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From: Hugh Dickins <hughd@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>,
	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 11:24:59 -0800 (PST)	[thread overview]
Message-ID: <alpine.LSU.2.11.2011261101230.2851@eggly.anvils> (raw)
In-Reply-To: <20201126121546.GN4327@casper.infradead.org>

On Thu, 26 Nov 2020, Matthew Wilcox wrote:
> On Wed, Nov 25, 2020 at 04:11:57PM -0800, Hugh Dickins wrote:
> > > +                               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);

Oh yes indeed, sorry for getting that wrong.  I'd misread the
pagevec_reinit() at the end as the old pagevec_release().  Do you
really need to do pagevec_remove_exceptionals() there if you're not
using pagevec_release()?

> 
> 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:

Right, but I do find it confusing that truncate_inode_partial_page()
does the unlock_page(),put_page() whereas truncate_inode_page() does
not: I think you would do better to leave them out of _partial_page(),
even if including them there saves a couple of lines somewhere else.

But right now it's the right fix that's important: ack to yours below.

I've not yet worked out the other issues I saw: will report when I have.
Rebooted this laptop, pretty sure it missed freeing a shmem swap entry,
not yet reproduced, will study the change there later, but the non-swap 
hang in generic/476 (later seen also in generic/112) more important.

Hugh

> 
> +++ 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 19:25 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
2020-11-26 19:24                   ` Hugh Dickins [this message]
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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