From: "Huang\, Ying" <ying.huang@intel.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
Zi Yan <ziy@nvidia.com>, Michal Hocko <mhocko@kernel.org>,
Minchan Kim <minchan@kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH] mm, migrate: Check return value of try_to_unmap()
Date: Tue, 03 Mar 2020 14:19:18 +0800 [thread overview]
Message-ID: <87blpe55ax.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <alpine.LSU.2.11.2003022150540.1344@eggly.anvils> (Hugh Dickins's message of "Mon, 2 Mar 2020 22:11:45 -0800")
Hi, Hugh,
Hugh Dickins <hughd@google.com> writes:
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 3900044cfaa6..981f8374a6ef 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1116,8 +1116,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
>> /* Establish migration ptes */
>> VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma,
>> page);
>> - try_to_unmap(page,
>> - TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
>> + if (!try_to_unmap(page,
>> + TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS)) {
>> + rc = -EIO;
>> + goto out_unlock_both;
>
> No: even if try_to_unmap() says that it did not entirely succeed,
> it may have unmapped some ptes, inserting migration entries in their
> place. Those need to be replaced by proper ptes before the page is
> unlocked, which page_was_mapped 1 and remove_migration_ptes() do;
> but this goto skips those.
Yes. You are right. I misunderstand the original code. Please ignore
this patch.
Best Regards,
Huang, Ying
prev parent reply other threads:[~2020-03-03 6:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-03 3:36 [PATCH] mm, migrate: Check return value of try_to_unmap() Huang, Ying
2020-03-03 6:11 ` Hugh Dickins
2020-03-03 6:19 ` Huang, Ying [this message]
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