linux-kernel - Re: [PATCH 2/4] mm/migrate: Defer allocating new page until needed

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Message-ID: <20191017112724.f74v2xqgb6swo7w7@box>
Date:   Thu, 17 Oct 2019 14:27:24 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        dan.j.williams@...el.com, keith.busch@...el.com
Subject: Re: [PATCH 2/4] mm/migrate: Defer allocating new page until needed

On Wed, Oct 16, 2019 at 03:11:51PM -0700, Dave Hansen wrote:
> 
> From: Keith Busch <keith.busch@...el.com>
> 
> Migrating pages had been allocating the new page before it was actually
> needed. Subsequent operations may still fail, which would have to handle
> cleaning up the newly allocated page when it was never used.
> 
> Defer allocating the page until we are actually ready to make use of
> it, after locking the original page. This simplifies error handling,
> but should not have any functional change in behavior. This is just
> refactoring page migration so the main part can more easily be reused
> by other code.

Well, the functional change I see is that now we allocate a new page under
page lock of old page.

It *should* be fine, but it has to be call out in the commit message.

-- 
 Kirill A. Shutemov