Re: [PATCH 3/4] bitmap: Introduce bitmap_size()

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Yury Norov <yury.norov@gmail.com>,
	agk@redhat.com, snitzer@kernel.org, dm-devel@redhat.com,
	vneethv@linux.ibm.com, oberpar@linux.ibm.com, hca@linux.ibm.com,
	gor@linux.ibm.com, agordeev@linux.ibm.com,
	borntraeger@linux.ibm.com, svens@linux.ibm.com,
	almaz.alexandrovich@paragon-software.com,
	linux@rasmusvillemoes.dk, linux-s390@vger.kernel.org,
	ntfs3@lists.linux.dev, linux-kernel@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: Re: [PATCH 3/4] bitmap: Introduce bitmap_size()
Date: Sun, 3 Jul 2022 18:20:53 +0300	[thread overview]
Message-ID: <YsGz1Xp0RDM5ZhVY@smile.fi.intel.com> (raw)
In-Reply-To: <4dc5d50a-2291-1d3a-efac-3f6378a15d69@wanadoo.fr>

On Sun, Jul 03, 2022 at 08:50:19AM +0200, Christophe JAILLET wrote:
> Le 02/07/2022 à 23:09, Yury Norov a écrit :
> > On Sat, Jul 02, 2022 at 08:29:36PM +0200, Christophe JAILLET wrote:

...

> > This should be dropped, for sure, and kmalloc() at line 128 should be
> > replaced with bitmap_alloc().
> 
> This kmalloc() is for a structure and a flexible array.
> 
> You mean re-arranging the code to allocate the structure alone at first,
> then the bitmap?

It's one way, but it will increase fragmentation of memory. The other one
as it seems to me is to name a new API properly, i.e. bitmap_size_to_bytes().

In such case you won't need renames to begin with. And then would be able
to convert driver-by-driver in cases of duplicated code.

I think that's what confused Yuri and I kinda agree that bitmap_size() should
return bits, and not bytes. Also argument for pure bitmap_size() would be
bitmap itself, but we have no way to detect the length of bitmap because we
are using POD and not a specific data structure for it.

-- 
With Best Regards,
Andy Shevchenko