linux-kernel - Re: [PATCH] mtd: Allocate bdi objects dynamically

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Date:   Sat, 17 Sep 2016 16:41:47 +0200
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     Sandeep Jain <Sandeep_Jain@...tor.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Steve Longerbeam <steve_longerbeam@...tor.com>,
        Jim Baxter <jim_baxter@...tor.com>
Subject: Re: [PATCH] mtd: Allocate bdi objects dynamically

On Thu, Aug 4, 2016 at 4:01 PM, Sandeep Jain <Sandeep_Jain@...tor.com> wrote:
> From: Steve Longerbeam <steve_longerbeam@...tor.com>
>
> The MTD backing dev info objects mtd_bdi was statically allocated.
> So when MTD is built as a loadable module, this object fall in the
> vmalloc address space.
>
> The problem with that, is that the BDI APIs use wake_up_bit(), which calls
> virt_to_page() to retrieve the memory zone of the page containing the
> wait_queue to wake up, and virt_to_page() is not valid for vmalloc or
> highmem addresses.
>
> Fix this by allocating the BDI objects dynamically with kmalloc. The
> objects now fall in the logical address space so that BDI APIs will
> work in all cases (mtd builtin or module).
>
> Signed-off-by: Steve Longerbeam <steve_longerbeam@...tor.com>
> Signed-off-by: Jim Baxter <jim_baxter@...tor.com>
> Signed-off-by: Sandeep Jain <Sandeep_Jain@...tor.com>

Reviewed-by: Richard Weinberger <richard@....at>

-- 
Thanks,
//richard