From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 69A7710A1E63 for ; Fri, 27 Mar 2026 02:14:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BC12E6B00A2; Thu, 26 Mar 2026 22:14:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B98F56B00A4; Thu, 26 Mar 2026 22:14:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AD5ED6B00A5; Thu, 26 Mar 2026 22:14:46 -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 9CE296B00A2 for ; Thu, 26 Mar 2026 22:14:46 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 683DC140CFB for ; Fri, 27 Mar 2026 02:14:46 +0000 (UTC) X-FDA: 84590224572.01.94FF6B1 Received: from out-186.mta1.migadu.com (out-186.mta1.migadu.com [95.215.58.186]) by imf20.hostedemail.com (Postfix) with ESMTP id B30EF1C0004 for ; Fri, 27 Mar 2026 02:14:44 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=HOqb9c3q; spf=pass (imf20.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.186 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774577684; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=sLE/jttxUNtNWJGXfdbfQ0fLOQxN3ImdDTn6kFnTkPI=; b=8plVNDcuDF96YXd8PEPStkz6Eos0u2Dfao85o6fz5W9NDnNuSDgxpm6ok0Ltp23nVXcrxJ JxDIgF5YqWHI41x3YENR9Y4zio1HqSlozuzUcNryHYxKaTVVXk09eyszkLaoycCzzFXCnC 7ulEsvuFxudhetUccSFcLiGKU+55fu0= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774577684; a=rsa-sha256; cv=none; b=mzozi4/zMFw3324DYsuSj/i1QCs8ig+ApbaM48/FgUR0CjoQHQbHAd0UUEAWjpgrKn6POv wUn1jg6jk/8CPy93oTweLdW7YMkyB60tE12XaZtbQJJ2HWHEoKxYuuqkIS0oI3Xzu5xeHF jTdjV+Idcy6gOlLOLLAlGR+3Vez54Zo= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=HOqb9c3q; spf=pass (imf20.hostedemail.com: domain of usama.arif@linux.dev designates 95.215.58.186 as permitted sender) smtp.mailfrom=usama.arif@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1774577683; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sLE/jttxUNtNWJGXfdbfQ0fLOQxN3ImdDTn6kFnTkPI=; b=HOqb9c3qtURSYEfsDks7zbx2QDtDTH9l8hI6RIZbNZVZjMBH564Y3pW5ZPIcsI8NKoiThq EoKp0vqkwqrK6t8HL7D5u0ey61UVlkvaX3oR+haZEDWM9M+SC4Ti9llRE18ryT8ip3fCx4 H6PgMQ7rNNkpgtUJP6NJzF9wyR2yris= From: Usama Arif To: Andrew Morton , david@kernel.org, Lorenzo Stoakes , willy@infradead.org, linux-mm@kvack.org Cc: fvdl@google.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, npache@redhat.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com, maddy@linux.ibm.com, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, linux-s390@vger.kernel.org, Usama Arif Subject: [v3 05/24] mm: thp: handle split failure in zap_pmd_range() Date: Thu, 26 Mar 2026 19:08:47 -0700 Message-ID: <20260327021403.214713-6-usama.arif@linux.dev> In-Reply-To: <20260327021403.214713-1-usama.arif@linux.dev> References: <20260327021403.214713-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: B30EF1C0004 X-Stat-Signature: cpt47xpaezzcase8yri8fskpnuhc4zsh X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1774577684-13643 X-HE-Meta: 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 iee2vIjX qg4jyEf9XrZABAXZojO2dH6JIedAAVjT8Z55/hK13FIpYbFpXoC3SUic/1VtvDnC6flxdpwfDCkNBLu4WAmtvuNTtx8isAQdbdwqLeqRlCB7v0Zqxh/eCdoghESN3GIPV2geUxxLgJASLEnsWY+jHCux7YTVQPbOtRllL7Il+nndtJEvuVnfixT0JE8TGogU/1fRepKNGk1m2YEsZlY04kZYcv8IFYg+yrojcY04/ixTd8EFMq38K3t8iptm7jw3wCCJHOP3BoL9g4UgttoGq/KPpug== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: zap_pmd_range() splits a huge PMD when the zap range doesn't cover the full PMD (partial unmap). If the split fails, the PMD stays huge. Falling through to zap_pte_range() would dereference the huge PMD entry as a PTE page table pointer. Skip the range covered by the PMD on split failure instead. The skip is safe across all call paths into zap_pmd_range(): - exit_mmap() and OOM reaper: the zap range covers entire VMAs, so every PMD is fully covered (next - addr == HPAGE_PMD_SIZE). The zap_huge_pmd() branch handles these without splitting. The split failure path is unreachable. - munmap / mmap overlay: vma_adjust_trans_huge() (called from __split_vma) splits any PMD straddling the VMA boundary before the VMA is split. If that PMD split fails, __split_vma() returns -ENOMEM and the munmap is aborted before reaching zap_pmd_range(). The split failure path is unreachable. - MADV_DONTNEED: advisory hint, the kernel is allowed to ignore it. The pages remain valid and accessible. A subsequent access returns existing data without faulting. Signed-off-by: Usama Arif --- mm/memory.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index e44469f9cf659..caf97c48cb166 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1985,9 +1985,18 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb, do { next = pmd_addr_end(addr, end); if (pmd_is_huge(*pmd)) { - if (next - addr != HPAGE_PMD_SIZE) - __split_huge_pmd(vma, pmd, addr, false); - else if (zap_huge_pmd(tlb, vma, pmd, addr)) { + if (next - addr != HPAGE_PMD_SIZE) { + /* + * If split fails, the PMD stays huge. + * Skip the range to avoid falling through + * to zap_pte_range, which would treat the + * huge PMD entry as a page table pointer. + */ + if (__split_huge_pmd(vma, pmd, addr, false)) { + addr = next; + continue; + } + } else if (zap_huge_pmd(tlb, vma, pmd, addr)) { addr = next; continue; } -- 2.52.0