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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 3B0F8C433DB for ; Thu, 28 Jan 2021 18:27:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E113A64E21 for ; Thu, 28 Jan 2021 18:27:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231138AbhA1S1L (ORCPT ); Thu, 28 Jan 2021 13:27:11 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:59299 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231470AbhA1SYr (ORCPT ); Thu, 28 Jan 2021 13:24:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611858201; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=iyMuffMtjf/EVXNn+ecq9C6TGwEH9qLW+UvyysSBchc=; b=GzfPrjai+6tCWV2Lqie2cDzuHlP061aAMlwSfyrPpxtjz48QeDOKtspqdyCw9Gf1jOtGM2 I//dfeuMxDDNwzOUpogMm8xRLuOdg54HZ7w95qtYwnQcEKr1XhIgCXzem807t9YKxxMixB f4pB+S4mIXci7Yql6EjHoAfU05JAn+w= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-323-NWMN6pM5MDW5TUfulNZfBw-1; Thu, 28 Jan 2021 13:23:19 -0500 X-MC-Unique: NWMN6pM5MDW5TUfulNZfBw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 12FE4107ACE8; Thu, 28 Jan 2021 18:23:18 +0000 (UTC) Received: from bfoster (ovpn-114-23.rdu2.redhat.com [10.10.114.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7346B5D9F1; Thu, 28 Jan 2021 18:23:17 +0000 (UTC) Date: Thu, 28 Jan 2021 13:23:15 -0500 From: Brian Foster To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, hch@infradead.org, david@fromorbit.com Subject: Re: [PATCH 10/13] xfs: try worst case space reservation upfront in xfs_reflink_remap_extent Message-ID: <20210128182315.GI2619139@bfoster> References: <161181366379.1523592.9213241916555622577.stgit@magnolia> <161181372121.1523592.2524488839590698117.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <161181372121.1523592.2524488839590698117.stgit@magnolia> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, Jan 27, 2021 at 10:02:01PM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong > > Now that we've converted xfs_reflink_remap_extent to use the new > xfs_trans_alloc_inode API, we can focus on its slightly unusual behavior > with regard to quota reservations. > > Since it's valid to remap written blocks into a hole, we must be able to > increase the quota count by the number of blocks in the mapping. > However, the incore space reservation process requires us to supply an > asymptotic guess before we can gain exclusive access to resources. We'd > like to reserve all the quota we need up front, but we also don't want > to fail a written -> allocated remap operation unnecessarily. > > The solution is to make the remap_extents function call the transaction > allocation function twice. The first time we ask to reserve enough > space and quota to handle the absolute worst case situation, but if that > fails, we can fall back to the old strategy: ask for the bare minimum > space reservation upfront and increase the quota reservation later if we > need to. > > This isn't a problem now, but in the next patchset we change the > transaction and quota code to try to reclaim space if we cannot reserve > free space or quota. Restructuring the remap_extent function in this > manner means that if the fallback increase fails, we can pass that back > to the caller knowing that the transaction allocation already tried > freeing space. > This looks pretty good to me, but I'd probably move this patch closer to the patch that depends on it.. Brian > Signed-off-by: Darrick J. Wong > --- > fs/xfs/xfs_reflink.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) > > > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > index ded86cc4764c..c6296fd1512f 100644 > --- a/fs/xfs/xfs_reflink.c > +++ b/fs/xfs/xfs_reflink.c > @@ -992,6 +992,7 @@ xfs_reflink_remap_extent( > xfs_off_t newlen; > int64_t qdelta = 0; > unsigned int resblks; > + bool quota_reserved = true; > bool smap_real; > bool dmap_written = xfs_bmap_is_written_extent(dmap); > int iext_delta = 0; > @@ -1007,10 +1008,26 @@ xfs_reflink_remap_extent( > * the same index in the bmap btree, so we only need a reservation for > * one bmbt split if either thing is happening. However, we haven't > * locked the inode yet, so we reserve assuming this is the case. > + * > + * The first allocation call tries to reserve enough space to handle > + * mapping dmap into a sparse part of the file plus the bmbt split. We > + * haven't locked the inode or read the existing mapping yet, so we do > + * not know for sure that we need the space. This should succeed most > + * of the time. > + * > + * If the first attempt fails, try again but reserving only enough > + * space to handle a bmbt split. This is the hard minimum requirement, > + * and we revisit quota reservations later when we know more about what > + * we're remapping. > */ > resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK); > - error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, resblks, 0, > - false, &tp); > + error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, > + resblks + dmap->br_blockcount, 0, false, &tp); > + if (error == -EDQUOT || error == -ENOSPC) { > + quota_reserved = false; > + error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, > + resblks, 0, false, &tp); > + } > if (error) > goto out; > > @@ -1077,7 +1094,7 @@ xfs_reflink_remap_extent( > * before we started. That should have removed all the delalloc > * reservations, but we code defensively. > */ > - if (!smap_real && dmap_written) { > + if (!quota_reserved && !smap_real && dmap_written) { > error = xfs_trans_reserve_quota_nblks(tp, ip, > dmap->br_blockcount, 0, false); > if (error) >