linux-kernel - Re: [PATCH v3 3/5] bitmap: Add bitmap_alloc(), bitmap_zalloc() and bitmap

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Message-ID: <c5756465375e091a528b8c68fae3d8f3061454bf.camel@linux.intel.com>
Date:   Tue, 26 Jun 2018 14:13:42 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, agk@...hat.com,
        Mike Snitzer <snitzer@...hat.com>,
        device-mapper development <dm-devel@...hat.com>,
        shli@...nel.org, linux-raid@...r.kernel.org,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        Yury Norov <ynorov@...iumnetworks.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v3 3/5] bitmap: Add bitmap_alloc(), bitmap_zalloc() and
 bitmap_free()

On Fri, 2018-06-22 at 11:46 -0700, Dmitry Torokhov wrote:
> On Thu, Jun 21, 2018 at 05:13:39AM +0300, Andy Shevchenko wrote:
> > On Tue, Jun 19, 2018 at 2:10 AM, Andrew Morton
> > <akpm@...ux-foundation.org> wrote:
> > > On Mon, 18 Jun 2018 15:01:43 -0700 Dmitry Torokhov <dmitry.torokho
> > > v@...il.com> wrote:
> > > > We can't as we end up including bitmap.h (by the way of
> > > > cpumask.h)
> > > > form slab.h, so we gen circular dependency.
> > 
> > It's not just so easy. See below.
> > 
> > > That info should have been in the changelog, and probably a code
> > > comment.
> > > 
> > > > Maybe if we removed memcg
> > > > stuff from slab.h so we do not need to include workqueue.h...
> > > 
> > > Or move the basic slab API stuff out of slab.h into a new
> > > header.  Or
> > > create a new, standalone work_struct.h - that looks pretty simple.
> > 
> > I tried to move out work_struct, it didn't help. There are actually
> > several circular dependencies that ends in bitmap.h either way or
> > another.
> > 
> > First one is
> > 
> > slab.h -> gfp.h -> mmzone.h -> nodemask.h -> bitmap.h
> > 
> > And so on...
> > 
> > Splitting out kXalloc stuff to a separate header won't help, I
> > think,
> > because of the above.
> > Splitting out struct work_struct is just a tip of an iceberg.
> > Splitting out memcg stuff won't help in the similar way.
> > 
> > I'm all ears for (a better) solution.
> 
> I think ultimately we'd want to untangle this, but allocating bitmaps
> is
> not in any hot paths so having them as non-inlined functions should
> not
> hurt us that much for time being.

Perhaps I can elaborate a bit in a commit message.

Thanks for review!

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy