> > +                               if (index > end)
> > +                                       end = indices[i] - 1;
> >                         }
> > -                       unlock_page(page);
> 
> The fix needed is here: instead of deleting that unlock_page(page)
> line, it needs to be } else { unlock_page(page); }

It also needs a put_page(page);

That's now taken care of by truncate_inode_partial_page(), so if we're
not calling that, we need to put the page as well.  ie this:

+++ b/mm/shmem.c
@@ -954,6 +954,9 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
                                                page, lstart, lend);
                                if (index > end)
                                        end = indices[i] - 1;
+                       } else {
+                               unlock_page(page);
+                               put_page(page);
                        }
                }
                index = indices[i - 1] + 1;

> >                 }
> > +               index = indices[i - 1] + 1;
> >                 pagevec_remove_exceptionals(&pvec);
> > -               pagevec_release(&pvec);
> > -               index++;
> > +               pagevec_reinit(&pvec);

  reply	other threads:[~2020-11-26 12:16 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12 21:26 Matthew Wilcox (Oracle)
2020-11-12 21:26 ` [PATCH v4 01/16] mm: Make pagecache tagged lookups return only head pages Matthew Wilcox (Oracle)
2020-11-14  9:53   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 02/16] mm/shmem: Use pagevec_lookup in shmem_unlock_mapping Matthew Wilcox (Oracle)
2020-11-14  9:53   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 03/16] mm/swap: Optimise get_shadow_from_swap_cache Matthew Wilcox (Oracle)
2020-11-14  9:53   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 04/16] mm: Add FGP_ENTRY Matthew Wilcox (Oracle)
2020-11-14 10:00   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 05/16] mm/filemap: Rename find_get_entry to mapping_get_entry Matthew Wilcox (Oracle)
2020-11-14 10:01   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 06/16] mm/filemap: Add helper for finding pages Matthew Wilcox (Oracle)
2020-11-14 10:03   ` Christoph Hellwig
2020-11-14 15:15     ` Matthew Wilcox
2020-11-12 21:26 ` [PATCH v4 07/16] mm/filemap: Add mapping_seek_hole_data Matthew Wilcox (Oracle)
2020-11-14 10:04   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 08/16] iomap: Use mapping_seek_hole_data Matthew Wilcox (Oracle)
2020-11-14 10:06   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 09/16] mm: Add and use find_lock_entries Matthew Wilcox (Oracle)
2020-11-14 10:07   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 10/16] mm: Add an 'end' parameter to find_get_entries Matthew Wilcox (Oracle)
2020-11-14 10:08   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 11/16] mm: Add an 'end' parameter to pagevec_lookup_entries Matthew Wilcox (Oracle)
2020-11-14 10:19   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 12/16] mm: Remove nr_entries parameter from pagevec_lookup_entries Matthew Wilcox (Oracle)
2020-11-14 10:19   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 13/16] mm: Pass pvec directly to find_get_entries Matthew Wilcox (Oracle)
2020-11-14 10:21   ` Christoph Hellwig
2020-11-14 15:22     ` Matthew Wilcox
2020-11-12 21:26 ` [PATCH v4 14/16] mm: Remove pagevec_lookup_entries Matthew Wilcox (Oracle)
2020-11-14 10:22   ` Christoph Hellwig
2020-11-12 21:26 ` [PATCH v4 15/16] mm/truncate,shmem: Handle truncates that split THPs Matthew Wilcox (Oracle)
2020-11-12 21:26 ` [PATCH v4 16/16] mm/filemap: Return only head pages from find_get_entries Matthew Wilcox (Oracle)
2020-11-14 10:23   ` Christoph Hellwig
2020-11-16 10:34 ` [PATCH v4 00/16] Overhaul multi-page lookups for THP Hugh Dickins
2020-11-16 15:14   ` Matthew Wilcox
2020-11-16 21:27     ` Hugh Dickins
2020-11-17 15:39   ` Matthew Wilcox
2020-11-17 16:26     ` Hugh Dickins
2020-11-17 19:15       ` Matthew Wilcox
2020-11-17 23:43         ` Matthew Wilcox
2020-11-25  2:32           ` Matthew Wilcox
2020-11-25  2:50             ` Hugh Dickins
2020-11-25  2:56               ` Hugh Dickins
2020-11-25 23:08             ` Andrew Morton
2020-11-26  0:11               ` Hugh Dickins
2020-11-26 12:15                 ` Matthew Wilcox [this message]
2020-11-26 19:24                   ` Hugh Dickins
2020-11-26 20:07                     ` Matthew Wilcox
2020-11-30 19:45                       ` Hugh Dickins
2020-12-01  4:52                         ` Hugh Dickins
     [not found]             ` <CGME20201203154604eucas1p200d001d25dd344a1dd1c7da34f35aad0@eucas1p2.samsung.com>
2020-12-03 15:46               ` Marek Szyprowski
     [not found]                 ` <CGME20201203172725eucas1p2fddec1d269c55095859d490942b78b93@eucas1p2.samsung.com>
2020-12-03 17:27                   ` Marek Szyprowski
2020-12-03 21:27                     ` Qian Cai
2020-12-03 22:19                       ` Hugh Dickins
2020-12-03 21:45                     ` Hugh Dickins
2021-02-23 22:58 ` Andrew Morton
2021-02-23 23:27   ` Matthew Wilcox

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