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[209.132.183.28]) by mx.google.com with ESMTPS id k20si8164402qkg.317.2019.06.25.01.03.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Jun 2019 01:03:52 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C15D936809; Tue, 25 Jun 2019 08:03:37 +0000 (UTC) Received: from [10.36.117.83] (ovpn-117-83.ams2.redhat.com [10.36.117.83]) by smtp.corp.redhat.com (Postfix) with ESMTP id D296619728; Tue, 25 Jun 2019 08:03:31 +0000 (UTC) Subject: Re: [PATCH v2 1/5] drivers/base/memory: Remove unneeded check in remove_memory_block_devices From: David Hildenbrand To: Oscar Salvador , akpm@linux-foundation.org Cc: mhocko@suse.com, dan.j.williams@intel.com, pasha.tatashin@soleen.com, Jonathan.Cameron@huawei.com, anshuman.khandual@arm.com, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190625075227.15193-1-osalvador@suse.de> <20190625075227.15193-2-osalvador@suse.de> <3e820fee-f82f-3336-ff34-31c66dbbbbfe@redhat.com> Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <3e820fee-f82f-3336-ff34-31c66dbbbbfe@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 25 Jun 2019 08:03:51 +0000 (UTC) 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 25.06.19 10:01, David Hildenbrand wrote: > On 25.06.19 09:52, Oscar Salvador wrote: >> remove_memory_block_devices() checks for the range to be aligned >> to memory_block_size_bytes, which is our current memory block size, >> and WARNs_ON and bails out if it is not. >> >> This is the right to do, but we do already do that in try_remove_memory(), >> where remove_memory_block_devices() gets called from, and we even are >> more strict in try_remove_memory, since we directly BUG_ON in case the range >> is not properly aligned. >> >> Since remove_memory_block_devices() is only called from try_remove_memory(), >> we can safely drop the check here. >> >> To be honest, I am not sure if we should kill the system in case we cannot >> remove memory. >> I tend to think that WARN_ON and return and error is better. > > I failed to parse this sentence. > >> >> Signed-off-by: Oscar Salvador >> --- >> drivers/base/memory.c | 4 ---- >> 1 file changed, 4 deletions(-) >> >> diff --git a/drivers/base/memory.c b/drivers/base/memory.c >> index 826dd76f662e..07ba731beb42 100644 >> --- a/drivers/base/memory.c >> +++ b/drivers/base/memory.c >> @@ -771,10 +771,6 @@ void remove_memory_block_devices(unsigned long start, unsigned long size) >> struct memory_block *mem; >> int block_id; >> >> - if (WARN_ON_ONCE(!IS_ALIGNED(start, memory_block_size_bytes()) || >> - !IS_ALIGNED(size, memory_block_size_bytes()))) >> - return; >> - >> mutex_lock(&mem_sysfs_mutex); >> for (block_id = start_block_id; block_id != end_block_id; block_id++) { >> mem = find_memory_block_by_id(block_id, NULL); >> > > As I said when I introduced this, I prefer to have such duplicate checks > in place in case we have dependent code splattered over different files. > (especially mm/ vs. drivers/base). Such simple checks avoid to document > "start and size have to be aligned to memory blocks". Lol, I even documented it as well. So yeah, if you're going to drop this once, also drop the one in create_memory_block_devices(). > > If you still insist, then also remove the same sequence from > create_memory_block_devices(). > -- Thanks, David / dhildenb