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[209.85.220.65]) by mx.google.com with SMTPS id a1sor21522772lji.35.2019.07.22.07.37.45 for (Google Transport Security); Mon, 22 Jul 2019 07:37:45 -0700 (PDT) Received-SPF: pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=cNYsnnjV; spf=pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jrdr.linux@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=SUH6arJbp14IVMjbkeZ0K94NO/z20TDutwCqOxsq4Fw=; b=cNYsnnjVLguyuhcKHqqxp7hSA5M3S1DZvaBoF80d1MZLvyCLSsdsxyzbqp+hAugfqB La4mTA+QaSN25eS7kR5jYbs5x37bIW38yuFEe9LoQUhA4BKZbg7G89i02FTdSaoa/LHD 0/lmUGsZBZhSpFQ3CDG0yu7d0XOEvaaddpieq56zgY56JIdUSioPyWlIQN+Coy+AXBhh i8jmWmQqzLzSlVGdTV2hn84KzjVBQl4pbwsL+KCS9KIx6GA7hL+D2ZJUFh8ilWXmzYh/ dAZFYOljbOddCkc8Zmh16FrOyiTux9Y7iKOyUucQi77FVxvyJCXpJp2vmP1KIUydFgVE 61bA== X-Google-Smtp-Source: APXvYqyUuyVhvpPVyaK0EtT6IHNJ3TNJikX6jVZCPNEmd7vcNDjv9sQO2bgfO2wFUz2CiCOMPgV4do0itfHJJ3iI0ko= X-Received: by 2002:a2e:b009:: with SMTP id y9mr25605680ljk.152.1563806265548; Mon, 22 Jul 2019 07:37:45 -0700 (PDT) MIME-Version: 1.0 References: <20190722094426.18563-1-hch@lst.de> <20190722094426.18563-2-hch@lst.de> In-Reply-To: <20190722094426.18563-2-hch@lst.de> From: Souptick Joarder Date: Mon, 22 Jul 2019 20:07:33 +0530 Message-ID: Subject: Re: [PATCH 1/6] mm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot} To: Christoph Hellwig Cc: =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jason Gunthorpe , Ben Skeggs , Ralph Campbell , Linux-MM , nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Felix Kuehling Content-Type: text/plain; charset="UTF-8" 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 Mon, Jul 22, 2019 at 3:14 PM Christoph Hellwig wrote: > > We should not have two different error codes for the same condition. In > addition this really complicates the code due to the special handling of > EAGAIN that drops the mmap_sem due to the FAULT_FLAG_ALLOW_RETRY logic > in the core vm. > > Signed-off-by: Christoph Hellwig > Reviewed-by: Ralph Campbell > Reviewed-by: Felix Kuehling > --- > Documentation/vm/hmm.rst | 2 +- > mm/hmm.c | 10 ++++------ > 2 files changed, 5 insertions(+), 7 deletions(-) > > diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst > index 7d90964abbb0..710ce1c701bf 100644 > --- a/Documentation/vm/hmm.rst > +++ b/Documentation/vm/hmm.rst > @@ -237,7 +237,7 @@ The usage pattern is:: > ret = hmm_range_snapshot(&range); > if (ret) { > up_read(&mm->mmap_sem); > - if (ret == -EAGAIN) { > + if (ret == -EBUSY) { > /* > * No need to check hmm_range_wait_until_valid() return value > * on retry we will get proper error with hmm_range_snapshot() > diff --git a/mm/hmm.c b/mm/hmm.c > index e1eedef129cf..16b6731a34db 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -946,7 +946,7 @@ EXPORT_SYMBOL(hmm_range_unregister); > * @range: range > * Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid > * permission (for instance asking for write and range is read only), > - * -EAGAIN if you need to retry, -EFAULT invalid (ie either no valid > + * -EBUSY if you need to retry, -EFAULT invalid (ie either no valid > * vma or it is illegal to access that range), number of valid pages > * in range->pfns[] (from range start address). > * > @@ -967,7 +967,7 @@ long hmm_range_snapshot(struct hmm_range *range) > do { > /* If range is no longer valid force retry. */ > if (!range->valid) > - return -EAGAIN; > + return -EBUSY; > > vma = find_vma(hmm->mm, start); > if (vma == NULL || (vma->vm_flags & device_vma)) > @@ -1062,10 +1062,8 @@ long hmm_range_fault(struct hmm_range *range, bool block) > > do { > /* If range is no longer valid force retry. */ > - if (!range->valid) { > - up_read(&hmm->mm->mmap_sem); > - return -EAGAIN; > - } > + if (!range->valid) > + return -EBUSY; Is it fine to remove up_read(&hmm->mm->mmap_sem) ? > > vma = find_vma(hmm->mm, start); > if (vma == NULL || (vma->vm_flags & device_vma)) > -- > 2.20.1 >