From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 6ABC86B000D for ; Mon, 2 Jul 2018 06:17:28 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id e19-v6so2471003pgv.11 for ; Mon, 02 Jul 2018 03:17:28 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id k16-v6si8021554pgt.519.2018.07.02.03.17.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 02 Jul 2018 03:17:27 -0700 (PDT) Date: Mon, 2 Jul 2018 12:17:25 +0200 From: Jan Kara Subject: Re: [PATCH v2 1/6] mm: get_user_pages: consolidate error handling Message-ID: <20180702101725.esnjyo4zp3726i3n@quack2.suse.cz> References: <20180702005654.20369-1-jhubbard@nvidia.com> <20180702005654.20369-2-jhubbard@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180702005654.20369-2-jhubbard@nvidia.com> Sender: owner-linux-mm@kvack.org List-ID: To: john.hubbard@gmail.com Cc: Matthew Wilcox , Michal Hocko , Christopher Lameter , Jason Gunthorpe , Dan Williams , Jan Kara , linux-mm@kvack.org, LKML , linux-rdma , linux-fsdevel@vger.kernel.org, John Hubbard On Sun 01-07-18 17:56:49, john.hubbard@gmail.com wrote: > From: John Hubbard > > An upcoming patch requires a way to operate on each page that > any of the get_user_pages_*() variants returns. > > In preparation for that, consolidate the error handling for > __get_user_pages(). This provides a single location (the "out:" label) > for operating on the collected set of pages that are about to be returned. > > As long every use of the "ret" variable is being edited, rename > "ret" --> "err", so that its name matches its true role. > This also gets rid of two shadowed variable declarations, as a > tiny beneficial a side effect. > > Signed-off-by: John Hubbard This looks nice! You can add: Reviewed-by: Jan Kara Honza > --- > mm/gup.c | 37 ++++++++++++++++++++++--------------- > 1 file changed, 22 insertions(+), 15 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index b70d7ba7cc13..73f0b3316fa7 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -660,6 +660,7 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > struct vm_area_struct **vmas, int *nonblocking) > { > long i = 0; > + int err = 0; > unsigned int page_mask; > struct vm_area_struct *vma = NULL; > > @@ -685,18 +686,19 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > if (!vma || start >= vma->vm_end) { > vma = find_extend_vma(mm, start); > if (!vma && in_gate_area(mm, start)) { > - int ret; > - ret = get_gate_page(mm, start & PAGE_MASK, > + err = get_gate_page(mm, start & PAGE_MASK, > gup_flags, &vma, > pages ? &pages[i] : NULL); > - if (ret) > - return i ? : ret; > + if (err) > + goto out; > page_mask = 0; > goto next_page; > } > > - if (!vma || check_vma_flags(vma, gup_flags)) > - return i ? : -EFAULT; > + if (!vma || check_vma_flags(vma, gup_flags)) { > + err = -EFAULT; > + goto out; > + } > if (is_vm_hugetlb_page(vma)) { > i = follow_hugetlb_page(mm, vma, pages, vmas, > &start, &nr_pages, i, > @@ -709,23 +711,25 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > * If we have a pending SIGKILL, don't keep faulting pages and > * potentially allocating memory. > */ > - if (unlikely(fatal_signal_pending(current))) > - return i ? i : -ERESTARTSYS; > + if (unlikely(fatal_signal_pending(current))) { > + err = -ERESTARTSYS; > + goto out; > + } > cond_resched(); > page = follow_page_mask(vma, start, foll_flags, &page_mask); > if (!page) { > - int ret; > - ret = faultin_page(tsk, vma, start, &foll_flags, > + err = faultin_page(tsk, vma, start, &foll_flags, > nonblocking); > - switch (ret) { > + switch (err) { > case 0: > goto retry; > case -EFAULT: > case -ENOMEM: > case -EHWPOISON: > - return i ? i : ret; > + goto out; > case -EBUSY: > - return i; > + err = 0; > + goto out; > case -ENOENT: > goto next_page; > } > @@ -737,7 +741,8 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > */ > goto next_page; > } else if (IS_ERR(page)) { > - return i ? i : PTR_ERR(page); > + err = PTR_ERR(page); > + goto out; > } > if (pages) { > pages[i] = page; > @@ -757,7 +762,9 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > start += page_increm * PAGE_SIZE; > nr_pages -= page_increm; > } while (nr_pages); > - return i; > + > +out: > + return i ? i : err; > } > > static bool vma_permits_fault(struct vm_area_struct *vma, > -- > 2.18.0 > -- Jan Kara SUSE Labs, CR