From: Andrew Morton <akpm@linux-foundation.org>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: david@redhat.com, ying.huang@intel.com, ziy@nvidia.com,
shy828301@gmail.com, apopple@nvidia.com,
jingshan@linux.alibaba.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] mm: migrate: Fix return value if all subpages of THPs are migrated successfully
Date: Fri, 21 Oct 2022 11:41:49 -0700 [thread overview]
Message-ID: <20221021114149.eadf6fafdd0b2c2409a46389@linux-foundation.org> (raw)
In-Reply-To: <fca6bb0bd48a0292a0ace2fadd0f44579a060cbb.1666335603.git.baolin.wang@linux.alibaba.com>
On Fri, 21 Oct 2022 18:16:23 +0800 Baolin Wang <baolin.wang@linux.alibaba.com> wrote:
> When THP migration, if THPs are split and all subpages are migrated successfully
> , the migrate_pages() will still return the number of THP that were not migrated.
> That will confuse the callers of migrate_pages(), for example, which will make
> the longterm pinning failed though all pages are migrated successfully.
>
> Thus we should return 0 to indicate all pages are migrated in this case.
>
This had me puzzled for a while. I think this wording is clearer?
: During THP migration, if THPs are not migrated but they are split and all
: subpages are migrated successfully, migrate_pages() will still return the
: number of THP pages that were not migrated. This will confuse the callers
: of migrate_pages(). For example, the longterm pinning will failed though
: all pages are migrated successfully.
:
: Thus we should return 0 to indicate that all pages are migrated in this
: case.
This is a fairly longstanding problem? No Fixes: we can identify?
Did you consider the desirability of a -stable backport?
next prev parent reply other threads:[~2022-10-21 18:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-21 10:16 [PATCH v2 1/2] mm: migrate: Fix return value if all subpages of THPs are migrated successfully Baolin Wang
2022-10-21 10:16 ` [PATCH v2 2/2] mm: migrate: Try again if THP split is failed due to page refcnt Baolin Wang
2022-10-24 1:41 ` Huang, Ying
2022-10-21 18:41 ` Andrew Morton [this message]
2022-10-21 20:55 ` [PATCH v2 1/2] mm: migrate: Fix return value if all subpages of THPs are migrated successfully Yang Shi
2022-10-24 1:56 ` Huang, Ying
2022-10-24 6:03 ` Baolin Wang
2022-10-24 2:36 ` Alistair Popple
2022-10-24 6:41 ` Baolin Wang
2022-10-24 7:24 ` Alistair Popple
2022-10-24 8:01 ` Baolin Wang
2022-10-24 8:06 ` Alistair Popple
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