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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB8ADC433DF for ; Fri, 3 Jul 2020 11:38:10 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A18E520870 for ; Fri, 3 Jul 2020 11:38:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="SD5J6vFT" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A18E520870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 021656B00BE; Fri, 3 Jul 2020 07:38:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F13826B00C0; Fri, 3 Jul 2020 07:38:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E02A66B00C1; Fri, 3 Jul 2020 07:38:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0025.hostedemail.com [216.40.44.25]) by kanga.kvack.org (Postfix) with ESMTP id CBF1B6B00BE for ; Fri, 3 Jul 2020 07:38:09 -0400 (EDT) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 42E53180AD804 for ; Fri, 3 Jul 2020 11:38:09 +0000 (UTC) X-FDA: 76996565898.12.owner41_5d115e526e91 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin12.hostedemail.com (Postfix) with ESMTP id 077E41801BF7E for ; Fri, 3 Jul 2020 11:38:09 +0000 (UTC) X-HE-Tag: owner41_5d115e526e91 X-Filterd-Recvd-Size: 4695 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Jul 2020 11:38:08 +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=jxMY/sjYHPMgsXoKZcO2Tjpd8qcWk4ZLnlW1zPQiZos=; b=SD5J6vFT+1Tw0Wjw31plD9IXaw LrSALOLcDbthbfpf9zjSDSLF6Xuq76HDWRsI0492sDO15gYcMKQb4pFpEuaH17S++AxwGzxGqXX9/ BA5N1nuRbSLEFyYUX+zdvpIzPZajaNCTnVCfuuxb08WMRzNLXAwZ7weBv/lw1mpdUtiwKpGxsJyAY Zkz43tmgB1qbFYJFkhiY5CiBqJvpMeLe46rF3juS6d0yswVl2Wb5muNOlb/9nULj0yYbSTUfgxrUY ku6lmsJzMRqxGed1HT+Izr3xmPlxlCLLea3YyLqjFnQPhoHKK8nlUAi9JOjYgDQSAH8YsP1EkbHs2 vPBPqM/w==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jrK13-000083-2w; Fri, 03 Jul 2020 11:38:01 +0000 Date: Fri, 3 Jul 2020 12:38:01 +0100 From: Matthew Wilcox To: Andreas Gruenbacher Cc: Linus Torvalds , Dave Chinner , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC v2 2/2] gfs2: Rework read and page fault locking Message-ID: <20200703113801.GD25523@casper.infradead.org> References: <20200703095325.1491832-1-agruenba@redhat.com> <20200703095325.1491832-3-agruenba@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200703095325.1491832-3-agruenba@redhat.com> X-Rspamd-Queue-Id: 077E41801BF7E X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 Fri, Jul 03, 2020 at 11:53:25AM +0200, Andreas Gruenbacher wrote: > So far, gfs2 has taken the inode glocks inside the ->readpage and > ->readahead address space operations. Since commit d4388340ae0b ("fs: > convert mpage_readpages to mpage_readahead"), gfs2_readahead is passed > the pages to read ahead locked. With that, the current holder of the > inode glock may be trying to lock one of those pages while > gfs2_readahead is trying to take the inode glock, resulting in a > deadlock. > > Fix that by moving the lock taking to the higher-level ->read_iter file > and ->fault vm operations. This also gets rid of an ugly lock inversion > workaround in gfs2_readpage. > > Signed-off-by: Andreas Gruenbacher Reviewed-by: Matthew Wilcox (Oracle) > -/** > - * __gfs2_readpage - readpage > - * @file: The file to read a page for > - * @page: The page to read > - * > - * This is the core of gfs2's readpage. It's used by the internal file > - * reading code as in that case we already hold the glock. Also it's > - * called by gfs2_readpage() once the required lock has been granted. > - */ > - > static int __gfs2_readpage(void *file, struct page *page) You could go a little further and rename this function to plain gfs2_readpage(). gfs2_internal_read() should switch from read_cache_page() to read_mapping_page(). > { > struct gfs2_inode *ip = GFS2_I(page->mapping->host); > struct gfs2_sbd *sdp = GFS2_SB(page->mapping->host); > - > int error; > > if (i_blocksize(page->mapping->host) == PAGE_SIZE && > @@ -505,36 +494,11 @@ static int __gfs2_readpage(void *file, struct page *page) > * gfs2_readpage - read a page of a file > * @file: The file to read > * @page: The page of the file > - * > - * This deals with the locking required. We have to unlock and > - * relock the page in order to get the locking in the right > - * order. > */ I'd drop the kernel-doc comments on method implementations entirely, unless there's something useful to say ... which there isn't any more (yay!) > @@ -598,16 +562,9 @@ static void gfs2_readahead(struct readahead_control *rac) > { > struct inode *inode = rac->mapping->host; > struct gfs2_inode *ip = GFS2_I(inode); > - struct gfs2_holder gh; > > - gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh); > - if (gfs2_glock_nq(&gh)) > - goto out_uninit; > if (!gfs2_is_stuffed(ip)) > mpage_readahead(rac, gfs2_block_map); I think you probably want to make this: if (i_blocksize(page->mapping->host) == PAGE_SIZE && !page_has_buffers(page)) error = iomap_readahead(rac, &gfs2_iomap_ops); else if (!gfs2_is_stuffed(ip)) error = mpage_readahead(rac, gfs2_block_map); ... but I understand not wanting to make that change at this point in the release cycle. I'm happy for the patches to go in as-is, just wanted to point out these improvements that could be made.