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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5AFE0C83F3E for ; Tue, 5 Sep 2023 06:47:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6E1DB8E001E; Tue, 5 Sep 2023 02:47:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 691AE8E001A; Tue, 5 Sep 2023 02:47:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 580FF8E001E; Tue, 5 Sep 2023 02:47:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 44BA48E001A for ; Tue, 5 Sep 2023 02:47:36 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 05B201CA65A for ; Tue, 5 Sep 2023 06:47:36 +0000 (UTC) X-FDA: 81201612912.16.7B22E45 Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) by imf15.hostedemail.com (Postfix) with ESMTP id 1B596A0016 for ; Tue, 5 Sep 2023 06:47:33 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=EvBiQDSG; spf=pass (imf15.hostedemail.com: domain of lstoakes@gmail.com designates 209.85.128.52 as permitted sender) smtp.mailfrom=lstoakes@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1693896454; 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=AsIlpZm/Q7WJcI9ZjnlyhKhWKNwVjgPwx9B6UP2Qye4=; b=h/9C5ggacj895FAYYwx4/2joRwWvV/dLSR9oZZAOCtuk3KGAwJDh59RyI615XTOCob5Zi0 qZtvoMgGAvjuo361JN54XDOX4sjR3bV/4BIYWGCucbSARjyqm9v/rJG2fgvTnwNxmhiRaU wZeZwbRAyznaVqJWg0naUmLlGhp6/B4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1693896454; a=rsa-sha256; cv=none; b=tws7Rg9pvH5Z0GhHRRRuAL1d9nSrwXLWOmrjNHUw8ardYv5MPxRTWiBVEzzy/wOckx3sYQ BGHanOAuCM5nzCQIEzxBy06j60/58fLDOPFqDoyoufrn1HJAucdAAYK+hGhTaZsROE4ybm eYeBdU24NhZBpoZruQ/14lJAD8ASRHY= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=EvBiQDSG; spf=pass (imf15.hostedemail.com: domain of lstoakes@gmail.com designates 209.85.128.52 as permitted sender) smtp.mailfrom=lstoakes@gmail.com; dmarc=pass (policy=none) header.from=gmail.com Received: by mail-wm1-f52.google.com with SMTP id 5b1f17b1804b1-401d6f6b2e0so17633255e9.1 for ; Mon, 04 Sep 2023 23:47:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1693896452; x=1694501252; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=AsIlpZm/Q7WJcI9ZjnlyhKhWKNwVjgPwx9B6UP2Qye4=; b=EvBiQDSGXQGS3ByJPezTqfURt0aWuapAgUU8aekAHpXhCW+5sPq+BdBe/GJPZAWN79 0IstPDcevSgKE6s9YvTwGRGpHO3sqDVGu8lDvZE1YUc/uZasmP9ZQFdSMuQhUCRq+/LZ mrt6T8BeASkNOrBySa+u+iOC3PL/6n72NK0TN2PQxEI78CtgDxXMtgi0CwpLDPcd3ooS p02DObvfIGy2n7u7DzQmegapxJ+zh+oy1wvCLB/JCNLlJCUIFV1lWSTwABr7N3ulVKZc ecM1YxzOlmB+FRo+SWKWpXHxtCEW5iFgvQtipYs2gNte8dPR99wKxeCWqw0XHknx0og8 sVnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693896452; x=1694501252; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=AsIlpZm/Q7WJcI9ZjnlyhKhWKNwVjgPwx9B6UP2Qye4=; b=Us1UQTV7/1UY5z01sHw9I8SP+96QQY6EdPL0RYZ5eESfgZmgQ9aPvk+zdAPnw+N6pj 8/LS/Ygw2CzxPdTqntahi1i5Jn04MeljVu/0d1bhWsi+toyWYH7hDv5Ji4EtmKzfseLX jpAegeMp0Qz8ZadXLjEqMbJYOkVmhr8jo1rySIR/CtMRTlgC/ENRRIjwUqY3mpgtN/7L MCJPHtYQIm16wLpYz6pHhOSG+Icb0yZ3/oCpBSkJIxb4sv6OPK43L8CgPuCouO65iUf9 RM768a8VgINCH5Pum7N4cI8NHQkXVLiKHRf48M9qvsdljD32plvEZaIV6LUrDA0TxcfV V7Xw== X-Gm-Message-State: AOJu0YzAfwNo3avBD23AMow2/u8/hjD1TaG7y3CvtaQsmLLPWL3IBjNR MHkRSG61B3uKm/W0U8EAhrg= X-Google-Smtp-Source: AGHT+IGpONnR47VKjbPdCEkGwBQyJ0MB1IECKLwIQe4RgkuBECQNtizBE8jYG7Guj/7+91bWfg6FUg== X-Received: by 2002:a5d:6451:0:b0:317:52ba:81f2 with SMTP id d17-20020a5d6451000000b0031752ba81f2mr11051958wrw.16.1693896452209; Mon, 04 Sep 2023 23:47:32 -0700 (PDT) Received: from localhost ([2a00:23c5:dc8c:8701:1663:9a35:5a7b:1d76]) by smtp.gmail.com with ESMTPSA id c20-20020a7bc854000000b003feef5b0bb7sm15846529wml.40.2023.09.04.23.47.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Sep 2023 23:47:31 -0700 (PDT) Date: Tue, 5 Sep 2023 07:47:30 +0100 From: Lorenzo Stoakes To: "Joel Fernandes (Google)" Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" , Suren Baghdasaryan , Kalesh Singh , Lokesh Gidra Subject: Re: [PATCH v6 2/7] mm/mremap: Allow moves within the same VMA for stack moves Message-ID: References: <20230903151328.2981432-1-joel@joelfernandes.org> <20230903151328.2981432-3-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230903151328.2981432-3-joel@joelfernandes.org> X-Rspamd-Queue-Id: 1B596A0016 X-Rspam-User: X-Stat-Signature: 8w9t5posjxjo1mp7fnkiyz8pahup6ng9 X-Rspamd-Server: rspam03 X-HE-Tag: 1693896453-613765 X-HE-Meta: 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 3HMBbsqb VXNlWKIZKlNQ6ZCCewxrsuTC/yaPNfP/aySasyn18eCG4/oNLhAM5kgupfJ32Ap3/JZcdUDMNL1zBlWTFAeojASOdhGx8k7qEkta0ttU1TEhLLUbxbAuWY7c04MNqi4yXZkGqooC0yTlJ7hhH0JknkiJv/j1Bn6ruAv90pTdB2pb9uMHKopsUecdZ8+wCjFhkHWyvDaGB2BCCb0Lwm38CfwlSwcndExaR8QTu4fNehQX2ajTU++If3uI+9cgGaknFnVZ6rUkCfL4GzNaCf38DN3t0TxFwbBanFcJcNtLQR2+608/o39l038UNpM0qXr4wx8cGZN3XuKa2HSPiWvqqMKMMdLbAHLoEBEnjdkFeyLvdtf0dM3HZ2GATWzvjpjp6hieeWYPhfLSZvM2kFdxKIKIWu1YskvYrupwImxCuwT7qRjyV8cIwIM+2zT8W2qY+Jeip9JjF8oIWHC519hI7Y46mZzy/LDqp1gqHL/f4nu5cKJc= 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: On Sun, Sep 03, 2023 at 03:13:23PM +0000, Joel Fernandes (Google) wrote: > For the stack move happening in shift_arg_pages(), the move is happening > within the same VMA which spans the old and new ranges. > > In case the aligned address happens to fall within that VMA, allow such > moves and don't abort the mremap alignment optimization. > > In the regular non-stack mremap case, we cannot allow any such moves as > will end up destroying some part of the mapping (either the source of > the move, or part of the existing mapping). So just avoid it for stack > moves. > > Signed-off-by: Joel Fernandes (Google) > --- > fs/exec.c | 2 +- > include/linux/mm.h | 2 +- > mm/mremap.c | 33 +++++++++++++++++++-------------- > 3 files changed, 21 insertions(+), 16 deletions(-) > > diff --git a/fs/exec.c b/fs/exec.c > index 1a827d55ba94..244925307958 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -712,7 +712,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) > * process cleanup to remove whatever mess we made. > */ > if (length != move_page_tables(vma, old_start, > - vma, new_start, length, false)) > + vma, new_start, length, false, true)) > return -ENOMEM; > > lru_add_drain(); > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 406ab9ea818f..e635d1fc73b6 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2458,7 +2458,7 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); > extern unsigned long move_page_tables(struct vm_area_struct *vma, > unsigned long old_addr, struct vm_area_struct *new_vma, > unsigned long new_addr, unsigned long len, > - bool need_rmap_locks); > + bool need_rmap_locks, bool for_stack); > > /* > * Flags used by change_protection(). For now we make it a bitmap so > diff --git a/mm/mremap.c b/mm/mremap.c > index 1011326b7b80..2b51f8b7cad8 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -490,12 +490,13 @@ static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, > } > > /* > - * A helper to check if a previous mapping exists. Required for > - * move_page_tables() and realign_addr() to determine if a previous mapping > - * exists before we can do realignment optimizations. > + * A helper to check if aligning down is OK. The aligned address should fall > + * on *no mapping*. For the stack moving down, that's a special move within > + * the VMA that is created to span the source and destination of the move, > + * so we make an exception for it. > */ > static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_align, > - unsigned long mask) > + unsigned long mask, bool for_stack) > { > unsigned long addr_masked = addr_to_align & mask; > > @@ -504,9 +505,13 @@ static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_ali > * of the corresponding VMA, we can't align down or we will destroy part > * of the current mapping. > */ > - if (vma->vm_start != addr_to_align) > + if (!for_stack && vma->vm_start != addr_to_align) > return false; > > + /* In the stack case we explicitly permit in-VMA alignment. */ > + if (for_stack && addr_masked >= vma->vm_start) > + return true; > + > /* > * Make sure the realignment doesn't cause the address to fall on an > * existing mapping. > @@ -517,7 +522,7 @@ static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_ali > /* Opportunistically realign to specified boundary for faster copy. */ > static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old_vma, > unsigned long *new_addr, struct vm_area_struct *new_vma, > - unsigned long mask) > + unsigned long mask, bool for_stack) > { > /* Skip if the addresses are already aligned. */ > if ((*old_addr & ~mask) == 0) > @@ -528,8 +533,8 @@ static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old > return; > > /* Ensure realignment doesn't cause overlap with existing mappings. */ > - if (!can_align_down(old_vma, *old_addr, mask) || > - !can_align_down(new_vma, *new_addr, mask)) > + if (!can_align_down(old_vma, *old_addr, mask, for_stack) || > + !can_align_down(new_vma, *new_addr, mask, for_stack)) > return; > > *old_addr = *old_addr & mask; > @@ -539,7 +544,7 @@ static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old > unsigned long move_page_tables(struct vm_area_struct *vma, > unsigned long old_addr, struct vm_area_struct *new_vma, > unsigned long new_addr, unsigned long len, > - bool need_rmap_locks) > + bool need_rmap_locks, bool for_stack) > { > unsigned long extent, old_end; > struct mmu_notifier_range range; > @@ -559,9 +564,9 @@ unsigned long move_page_tables(struct vm_area_struct *vma, > * If possible, realign addresses to PMD boundary for faster copy. > * Only realign if the mremap copying hits a PMD boundary. > */ > - if ((vma != new_vma) > - && (len >= PMD_SIZE - (old_addr & ~PMD_MASK))) > - try_realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK); > + if (len >= PMD_SIZE - (old_addr & ~PMD_MASK)) > + try_realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK, > + for_stack); > > flush_cache_range(vma, old_addr, old_end); > mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm, > @@ -708,7 +713,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, > } > > moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, > - need_rmap_locks); > + need_rmap_locks, false); > if (moved_len < old_len) { > err = -ENOMEM; > } else if (vma->vm_ops && vma->vm_ops->mremap) { > @@ -722,7 +727,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, > * and then proceed to unmap new area instead of old. > */ > move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, > - true); > + true, false); > vma = new_vma; > old_len = new_len; > old_addr = new_addr; > -- > 2.42.0.283.g2d96d420d3-goog > Looks good to me, thanks Reviewed-by: Lorenzo Stoakes