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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 To: Andrei Vagin References: <20230808104309.357852-1-usama.anjum@collabora.com> <20230808104309.357852-3-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: rspam06 X-Rspamd-Queue-Id: 6610E40009 X-Stat-Signature: kwraojzaphbdxin1k3trokdfdxerefhk X-HE-Tag: 1691523313-796259 X-HE-Meta: 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 4vzwLse7 IXI1LD6hxoH5hFvWarapGzKJrJIos1vboz7Tg7INetxWLXLwJLydMmvPftanewKmQIGn1H9EYkMAMygtX6ySg6ybTluNYrdc3D5Vny0/G5xJ6Kd6amS3Wk0d8H159HeDCisbvy8H0eGvEPB10NI5uO/dDgH7lmehDK5u5hb61v86wc5uE3tWzRHalEqZQWOLt+0BRkHHYk2bcUfj0R8jUcoKHDWjTKgWkqL1s5CFP2MgK2UoFFEFoooufxpQDvqkBTt7kJgKFear6xY5sz6ZETAzmMYXkyFZREnkx/rzMM7uJtfeWkwvANYduutYNdOW9NQd6soLaxABWRP5leJqWcyDUQ+apIvByPEQmkqbJDTFVtrAEvQnUL+IjDVVg09PMlrxg6hxp9UhKBn0= 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 12:21 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. > >> + 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