From: Richard Weinberger Date: Sat, 22 Nov 2025 21:19:20 +0000 (+0100) Subject: pagemap: update BUDDY flag documentation X-Git-Tag: v6.19-rc1~112^2~15 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=84a8d467cc426eb3c9eb34092423dcc54493dd7e;p=thirdparty%2Fkernel%2Flinux.git pagemap: update BUDDY flag documentation 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. Link: https://lkml.kernel.org/r/20251122211920.3410371-1-richard@nod.at Signed-off-by: Richard Weinberger Reviewed-by: Lorenzo Stoakes Acked-by: David Hildenbrand (Red Hat) Reviewed-by: Mike Rapoport (Microsoft) Cc: Vladimir Davydov > Cc: Konstantin Khlebnikov Cc: Naoya Horiguchi Signed-off-by: Andrew Morton --- 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