linux-kernel - Re: [PATCH] ubifs: Get/put page when changing PG

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Message-ID: <20181217105944.a7eylrxi5pni4mqq@kshutemo-mobl1>
Date:   Mon, 17 Dec 2018 13:59:44 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Richard Weinberger <richard@....at>
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, hsiangkao@...l.ru,
        kirill.shutemov@...ux.intel.com, stable@...r.kernel.org,
        zhangjun <openzhangj@...il.com>
Subject: Re: [PATCH] ubifs: Get/put page when changing PG_private

On Sat, Dec 15, 2018 at 04:01:30PM +0100, Richard Weinberger wrote:
> The page migration code assumes that a page with PG_private
> set has its page count elevated by 1.
> UBIFS never did this and therefore the migration code was unable
> to migrate some pages owned by UBIFS.
> The lead to situations where the CMA memory allocator failed to
> allocate memory.
> 
> Fix this by using get/put_page when changing PG_private.

Looks good to me.

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

> Cc: <stable@...r.kernel.org>
> Cc: zhangjun <openzhangj@...il.com>
> Fixes: 4ac1c17b2044 ("UBIFS: Implement ->migratepage()")

It is fair to reference the commit here. But I believe the bug itself
predates the commit and relevant not only for migration.

We might make it clear in the commit message.

-- 
 Kirill A. Shutemov