From nobody Tue Dec 2 00:46:48 2025 Received: from lithops.sigma-star.at (mailout.nod.at [116.203.167.152]) (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 83160257851; Sat, 22 Nov 2025 21:28:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=116.203.167.152 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763846912; cv=none; b=HWVCeecTCLZwVEmNVwfJB1/vWJ715w+ivad0eQ7FI1J1rFSfso9MthlBzxaTeMd4Y3Z43Rpc161uVSt1buAR8JQUdwDmB/P81PhFB9pzc4kxkeK4I4RlGzndi0/5fmhu2loIjmHey88qk2tuaHjyjZWNPluKCMH7wmwTFCsUBAc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763846912; c=relaxed/simple; bh=O7bJcChPkT7xMOVHD6IAp5F4GI3Zzx+LfHPbPi4iXN8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=I6sFrhdgq0fUz5BfsPe0Lm7+9qptK7s7+fYYA9SKu1fu36xZKj0RYHNVfUZQsewmKyqfr3I4dFNaogUmq7oBw3NBNs3x40PsEOZ0qHo/Zx2cj3ET9qn6gUpa4loa8Hc5CJpZ76gIm5no/pOGIQ/y9VfzEJSY+lTlf3eKi5htFBM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=nod.at; spf=fail smtp.mailfrom=nod.at; arc=none smtp.client-ip=116.203.167.152 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=nod.at Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nod.at Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 5F9A02BA973; Sat, 22 Nov 2025 22:19:27 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id 3Il8KscnqSO8; Sat, 22 Nov 2025 22:19:26 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 196282BA979; Sat, 22 Nov 2025 22:19:26 +0100 (CET) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id uSCWT8cKas0p; Sat, 22 Nov 2025 22:19:25 +0100 (CET) Received: from nailgun.corp.sigma-star.at (85-127-105-34.dsl.dynamic.surfer.at [85.127.105.34]) by lithops.sigma-star.at (Postfix) with ESMTPSA id 5146F2BA973; Sat, 22 Nov 2025 22:19:25 +0100 (CET) From: Richard Weinberger To: linux-mm@kvack.org Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, corbet@lwn.net, mhocko@suse.com, surenb@google.com, rppt@kernel.org, vbabka@suse.cz, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@kernel.org, akpm@linux-foundation.org, Richard Weinberger , Vladimir Davydov , Konstantin Khlebnikov , Naoya Horiguchi , Linus Torvalds Subject: [PATCH] pagemap: Update BUDDY flag documentation Date: Sat, 22 Nov 2025 22:19:20 +0100 Message-ID: <20251122211920.3410371-1-richard@nod.at> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 p= ages") 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 Acked-by: David Hildenbrand (Red Hat) Reviewed-by: Lorenzo Stoakes 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 f= lag - 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 pag= es. A compound page with order 2 takes the form of "HTTT", where H donates= its --=20 2.51.0