From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2426127-1521056742-2-10066821156183393222 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='198.145.29.99', Host='mail.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: SRS0=5xW2=GE=gmail.com=htejun@kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1521056742; b=lsfE4YF5XUKZHqdCk9fziMFRNGabTjA8anUgXtl0j2r3by7 0w0aasi5qNyQDT/vSg/h+xiT0RagyIbHS8eS3OqbXSdY0mskuoFwr/bsmS1O0vVN gG9sw7Cw4O8vn7sq1NMD52ip9AwgNI/w47pArUSGizGAOZheNXK7CL5w11zXN1Nk bijZQwZWnK09L1XIosfQu81P/pmziFkxO4fMDUetCGCsdSYEFYBiwNSqPScRkVBC MyLQLdB/nZnDqDOrEjzEAe+BSTdMnxLchACtN1tSt4CAPHWMZq1Hx6Detfd+uRi8 MEfgbvdU72VstewcJcIkE1btA9gty6IzW2sTLPg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=sender:from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-type :content-transfer-encoding; s=arctest; t=1521056742; bh=H2dPffxI d0/mpW4kkiOVKDPkETwdBaQs++EKyblVulA=; b=boFBsZJM3llwVM5oqHWt36ME pA9w1pR5wLXu65XRMUDynN2ndcCy2Jab4sgf5Y58YdJHl+hI3DFn5M3kcjv8gdJK 8e6uKFW+4TojtACQayZckkiCeANzxojl5GKMPnC90KziVo1V9yinBp9JRVgpfQnR hgjXj7LcKXSuYu/BFA6Naoo6k2skWbKOlzIlY7yw4wnIJQykRsL3lmC7i4pbKhq2 0ARBUBWCIMGuvMAxxHAnfbW2r6Fp1TXeHoUdeiVWOU4EuoS2gzOes83tvF4Gu4LI SG81rs1qohiZ8CDfg+DCcAn7D+VNkhTt248945QQ8g1Jw0t4Sr9yuw1oqryTGg== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=FhWGkPA1 x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=5xW2=GE=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=0 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=fHPThlNe; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=FhWGkPA1 x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=5xW2=GE=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=0 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=fHPThlNe; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 X-Remote-Delivered-To: security@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D40032077A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=htejun@gmail.com X-Google-Smtp-Source: AG47ELvjG0LbvJbGzQ4cLkGF+uneTrUUzyxGFpOi8BYB5VN4Loki/Tiz4hjwMNJ5F1IirvKhuspskA== Sender: Tejun Heo From: Tejun Heo To: torvalds@linux-foundation.org, jannh@google.com, paulmck@linux.vnet.ibm.com, bcrl@kvack.org, viro@zeniv.linux.org.uk, kent.overstreet@gmail.com Cc: security@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Tejun Heo , linux-mm@kvack.org Subject: [PATCH 4/8] HMM: Remove superflous RCU protection around radix tree lookup Date: Wed, 14 Mar 2018 12:45:11 -0700 Message-Id: <20180314194515.1661824-4-tj@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20180314194515.1661824-1-tj@kernel.org> References: <20180314194205.1651587-1-tj@kernel.org> <20180314194515.1661824-1-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: hmm_devmem_find() requires rcu_read_lock_held() but there's nothing which actually uses the RCU protection. The only caller is hmm_devmem_pages_create() which already grabs the mutex and does superflous rcu_read_lock/unlock() around the function. This doesn't add anything and just adds to confusion. Remove the RCU protection and open-code the radix tree lookup. If this needs to become more sophisticated in the future, let's add them back when necessary. Signed-off-by: Tejun Heo Reviewed-by: Jérôme Glisse Cc: linux-mm@kvack.org Cc: Linus Torvalds --- Hello, Jérôme, how do you want to route this patch? If you prefer, I can route it together with other patches. Thanks. mm/hmm.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index 320545b98..d4627c5 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -845,13 +845,6 @@ static void hmm_devmem_release(struct device *dev, void *data) hmm_devmem_radix_release(resource); } -static struct hmm_devmem *hmm_devmem_find(resource_size_t phys) -{ - WARN_ON_ONCE(!rcu_read_lock_held()); - - return radix_tree_lookup(&hmm_devmem_radix, phys >> PA_SECTION_SHIFT); -} - static int hmm_devmem_pages_create(struct hmm_devmem *devmem) { resource_size_t key, align_start, align_size, align_end; @@ -892,9 +885,8 @@ static int hmm_devmem_pages_create(struct hmm_devmem *devmem) for (key = align_start; key <= align_end; key += PA_SECTION_SIZE) { struct hmm_devmem *dup; - rcu_read_lock(); - dup = hmm_devmem_find(key); - rcu_read_unlock(); + dup = radix_tree_lookup(&hmm_devmem_radix, + key >> PA_SECTION_SHIFT); if (dup) { dev_err(device, "%s: collides with mapping for %s\n", __func__, dev_name(dup->device)); -- 2.9.5