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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251122211920.3410371-1-richard@nod.at> X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A4C5C180004 X-Stat-Signature: kwgihijpeguqpk4kzo9e6ksjw4dei7tc X-HE-Tag: 1763890154-474046 X-HE-Meta: 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 6u9phhen yaDrqTVzNz+6DpTOE/quSVlrAidcZRpWqVoGJECW1T0jILZGJENg9V2Sgl0yRvjLD6/zx5IyGHwo+PgWYdKDzk2AoFJawB6ikjkqq2uffnHIqMWOLBhk4dKlEfCrPqNEmb/5OV8N/Wxp8EXOvSV5VUYJL4LZj2jpw0yreX1K20/e5N3rZaUeMi1LIF+KYaANNkORIok43U4dRpN8EHamPbAqCsbfRUkDnqKzB3DGU1Bqx+PHm3RRwish2oqxtbkEVSsolqFvOeBh43qO9ANUJetNCtFQ5mCGEbIJIptpumtFpLUKM5HYb7QA3K3HeE8UBLQomXzI/N6QE+EdKBZ2eK2QxO1A3t8v/7xUDoBlNqF+3yfJLUH2opSsZlhrLT5/VudHdOv9jZyAg096knkXCdFTdeD+Ae/Y7i3mOC4i+qBy0sTFyLUp5xMA4eHeadgO2NafR X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.