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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, =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Subject: Re: [PATCH v27 2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs Content-Language: en-US To: Andrei Vagin References: <20230808104309.357852-1-usama.anjum@collabora.com> <20230808104309.357852-3-usama.anjum@collabora.com> <624cfa26-5650-ee0d-8e0a-1d844175bcaf@collabora.com> From: Muhammad Usama Anjum In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: nwhyrq469yn8eaocrxjkg8bbtohqstd9 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 8C9548000D X-Rspam-User: X-HE-Tag: 1691555488-909980 X-HE-Meta: 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 vtzCSvxy xveZoAwUWFe09sW7UsCLuRrvoo66lzUE9b4sPJYr+/ws4vx689zdlZBY/9fC+RTeGB5O4h0AJqDDhxX6T/PQr1N/a7bB+Zf67cTGjlt9OKd+9bIakVvFDFGWMwq8Tr0Ue3VjqrO+3bHOzJx6/slq2mKvNsDphloaqU9UpSTMBdnOeLFZMqB62xgwWm+9Zy87S2Oi04pdnUkridBtt6RAEU15dcqxqp5r6eLA73sX3pnNaTz+CG5yyOrshjKy/pjKExQcqUD/7BzcSSAyl4egYMem7zQ8/r3Hcgp05iOEH0MqDqoM773bvXQCPT4Q2qMYUqv1puYD5zeMEXy1US0ZRueECtivt1jgHxyrOTvBUix5vySd6rd3yNq/i3Wy9tPUSNzH2aVsS7brCal8= 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 8/9/23 12:55 AM, Andrei Vagin wrote: > On Tue, Aug 8, 2023 at 12:35 PM Muhammad Usama Anjum > wrote: >> >> On 8/9/23 12:21 AM, Andrei Vagin wrote: >>> On Tue, Aug 8, 2023 at 3:43 AM Muhammad Usama Anjum >>> wrote: >>> >>> .... >>> >>>> +static int pagemap_scan_output(unsigned long categories, >>>> + struct pagemap_scan_private *p, >>>> + unsigned long addr, unsigned long *end) >>>> +{ >>>> + unsigned long n_pages, total_pages; >>>> + int ret = 0; >>>> + >>>> + if (!p->vec_buf) >>>> + return 0; >>>> + >>>> + categories &= p->arg.return_mask; >>>> + >>>> + n_pages = (*end - addr) / PAGE_SIZE; >>>> + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || //TODO >>> >>> Need to fix this TODO. >> Sorry, I forgot to remove the "//TODO". As far as I've understood, the last >> discussion ended in keeping the check_add_overflow(). [1] I'll just remove >> the TODO. >> >> https://lore.kernel.org/all/CABb0KFEfmRz+Z_-7GygTL12E5Y254dvoUfWe4uSv9-wOx+Cs8w@mail.gmail.com >> >> >>> >>>> + total_pages > p->arg.max_pages) { >>>> + size_t n_too_much = total_pages - p->arg.max_pages; >>>> + *end -= n_too_much * PAGE_SIZE; >>>> + n_pages -= n_too_much; >>>> + ret = -ENOSPC; >>>> + } >>>> + >>>> + if (!pagemap_scan_push_range(categories, p, addr, *end)) { >>>> + *end = addr; >>>> + n_pages = 0; >>>> + ret = -ENOSPC; >>>> + } >>>> + >>>> + p->found_pages += n_pages; >>>> + if (ret) >>>> + p->walk_end_addr = *end; >>>> + >>>> + return ret; >>>> +} >>>> + >>> >>> ... >>> >>>> +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) >>>> +{ >>>> + struct mmu_notifier_range range; >>>> + struct pagemap_scan_private p; >>>> + unsigned long walk_start; >>>> + size_t n_ranges_out = 0; >>>> + int ret; >>>> + >>>> + memset(&p, 0, sizeof(p)); >>>> + ret = pagemap_scan_get_args(&p.arg, uarg); >>>> + if (ret) >>>> + return ret; >>>> + >>>> + p.masks_of_interest = MASKS_OF_INTEREST(p.arg); >>>> + ret = pagemap_scan_init_bounce_buffer(&p); >>>> + if (ret) >>>> + return ret; >>>> + >>>> + /* Protection change for the range is going to happen. */ >>>> + if (p.arg.flags & PM_SCAN_WP_MATCHING) { >>>> + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, >>>> + mm, p.arg.start, p.arg.end); >>>> + mmu_notifier_invalidate_range_start(&range); >>>> + } >>>> + >>>> + walk_start = p.arg.start; >>>> + for (; walk_start < p.arg.end; walk_start = p.arg.walk_end) { >>>> + int n_out; >>>> + >>>> + if (fatal_signal_pending(current)) { >>>> + ret = -EINTR; >>>> + break; >>>> + } >>>> + >>>> + ret = mmap_read_lock_killable(mm); >>>> + if (ret) >>>> + break; >>>> + ret = walk_page_range(mm, walk_start, p.arg.end, >>>> + &pagemap_scan_ops, &p); >>>> + mmap_read_unlock(mm); >>>> + >>>> + n_out = pagemap_scan_flush_buffer(&p); >>>> + if (n_out < 0) >>>> + ret = n_out; >>>> + else >>>> + n_ranges_out += n_out; >>>> + >>>> + if (ret != -ENOSPC || p.arg.vec_len - 1 == 0 || >>>> + p.found_pages == p.arg.max_pages) { >>>> + p.walk_end_addr = p.arg.end; >>> >>> You should not change p.walk_end_addr If ret is ENOSPC. Pls add a test >>> case to check this. >> Yeah, I'm not setting walk_end_addr if ret is ENOSPC. >> >> I'm setting walk_end_addr only when ret = 0. I'd added this as a result of >> a test case in my local test application. I can look at adding some tests >> in pagemap_ioctl.c kselftest as well. > > I am not sure that I understand what you mean here. ENOSPC can be returned > when the vec array is full and in this case, walk_end_addr should be > the address when it stops scanning. I'll copy a test case in kselftest to prove or dis-prove the correctness of walk_end address. > >> >>> >>>> + break; >>>> + } >>>> + } >>>> + >>>> + if (p.cur_buf.start != p.cur_buf.end) { >>>> + if (copy_to_user(p.vec_out, &p.cur_buf, sizeof(p.cur_buf))) >>>> + ret = -EFAULT; >>>> + else >>>> + ++n_ranges_out; >>>> + } >>>> + >>>> + /* ENOSPC signifies early stop (buffer full) from the walk. */ >>>> + if (!ret || ret == -ENOSPC) >>>> + ret = n_ranges_out; >>>> + >>>> + p.arg.walk_end = p.walk_end_addr ? p.walk_end_addr : walk_start; >>>> + if (pagemap_scan_writeback_args(&p.arg, uarg)) >>>> + ret = -EFAULT; >>>> + >>>> + if (p.arg.flags & PM_SCAN_WP_MATCHING) >>>> + mmu_notifier_invalidate_range_end(&range); >>>> + >>>> + kfree(p.vec_buf); >>>> + return ret; >>>> +} >>> >>> Thanks, >>> Andrei >> >> -- >> BR, >> Muhammad Usama Anjum -- BR, Muhammad Usama Anjum