From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 450F960A260B for ; Mon, 26 Oct 2026 17:26:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=shutemov.name header.i=@shutemov.name header.a=rsa-sha256 header.s=fm1 header.b=b8VWtkd6; dkim=pass (2048-bit key, unprotected) header.d=messagingengine.com header.i=@messagingengine.com header.a=rsa-sha256 header.s=fm2 header.b=y+0ALcDW Received: by kanga.kvack.org (Postfix) id 600AA6B05B0; Mon, 26 Oct 2026 13:26:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5B1DB6B05B1; Mon, 26 Oct 2026 13:26:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4A0D76B05B4; Mon, 26 Oct 2026 13:26:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 2592C6B05B0 for ; Mon, 26 Oct 2026 13:26:19 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 8AF971A0312 for ; Mon, 26 Oct 2026 17:26:18 +0000 (UTC) X-FDA: 85365456036.04.DDA2B74 Received: from flow-a7-smtp.messagingengine.com (flow-a7-smtp.messagingengine.com [103.168.172.142]) by imf24.hostedemail.com (Postfix) with ESMTP id 6C768180003 for ; Mon, 26 Oct 2026 17:26:16 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm1 header.b="b 8VWtkd"; dkim=pass header.d=messagingengine.com header.s=fm2 header.b=y+0ALcDW; spf=pass (imf24.hostedemail.com: domain of kirill@shutemov.name designates 103.168.172.142 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793035576; b=GaIA5MDBhJynMQB7AVNcgkbOVepnlYp4Hk1AdAkxIeMIQUY7tL8Hhjg4+EP8ptxCdKjObg RkZwxMDxfJbgla84kRVcMtWIi6tR01ydB03pjejFNtDw1jdyWvMpL/CstfHKwRrXFD8OYj gS9SsmVNCo90lYsVuPbFXBic1J+LRXU= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=shutemov.name header.s=fm1 header.b="b 8VWtkd"; dkim=pass header.d=messagingengine.com header.s=fm2 header.b=y+0ALcDW; spf=pass (imf24.hostedemail.com: domain of kirill@shutemov.name designates 103.168.172.142 as permitted sender) smtp.mailfrom=kirill@shutemov.name; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793035576; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gozRlQP2gdqbfsNX2AM4B2Y+PLg6RWuvQqaTDn2tvas=; b=GJ/dBewjmdOw4wrNhNmts9gBQyvzdWzfeFmQjohbLiIxwiIrzNU7i85SWE4S0aEml5UH7+ E9svd5+mR05ejdB7BFNCJqDS0fBRquTI2kH/xZoIY0v4jnj5QwBW6gMZSS+T6/3v+YvKnN AY/bP4Tppn15mLYPzqdL0w2bMTgzgbI= Received: from phl-compute-07.internal (phl-compute-07.internal [10.202.2.47]) by mailflow.phl.internal (Postfix) with ESMTP id F3DB813802FB for ; Mon, 26 Oct 2026 13:26:15 -0400 (EDT) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-07.internal (MEProxy); Mon, 26 Oct 2026 13:26:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov.name; h=cc:cc:content-type:content-type:date:date:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:subject:subject:to:to; s=fm1; t=1793035575; x= 1793042775; bh=gozRlQP2gdqbfsNX2AM4B2Y+PLg6RWuvQqaTDn2tvas=; b=b 8VWtkd6ivSPvtKaIADrhl8vqZ0T7gVGFJChcXopg/CW0OT0MZK6KUzDk1DUInA3A DQXd7M/ANUBd3ZGolmlHwqbsN2t/n007uoNRPupxYUYsf2lGZ05faE0Z3xgp+iHP HNyJ3XTI7DVt2nt135NlJXphagsj//Ts17Z1fgZAoPDu0llimgoHavU/362eOt/x 0fTYYihiI0pDObelXPDCdxO4Xvz4jPE8gmo1lK+V75WNMEHTG92aptK5kcxgiijd lqYcZgDn77WVHVeoFDrLFs6TEYS0Hrt0pEVVsHOsI0DBjHkw1ctsgNaZwj+x41yk BLTHWJFls30fC5YMeCAUQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:subject:subject:to :to:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; t= 1793035575; x=1793042775; bh=gozRlQP2gdqbfsNX2AM4B2Y+PLg6RWuvQqa TDn2tvas=; b=y+0ALcDWLZbbQexG18HzxDCXYXQAj67ZHExGPDL+IMp+bC3VD6M 9RGkovUeJzcVXxyvTEc/PNnXsjMIVtA4V+Nbw9Os77A9561EjSbyblmgaaTpurPN aB/nqJnyyAmDiOB+vCccGJa5uCJ6r+4FNX88+pCB7TPAH2ohsWrxnHPu2aXdVh92 sl4TGQxUbC+pGTYa9tt3f2ZKOkKcbMi7285KQMEnndcWqzKN+LrlY0F+aY31jaIE jvz3wICN6CNwwlYl3Wbu+Che/AtxxVmW0Vtu379Ed8D4RYpG8dy6eNOa7BSaqs+t f0HftapAQoHnG8Ip0t2HWoHADZDwhokWXZw== X-DKIM2-Info: draft=ietf-dkim-dkim2-spec-07; repo=github.com/dkim2wg/interop; date=2026-10-18; sw=lmtpprox; action=sign d=shutemov.name a=rsa-sha256; DKIM2-Signature: i=1; m=1; t=1793035575; d=shutemov.name; mf=PGtpcmlsbEBzaHV0ZW1vdi5uYW1lPg==; rt=PGxpbnV4LW1tQGt2YWNrLm9yZz4=; s=fm1:rsa-sha256:CbzetVHX9Q75tzu09KXQ6xH7/MmL4rAJWQ0dtjdyddDQ8iu Mk+EDxmm4emDDGtN9veaMakEwELQzqwnlM4KFEJpu/DuhFafWf09LiSssqRWkNI3 czP+Yggrdz2KuKnPRxmkNi6Ri2V9tzXQB2WsVYi5I7iOsZE0eGQzV4e9bLcHEaYH rvVdwPC1N0g6keyJQ407jwoxEzlMVeHnf4dBxxLvQOfUtSjgjMaBfOfjeCh6j/4Z 6civtheTc9pvE5a8pqTg+Hv3DTfTIVwMO+xVnsSN5Cu4I+oNRUVCUwrAOPY7Xxmn SLXvEZDDnr8hbj4Xf2x49uMdOvxgDOfuIOrckxQ==; X-DKIM2-Info: draft=ietf-dkim-dkim2-spec-07; repo=github.com/dkim2wg/interop; date=2026-10-18; sw=lmtpprox; action=mi-m=1; hc=12; hn=cc,content-disposition,content-type,date,feedback-id,from, in-reply-to,message-id,mime-version,references,subject,to; Message-Instance: m=1; h=sha256:GufLRvjeK9T9oNyQQq/JPRD8A7tK4hGwgAEL7dOtYz4=:IGb6NM7NJpowcOS7AREsu1vwVu3cjYvnaSjEGyip5II=; X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTFhALYc8iJiMlQC3g5bs7hQtPkv6lAItKCPDxNXrELyHy6SwWe3pV3Af7XmlPOZjP +TGoPutgWE/CDwNnpX69avMckpL8UV8zdpnMdPlXKkri7okyrxzdU8T+p+iF9UHx5tvwf9 75PBrpgk4RnZYSRHo2SZqaMsBdjNFcnEnMHBP0yK25AuDlaeYBfs/9A2LCP9q3CXEEm2Dh 7ofMwg9geSlYFfQZ8DFQkdWXrwTAhyDer5ayPZp94JeOiWCWbBcDXCQnyH0azeXwmi2avE rsXZXiu6K0AydSc5T10UD80G0DXte/dNSaj9nP8KPL+lJYKrQdzkiSpt2ehaeU9npH81r/ 1/AKY5HfzGsR+NtE6hNBVXFH3G64hnQZ9RwKPe/xNtu8bHQ4XuiNnrpZI5Rcxa8r+0NLU0 GvNra05Tp9OSU9uDAFiV/4tE37bQglwCh8hd28PMLvcigB+mXgrhVhMisbG+TQ62dJsxZs KsYT2BVS+gQxwLKelcDnyHj2IjigAOXAebzcxhfuBrKuHXbep04KDU8m5elSe5h980yVQD ZUXdForo2hfXobY6hSzY4uvgQUxvw1a5aaAAOT2vhnO1WjAwUr24Al0+BP190B8R0goZHn qNRNozquHcwa7iqNx6dZHBD+6JdAZczycQaU9UNuL9bgcrvMkFpGT+CpfJCg X-ME-Proxy: Feedback-ID: ie3994620:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 26 Oct 2026 13:26:11 -0400 (EDT) Date: Mon, 26 Oct 2026 17:26:10 +0000 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Gregory Price , Zi Yan , Joshua Hahn , Rakie Kim , Ying Huang , Johannes Weiner , Vladimir Davydov , Michal Hocko , Hugh Dickins , Baolin Wang , Lukas Czerner , Carlos Maiolino , Christian Brauner , Jan Kara , Daniel Verkamp , Jeff Xu , Muchun Song , Oscar Salvador , David Stevens , "Matthew Wilcox (Oracle)" , William Kucharski , Chris Li , Kairui Song , Nhat Pham , Miaohe Lin , Naoya Horiguchi , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 11/16] mm/shmem: rescan after nonuniform folio splitting Message-ID: References: <20261026-fixes_shmem-v1-0-703206d5fa0c@kernel.org> <20261026-fixes_shmem-v1-11-703206d5fa0c@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261026-fixes_shmem-v1-11-703206d5fa0c@kernel.org> X-Stat-Signature: oskuzexyq5iiipxbqi1y8zct3r51njao X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 6C768180003 X-Rspam-User: X-HE-Tag: 1793035576-721203 X-HE-Meta: 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 oXP2S4p/ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Oct 26, 2026 at 10:40:44AM +0100, David Hildenbrand (Arm) wrote: > The final scan in shmem_undo_range() restarts after a successful split > only if the original folio is no longer large. A nonuniform split can > leave that folio large, so the scan skips the newly created folios. > Hole punching then leaves pages within the hole allocated even though > they could be discarded. > > For example, a fault below the hole can allocate a 2 MiB folio after > boundary handling. Punching a 1 MiB hole at offset 64 KiB splits the > folio successfully but leaves the original folio at order 4. The scan > continues past all 512 pages, leaving 2 MiB allocated instead of 1 MiB. > The hole reads as zero, but the pages and their block charges remain. > > Restart when the original folio is still in the mapping after partial > truncation, identified by checking folio->mapping. If the helper > removed the whole folio, no rescan is needed. > > Fixes: 7460b470a131f ("mm/truncate: use folio_split() in truncate operation") > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) Acked-by: Kiryl Shutsemau (Meta) Do we want split state after truncate_inode_partial_folio() to be communicated more explicit? ->mapping check works, but it might not be obvious why. Just an idea for a follow up. -- Kiryl Shutsemau / Kirill A. Shutemov