From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 85BC113A406; Thu, 13 Jun 2024 11:51:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718279478; cv=none; b=Qpd8BWu84pOk1OOa4MUuRVwOzMhOxHgGCRH7VxpyWfnL0832s0xpfNIWRSaRxwj9kpw1/bIFM+L8Kf5/OGFPIwchXApfplt0l3zfsz+IKgdc3E+5O1xKpA0WXdIjSJv7zoJdW6JTaREo5SqqyvHS8RksM6Blj88Xw1K75+aOtBo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718279478; c=relaxed/simple; bh=xED1xYIGhhDWeYJqKX6epqQ3P6cR/gH3oDn1gpFblgg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BkniRFWNn+7WOMQzi7hyZz2wq+Wq74jb8u5bCwxciI72ewR6SaK66TSI/mBONBQ8KGvaYRoUr4fIQsAQRO2AvdGYrl1r/DVALJfn9QW8M3qubsQs0U1gozl7nwQoPfrNzRS2ExX+QbiM6a7c546+eBtS0JbNRIrlz9tOWQxGVQM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UL1GiTPj; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="UL1GiTPj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B6808C2BBFC; Thu, 13 Jun 2024 11:51:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1718279478; bh=xED1xYIGhhDWeYJqKX6epqQ3P6cR/gH3oDn1gpFblgg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UL1GiTPjorkYCWtFB0ClZq7qNg7r9cEBEUEt+R2n9yQHXh1lUNcMfOtPCRwT4xzCe ujVwEIx2Z2pwj33An4yLouwEFMoEAbBz+3hFpjUYeUhSdIlTQWItMDTyYP1yt1y/ds XF6gPiwdlR9lbs4BCabmr/VGRsIMvfMPs317/09M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chengming Zhou , David Hildenbrand , Andrea Arcangeli , Hugh Dickins , Ran Xiaokai , Stefan Roesch , xu xin , Yang Yang , Andrew Morton Subject: [PATCH 6.9 088/157] mm/ksm: fix ksm_zero_pages accounting Date: Thu, 13 Jun 2024 13:33:33 +0200 Message-ID: <20240613113230.830664536@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240613113227.389465891@linuxfoundation.org> References: <20240613113227.389465891@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chengming Zhou commit c2dc78b86e0821ecf9a9d0c35dba2618279a5bb6 upstream. We normally ksm_zero_pages++ in ksmd when page is merged with zero page, but ksm_zero_pages-- is done from page tables side, where there is no any accessing protection of ksm_zero_pages. So we can read very exceptional value of ksm_zero_pages in rare cases, such as -1, which is very confusing to users. Fix it by changing to use atomic_long_t, and the same case with the mm->ksm_zero_pages. Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-2-34bb358fdc13@linux.dev Fixes: e2942062e01d ("ksm: count all zero pages placed by KSM") Fixes: 6080d19f0704 ("ksm: add ksm zero pages for each process") Signed-off-by: Chengming Zhou Acked-by: David Hildenbrand Cc: Andrea Arcangeli Cc: Hugh Dickins Cc: Ran Xiaokai Cc: Stefan Roesch Cc: xu xin Cc: Yang Yang Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 2 +- include/linux/ksm.h | 17 ++++++++++++++--- include/linux/mm_types.h | 2 +- mm/ksm.c | 11 +++++------ 4 files changed, 21 insertions(+), 11 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3214,7 +3214,7 @@ static int proc_pid_ksm_stat(struct seq_ mm = get_task_mm(task); if (mm) { seq_printf(m, "ksm_rmap_items %lu\n", mm->ksm_rmap_items); - seq_printf(m, "ksm_zero_pages %lu\n", mm->ksm_zero_pages); + seq_printf(m, "ksm_zero_pages %ld\n", mm_ksm_zero_pages(mm)); seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages); seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm)); mmput(mm); --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -33,16 +33,27 @@ void __ksm_exit(struct mm_struct *mm); */ #define is_ksm_zero_pte(pte) (is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte)) -extern unsigned long ksm_zero_pages; +extern atomic_long_t ksm_zero_pages; + +static inline void ksm_map_zero_page(struct mm_struct *mm) +{ + atomic_long_inc(&ksm_zero_pages); + atomic_long_inc(&mm->ksm_zero_pages); +} static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte) { if (is_ksm_zero_pte(pte)) { - ksm_zero_pages--; - mm->ksm_zero_pages--; + atomic_long_dec(&ksm_zero_pages); + atomic_long_dec(&mm->ksm_zero_pages); } } +static inline long mm_ksm_zero_pages(struct mm_struct *mm) +{ + return atomic_long_read(&mm->ksm_zero_pages); +} + static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) { int ret; --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -988,7 +988,7 @@ struct mm_struct { * Represent how many empty pages are merged with kernel zero * pages when enabling KSM use_zero_pages. */ - unsigned long ksm_zero_pages; + atomic_long_t ksm_zero_pages; #endif /* CONFIG_KSM */ #ifdef CONFIG_LRU_GEN_WALKS_MMU struct { --- a/mm/ksm.c +++ b/mm/ksm.c @@ -296,7 +296,7 @@ static bool ksm_use_zero_pages __read_mo static bool ksm_smart_scan = true; /* The number of zero pages which is placed by KSM */ -unsigned long ksm_zero_pages; +atomic_long_t ksm_zero_pages = ATOMIC_LONG_INIT(0); /* The number of pages that have been skipped due to "smart scanning" */ static unsigned long ksm_pages_skipped; @@ -1428,8 +1428,7 @@ static int replace_page(struct vm_area_s * the dirty bit in zero page's PTE is set. */ newpte = pte_mkdirty(pte_mkspecial(pfn_pte(page_to_pfn(kpage), vma->vm_page_prot))); - ksm_zero_pages++; - mm->ksm_zero_pages++; + ksm_map_zero_page(mm); /* * We're replacing an anonymous page with a zero page, which is * not anonymous. We need to do proper accounting otherwise we @@ -3368,7 +3367,7 @@ static void wait_while_offlining(void) #ifdef CONFIG_PROC_FS long ksm_process_profit(struct mm_struct *mm) { - return (long)(mm->ksm_merging_pages + mm->ksm_zero_pages) * PAGE_SIZE - + return (long)(mm->ksm_merging_pages + mm_ksm_zero_pages(mm)) * PAGE_SIZE - mm->ksm_rmap_items * sizeof(struct ksm_rmap_item); } #endif /* CONFIG_PROC_FS */ @@ -3657,7 +3656,7 @@ KSM_ATTR_RO(pages_skipped); static ssize_t ksm_zero_pages_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sysfs_emit(buf, "%ld\n", ksm_zero_pages); + return sysfs_emit(buf, "%ld\n", atomic_long_read(&ksm_zero_pages)); } KSM_ATTR_RO(ksm_zero_pages); @@ -3666,7 +3665,7 @@ static ssize_t general_profit_show(struc { long general_profit; - general_profit = (ksm_pages_sharing + ksm_zero_pages) * PAGE_SIZE - + general_profit = (ksm_pages_sharing + atomic_long_read(&ksm_zero_pages)) * PAGE_SIZE - ksm_rmap_items * sizeof(struct ksm_rmap_item); return sysfs_emit(buf, "%ld\n", general_profit);