From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:57722 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728190AbgBNW1r (ORCPT ); Fri, 14 Feb 2020 17:27:47 -0500 From: Christian Borntraeger Subject: [PATCH v2 39/42] example for future extension: mm:gup/writeback: add callbacks for inaccessible pages: error cases Date: Fri, 14 Feb 2020 17:26:55 -0500 Message-Id: <20200214222658.12946-40-borntraeger@de.ibm.com> In-Reply-To: <20200214222658.12946-1-borntraeger@de.ibm.com> References: <20200214222658.12946-1-borntraeger@de.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Christian Borntraeger , Janosch Frank , Andrew Morton Cc: KVM , Cornelia Huck , David Hildenbrand , Thomas Huth , Ulrich Weigand , Claudio Imbrenda , linux-s390 , Michael Mueller , Vasily Gorbik , Andrea Arcangeli , linux-mm@kvack.org, Will Deacon , Sean Christopherson From: Claudio Imbrenda This is a potential extension to do error handling if we fail to make the page accessible if we know what others need. Signed-off-by: Claudio Imbrenda --- mm/gup.c | 17 ++++++++++++----- mm/page-writeback.c | 6 +++++- 2 files changed, 17 insertions(+), 6 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index a1c15d029f7c..354bcfbd844b 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -193,6 +193,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, struct page *page; spinlock_t *ptl; pte_t *ptep, pte; + int ret; /* FOLL_GET and FOLL_PIN are mutually exclusive. */ if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == @@ -250,8 +251,6 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, if (is_zero_pfn(pte_pfn(pte))) { page = pte_page(pte); } else { - int ret; - ret = follow_pfn_pte(vma, address, ptep, flags); page = ERR_PTR(ret); goto out; @@ -259,7 +258,6 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, } if (flags & FOLL_SPLIT && PageTransCompound(page)) { - int ret; get_page(page); pte_unmap_unlock(ptep, ptl); lock_page(page); @@ -276,7 +274,12 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, page = ERR_PTR(-ENOMEM); goto out; } - arch_make_page_accessible(page); + ret = arch_make_page_accessible(page); + if (ret) { + put_page(page); + page = ERR_PTR(ret); + goto out; + } } if (flags & FOLL_TOUCH) { if ((flags & FOLL_WRITE) && @@ -1920,7 +1923,11 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON_PAGE(compound_head(page) != head, page); - arch_make_page_accessible(page); + ret = arch_make_page_accessible(page); + if (ret) { + put_page(head); + goto pte_unmap; + } SetPageReferenced(page); pages[*nr] = page; (*nr)++; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 4c020e4ae71c..558d7063c117 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2807,7 +2807,11 @@ int __test_set_page_writeback(struct page *page, bool keep_write) inc_zone_page_state(page, NR_ZONE_WRITE_PENDING); } unlock_page_memcg(page); - arch_make_page_accessible(page); + /* + * If writeback has been triggered on a page that cannot be made + * accessible, it is too late. + */ + WARN_ON(arch_make_page_accessible(page)); return ret; } -- 2.25.0