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 5786CEB64DA for ; Tue, 18 Jul 2023 08:18:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 879E56B0075; Tue, 18 Jul 2023 04:18:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 82A356B0078; Tue, 18 Jul 2023 04:18:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6CA988D0001; Tue, 18 Jul 2023 04:18:46 -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 5C7656B0075 for ; Tue, 18 Jul 2023 04:18:46 -0400 (EDT) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 1720180216 for ; Tue, 18 Jul 2023 08:18:46 +0000 (UTC) X-FDA: 81024031452.29.A5CBDAE Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by imf22.hostedemail.com (Postfix) with ESMTP id E7C22C0003 for ; Tue, 18 Jul 2023 08:18:43 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=collabora.com header.s=mail header.b=W6Amq6SJ; dmarc=pass (policy=quarantine) header.from=collabora.com; spf=pass (imf22.hostedemail.com: domain of usama.anjum@collabora.com designates 46.235.227.172 as permitted sender) smtp.mailfrom=usama.anjum@collabora.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689668324; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=YUBO61YAVbeeaoyTDvkQCHQ1YWkwm7vtUQ8MeWBqu4w=; b=OEg65xI4yoiy68CXBTPs4s0EnKHAm5V4wv27CSdyWjZQm9MW8d4Jzh7JtzG30DZvEwVsi+ 8/+ce/e+6679sgolr7suOuDHwUdDxyGS22LIOlW3GuxyFXj7FUs3ItnM3JnzuGgTcCL0TI Yg5DX/qw1uFFYmRqmdbRLUj8jhpjbg0= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=collabora.com header.s=mail header.b=W6Amq6SJ; dmarc=pass (policy=quarantine) header.from=collabora.com; spf=pass (imf22.hostedemail.com: domain of usama.anjum@collabora.com designates 46.235.227.172 as permitted sender) smtp.mailfrom=usama.anjum@collabora.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689668324; a=rsa-sha256; cv=none; b=uYTpC8vujR1aF8chViSW/hPU1VEjMY0bjDZbpVQzGOMyr7k0cAfw2okJT8f+5u+f1/j+H4 FukYHV/RPJkf0y95BDIrE6uNJP3z9lfleckd5+WAZIwp3j4LxOJDOVCREeRTxKuETTYEXB RqxUGU/m8WJeBrTnOqNE3HToQxwAVBk= Received: from [192.168.100.7] (unknown [39.34.184.252]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: usama.anjum) by madras.collabora.co.uk (Postfix) with ESMTPSA id D5ABB6606F57; Tue, 18 Jul 2023 09:18:30 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1689668322; bh=GXEFGsC9SUGK5m98awHTNhzDO+f2wnzuuFO+W/trtiM=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=W6Amq6SJzgITAcbMOnARj16Z44YPtUvRxjDHpFe6P5NLuW8vak1ZvUdWQOgbsYby0 hxil9JBXc2l9fSIXUIruSCxxXgcwlEPuteCUEPBSMCpi3YlJ9sCmjFAKiy2LLWjCM8 1gr75YCmkUXDCSArd6NHlISPEwsDeO601Pm3FgDqEWueRVEh3HuPYUy9q0Tck3fT0t 9jeZsy1/XT3Sayi9zXx4UiPawuDytySzZTrcB3s1FEaxImGYvAQwaOIZzh0MC6qwKF nXmRUxByC9AmDbjL+2o9jNeV8aHY1QWQDwih9nxV2qcKJK3lLtnOzNfoYp6qnS1lqs ayIzB6/MFSR+g== Message-ID: Date: Tue, 18 Jul 2023 13:18:20 +0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Cc: Muhammad Usama Anjum , Peter Xu , David Hildenbrand , Andrew Morton , =?UTF-8?B?TWljaGHFgiBNaXJvc8WC?= =?UTF-8?Q?aw?= , Danylo Mocherniuk , Paul Gofman , Cyrill Gorcunov , Mike Rapoport , Nadav Amit , Alexander Viro , Shuah Khan , Christian Brauner , Yang Shi , Vlastimil Babka , "Liam R . Howlett" , Yun Zhou , Suren Baghdasaryan , Alex Sierra , Matthew Wilcox , Pasha Tatashin , Axel Rasmussen , "Gustavo A . R . Silva" , Dan Williams , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Greg KH , kernel@collabora.com Subject: Re: [PATCH v25 2/5] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs To: Andrei Vagin References: <20230713101415.108875-1-usama.anjum@collabora.com> <20230713101415.108875-3-usama.anjum@collabora.com> Content-Language: en-US From: Muhammad Usama Anjum In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: E7C22C0003 X-Stat-Signature: defbtftscoks7kx3mnkx6skop956njw9 X-HE-Tag: 1689668323-332943 X-HE-Meta: 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 8NtTwjiU 3E7QU6DTXmfK19qp4FKRTtufDmUAETEKLkqvJGuIAH29hWlfl8uLPJourqA595Vyv4FHL24Gg65o/ZfojPILkJ5mfURLev7UeiRDs20CHdm0RZY5GKm7sF9ZJ8o+Lep5CzRSHORB8DLmrpRDJtf1XCX7H18qEPM5uQoElVnP/0tesBngrLBAxWCmiiDDWtaXGfWz4S9zUO3zEEbA9+mmH8kscEHKVLDE6CdsaxnILT9+Sq8vMLcjuSNc9SMIelVJH6YZViiXmn451sPsvVnmfOmuH3IDHvZNdSgdFLCjBKYUUQ/NQ9jAkTL4k/HK07NvUB1ryI5W6zHuXbuU= 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 7/17/23 10:26 PM, Andrei Vagin wrote: > On Thu, Jul 13, 2023 at 3:14 AM Muhammad Usama Anjum > wrote: >> >> This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear >> the info about page table entries. The following operations are supported >> in this ioctl: >> - Get the information if the pages have been written-to (PAGE_IS_WRITTEN), >> file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT), swapped >> (PAGE_IS_SWAPPED) or page has pfn zero (PAGE_IS_PFNZERO). >> - Find pages which have been written-to and/or write protect the pages >> (atomic PM_SCAN_OP_GET + PM_SCAN_OP_WP) >> >> This IOCTL can be extended to get information about more PTE bits. The >> entire address range passed by user [start, end) is scanned until either >> the user provided buffer is full or max_pages have been found. >> > > Reviewed-by: Andrei Vagin Thank you. > > Here are a few inline comments. > >> Signed-off-by: Muhammad Usama Anjum >> --- >> Changes in v25: >> - Do proper filtering on hole as well (hole got missed earlier) >> >> Changes in v24: >> - Place WP markers in case of hole as well >> >> Changes in v23: >> - Set vec_buf_index to 0 only when vec_buf_index is set >> - Return -EFAULT instead of -EINVAL if vec is NULL >> - Correctly return the walk ending address to the page granularity >> >> Changes in v22: >> - Interface change to return walk ending address to user: >> - Replace [start start + len) with [start, end) >> - Return the ending address of the address walk in start >> >> Changes in v21: >> - Abort walk instead of returning error if WP is to be performed on >> partial hugetlb >> - Changed the data types of some variables in pagemap_scan_private to >> long >> >> Changes in v20: >> - Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO >> >> Changes in v19: >> - Interface changes such as renaming, return mask and WP can be used >> with any flags specified in masks >> - Internal code changes >> >> Changes in v18: >> - Rebased on top of next-20230613 >> - ptep_get() updates >> - remove pmd_trans_unstable() and add ACTION_AGAIN >> - Review updates (Micheal) >> >> Changes in v17: >> - Rebased on next-20230606 >> - Made make_uffd_wp_*_pte() better and minor changes >> >> Changes in v16: >> - Fixed a corner case where kernel writes beyond user buffer by one >> element >> - Bring back exclusive PM_SCAN_OP_WP >> - Cosmetic changes >> >> Changes in v15: >> - Build fix: >> - Use generic tlb flush function in pagemap_scan_pmd_entry() instead of >> using x86 specific flush function in do_pagemap_scan() >> - Remove #ifdef from pagemap_scan_hugetlb_entry() >> - Use mm instead of undefined vma->vm_mm >> >> Changes in v14: >> - Fix build error caused by #ifdef added at last minute in some configs >> >> Changes in v13: >> - Review updates >> - mmap_read_lock_killable() instead of mmap_read_lock() >> - Replace uffd_wp_range() with helpers which increases performance >> drastically for OP_WP operations by reducing the number of tlb >> flushing etc >> - Add MMU_NOTIFY_PROTECTION_VMA notification for the memory range >> >> Changes in v12: >> - Add hugetlb support to cover all memory types >> - Merge "userfaultfd: Define dummy uffd_wp_range()" with this patch >> - Review updates to the code >> >> Changes in v11: >> - Find written pages in a better way >> - Fix a corner case (thanks Paul) >> - Improve the code/comments >> - remove ENGAGE_WP + ! GET operation >> - shorten the commit message in favour of moving documentation to >> pagemap.rst >> >> Changes in v10: >> - move changes in tools/include/uapi/linux/fs.h to separate patch >> - update commit message >> >> Change in v8: >> - Correct is_pte_uffd_wp() >> - Improve readability and error checks >> - Remove some un-needed code >> >> Changes in v7: >> - Rebase on top of latest next >> - Fix some corner cases >> - Base soft-dirty on the uffd wp async >> - Update the terminologies >> - Optimize the memory usage inside the ioctl >> --- >> fs/proc/task_mmu.c | 591 ++++++++++++++++++++++++++++++++++++++++ >> include/linux/hugetlb.h | 1 + >> include/uapi/linux/fs.h | 55 ++++ >> mm/hugetlb.c | 2 +- >> 4 files changed, 648 insertions(+), 1 deletion(-) >> >> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c >> index cfab855fe7e9..596fdfdc4387 100644 >> --- a/fs/proc/task_mmu.c >> +++ b/fs/proc/task_mmu.c >> @@ -19,6 +19,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include >> @@ -1768,11 +1769,601 @@ static int pagemap_release(struct inode *inode, struct file *file) >> return 0; >> } >> >> +#define PM_SCAN_REQUIRE_UFFD (1ULL << 63) >> + >> +#define PM_SCAN_FOUND_MAX_PAGES (1) >> +#define PM_SCAN_END_WALK (-256) > > I would add a comment to explain why one is negative and another one > is positive. Sure. I'll add. > >> + >> +#define PM_SCAN_BITS_ALL (PAGE_IS_WRITTEN | PAGE_IS_FILE | \ >> + PAGE_IS_PRESENT | PAGE_IS_SWAPPED | \ >> + PAGE_IS_PFNZERO) >> +#define PM_SCAN_OPS (PM_SCAN_OP_GET | PM_SCAN_OP_WP) >> +#define IS_PM_SCAN_GET(flags) (flags & PM_SCAN_OP_GET) >> +#define IS_PM_SCAN_WP(flags) (flags & PM_SCAN_OP_WP) >> + >> +#define PM_SCAN_FLAGS(wt, file, present, swap, pfnzero) \ >> + ((wt) | ((file) << 1) | ((present) << 2) | \ >> + ((swap) << 3) | ((pfnzero) << 4)) > > it is better to use PAGE_IS_* constants here #define PAGE_IS_PFNZERO (1 << 4) PAGE_IS_PFNZERO macro cannot be used here. > >> + >> +struct pagemap_scan_private { >> + struct page_region *vec_buf, cur_buf; >> + unsigned long vec_buf_len, vec_buf_index, max_pages, found_pages; >> + unsigned long long flags, required_mask, anyof_mask, excluded_mask, return_mask, end_addr; > > end_addr has to be unsigned long. Sure. > >> +}; >> + >> +static inline bool is_pte_uffd_wp(pte_t pte) >> +{ >> + return (pte_present(pte) && pte_uffd_wp(pte)) || >> + pte_swp_uffd_wp_any(pte); >> +} >> + >> +static inline void make_uffd_wp_pte(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *pte) >> +{ >> + pte_t ptent = ptep_get(pte); >> + >> + if (pte_present(ptent)) { >> + pte_t old_pte; >> + >> + old_pte = ptep_modify_prot_start(vma, addr, pte); >> + ptent = pte_mkuffd_wp(ptent); >> + ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); >> + } else if (is_swap_pte(ptent)) { >> + ptent = pte_swp_mkuffd_wp(ptent); >> + set_pte_at(vma->vm_mm, addr, pte, ptent); >> + } else { >> + set_pte_at(vma->vm_mm, addr, pte, >> + make_pte_marker(PTE_MARKER_UFFD_WP)); >> + } >> +} >> + >> +static inline bool pagemap_scan_is_file(struct vm_area_struct *vma, pte_t ptent, >> + unsigned long addr) >> +{ >> + struct page *page = NULL; >> + swp_entry_t entry; >> + >> + if (pte_present(ptent)) { >> + page = vm_normal_page(vma, addr, ptent); >> + } else { >> + entry = pte_to_swp_entry(ptent); >> + if (is_pfn_swap_entry(entry)) >> + page = pfn_swap_entry_to_page(entry); >> + } >> + >> + if (page && !PageAnon(page)) >> + return true; >> + >> + return false; >> +} >> + >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> +static inline bool is_pmd_uffd_wp(pmd_t pmd) >> +{ >> + return (pmd_present(pmd) && pmd_uffd_wp(pmd)) || >> + (is_swap_pmd(pmd) && pmd_swp_uffd_wp(pmd)); >> +} >> + >> +static inline void make_uffd_wp_pmd(struct vm_area_struct *vma, >> + unsigned long addr, pmd_t *pmdp) >> +{ >> + pmd_t old, pmd = *pmdp; >> + >> + if (pmd_present(pmd)) { >> + old = pmdp_invalidate_ad(vma, addr, pmdp); >> + pmd = pmd_mkuffd_wp(old); >> + set_pmd_at(vma->vm_mm, addr, pmdp, pmd); >> + } else if (is_migration_entry(pmd_to_swp_entry(pmd))) { >> + pmd = pmd_swp_mkuffd_wp(pmd); >> + set_pmd_at(vma->vm_mm, addr, pmdp, pmd); >> + } >> +} >> +#endif >> + >> +#ifdef CONFIG_HUGETLB_PAGE >> +static inline bool is_huge_pte_uffd_wp(pte_t pte) >> +{ >> + return (pte_present(pte) && huge_pte_uffd_wp(pte)) || >> + pte_swp_uffd_wp_any(pte); >> +} >> + >> +static inline void make_uffd_wp_huge_pte(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep, >> + pte_t ptent) >> +{ >> + if (is_hugetlb_entry_hwpoisoned(ptent) || is_pte_marker(ptent)) >> + return; >> + >> + if (is_hugetlb_entry_migration(ptent)) >> + set_huge_pte_at(vma->vm_mm, addr, ptep, >> + pte_swp_mkuffd_wp(ptent)); >> + else if (!huge_pte_none(ptent)) >> + huge_ptep_modify_prot_commit(vma, addr, ptep, ptent, >> + huge_pte_mkuffd_wp(ptent)); >> + else >> + set_huge_pte_at(vma->vm_mm, addr, ptep, >> + make_pte_marker(PTE_MARKER_UFFD_WP)); >> +} >> + >> +static inline bool pagemap_scan_is_huge_file(pte_t pte) >> +{ >> + if (pte_present(pte) && (!PageAnon(pte_page(pte)))) >> + return true; >> + >> + return false; >> +} >> +#endif >> + >> +static int pagemap_scan_test_walk(unsigned long start, unsigned long end, >> + struct mm_walk *walk) >> +{ >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + >> + if ((p->flags & PM_SCAN_REQUIRE_UFFD) && (!userfaultfd_wp_async(vma) || >> + !userfaultfd_wp_use_markers(vma))) >> + return -EPERM; >> + >> + if (vma->vm_flags & VM_PFNMAP) >> + return 1; >> + >> + return 0; >> +} >> + >> +static int pagemap_scan_output(unsigned long bitmap, >> + struct pagemap_scan_private *p, >> + unsigned long addr, unsigned int n_pages) >> +{ >> + struct page_region *cur_buf = &p->cur_buf; >> + >> + bitmap &= p->return_mask; >> + >> + if (cur_buf->flags == bitmap && >> + cur_buf->start + cur_buf->len * PAGE_SIZE == addr) { >> + cur_buf->len += n_pages; >> + p->found_pages += n_pages; >> + } else { >> + if (cur_buf->len) { >> + if (p->vec_buf_index >= p->vec_buf_len) { >> + p->end_addr = addr; >> + return PM_SCAN_END_WALK; >> + } >> + >> + memcpy(&p->vec_buf[p->vec_buf_index], cur_buf, >> + sizeof(*p->vec_buf)); >> + p->vec_buf_index++; >> + } >> + >> + cur_buf->start = addr; >> + cur_buf->len = n_pages; >> + cur_buf->flags = bitmap; >> + p->found_pages += n_pages; >> + } >> + >> + if (p->found_pages == p->max_pages) { >> + p->end_addr = addr + n_pages * PAGE_SIZE; >> + return PM_SCAN_FOUND_MAX_PAGES; >> + } >> + >> + return 0; >> +} >> + >> +static bool pagemap_scan_is_interesting_page(unsigned long bitmap, >> + struct pagemap_scan_private *p) >> +{ >> + if ((p->required_mask & bitmap) != p->required_mask) >> + return false; >> + if (p->anyof_mask && !(p->anyof_mask & bitmap)) >> + return false; >> + if (p->excluded_mask & bitmap) >> + return false; >> + >> + return true; >> +} >> + >> +static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, >> + unsigned long end, struct mm_walk *walk) >> +{ >> + bool is_written, flush = false, interesting = true; >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + unsigned long bitmap, addr = end; >> + pte_t *pte, *orig_pte, ptent; >> + spinlock_t *ptl; >> + int ret = 0; >> + >> + arch_enter_lazy_mmu_mode(); >> + >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE >> + ptl = pmd_trans_huge_lock(pmd, vma); >> + if (ptl) { >> + unsigned long n_pages = (end - start)/PAGE_SIZE; >> + >> + if (n_pages > p->max_pages - p->found_pages) >> + n_pages = p->max_pages - p->found_pages; >> + >> + is_written = !is_pmd_uffd_wp(*pmd); >> + >> + bitmap = PM_SCAN_FLAGS(is_written, false, >> + pmd_present(*pmd), is_swap_pmd(*pmd), >> + pmd_present(*pmd) && is_zero_pfn(pmd_pfn(*pmd))); >> + >> + if (IS_PM_SCAN_GET(p->flags)) >> + interesting = pagemap_scan_is_interesting_page(bitmap, p); >> + >> + if (interesting) { >> + /* >> + * Break huge page into small pages if the WP operation >> + * need to be performed is on a portion of the huge page. >> + */ >> + if (is_written && IS_PM_SCAN_WP(p->flags) && >> + n_pages < HPAGE_SIZE/PAGE_SIZE) { >> + spin_unlock(ptl); >> + >> + split_huge_pmd(vma, pmd, start); >> + goto process_smaller_pages; >> + } >> + >> + if (IS_PM_SCAN_GET(p->flags)) >> + ret = pagemap_scan_output(bitmap, p, start, n_pages); >> + >> + if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) { >> + make_uffd_wp_pmd(vma, start, pmd); >> + flush_tlb_range(vma, start, end); >> + } >> + } >> + >> + spin_unlock(ptl); >> + arch_leave_lazy_mmu_mode(); >> + >> + return ret; >> + } >> + >> +process_smaller_pages: >> +#endif >> + >> + orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); >> + if (!pte) { >> + walk->action = ACTION_AGAIN; >> + return 0; >> + } >> + >> + for (addr = start; addr < end && !ret; pte++, addr += PAGE_SIZE) { >> + ptent = ptep_get(pte); >> + is_written = !is_pte_uffd_wp(ptent); >> + >> + bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_file(vma, ptent, addr), >> + pte_present(ptent), is_swap_pte(ptent), >> + pte_present(ptent) && is_zero_pfn(pte_pfn(ptent))); >> + >> + if (IS_PM_SCAN_GET(p->flags)) { >> + interesting = pagemap_scan_is_interesting_page(bitmap, p); >> + if (interesting) >> + ret = pagemap_scan_output(bitmap, p, addr, 1); >> + } >> + >> + if (IS_PM_SCAN_WP(p->flags) && is_written && interesting && >> + ret >= 0) { >> + make_uffd_wp_pte(vma, addr, pte); >> + flush = true; >> + } >> + } >> + >> + if (flush) >> + flush_tlb_range(vma, start, addr); >> + >> + pte_unmap_unlock(orig_pte, ptl); >> + arch_leave_lazy_mmu_mode(); >> + >> + cond_resched(); >> + return ret; >> +} >> + >> +#ifdef CONFIG_HUGETLB_PAGE >> +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask, >> + unsigned long start, unsigned long end, >> + struct mm_walk *walk) >> +{ >> + unsigned long n_pages = (end - start)/PAGE_SIZE; >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + bool is_written, interesting = true; >> + struct hstate *h = hstate_vma(vma); >> + unsigned long bitmap; >> + spinlock_t *ptl; >> + int ret = 0; >> + pte_t ptent; >> + >> + if (IS_PM_SCAN_WP(p->flags) && n_pages < HPAGE_SIZE/PAGE_SIZE) { >> + p->end_addr = start; >> + return -EINVAL; >> + } >> + >> + if (n_pages > p->max_pages - p->found_pages) >> + n_pages = p->max_pages - p->found_pages; >> + >> + if (IS_PM_SCAN_WP(p->flags)) { >> + i_mmap_lock_write(vma->vm_file->f_mapping); >> + ptl = huge_pte_lock(h, vma->vm_mm, ptep); >> + } >> + >> + ptent = huge_ptep_get(ptep); >> + is_written = !is_huge_pte_uffd_wp(ptent); >> + >> + bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_huge_file(ptent), >> + pte_present(ptent), is_swap_pte(ptent), >> + pte_present(ptent) && is_zero_pfn(pte_pfn(ptent))); >> + >> + if (IS_PM_SCAN_GET(p->flags)) >> + interesting = pagemap_scan_is_interesting_page(bitmap, p); >> + >> + if (interesting) { >> + /* >> + * Partial hugetlb page clear isn't supported >> + */ >> + if (is_written && IS_PM_SCAN_WP(p->flags) && >> + n_pages < HPAGE_SIZE/PAGE_SIZE) { >> + ret = PM_SCAN_END_WALK; >> + p->end_addr = start; >> + goto unlock_and_return; >> + } >> + >> + if (IS_PM_SCAN_GET(p->flags)) >> + ret = pagemap_scan_output(bitmap, p, start, n_pages); >> + >> + if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) { >> + make_uffd_wp_huge_pte(vma, start, ptep, ptent); >> + flush_hugetlb_tlb_range(vma, start, end); >> + } >> + } >> + >> +unlock_and_return: >> + if (IS_PM_SCAN_WP(p->flags)) { >> + spin_unlock(ptl); >> + i_mmap_unlock_write(vma->vm_file->f_mapping); >> + } >> + >> + return ret; >> +} >> +#else >> +#define pagemap_scan_hugetlb_entry NULL >> +#endif >> + >> +static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end, >> + int depth, struct mm_walk *walk) >> +{ >> + unsigned long n_pages = (end - addr)/PAGE_SIZE; >> + struct pagemap_scan_private *p = walk->private; >> + struct vm_area_struct *vma = walk->vma; >> + bool interesting = true; >> + unsigned long bitmap; >> + int ret = 0; >> + >> + if (!vma) >> + return 0; >> + >> + bitmap = PM_SCAN_FLAGS(false, false, false, false, false); >> + >> + if (IS_PM_SCAN_GET(p->flags)) >> + interesting = pagemap_scan_is_interesting_page(bitmap, p); >> + >> + if (interesting) { >> + if (IS_PM_SCAN_GET(p->flags)) { >> + if (n_pages > p->max_pages - p->found_pages) >> + n_pages = p->max_pages - p->found_pages; >> + >> + ret = pagemap_scan_output(bitmap, p, addr, n_pages); >> + } >> + >> + if (IS_PM_SCAN_WP(p->flags) && !ret && >> + uffd_wp_range(vma, addr, end - addr, true) < 0) > > Why do we need to call uffd_wp_range for holes? Should we call > flush_tlb_range after it? > >> + ret = -EINVAL; >> + } >> + >> + return ret; >> +} >> + >> +static const struct mm_walk_ops pagemap_scan_ops = { >> + .test_walk = pagemap_scan_test_walk, >> + .pmd_entry = pagemap_scan_pmd_entry, >> + .pte_hole = pagemap_scan_pte_hole, >> + .hugetlb_entry = pagemap_scan_hugetlb_entry, >> +}; >> + >> +static int pagemap_scan_args_valid(struct pm_scan_arg *arg, unsigned long start, >> + unsigned long end, struct page_region __user *vec) >> +{ >> + /* Detect illegal size, flags, len and masks */ >> + if (arg->size != sizeof(struct pm_scan_arg)) >> + return -EINVAL; >> + if (!arg->flags) >> + return -EINVAL; >> + if (arg->flags & ~PM_SCAN_OPS) >> + return -EINVAL; >> + if (!(end - start)) >> + return -EINVAL; >> + if ((arg->required_mask | arg->anyof_mask | arg->excluded_mask | >> + arg->return_mask) & ~PM_SCAN_BITS_ALL) >> + return -EINVAL; >> + if (!arg->required_mask && !arg->anyof_mask && >> + !arg->excluded_mask) >> + return -EINVAL; >> + if (!arg->return_mask) >> + return -EINVAL; >> + >> + /* Validate memory range */ >> + if (!IS_ALIGNED(start, PAGE_SIZE)) >> + return -EINVAL; >> + if (!access_ok((void __user *)start, end - start)) >> + return -EFAULT; >> + >> + if (IS_PM_SCAN_GET(arg->flags)) { >> + if (arg->vec_len == 0) >> + return -EINVAL; >> + if (!vec) >> + return -EFAULT; >> + if (!access_ok((void __user *)vec, >> + arg->vec_len * sizeof(struct page_region))) >> + return -EFAULT; >> + } >> + >> + if (IS_PM_SCAN_WP(arg->flags) && !IS_PM_SCAN_GET(arg->flags) && >> + arg->max_pages) >> + return -EINVAL; >> + >> + return 0; >> +} >> + >> +static long do_pagemap_scan(struct mm_struct *mm, unsigned long __arg) >> +{ >> + struct pm_scan_arg __user *uarg = (struct pm_scan_arg __user *)__arg; >> + unsigned long long start, end, walk_start, walk_end; >> + unsigned long empty_slots, vec_index = 0; >> + struct mmu_notifier_range range; >> + struct page_region __user *vec; >> + struct pagemap_scan_private p; >> + struct pm_scan_arg arg; >> + int ret = 0; >> + >> + if (copy_from_user(&arg, uarg, sizeof(arg))) >> + return -EFAULT; >> + >> + start = untagged_addr((unsigned long)arg.start); >> + end = untagged_addr((unsigned long)arg.end); >> + vec = (struct page_region __user *)untagged_addr((unsigned long)arg.vec); >> + >> + ret = pagemap_scan_args_valid(&arg, start, end, vec); >> + if (ret) >> + return ret; >> + >> + p.max_pages = (arg.max_pages) ? arg.max_pages : ULONG_MAX; >> + p.found_pages = 0; >> + p.required_mask = arg.required_mask; >> + p.anyof_mask = arg.anyof_mask; >> + p.excluded_mask = arg.excluded_mask; >> + p.return_mask = arg.return_mask; >> + p.flags = arg.flags; >> + p.flags |= ((p.required_mask | p.anyof_mask | p.excluded_mask) & >> + PAGE_IS_WRITTEN) ? PM_SCAN_REQUIRE_UFFD : 0; >> + p.cur_buf.start = p.cur_buf.len = p.cur_buf.flags = 0; >> + p.vec_buf = NULL; >> + p.vec_buf_len = PAGEMAP_WALK_SIZE >> PAGE_SHIFT; >> + p.vec_buf_index = 0; >> + p.end_addr = 0; >> + >> + /* >> + * Allocate smaller buffer to get output from inside the page walk >> + * functions and walk page range in PAGEMAP_WALK_SIZE size chunks. As >> + * we want to return output to user in compact form where no two >> + * consecutive regions should be continuous and have the same flags. >> + * So store the latest element in p.cur_buf between different walks and >> + * store the p.cur_buf at the end of the walk to the user buffer. >> + */ >> + if (IS_PM_SCAN_GET(p.flags)) { >> + p.vec_buf = kmalloc_array(p.vec_buf_len, sizeof(*p.vec_buf), >> + GFP_KERNEL); >> + if (!p.vec_buf) >> + return -ENOMEM; >> + } >> + >> + /* >> + * Protection change for the range is going to happen. >> + */ >> + if (IS_PM_SCAN_WP(p.flags)) { >> + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, >> + mm, start, end); >> + mmu_notifier_invalidate_range_start(&range); >> + } >> + >> + walk_start = walk_end = start; >> + while (walk_end < end && !ret) { >> + if (IS_PM_SCAN_GET(p.flags)) { >> + /* >> + * All data is copied to cur_buf first. When more data >> + * is found, we push cur_buf to vec_buf and copy new >> + * data to cur_buf. Subtract 1 from length as the >> + * index of cur_buf isn't counted in length. >> + */ >> + empty_slots = arg.vec_len - vec_index; >> + p.vec_buf_len = min(p.vec_buf_len, empty_slots - 1); >> + } >> + > > I still don't understand why we don't want/need to check for pending signals. We haven't added it as other existing code such as mincore() and pagemap_read() don't have it either. Also mmap_read_lock_killable would return error if there is some critical single pending. > >> + ret = mmap_read_lock_killable(mm); >> + if (ret) >> + goto out; >> + >> + walk_end = min((walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, end); >> + >> + ret = walk_page_range(mm, walk_start, walk_end, >> + &pagemap_scan_ops, &p); >> + mmap_read_unlock(mm); >> + >> + if (ret == PM_SCAN_FOUND_MAX_PAGES || ret == PM_SCAN_END_WALK) >> + arg.start = p.end_addr; > > nit: this check can be moved out of the loop. No, ret could get replaced by error if copy_to_user() fails. So we have to do this before that. > >> + >> + if (ret && ret != PM_SCAN_FOUND_MAX_PAGES && >> + ret != PM_SCAN_END_WALK) >> + goto out; >> + >> + if (p.vec_buf_index) { >> + if (copy_to_user(&vec[vec_index], p.vec_buf, >> + p.vec_buf_index * sizeof(*p.vec_buf))) { >> + /* >> + * Return error even though the OP succeeded >> + */ >> + ret = -EFAULT; >> + goto out; >> + } >> + vec_index += p.vec_buf_index; >> + p.vec_buf_index = 0; >> + } >> + walk_start = walk_end; >> + } >> + >> + if (p.cur_buf.len) { >> + if (copy_to_user(&vec[vec_index], &p.cur_buf, sizeof(p.cur_buf))) { >> + ret = -EFAULT; >> + goto out; >> + } >> + vec_index++; >> + } >> + >> + ret = vec_index; >> + >> +out: >> + if (!p.end_addr) >> + arg.start = walk_start; >> + if (copy_to_user(&uarg->start, &arg.start, sizeof(arg.start))) >> + ret = -EFAULT; >> + >> + if (IS_PM_SCAN_WP(p.flags)) >> + mmu_notifier_invalidate_range_end(&range); >> + >> + kfree(p.vec_buf); >> + return ret; >> +} >> + >> +static long do_pagemap_cmd(struct file *file, unsigned int cmd, >> + unsigned long arg) >> +{ >> + struct mm_struct *mm = file->private_data; >> + >> + switch (cmd) { >> + case PAGEMAP_SCAN: >> + return do_pagemap_scan(mm, arg); >> + >> + default: >> + return -EINVAL; >> + } >> +} >> + >> const struct file_operations proc_pagemap_operations = { >> .llseek = mem_lseek, /* borrow this */ >> .read = pagemap_read, >> .open = pagemap_open, >> .release = pagemap_release, >> + .unlocked_ioctl = do_pagemap_cmd, >> + .compat_ioctl = do_pagemap_cmd, >> }; >> #endif /* CONFIG_PROC_PAGE_MONITOR */ >> >> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h >> index 623e98d62df3..c44e7bde0339 100644 >> --- a/include/linux/hugetlb.h >> +++ b/include/linux/hugetlb.h >> @@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma, >> unsigned long cp_flags); >> >> bool is_hugetlb_entry_migration(pte_t pte); >> +bool is_hugetlb_entry_hwpoisoned(pte_t pte); >> void hugetlb_unshare_all_pmds(struct vm_area_struct *vma); >> >> #else /* !CONFIG_HUGETLB_PAGE */ >> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h >> index b7b56871029c..ac684d99e68f 100644 >> --- a/include/uapi/linux/fs.h >> +++ b/include/uapi/linux/fs.h >> @@ -305,4 +305,59 @@ typedef int __bitwise __kernel_rwf_t; >> #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ >> RWF_APPEND) >> >> +/* Pagemap ioctl */ >> +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg) >> + >> +/* Bits are set in flags of the page_region and masks in pm_scan_args */ >> +#define PAGE_IS_WRITTEN (1 << 0) >> +#define PAGE_IS_FILE (1 << 1) >> +#define PAGE_IS_PRESENT (1 << 2) >> +#define PAGE_IS_SWAPPED (1 << 3) >> +#define PAGE_IS_PFNZERO (1 << 4) >> + >> +/* >> + * struct page_region - Page region with flags >> + * @start: Start of the region >> + * @len: Length of the region in pages >> + * @bitmap: Bits sets for the region >> + */ >> +struct page_region { >> + __u64 start; >> + __u64 len; >> + __u64 flags; >> +}; >> + >> +/* >> + * struct pm_scan_arg - Pagemap ioctl argument >> + * @size: Size of the structure >> + * @flags: Flags for the IOCTL >> + * @start: Starting address of the region >> + * (Ending address of the walk is also returned in it) >> + * @end: Ending address of the region >> + * @vec: Address of page_region struct array for output >> + * @vec_len: Length of the page_region struct array >> + * @max_pages: Optional max return pages >> + * @required_mask: Required mask - All of these bits have to be set in the PTE >> + * @anyof_mask: Any mask - Any of these bits are set in the PTE >> + * @excluded_mask: Exclude mask - None of these bits are set in the PTE >> + * @return_mask: Bits that are to be reported in page_region >> + */ >> +struct pm_scan_arg { >> + __u64 size; >> + __u64 flags; >> + __u64 start; >> + __u64 end; >> + __u64 vec; >> + __u64 vec_len; >> + __u64 max_pages; >> + __u64 required_mask; >> + __u64 anyof_mask; >> + __u64 excluded_mask; >> + __u64 return_mask; >> +}; >> + >> +/* Supported flags */ >> +#define PM_SCAN_OP_GET (1 << 0) >> +#define PM_SCAN_OP_WP (1 << 1) >> + >> #endif /* _UAPI_LINUX_FS_H */ >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index ee88a2a6649f..f7cefdcb114c 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -4981,7 +4981,7 @@ bool is_hugetlb_entry_migration(pte_t pte) >> return false; >> } >> >> -static bool is_hugetlb_entry_hwpoisoned(pte_t pte) >> +bool is_hugetlb_entry_hwpoisoned(pte_t pte) >> { >> swp_entry_t swp; >> >> -- >> 2.39.2 >> -- BR, Muhammad Usama Anjum