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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7AE7EB64DD for ; Fri, 23 Jun 2023 16:40:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232465AbjFWQkq (ORCPT ); Fri, 23 Jun 2023 12:40:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49706 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231894AbjFWQk2 (ORCPT ); Fri, 23 Jun 2023 12:40:28 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EF559271F for ; Fri, 23 Jun 2023 09:40:23 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id 41be03b00d2f7-53f06f7cc74so549769a12.1 for ; Fri, 23 Jun 2023 09:40:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1687538423; x=1690130423; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=bgkvS77jKBasQJ+d6+AqQuQkcASYxscDuOzFX9WAgds=; b=5jLczQMp0KSTUIagObRwmH0mr7CUCxFkzN7ENpojhmLHZ5GyofnMb+Nwwg0KbCrGdj 3WAW+iB30hh1CIP2jXtjzzqMP6aQHq0SumA8ktu4p1yPKHIcW5cNVVYSJhPCOejXnvPu nKl3TIA+Sl6yCFYzA+PCG++nBBaxmuxCyqVDC21b2OKlQOdzRKNglDYsR9F3RTTJRMYl AAMVjrlGjICuPd2odT2iHSoPtCqMZtxg6+MlTsPgioLvqTryZxWthG+Vh2bh22MjQDaQ 9B3I8J2H+/UZPeZ9NSrWwZ6tFvGN95BBwimNdsppJUqYqfC4usU/76Fm0JacOMdSXTse zXfw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687538423; x=1690130423; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=bgkvS77jKBasQJ+d6+AqQuQkcASYxscDuOzFX9WAgds=; b=bbmQA4hbEWOdzHKmRJuLjNnmXN6BVrOGgZuHl3zpy6po5SfZKydHVurMsjF8oRMizW 6pdL00kUMtbvgRb5b/gBk1m58osQ/l+8T+EJP+Vh25GqafjnHswtaK2Jp7WV42pUASHU fn6iwOsel3hv193+zL8F6wiXceQxrAH9FB84cKODnnqkrpX4w2tHlHi6iwE6G0VJ17+t sy4k1EXgZVKtEb41hMbJC63B6mEKzASVo1/trxFRByHewvxntL7iNLlH1ru63NNlAuNW SOqE6rDlyMC7JeSoD8fKWNpL0mKH39woFYS45azydADvtZ/OJv89/9tNFqw4QvdAeotV V7Kg== X-Gm-Message-State: AC+VfDz57/pOeeiZY0tKCGipU0DOa64ay0+WTpaq0eVv1pOZpGyXIk2f Kc8bGm9dGO7K3ByEEn0pEcXRo4RIRlKbhw== X-Google-Smtp-Source: ACHHUZ7SVzvvZkW36k+iXmGUMtIymkIH4w+s1GAMmdhSj7Lx2MUYP2jnFMjcbaXPnGb5kaXvodFcOEtl1lhEHg== X-Received: from yjq3.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:272f]) (user=jiaqiyan job=sendgmr) by 2002:a63:fc01:0:b0:557:2a54:cf08 with SMTP id j1-20020a63fc01000000b005572a54cf08mr1060696pgi.6.1687538423324; Fri, 23 Jun 2023 09:40:23 -0700 (PDT) Date: Fri, 23 Jun 2023 16:40:14 +0000 In-Reply-To: <20230623164015.3431990-1-jiaqiyan@google.com> Mime-Version: 1.0 References: <20230623164015.3431990-1-jiaqiyan@google.com> X-Mailer: git-send-email 2.41.0.162.gfafddb0af9-goog Message-ID: <20230623164015.3431990-4-jiaqiyan@google.com> Subject: [PATCH v2 3/4] hugetlbfs: improve read HWPOISON hugepage From: Jiaqi Yan To: mike.kravetz@oracle.com, naoya.horiguchi@nec.com Cc: songmuchun@bytedance.com, shy828301@gmail.com, linmiaohe@huawei.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, duenwen@google.com, axelrasmussen@google.com, jthoughton@google.com, Jiaqi Yan Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a hugepage contains HWPOISON pages, read() fails to read any byte of the hugepage and returns -EIO, although many bytes in the HWPOISON hugepage are readable. Improve this by allowing hugetlbfs_read_iter returns as many bytes as possible. For a requested range [offset, offset + len) that contains HWPOISON page, return [offset, first HWPOISON page addr); the next read attempt will fail and return -EIO. Signed-off-by: Jiaqi Yan --- fs/hugetlbfs/inode.c | 58 +++++++++++++++++++++++++++++++++++++++----- 1 file changed, 52 insertions(+), 6 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 90361a922cec..86879ca3ff1e 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -282,6 +282,42 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, } #endif +/* + * Someone wants to read @bytes from a HWPOISON hugetlb @page from @offset. + * Returns the maximum number of bytes one can read without touching the 1st raw + * HWPOISON subpage. + * + * The implementation borrows the iteration logic from copy_page_to_iter*. + */ +static size_t adjust_range_hwpoison(struct page *page, size_t offset, size_t bytes) +{ + size_t n = 0; + size_t res = 0; + struct folio *folio = page_folio(page); + + /* First subpage to start the loop. */ + page += offset / PAGE_SIZE; + offset %= PAGE_SIZE; + while (1) { + if (is_raw_hwp_subpage(folio, page)) + break; + + /* Safe to read n bytes without touching HWPOISON subpage. */ + n = min(bytes, (size_t)PAGE_SIZE - offset); + res += n; + bytes -= n; + if (!bytes || !n) + break; + offset += n; + if (offset == PAGE_SIZE) { + page++; + offset = 0; + } + } + + return res; +} + /* * Support for read() - Find the page attached to f_mapping and copy out the * data. This provides functionality similar to filemap_read(). @@ -300,7 +336,7 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to) while (iov_iter_count(to)) { struct page *page; - size_t nr, copied; + size_t nr, copied, want; /* nr is the maximum number of bytes to copy from this page */ nr = huge_page_size(h); @@ -328,16 +364,26 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to) } else { unlock_page(page); - if (PageHWPoison(page)) { - put_page(page); - retval = -EIO; - break; + if (!PageHWPoison(page)) + want = nr; + else { + /* + * Adjust how many bytes safe to read without + * touching the 1st raw HWPOISON subpage after + * offset. + */ + want = adjust_range_hwpoison(page, offset, nr); + if (want == 0) { + put_page(page); + retval = -EIO; + break; + } } /* * We have the page, copy it to user space buffer. */ - copied = copy_page_to_iter(page, offset, nr, to); + copied = copy_page_to_iter(page, offset, want, to); put_page(page); } offset += copied; -- 2.41.0.162.gfafddb0af9-goog