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[209.85.220.65]) by mx.google.com with SMTPS id f8-v6sor2890192ljg.0.2019.01.31.02.13.52 for (Google Transport Security); Thu, 31 Jan 2019 02:13:52 -0800 (PST) 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=WsGlgijO; 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=i7aqIU67iTXfnMOyJql1uNrnoPFgHw1gIYpbByUl8SQ=; b=WsGlgijO3cknHXg1mEI+dHF6KGXSU6wDgOORDOLKHOpHi0m1l1JKujU0tp7ZlYc9P/ bRvhwLAUOzl9V9aJKStjWeHqNi4xsROdHbSBe53DVTdSScRktYADRRc0vzdv4cDiTm4F 9T0KugzXwzP85vvF8hZbi+Se8r6pYBcDfIVI+SFvtze0wl2aemZC+nP2bxGrTNkR/7xE 1Y+PLTRpZfThQ6XeAl/2KYZ5vQmW4Y2XZbdwT9uvbzK5lrEBldjdC5GRg3M2nLtBgyd3 bhICRRdwsmbCEkyPJP7Tv3yA1gAf/1TfDAGqj8hQQhNaq8AJI6KmXOirb7XINlvrjq/3 MF+g== X-Google-Smtp-Source: ALg8bN5d9Tpv6yTO6iC1E2jXBwzQgeTYpfILSW2IqBb3XFVwUI9hGn0qP+a8Il7n8MA2pe75YkgVoxkOXZD+HBbfEaQ= X-Received: by 2002:a2e:9849:: with SMTP id e9-v6mr27364491ljj.9.1548929631905; Thu, 31 Jan 2019 02:13:51 -0800 (PST) MIME-Version: 1.0 References: <20190131030812.GA2174@jordon-HP-15-Notebook-PC> <20190131083842.GE28876@rapoport-lnx> In-Reply-To: <20190131083842.GE28876@rapoport-lnx> From: Souptick Joarder Date: Thu, 31 Jan 2019 15:43:39 +0530 Message-ID: Subject: Re: [PATCHv2 1/9] mm: Introduce new vm_insert_range and vm_insert_range_buggy API To: Mike Rapoport Cc: Andrew Morton , Matthew Wilcox , Michal Hocko , "Kirill A. Shutemov" , vbabka@suse.cz, Rik van Riel , Stephen Rothwell , rppt@linux.vnet.ibm.com, Peter Zijlstra , Russell King - ARM Linux , robin.murphy@arm.com, iamjoonsoo.kim@lge.com, treding@nvidia.com, Kees Cook , Marek Szyprowski , stefanr@s5r6.in-berlin.de, hjc@rock-chips.com, Heiko Stuebner , airlied@linux.ie, oleksandr_andrushchenko@epam.com, joro@8bytes.org, pawel@osciak.com, Kyungmin Park , mchehab@kernel.org, Boris Ostrovsky , Juergen Gross , linux-kernel@vger.kernel.org, Linux-MM , linux-arm-kernel@lists.infradead.org, linux1394-devel@lists.sourceforge.net, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, xen-devel@lists.xen.org, iommu@lists.linux-foundation.org, linux-media@vger.kernel.org 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 Thu, Jan 31, 2019 at 2:09 PM Mike Rapoport wrote: > > On Thu, Jan 31, 2019 at 08:38:12AM +0530, Souptick Joarder wrote: > > Previouly drivers have their own way of mapping range of > > kernel pages/memory into user vma and this was done by > > invoking vm_insert_page() within a loop. > > > > As this pattern is common across different drivers, it can > > be generalized by creating new functions and use it across > > the drivers. > > > > vm_insert_range() is the API which could be used to mapped > > kernel memory/pages in drivers which has considered vm_pgoff > > > > vm_insert_range_buggy() is the API which could be used to map > > range of kernel memory/pages in drivers which has not considered > > vm_pgoff. vm_pgoff is passed default as 0 for those drivers. > > > > We _could_ then at a later "fix" these drivers which are using > > vm_insert_range_buggy() to behave according to the normal vm_pgoff > > offsetting simply by removing the _buggy suffix on the function > > name and if that causes regressions, it gives us an easy way to revert. > > > > Signed-off-by: Souptick Joarder > > Suggested-by: Russell King > > Suggested-by: Matthew Wilcox > > --- > > include/linux/mm.h | 4 +++ > > mm/memory.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > mm/nommu.c | 14 ++++++++++ > > 3 files changed, 99 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 80bb640..25752b0 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -2565,6 +2565,10 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, > > int remap_pfn_range(struct vm_area_struct *, unsigned long addr, > > unsigned long pfn, unsigned long size, pgprot_t); > > int vm_insert_page(struct vm_area_struct *, unsigned long addr, struct page *); > > +int vm_insert_range(struct vm_area_struct *vma, struct page **pages, > > + unsigned long num); > > +int vm_insert_range_buggy(struct vm_area_struct *vma, struct page **pages, > > + unsigned long num); > > vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr, > > unsigned long pfn); > > vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, > > diff --git a/mm/memory.c b/mm/memory.c > > index e11ca9d..0a4bf57 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -1520,6 +1520,87 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, > > } > > EXPORT_SYMBOL(vm_insert_page); > > > > +/** > > + * __vm_insert_range - insert range of kernel pages into user vma > > + * @vma: user vma to map to > > + * @pages: pointer to array of source kernel pages > > + * @num: number of pages in page array > > + * @offset: user's requested vm_pgoff > > + * > > + * This allows drivers to insert range of kernel pages they've allocated > > + * into a user vma. > > + * > > + * If we fail to insert any page into the vma, the function will return > > + * immediately leaving any previously inserted pages present. Callers > > + * from the mmap handler may immediately return the error as their caller > > + * will destroy the vma, removing any successfully inserted pages. Other > > + * callers should make their own arrangements for calling unmap_region(). > > + * > > + * Context: Process context. > > + * Return: 0 on success and error code otherwise. > > + */ > > +static int __vm_insert_range(struct vm_area_struct *vma, struct page **pages, > > + unsigned long num, unsigned long offset) > > +{ > > + unsigned long count = vma_pages(vma); > > + unsigned long uaddr = vma->vm_start; > > + int ret, i; > > + > > + /* Fail if the user requested offset is beyond the end of the object */ > > + if (offset > num) > > + return -ENXIO; > > + > > + /* Fail if the user requested size exceeds available object size */ > > + if (count > num - offset) > > + return -ENXIO; > > + > > + for (i = 0; i < count; i++) { > > + ret = vm_insert_page(vma, uaddr, pages[offset + i]); > > + if (ret < 0) > > + return ret; > > + uaddr += PAGE_SIZE; > > + } > > + > > + return 0; > > +} > > + > > +/** > > + * vm_insert_range - insert range of kernel pages starts with non zero offset > > + * @vma: user vma to map to > > + * @pages: pointer to array of source kernel pages > > + * @num: number of pages in page array > > + * > > + * Maps an object consisting of `num' `pages', catering for the user's > > + * requested vm_pgoff > > + * > > The elaborate description you've added to __vm_insert_range() is better put > here, as this is the "public" function. Ok, will add it in v3. Which means __vm_insert_range() still needs a short description ? > > > + * Context: Process context. Called by mmap handlers. > > + * Return: 0 on success and error code otherwise. > > + */ > > +int vm_insert_range(struct vm_area_struct *vma, struct page **pages, > > + unsigned long num) > > +{ > > + return __vm_insert_range(vma, pages, num, vma->vm_pgoff); > > +} > > +EXPORT_SYMBOL(vm_insert_range); > > + > > +/** > > + * vm_insert_range_buggy - insert range of kernel pages starts with zero offset > > + * @vma: user vma to map to > > + * @pages: pointer to array of source kernel pages > > + * @num: number of pages in page array > > + * > > + * Maps a set of pages, always starting at page[0] > > Here I'd add something like: > > Similar to vm_insert_range(), except that it explicitly sets @vm_pgoff to > 0. This function is intended for the drivers that did not consider > @vm_pgoff. Ok. > > > vm_insert_range_buggy() is the API which could be used to map > > range of kernel memory/pages in drivers which has not considered > > vm_pgoff. vm_pgoff is passed default as 0 for those drivers. > > > + * > > + * Context: Process context. Called by mmap handlers. > > + * Return: 0 on success and error code otherwise. > > + */ > > +int vm_insert_range_buggy(struct vm_area_struct *vma, struct page **pages, > > + unsigned long num) > > +{ > > + return __vm_insert_range(vma, pages, num, 0); > > +} > > +EXPORT_SYMBOL(vm_insert_range_buggy); > > + > > static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr, > > pfn_t pfn, pgprot_t prot, bool mkwrite) > > { > > diff --git a/mm/nommu.c b/mm/nommu.c > > index 749276b..21d101e 100644 > > --- a/mm/nommu.c > > +++ b/mm/nommu.c > > @@ -473,6 +473,20 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr, > > } > > EXPORT_SYMBOL(vm_insert_page); > > > > +int vm_insert_range(struct vm_area_struct *vma, struct page **pages, > > + unsigned long num) > > +{ > > + return -EINVAL; > > +} > > +EXPORT_SYMBOL(vm_insert_range); > > + > > +int vm_insert_range_buggy(struct vm_area_struct *vma, struct page **pages, > > + unsigned long num) > > +{ > > + return -EINVAL; > > +} > > +EXPORT_SYMBOL(vm_insert_range_buggy); > > + > > /* > > * sys_brk() for the most part doesn't need the global kernel > > * lock, except when an application is doing something nasty > > -- > > 1.9.1 > > > > -- > Sincerely yours, > Mike. >