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 20906C433FE for ; Fri, 18 Nov 2022 08:01:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6A3AA6B0071; Fri, 18 Nov 2022 03:01:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6535C6B0072; Fri, 18 Nov 2022 03:01:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 542746B0073; Fri, 18 Nov 2022 03:01:53 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 4502E6B0071 for ; Fri, 18 Nov 2022 03:01:53 -0500 (EST) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 0A085121254 for ; Fri, 18 Nov 2022 08:01:53 +0000 (UTC) X-FDA: 80145819306.01.812BD45 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf10.hostedemail.com (Postfix) with ESMTP id 76BD7C000F for ; Fri, 18 Nov 2022 08:01:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=KQNE2xd9tPn0Zb+jKbifQFfOM1ctrKpJPYI8m278BgE=; b=STi4dfBwrwhIaA6LQJCigXd/CS QJd+ZKlBmAivBILmPYix3Bojwl11I7oysAfqyycSgTjfUBzj5uvir5xD0lpGJuJk/eU7UJK0y0j8g /bs9y8EFW8cHZLWbR8lBRBgaPwv3MrU65OYE+NzKodQt31mzucr8gtXATlRFynUBWAUeyUmaUtVLB fw6SW67c2V3NERVa/mtEFfx5w5cV1fhorDMo6IZYHr6scYXnaeeP2pByG03vbTn3EMcPjeIIeLovj jleiqGne2VVPnKAhBAsbSPqCbVPPg261JoPjMP5FWwYN7YQ+vrje9JG3sFvDLs0cnyP0Xbbxu3xG1 BN6hz7qw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1ovwJq-0024WM-Tv; Fri, 18 Nov 2022 08:01:50 +0000 Date: Fri, 18 Nov 2022 08:01:50 +0000 From: Matthew Wilcox To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, stephen.s.brennan@oracle.com, urezki@gmail.com, hch@infradead.org Subject: Re: [PATCH RFC 3/3] mm/vmalloc.c: allow vread() to read out vm_map_ram areas Message-ID: References: <20221109033535.269229-1-bhe@redhat.com> <20221109033535.269229-4-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221109033535.269229-4-bhe@redhat.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668758512; a=rsa-sha256; cv=none; b=YZ9jkurfRyHtHKQObqsLKLTfUp0gT1MME5SGwyjD5oOiW2mw3aN1Yo/7PoJUjtLPCmffrb 2PW84sA3TVXZ+sZTNHP6j7bT2XwrROcCHZBsv/dE9MsBSEjgR6rbgGQ408N9Md4kSioMse 3i0dyUffKe7WhCkPanXxpKyNnyDqRyk= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=STi4dfBw; dmarc=none; spf=none (imf10.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668758512; 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=KQNE2xd9tPn0Zb+jKbifQFfOM1ctrKpJPYI8m278BgE=; b=Ro2rQCBlMvOuY174lNzo02ZxwKPIevkpXU+7qmG530tS4mYQCXgfjLrGAaEQ1lTfShXXMB Aj4AlM0IVsMGYxkyFmzlgI8r6yfwsxdU8g8vNgr+lnQMZthLi3DbFwhRudPeiTeroV7wkZ vudrQokm17dqXmCFW+f1A4XppEHmIRw= X-Stat-Signature: i8w68t53neeqrxydcexbi86imxzisn1b X-Rspamd-Queue-Id: 76BD7C000F X-Rspam-User: Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=STi4dfBw; dmarc=none; spf=none (imf10.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org X-Rspamd-Server: rspam09 X-HE-Tag: 1668758512-748908 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, Nov 09, 2022 at 11:35:34AM +0800, Baoquan He wrote: > Currently, vread() can read out vmalloc areas which is associated with > a vm_struct. While this doesn't work for areas created by vm_map_ram() > interface because it doesn't allocate a vm_struct. Then in vread(), > these areas will be skipped. > > Here, add a new function vb_vread() to read out areas managed by > vmap_block specifically. Then recognize vm_map_ram areas via vmap->flags > and handle them respectively. i don't understand how this deals with the original problem identified, that the vread() can race with an unmap.