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[24.6.216.183]) by smtp.gmail.com with ESMTPSA id 6-20020a631446000000b0046f7e1ca434sm1594012pgu.0.2022.10.29.17.54.45 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 29 Oct 2022 17:54:46 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) Subject: Re: [PATCH v2] hugetlb: don't delete vma_lock in hugetlb MADV_DONTNEED processing From: Nadav Amit In-Reply-To: Date: Sat, 29 Oct 2022 17:54:44 -0700 Cc: Peter Xu , Linux-MM , kernel list , Naoya Horiguchi , David Hildenbrand , Axel Rasmussen , Mina Almasry , Rik van Riel , Vlastimil Babka , Matthew Wilcox , Andrew Morton , Wei Chen , stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <7048D2B5-5FA5-4F72-8FDC-A02411CFD71D@gmail.com> References: <20221023025047.470646-1-mike.kravetz@oracle.com> To: Mike Kravetz X-Mailer: Apple Mail (2.3696.120.41.1.1) ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="EraN1j/t"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf21.hostedemail.com: domain of nadav.amit@gmail.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=nadav.amit@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667091288; a=rsa-sha256; cv=none; b=Qd0xJI9tHrtTgQkKh7os6nXty2KWjAOC9OMs/Td5IkT/XJcLUYsTDR/izT0aFTNbl3I41J C0DaU6zx8lwd1N3vO7RU+DaA3U59Ode2wZH96LTvSujSSJqBodnkpoyJJmCk7pEDxzFYgQ 8DhNk2LCNHSTcx2ixFvT25TjbmlM90Q= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1667091288; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=77q2Cu689tqGNFEGpDkfXqQD5HzMzl1ec5TJSSyQvvA=; b=2rlFRXkF/z54EV8y4UE5BbZazbL+M2G4IuvrHWxMeIzcFWFgItihvBfbmQKkXccFBSdchG CWTwBUnHrQ1kxqyvwkjaSczOkeO2HWYqP2uerEQJS/buS7qBYOVyl3n+DUq2aCfllhAaoE FdZKb0H3xP5BRAJYJCZ6Nnhm/LQT510= Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="EraN1j/t"; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf21.hostedemail.com: domain of nadav.amit@gmail.com designates 209.85.214.181 as permitted sender) smtp.mailfrom=nadav.amit@gmail.com X-Rspam-User: X-Stat-Signature: xysgfczutm4376i6cbxi9bw3ekbjii5z X-Rspamd-Queue-Id: D914F1C0009 X-Rspamd-Server: rspam11 X-HE-Tag: 1667091288-2456 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 Oct 29, 2022, at 5:15 PM, Mike Kravetz = wrote: > zap_page_range is a bit confusing. It appears that the passed range = can > span multiple vmas. Otherwise, there would be no do while loop. Yet, = there > is only one mmu_notifier_range_init call specifying the passed vma. >=20 > It appears all callers pass a range entirely within a single vma. >=20 > The modifications above would work for a range within a single vma. = However, > things would be more complicated if the range can indeed span multiple = vmas. > For multiple vmas, we would need to check the first and last vmas for > pmd sharing. >=20 > Anyone know more about this seeming confusing behavior? Perhaps, = range > spanning multiple vmas was left over earlier code? I don=E2=80=99t have personal knowledge, but I noticed that it does not = make much sense, at least for MADV_DONTNEED. I tried to batch the TLB flushes = across VMAs for madvise=E2=80=99s. [1] Need to get to it sometime. [1] = https://lore.kernel.org/lkml/20210926161259.238054-7-namit@vmware.com/