From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F579C021B8 for ; Wed, 26 Feb 2025 16:16:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D85F928000B; Wed, 26 Feb 2025 11:16:40 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D35BA280008; Wed, 26 Feb 2025 11:16:40 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BFDB128000B; Wed, 26 Feb 2025 11:16:40 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 4654C280008 for ; Wed, 26 Feb 2025 11:16:40 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 6A8A21CB7F5 for ; Wed, 26 Feb 2025 16:16:39 +0000 (UTC) X-FDA: 83162598918.16.CF8C189 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf27.hostedemail.com (Postfix) with ESMTP id 97F5040037 for ; Wed, 26 Feb 2025 16:16:37 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=M32g03qz; spf=none (imf27.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1740586597; 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=KibP9ZXbVPA77tsDBIt7YejKy8jux7lGMAtKocjYqYo=; b=WElm4tGsrFqbBivZnlZhQqIQ50W9DdG4v9kBJP5yuiNz/6igyX0U3ObY92fOeFnVMvpNLd sKd3rAxQC5pcT3yCmtma8N3kQyYRN4edYHjjE65bRwHrFWi+fx9Fjypg09oCZqxTXT+qKz 8mm4bzOsFzCWXw+hO29cIS6iR+o5d/g= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=M32g03qz; spf=none (imf27.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1740586597; a=rsa-sha256; cv=none; b=HxR3zcSyRjn8/w3UlA9IyidYv965cwTa3uHZDoHOiN0RvTArhNHnPcvOgkWbi23jL9nnvy 52zv2HyM/R5G+hmyLgNUNGIsaXVFjfxreOAHKes/M/XsHedKHVK36GC51HDby0j2Mx9qzk BoDtLuvVdFoM45kzoCH1pbxv/WcNOCo= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=KibP9ZXbVPA77tsDBIt7YejKy8jux7lGMAtKocjYqYo=; b=M32g03qz5Dfjn8teCFxFB+oxGB qpPSIAy3TukZOOIh8d8oJy65f5eXvPNL0sZQ5mCUm8oevnsWkg8BCriGClhX0mUrrzKPeATgtJTmG jcfMDkuoBf5u4kHmszo36IQK11Z+DBTv/TV2/g8j17zV89SdSvkdlGjESNrODNTd6MvGeAYWULo1p GYsLpWNeEtX/A2oOX5MkO1Sf/wz2qI7FfF7ta3aRph0FpSKkmgeAq6zIDQJiKxnhf3VVYwp1h8z1j kIueEgRrYjNaO/bZWT+WLZ7HczMPQDtjIuaG3NpPpOJWnH7gM2oGKE+yXtGujO+06LdY9qQT3cJ/A tz1XP+3w==; Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tnK5J-0000000Fu3E-2JPE; Wed, 26 Feb 2025 16:16:33 +0000 Date: Wed, 26 Feb 2025 16:16:33 +0000 From: Matthew Wilcox To: Suren Baghdasaryan Cc: "Liam R. Howlett" , akpm@linux-foundation.org, lokeshgidra@google.com, aarcange@redhat.com, 21cnbao@gmail.com, v-songbaohua@oppo.com, david@redhat.com, peterx@redhat.com, lorenzo.stoakes@oracle.com, hughd@google.com, jannh@google.com, kaleshsingh@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] userfaultfd: do not block on locking a large folio with raised refcount Message-ID: References: <20250225204613.2316092-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 97F5040037 X-Stat-Signature: c34tycuofrq7cjn9dscdydptdh58q8pn X-HE-Tag: 1740586597-996393 X-HE-Meta: U2FsdGVkX18zikIHcdC84pvKb/iimFxxyRwRH1gWMJcBO1vTo5X27OXXi0DciX74bkbjgu7K+w3i2jtnkKXgYF3RL0SwkOKwdWiZx/U7bEjeM2NahGGhY+Lvv+Z+b/9JwPg39nGfp5/XXMK6RBFqs4DjbcJBvsjG8lr48A0MqQdUO0AItGfQFgroLueB6aEJQ4TX89wardCAGgGZJW/cPuIe68zE4cmcAwR3nydkdheesCErHVO+GuFmrjto3/Nm0ma/i7OGagFSfPwT9jxqbYq+11QTeTxDnUJGAjfMzO5femSNz3HiPSGBMSAv0jcccX5HOyGTsvANO20FC1HWVR5LLJ41Lbww22AC0z/XAMTKoPe12FPxS7/jVieCFcrubydL3RfJSnyzHa4j2rBm5uV+9pruYB6O3RlpGLvV5U9l/+tZgqYeEVVYTIzYPcx8k5GB0NZ7xEK9Tr4XmturI9kdVvpb7rh4Kff/3FLWmPo9OxxF6y+WYlvug9B+hNEk6bhXVzVNEoNZHghAx4kw6MXEat/E813nPwaMdpMEOb6HmztdmKF2b4v9Ikk1pm6q77nqfzcSMnzIYZvZEZYKbHfQO+EqBFZiXNnF28Ik7sxsAv4C+TFNFubmVXhXVnIJCOQdOPuxBHboUkVXBa4CuBxnD+ngX45HkcrDZNfKVtUtIVXeMtyOdZmT+p/dyLT8f86B4A9xari6H2d/mMOLxPj7fmkl0LqJO0+zyCdyOAxsiYU+PLyXw93NYAEeYXqf7ZvF7cuDrz37mc2VEZigO7Qn+gSWrW3id71hvKOqNFAfX0eD1I9UYA1y6aVZH+W6bOCqgM7gXkNq8fsbUpEcONhqU6IKqNSG9IsPXisxVaz8dAFQiwHuqJjcN87eOqHpLWLeNC92f0rGDIyBag/syxFviVuU+fje3x66t7inJeG/UVb4LKvzwsXdFdNOjUzs4OupxfkE2wC9yQLSbbA mWrBcIuN hfNqfKS+zx6h+gNv5fhMdUOljoesjVOH7uxNrC88iLFI/EISI6idsk6kbEPQNw5oxqhViGffCfkxggAckb/QqR1SuykOWuOcYLA+QPZR1p4/SS37P/BKp5aL8h8Lg/FnsnvRHPwTFY8JjJbsKCh/JFaQIK6Md/MarA/i9EGZzEqA+wvthqD2jB484jCfP6eRyJfo1H7XhbCJRUPiCAo9mqA2lJBL3h6TrySVpijfHDyrfPRcgFfn400rlde36agxhNRCH2UE95vAnf7q+2teX5awLjw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000332, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 26, 2025 at 08:11:25AM -0800, Suren Baghdasaryan wrote: > On Wed, Feb 26, 2025 at 6:59 AM Liam R. Howlett wrote: > > Reversing the locking/folio_get() is okay because of the src_ptl spin > > lock, right? It might be worth saying something about it in the > > comment? > > That is correct. We take both folio lock and refcount before we drop > PTL. I'll add a comment. Thanks! In the commit message, not in the code, please.