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([2a02:908:1252:fb60:be8a:bd56:1f94:86e7]) by smtp.gmail.com with ESMTPSA id j18sm10177649ejc.111.2020.10.12.01.11.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Oct 2020 01:11:32 -0700 (PDT) Reply-To: christian.koenig@amd.com Subject: Re: [PATCH 2/6] mm: introduce vma_set_file function v3 To: Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, chris@chris-wilson.co.uk, airlied@redhat.com, akpm@linux-foundation.org, daniel@ffwll.ch, sumit.semwal@linaro.org, willy@infradead.org, jhubbard@nvidia.com References: <20201009150342.1979-1-christian.koenig@amd.com> <20201009150342.1979-2-christian.koenig@amd.com> <20201009151418.GW5177@ziepe.ca> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <9592e3da-a105-b0ec-3fb2-be349c464c2c@gmail.com> Date: Mon, 12 Oct 2020 10:11:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201009151418.GW5177@ziepe.ca> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 09.10.20 um 17:14 schrieb Jason Gunthorpe: > On Fri, Oct 09, 2020 at 05:03:38PM +0200, Christian König wrote: >> +/* >> + * Change backing file, only valid to use during initial VMA setup. >> + */ >> +void vma_set_file(struct vm_area_struct *vma, struct file *file) >> +{ >> + if (file) >> + get_file(file); >> + >> + swap(vma->vm_file, file); >> + >> + if (file) >> + fput(file); >> +} > fput crashes when file is NULL so the error handling after > unmap_and_free_vma: can't handle this case, similarly vm_file can't be > NULL either. > > So just simply: > > swap(vma->vm_file, file); > get_file(vma->vm_file); > fput(file); > > Will do? I was considering this as well, yes. > Just let it crash if any of them are wrongly NULL. Mhm, changing from anonymous to file backed or reverse is probably not such a good idea. So yes catching those problems early is probably the best approach we could do. Going to do this in v4 if nobody objects. Regards, Christian. > > Jason