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d=linux-foundation.org; s=korg; t=1688490349; bh=EHnWzHDuJUTw0Pw5eMhRe3eZnnHetbaAkd4tQqIIqaw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=HtVKqhxeFf3El0FfxmkM7WWfBMeOQttBDhPoYNWjA2NkE4Bo/5vKYr054IPH3boNU aedPlBeJKNhKqDuCZ6gAzMBSZffvzFVpuyb6s7dQb0QInF85P7o2j5GYu2gFScnNmL Hnj9Tsr0Ns751rAiEuz5Df1QmxzkLihvlVx6pRbU= Date: Tue, 4 Jul 2023 10:05:48 -0700 From: Andrew Morton To: Kemeng Shi Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm: remove redundant check in page_vma_mapped_walk Message-Id: <20230704100548.11bce56bb79be4a7d1d8482c@linux-foundation.org> In-Reply-To: <20230704213932.1339204-2-shikemeng@huaweicloud.com> References: <20230704213932.1339204-1-shikemeng@huaweicloud.com> <20230704213932.1339204-2-shikemeng@huaweicloud.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E91C28000A X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: xdczio5uygzdjjumhr5wxau1hg1kyam8 X-HE-Tag: 1688490350-426761 X-HE-Meta: U2FsdGVkX1/ZqIxHypY5q0E66S1T+sP56F2Oio9PTaw3VIzfWqrigVnw+eCwtk0KIkUS8E6LIN1YvVfbCLAnE+ZAOCSKwJ2SzPLTvSLn8j4emgQkKpv6ibzKRmDljJt/HQpS+mMKpSS8F/LGn7cv3VXWijSrlPa5CEgJDzOY+qNgRLsyjfSayhVJj959OWatmmw+L91xxPw+GQ8npkfSOAOSC2PU5NQPvtSuDeXkMvMwWLw12V0pMdNntUWzf3JswGgAItkbjAb6yA2DvuDEASv+yU1yAhRGBcOajsGrpVrXmv3QE0yoKfHhpi6u+8rQlXMSUIaeVIhAHiBJag1VAc/+T2dM7NHMeFOpqiaexDXODYwDG9zYG10OgI4EQcI+ExrR7omFBHyPD4iQw74Ng1OycNBa/xcVLxHySgV0VBHE0AptzSgiixPmFLGiSIjXSNqKkQyhU9IPVG+fkEiRnWCq7PRyLhQgJlp21Su3P9ESExjLtVz4c0tsyqltwvXdCDTBvL1SfumD13VzDgwbpOcGHK6Xii89H5FL2q+9pxV5dtBjI34uH6/1C6JvUcpMV1zyO1DTvBmrZGDXzy6ViBDDZwDVK1Z7PeU7m7/9myq1cIUy6pO/gnoRVeiBrcC9RfgWvy9fg8f0ANyVOIL4vASHpB3z/52FDL0AOiGifp1gx4vgNnC0qu0EclEOIVIIzCinXE3z8rUZvn51rH0LR9sRKEVAX9JIl8lT8CKRTPKWlcc1O7sKlPX6MqI48J+jFR1umHKSQfTN/pgO9M88NGJUVRlGe7qrTZC0vSVZF71biwINZj0dtX/jEFvH+frBP6IgxsdiQ+ld64uIYfPQyqW7ocIt97FAoMhiwm4iP3+PwCZjmqSUVV63sOHpPLHtsKvoypjhZOE6b3M+BvDWVZ0xEB8S/f/kAe8XmLDOeVwlDrtKwYhvYOQNp1mw23b3TxZo63NKasEzmkxgnts PTpJtrpq 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 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 Wed, 5 Jul 2023 05:39:31 +0800 Kemeng Shi wrote: > For PVMW_SYNC case, we always take pte lock when get first pte of > PTE-mapped THP in map_pte and hold it until: > 1. scan of pmd range finished or > 2. scan of user input range finished or > 3. user stop walk with page_vma_mapped_walk_done. > In each case. pte lock will not be freed during middle scan of PTE-mapped > THP. > > ... > > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -275,10 +275,6 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) > goto restart; > } > pvmw->pte++; > - if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) { > - pvmw->ptl = pte_lockptr(mm, pvmw->pmd); > - spin_lock(pvmw->ptl); > - } > } while (pte_none(*pvmw->pte)); > > if (!pvmw->ptl) { This code has changed significantly since 6.4. Please develop against the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm, thanks.