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Fri, 21 Sep 2018 11:52:54 +0000 Subject: Re: [PATCH] kernel/kcov: Replace vm_insert_page with vmf_insert_page To: Souptick Joarder Cc: Matthew Wilcox , Andrew Morton , Mark Rutland , Dmitry Vyukov , Thomas Gleixner , Greg KH , tchibo@google.com, linux-kernel@vger.kernel.org References: <20180920191254.GA22764@jordon-HP-15-Notebook-PC> <6fa7d32b-07f0-ab6d-8053-021b171153e6@virtuozzo.com> From: Andrey Ryabinin Message-ID: <68b8cbf3-1b5a-2311-ac09-a8676280e85e@virtuozzo.com> Date: Fri, 21 Sep 2018 14:53:15 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [185.231.240.5] X-ClientProxiedBy: AM4PR0101CA0050.eurprd01.prod.exchangelabs.com (2603:10a6:200:41::18) To AM6PR08MB3254.eurprd08.prod.outlook.com (2603:10a6:209:47::19) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: dc599be9-8033-4d34-b915-08d61fb8c440 X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989299)(4534165)(4627221)(201703031133081)(201702281549075)(8990200)(5600074)(711020)(2017052603328)(7153060)(7193020);SRVR:AM6PR08MB3254; 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As part of it, converting vm_insert_page >>> to use vmf_insert_page. >>> >>> Signed-off-by: Souptick Joarder >>> --- >>> kernel/kcov.c | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/kernel/kcov.c b/kernel/kcov.c >>> index 3ebd09e..8900d8e 100644 >>> --- a/kernel/kcov.c >>> +++ b/kernel/kcov.c >>> @@ -293,8 +293,9 @@ static int kcov_mmap(struct file *filep, struct vm_area_struct *vma) >>> spin_unlock(&kcov->lock); >>> for (off = 0; off < size; off += PAGE_SIZE) { >>> page = vmalloc_to_page(kcov->area + off); >>> - if (vm_insert_page(vma, vma->vm_start + off, page)) >>> - WARN_ONCE(1, "vm_insert_page() failed"); >>> + if (vmf_insert_page(vma, vma->vm_start + off, page) >>> + != VM_FAULT_NOPAGE) >>> + WARN_ONCE(1, "vmf_insert_page() failed"); >> >> Nack, don't see the reason for such change, it only makes code worse. > > Yes, it needed. No, it's not needed. vm_insert_page() works perfectly fine here. > Going forward vm_insert_page will be converted to > vmf_insert_page. As part of it, this code has to be converted to use > vmf_insert_page(). This doesn't explain why such conversion would make sense for kcov_mmap(). > please refer below commit on linus tree - > 1c8f422059ae5da07db74 That the commit has nothing to deal with kcov, it doesn't explain why kcov_mmap() can't keep using vm_insert_page() and/or why we should prefer vmf_insert_page() over vm_insert_page() particularly in the case of kcov_mmap().