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 D645425BEE7; Sun, 23 Nov 2025 09:29:13 +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=1763890154; cv=none; b=N7vMfXrfUSj/llLexKVCb8236ErkVPD//OsnpMLUOOz3ZJH6jyRArb0sMo7x8k9uKcyPkOUtYR6UUG5LQm+Fl3Tu/K1b+McWiDcsEsu6K+JheGySMlcwWudxIYCz29gskPM6DLsGzwdtMuCcL7AHBuMmLnnbzhTwakxImtq0uRw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763890154; c=relaxed/simple; bh=BsCF5Vo0XWlxKJ/sd2YtUXNzzKo8ijMIlbF7CAcmddQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=L/uW4d6RXfK88dF7WIwNwM53BJlbSskPXuCFcsFa01z1/IGv+RVjipuqxHLSKiYtIgnKLiLlQB97Amjngje0wUCXeFTKzlepycabC5Q57celTMWS2Xi9OcFDZVehaHoAxmz+3eAQj/S9sp7b6d3BRFfmiWKUiXEoFF8W/DVV0Fo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=khHRGrer; 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="khHRGrer" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9630EC16AAE; Sun, 23 Nov 2025 09:29:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763890153; bh=BsCF5Vo0XWlxKJ/sd2YtUXNzzKo8ijMIlbF7CAcmddQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=khHRGrerO0B4QAeiYUvcoYrCRZ7uhsJTe+ITJfW9iphjYhW1N0sKuW0fM2MRwJw5g l5TQWitHCTush7XpYYXn86yoAgIkRd9Jwskf2hII2lEiVCE7zf5OOfdvlMrwa8vZjW Ik5A1AzJIUJHNbsmi9XzwA+YcND1G9ACaXTYc4WHni5+e1Z1jhbXz3uCmnpCgQ2m3H xVSHgwZBltr02JD/bKnR+CeUVLQl/hSqnsw87N+adQ/1gUneAjaJhpHJc+n/0k18+T x1fX5UifmLzM5F0ekSp9B9Kvbm9Hhy2/LQg7y3Qe21gYlJvr175L8foN4YrQkfmFk/ c90tmT+r9YtYg== Date: Sun, 23 Nov 2025 11:29:04 +0200 From: Mike Rapoport To: Richard Weinberger Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, corbet@lwn.net, mhocko@suse.com, surenb@google.com, vbabka@suse.cz, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@kernel.org, akpm@linux-foundation.org, Vladimir Davydov , Konstantin Khlebnikov , Naoya Horiguchi , Linus Torvalds Subject: Re: [PATCH] pagemap: Update BUDDY flag documentation Message-ID: References: <20251122211920.3410371-1-richard@nod.at> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251122211920.3410371-1-richard@nod.at> On Sat, Nov 22, 2025 at 10:19:20PM +0100, Richard Weinberger wrote: > Since v4.6 the BUDDY flag is set for _all_ pages in the block > and no longer just for the first one. > This change was introduced by: > commit 832fc1de01ae ("/proc/kpageflags: return KPF_BUDDY for "tail" buddy pages") > > Strictly speaking, this was an ABI change, but as nobody has noticed > since 2016, let's just update the documentation. > > Cc: Vladimir Davydov > > Cc: Konstantin Khlebnikov > Cc: Naoya Horiguchi > Cc: Andrew Morton > Cc: Linus Torvalds > Signed-off-by: Richard Weinberger Reviewed-by: Mike Rapoport (Microsoft) > --- > Documentation/admin-guide/mm/pagemap.rst | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst > index e60e9211fd9b2..c57e61b5d8aa8 100644 > --- a/Documentation/admin-guide/mm/pagemap.rst > +++ b/Documentation/admin-guide/mm/pagemap.rst > @@ -115,7 +115,8 @@ Short descriptions to the page flags > A free memory block managed by the buddy system allocator. > The buddy system organizes free memory in blocks of various orders. > An order N block has 2^N physically contiguous pages, with the BUDDY flag > - set for and _only_ for the first page. > + set for all pages. > + Before 4.6 only the first page of the block had the flag set. > 15 - COMPOUND_HEAD > A compound page with order N consists of 2^N physically contiguous pages. > A compound page with order 2 takes the form of "HTTT", where H donates its > -- > 2.51.0 > > -- Sincerely yours, Mike.