From: Alistair Popple <apopple@nvidia.com>
To: <akpm@linux-foundation.org>, Matthew Wilcox <willy@infradead.org>
Cc: <dhowells@redhat.com>, <hughd@google.com>, <jgg@nvidia.com>,
<jglisse@redhat.com>, <jhubbard@nvidia.com>,
<mm-commits@vger.kernel.org>, <rcampbell@nvidia.com>
Subject: Re: + mm-migratec-rework-migration_entry_wait-to-not-take-a-pageref.patch added to -mm tree
Date: Mon, 13 Dec 2021 22:30:55 +1100 [thread overview]
Message-ID: <2420988.TeagO0yf0P@nvdebian> (raw)
In-Reply-To: <YbQqXKrwVtr+HRLe@casper.infradead.org>
On Saturday, 11 December 2021 3:34:36 PM AEDT Matthew Wilcox wrote:
> On Thu, Nov 18, 2021 at 01:54:27PM -0800, akpm@linux-foundation.org wrote:
> > +++ a/mm/migrate.c
> > @@ -305,15 +305,7 @@ void __migration_entry_wait(struct mm_st
> > page = pfn_swap_entry_to_page(entry);
> > page = compound_head(page);
> >
> > - /*
> > - * Once page cache replacement of page migration started, page_count
> > - * is zero; but we must not call put_and_wait_on_page_locked() without
> > - * a ref. Use get_page_unless_zero(), and just fault again if it fails.
> > - */
> > - if (!get_page_unless_zero(page))
> > - goto out;
> > - pte_unmap_unlock(ptep, ptl);
> > - put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE);
> > + migration_entry_wait_on_locked(page_folio(page), ptep, ptl);
>
> This is clearly bogus. The 'page = compound_head(page)' line should
> be deleted.
>
> But I think we should go further and turn this into:
>
> migration_entry_wait_on_locked(entry, ptep, ptl);
>
> Neither caller has anything useful to do with the page any more.
Thanks for spotting that, I have posted a new version which does that.
prev parent reply other threads:[~2021-12-13 11:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-18 21:54 + mm-migratec-rework-migration_entry_wait-to-not-take-a-pageref.patch added to -mm tree akpm
2021-12-11 4:34 ` Matthew Wilcox
2021-12-13 11:30 ` Alistair Popple [this message]
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