From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7C0E43D16F0; Wed, 8 Apr 2026 13:49:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775656195; cv=none; b=BYmBUWMtp9CYPb5L2adB/X4ca4kfTDxlquR4BmwljIJNIGcxgAlnmO4nHEpRbqCHuYBm0f7pYTzNihPkTDtQwzYshsbayizvIXW1GN2CJgv3S4dysOEY7IMaiF1xOS/PgIgenlpfhUf2IIaxZ09UsHNBJdyDGpCsWO2UQuHRz+k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775656195; c=relaxed/simple; bh=AkaqZanasyw6+3Ot9d9earOaZwptTig0HHZPJjjxNz8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=h6vumejOJmAOBD9FJbhaZ9IEF244iau0m2ld5OmA8UwDQiNHUbVg35mI+4PqC7SaXQd9087c31w/P+6+UDiMfl8K8zSbCTpClxERWxvnTXasl2EFD+9F9V45mgyQj5LwMdiizcLtwhANUwjYlQZMae7aJ/VcN2ow+ly16r2cXc4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=f8jokZQd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="f8jokZQd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05258C19421; Wed, 8 Apr 2026 13:49:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775656194; bh=AkaqZanasyw6+3Ot9d9earOaZwptTig0HHZPJjjxNz8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=f8jokZQdo/YAbj2sX1qFtabEa94PpkJC5kckGukBJZDVJf1GgNmFyRqqLoj/To6z6 ilcuxiLLGOGKJvmesWvXIRJgEoO1OPQKdyu9vrZJ0FVj7d0BcvAuKtC+Tj2O8PeniX ae4SeU4eREwt1rOtpzGC02HH+l6bjYC/inYGQZebY8sAfoyTRujjVO/vij++Iim4Hl Bs24OnKkgOAsLapi4NLS6pVK0Zx0FTQM3tNDwdu0ZgPVD8+6WneILIFDJK2/628N5d Ayuk1zjSaUiPObgKBaW4XUo4LR4zQGljJK6G6BOU7dzgOcqJ9P/urBfzE+YyF3+tq1 7zQc4uoFLRM6g== Message-ID: <994cccff-ba44-41e1-b8ae-e2750455dbe0@kernel.org> Date: Wed, 8 Apr 2026 15:49:51 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] virtio_mem: add bitmap_test_range_all_set/zero helpers To: Luan Haickel Araujo , mst@redhat.com, jasowang@redhat.com Cc: xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org References: <20260405213210.108533-1-luanharaujo@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/5/26 23:32, Luan Haickel Araujo wrote: > Encapsulate find_next_bit and find_next_zero_bit calls into helpers > to verify if a range of subblocks is entirely plugged or unplugged. > > This improves readability as requested by the TODO comments in the > source code. > > Validation confirms the change is binary-neutral on ARM64, with the > generated instructions remaining identical. > > Suggested-by: David Hildenbrand > > Signed-off-by: Luan Haickel Araujo > --- > Hi David, > Hi! > This is my first patch contribution to the Linux kernel, following up on > your TODO notes in virtio_mem.c. > > As part of my learning process (LFX 103), I verified the change in a > QEMU (KVM) environment with test_bitmap. I also compared the generated > assembly on ARM64 and it remains identical, confirming the helpers are > binary-neutral as expected. > > I noticed these helpers could also be useful in include/linux/bitmap.h in > the future. If you think it makes sense to move them there, I'd be happy > to work on that in a next step. Right, the TODO really indicated that core code should provide such helpers, not virtio-mem itself. There is no real benefit in having these local helpers. > > Looking forward to your feedback. > > Luan. > drivers/virtio/virtio_mem.c | 24 ++++++++++++++++++------ > 1 file changed, 18 insertions(+), 6 deletions(-) > > diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c > index 48051e9e98ab..e94e30af3a5d 100644 > --- a/drivers/virtio/virtio_mem.c > +++ b/drivers/virtio/virtio_mem.c > @@ -538,6 +538,22 @@ static void virtio_mem_sbm_set_sb_unplugged(struct virtio_mem *vm, > __bitmap_clear(vm->sbm.sb_states, bit, count); > } > > +static inline bool bitmap_test_range_all_set(const unsigned long *map, > + unsigned int start, unsigned int nbits) > +{ > + unsigned int next_zero_bit = find_next_zero_bit(map, start + nbits, start); > + > + return next_zero_bit >= start + nbits; > +} > + > +static inline bool bitmap_test_range_all_zero(const unsigned long *map, > + unsigned int start, unsigned int nbits) > +{ > + unsigned int next_set_bit = find_next_bit(map, start + nbits, start); > + > + return next_set_bit >= start + nbits; > +} If you look closely, fs/btrfs/misc.h provides these functions. So they should probably be factored out into common code. Then, virtio-mem could just naturally reuse them. But, I wonder whether we want to call them bitmap_test_set() bitmap_test_clear() Given that they have the exact same interface as bitmap_set/bitmap_clear, consuming a range. -- Cheers, David