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 2919FC369CB for ; Sun, 20 Apr 2025 02:42:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 53DDD6B00AB; Sat, 19 Apr 2025 22:42:01 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4EC4F6B00AC; Sat, 19 Apr 2025 22:42:01 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3B5466B00AD; Sat, 19 Apr 2025 22:42:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 1FA986B00AB for ; Sat, 19 Apr 2025 22:42:01 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 6CF6E1A0BAC for ; Sun, 20 Apr 2025 02:42:01 +0000 (UTC) X-FDA: 83352872442.01.9D18205 Received: from mail-pl1-f179.google.com (mail-pl1-f179.google.com [209.85.214.179]) by imf06.hostedemail.com (Postfix) with ESMTP id A19F2180004 for ; Sun, 20 Apr 2025 02:41:59 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=PYrIp0cB; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf06.hostedemail.com: domain of rientjes@google.com designates 209.85.214.179 as permitted sender) smtp.mailfrom=rientjes@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1745116919; a=rsa-sha256; cv=none; b=MGa7b2oXEMakgL4XFIIkrFBnXqimzoF8atrwqO6p/x425Wn3HPZiVL6+M9XxJA5kiMilOc 6HP9TXG/V4PV4qbatkRmC7rpUgVhHisJbA5ze3Mp3+8O2Ksqeu8hl2vglCwxGAzIgu4f/C xKCW/1VSwt9AFUCi3PE5L7E7uwEidtk= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=PYrIp0cB; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf06.hostedemail.com: domain of rientjes@google.com designates 209.85.214.179 as permitted sender) smtp.mailfrom=rientjes@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1745116919; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IyJl48UbRWmHPVEV8YJtbC6bLnrflYmUro9MxdcNyl4=; b=bjGhLNF8xoYnSQsmnuIMK6oHtplDd6+SRBoLlWFpxV0lNZNe0qifgWaB7zikRLA54oDS4a v5hatZPQaGxYj9LEOeEqBUo1XJ5n+VODO6eHvllxu4RAi3JBZ5WW911elW3+v4kldtp/f9 52iJX9ELW/2QATfdIYruh+yXS3i+RzE= Received: by mail-pl1-f179.google.com with SMTP id d9443c01a7336-2240aad70f2so442195ad.0 for ; Sat, 19 Apr 2025 19:41:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1745116918; x=1745721718; darn=kvack.org; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:from:to:cc:subject:date:message-id:reply-to; bh=IyJl48UbRWmHPVEV8YJtbC6bLnrflYmUro9MxdcNyl4=; b=PYrIp0cBdCp1LvONJLqliHdiVdbrKLfVxzdwjv38V6S/u7ih8NiS/uEFONmeAUCMtk wJq5PyDl6oShH+8B/qKTiRHYXqRz2fl70NNTAanni6a7dNGiMt8G3L3OFWn72Nt2FT94 DzGqWoOYBvBUZZSshRsOiY12PLl7Hc89E1n3YHQHyHBcd6INWfo4L2HR2x3H2rzE/4mZ 0Ce46w5TsoQRdTnT2YONF8Fct0k4WswN791VGFt93CHpQwkYSvGLnq2Eeih/9YbSzpOK 3+j01FJRSavPSUkX+yo4q4PO4XfKBaAfu7fZEwfR1403xHJyxy63T5mD26k/fn2Cur6A nYyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1745116918; x=1745721718; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=IyJl48UbRWmHPVEV8YJtbC6bLnrflYmUro9MxdcNyl4=; b=jcAijQFRpqNPmmygVXRkA0W5U8iTzW2y9WbsUBu3v3Y5wlpEjclBPx4g2NKKfuz1wu CLAlTkIqPwKsEC/ggu1hht4qKtUff2votFx3hRTJHOVEutgytP/U7XYKevgZsHLBdVyw KO113Boy6O/32Y1NnDn8R8uLJrTO130j2GkAMXIjZHkAejA7YZhyT8HxqBSAVXWF1n7H HSFHDu7wyNCrtcVjWFVM5iX6xhgHFVnA80IdJM+tkkfYD8EctNp3XVXv/6nmI96IqWWW Dq29kxi6bnUPH9uUk+8GO0tDdFVZCnlXNythdicG7SkvTuxtfe6bXDAvV6hYM9+U0mL4 Xzkg== X-Forwarded-Encrypted: i=1; AJvYcCXYUvtmDLNLDQfpOTdCoSDN2g/LxyDRzTCMp55A7NuidToGbnug+hWNMorWQ786ZqSMuAl/Ykjjgg==@kvack.org X-Gm-Message-State: AOJu0YxW1RpvZ9y/59aheh6pEutWowSSy1tixxC4miD5p1AtLOYecHLd 5FdwyFLQWC+kyiG2v0cB87WODTnck3/UmJ5MqX71JEewI/+TyN2nI08rFDtmaA== X-Gm-Gg: ASbGncuTHGanEAgaqxt764uyIm+ltntgrY+6r1dFuzvVMGMR1ZR0jIlCsjZ3L670aKy Cq4nyypPvBRActdH+Y5hAsZb05Hd7WtEadXeupBIWutIkldqcZ10Dp7yDbyCrfZF+n7cFr7qElZ 6EKWO4DRvmVT4TnZYoFhdBdo/tGuXDnK+XNUkN/T2GpKZy2e3DhScXv5X74wOKvHY949Bkp3u09 lClV3H4YZZLK+9dPTg7S7LiFqyf7ig6O0HGYxtVcpN6njeMxzi9MZgfvPPUS3UgJU5C91HDRU7L MTyo0j63lk4Mn7ZC9kUMdtOHlbnUrzLXsTC6UgvCHotAOjZoOy4ZNyj3/OAbnubH7dHtOHjQaGk 86fGcZqBObm0EHDGMcQ0qoRPNvr7Lxw8YP4E= X-Google-Smtp-Source: AGHT+IFffG++ZNCXjIYAXIHvm5JPLT6e3OkmI3o5z5eOZuOEq8hl3KT5kPcbeOpJHSizJuMeoYpnOg== X-Received: by 2002:a17:903:19cb:b0:215:7ced:9d67 with SMTP id d9443c01a7336-22c52a93f91mr5405815ad.24.1745116918150; Sat, 19 Apr 2025 19:41:58 -0700 (PDT) Received: from [2a00:79e0:2eb0:8:3e8e:d566:514d:339b] ([2a00:79e0:2eb0:8:3e8e:d566:514d:339b]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22c50ed2971sm40466615ad.210.2025.04.19.19.41.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Apr 2025 19:41:57 -0700 (PDT) Date: Sat, 19 Apr 2025 19:41:56 -0700 (PDT) From: David Rientjes To: Harry Yoo cc: Vlastimil Babka , Matthew Wilcox , linux-mm@kvack.org, Christoph Lameter , Andrew Morton Subject: Re: [PATCH RFC] mm, slab: warn when increasing refcount on large kmalloc page In-Reply-To: Message-ID: <8da1a88e-0cbf-fa65-bca9-4843ceb0c8dd@google.com> References: <20250417074102.4543-2-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Queue-Id: A19F2180004 X-Rspamd-Server: rspam04 X-Stat-Signature: gs6z8twkw1tgb98m3nrfafhi86hh3d3j X-HE-Tag: 1745116919-375982 X-HE-Meta: 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 jFroCUuq WqfH9ikOm0azb6XRYtxSmktpR74B2eID6N7S7q/Ki3LNMvg+ySnt+oe+hh1pY8eXbvlF/N0yDzWgFsaZXXEtSXuUaefWf9q6GAW1Vm9N3FEYjlphZFOli28QXo6/TQdFMos7uB5v5dan0by2G5ZkOY85s4S0Bm9/wGR8UHM0h0bJgbjArPjArTr9YDmtBFJKOYYwC7mmAA6jd+10W2iw1Fn1CIL4d9+2gIfn6E3mRgQolhygzjykYMgBnaZ7MmTsdNJG/3U6KvpxmR50NXIefITxwzv0jAOzWZwlaiQBgg6sb9zDAPQu023Oy2KGmsIEbR3Pz5RUyfqSYaYoJmdwZ3fpFF2F1rkRxWP+FMi+LJon5oHI= 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: List-Subscribe: List-Unsubscribe: On Fri, 18 Apr 2025, Harry Yoo wrote: > > Since slab pages are now frozen, increasing refcount on a page > > containing a kmalloc() allocation is not possible anymore. Large kmalloc > > pages should ideally behave the same, because the decision for which > > allocation size to use them is the slab allocator's implementation > > detail, and sizes passed to kmalloc() might depend on e.g. user input. > > Agreed. > > > Because of some unexpected fallout in the slab pages case (see commit > > b9c0e49abfca ("mm: decline to manipulate the refcount on a slab page"), > > let's take a more cautious approach and before making large kmalloc > > pages actually frozen, start warning about code that would try to > > increase refcount on them. > > > > Signed-off-by: Vlastimil Babka > > --- > > I'd like to expose this via slab-next and see if there are any reports. > > If not for few weeks, maybe proceed immediately to freezing refcount and > > handling it in get_page/put_page exactly like folio_test_slab. Thoughts? > > +1 > > Let's give testing a try. > > ...at least it does not hit anything on my box. > Same, I ran this through a number of benchmarks on x86 and couldn't find any occurrences of the warning.