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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 2DB3EC43603 for ; Mon, 16 Dec 2019 12:23:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DE063206CB for ; Mon, 16 Dec 2019 12:23:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EhNllUyF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727453AbfLPMXm (ORCPT ); Mon, 16 Dec 2019 07:23:42 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:28824 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727443AbfLPMXm (ORCPT ); Mon, 16 Dec 2019 07:23:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1576499019; 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=KnVSIs8eA9dtf/n/gCxuty+LQYH/YGkiloa/qM6Bm2g=; b=EhNllUyFlko/NJSR+YLAMwS7MuTMnTflGZ4Tr10v2OcGmlbBdSeSHaY6mQVjgssXGuy6+q kt+lvTUXWHe6+nxbhTOgx8wDqbYjXieF0aTaQV72Tq92qc2cg0csECgmkN1oKpzQWDU1eV j6k7bgtrOK4au5gAKXyoSdqhKq7Y5ao= 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-367-_rEgDHDcPSu949SQKB6TYQ-1; Mon, 16 Dec 2019 07:23:36 -0500 X-MC-Unique: _rEgDHDcPSu949SQKB6TYQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3386A107ACE6; Mon, 16 Dec 2019 12:23:35 +0000 (UTC) Received: from bfoster (dhcp-41-2.bos.redhat.com [10.18.41.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 87D5B60BF7; Mon, 16 Dec 2019 12:23:34 +0000 (UTC) Date: Mon, 16 Dec 2019 07:23:32 -0500 From: Brian Foster To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, Omar Sandoval , Dave Chinner Subject: Re: [PATCH] xfs: fix log reservation overflows when allocating large rt extents Message-ID: <20191216122332.GA10536@bfoster> References: <20191204163809.GP7335@magnolia> <20191213121840.GA43376@bfoster> <20191213201957.GI99875@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191213201957.GI99875@magnolia> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Fri, Dec 13, 2019 at 12:19:57PM -0800, Darrick J. Wong wrote: > On Fri, Dec 13, 2019 at 07:18:40AM -0500, Brian Foster wrote: > > On Wed, Dec 04, 2019 at 08:38:09AM -0800, Darrick J. Wong wrote: > > > From: Darrick J. Wong > > > > > > Omar Sandoval reported that a 4G fallocate on the realtime device causes > > > filesystem shutdowns due to a log reservation overflow that happens when > > > we log the rtbitmap updates. Factor rtbitmap/rtsummary updates into the > > > the tr_write and tr_itruncate log reservation calculation. > > > > > > "The following reproducer results in a transaction log overrun warning > > > for me: > > > > > > mkfs.xfs -f -r rtdev=/dev/vdc -d rtinherit=1 -m reflink=0 /dev/vdb > > > mount -o rtdev=/dev/vdc /dev/vdb /mnt > > > fallocate -l 4G /mnt/foo > > > > > > Reported-by: Omar Sandoval > > > Signed-off-by: Darrick J. Wong > > > --- > > > > Looks reasonable enough given my limited knowledge on the rt bits. One > > question.. > > > > > fs/xfs/libxfs/xfs_trans_resv.c | 96 ++++++++++++++++++++++++++++++++-------- > > > 1 file changed, 77 insertions(+), 19 deletions(-) > > > > > > diff --git a/fs/xfs/libxfs/xfs_trans_resv.c b/fs/xfs/libxfs/xfs_trans_resv.c > > > index c55cd9a3dec9..824073a839ac 100644 > > > --- a/fs/xfs/libxfs/xfs_trans_resv.c > > > +++ b/fs/xfs/libxfs/xfs_trans_resv.c > > > @@ -196,6 +196,24 @@ xfs_calc_inode_chunk_res( > > > return res; > > > } > > > > > > +/* > > > + * Per-extent log reservation for the btree changes involved in freeing or > > > + * allocating a realtime extent. We have to be able to log as many rtbitmap > > > + * blocks as needed to mark inuse MAXEXTLEN blocks' worth of realtime extents, > > > + * as well as the realtime summary block. > > > + */ > > > +unsigned int > > > +xfs_rtalloc_log_count( > > > + struct xfs_mount *mp, > > > + unsigned int num_ops) > > > +{ > > > + unsigned int blksz = XFS_FSB_TO_B(mp, 1); > > > + unsigned int rtbmp_bytes; > > > + > > > + rtbmp_bytes = (MAXEXTLEN / mp->m_sb.sb_rextsize) / NBBY; > > > + return (howmany(rtbmp_bytes, blksz) + 1) * num_ops; > > > +} > > > + > > > /* > > > * Various log reservation values. > > > * > > > @@ -218,13 +236,21 @@ xfs_calc_inode_chunk_res( > > > > > > /* > > > * In a write transaction we can allocate a maximum of 2 > > > - * extents. This gives: > > > + * extents. This gives (t1): > > > * the inode getting the new extents: inode size > > > * the inode's bmap btree: max depth * block size > > > * the agfs of the ags from which the extents are allocated: 2 * sector > > > * the superblock free block counter: sector size > > > * the allocation btrees: 2 exts * 2 trees * (2 * max depth - 1) * block size > > > - * And the bmap_finish transaction can free bmap blocks in a join: > > > + * Or, if we're writing to a realtime file (t2): > > > + * the inode getting the new extents: inode size > > > + * the inode's bmap btree: max depth * block size > > > + * the agfs of the ags from which the extents are allocated: 2 * sector > > > + * the superblock free block counter: sector size > > > + * the realtime bitmap: ((MAXEXTLEN / rtextsize) / NBBY) bytes > > > + * the realtime summary: 1 block > > > + * the allocation btrees: 2 trees * (2 * max depth - 1) * block size > > > > Why do we include the allocation btrees in the rt reservations? I > > thought that we'd either allocate (or free) out of one pool or the > > other. Do we operate on both sets of structures in the same transaction? > > I read "allocation btrees: 2 exts * 2 trees..." for t1 to mean that we > need to be able to allocate one datadev extent (which could cause a full > bnobt/cntbt split) for the actual file data, and then the second extent is > to handle allocating a new bmbt block to the bmap btree. > Ah, metadata out of the traditional trees.. that makes sense. My general understanding is that we have two sets of free space and thus two associated free space tracking structures: the traditional perag btrees for the local device and some bitmap indexing scheme for the external realtime device. Based on that, it looks like a file data allocation falls down into xfs_bmap_rtalloc() to allocate data blocks via the RT subsystem and the subsequent bmap update falls into the bmapbt code that uses xfs_alloc_vextent() directly to allocate blocks for the bmbt. With regard to the 2 extents, the first sentence in the comment above suggests to me that the two extents is a per-transaction operational limit. IOW, a write transaction supports two xfs_bmapi_write() calls, for example, as opposed to referring to the two lower level allocations outlined above. That seems consistent with the "2 * sector" AGF portion of the reservation as well, but I could easily be wrong about that. BTW I'm not following what you mean by a datadev extent causing a bnobt/cntbt split. Doesn't the data extent come from the RT free space, or are you just indirectly referring to the supporting bmbt block allocation causing a split..? > Based on that, I concluded that we still need to reserve space for that > "second" extent to handle allocating a new bmbt block (on the datadev). > > While pondering that, I wondered if even that's really true because what > happens if you suffer a full bmbt split, the free space is so fragmented > that each level of the bmbt split ends up allocating a new block from a > different part of the free space btrees and that in turn causes splits > in the free space btrees? > > I think the answer is "no we're fine" because even if each new bmbt > block comes from a different bnobt record, a full bmbt split will never > hollow out more than half of one bnobt block's worth of free space > records. > Yeah. I couldn't say for sure, but this strikes me as something we'd see reports of if it were possible/likely to occur in practice, particularly since this is the basis of how the allocation transaction reservations are calculated in general (not just for RT). Brian > --D > > > Brian > > > > > + * And the bmap_finish transaction can free bmap blocks in a join (t3): > > > * the agfs of the ags containing the blocks: 2 * sector size > > > * the agfls of the ags containing the blocks: 2 * sector size > > > * the super block free block counter: sector size > > > @@ -234,40 +260,72 @@ STATIC uint > > > xfs_calc_write_reservation( > > > struct xfs_mount *mp) > > > { > > > - return XFS_DQUOT_LOGRES(mp) + > > > - max((xfs_calc_inode_res(mp, 1) + > > > + unsigned int t1, t2, t3; > > > + unsigned int blksz = XFS_FSB_TO_B(mp, 1); > > > + > > > + t1 = xfs_calc_inode_res(mp, 1) + > > > + xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK), blksz) + > > > + xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) + > > > + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz); > > > + > > > + if (xfs_sb_version_hasrealtime(&mp->m_sb)) { > > > + t2 = xfs_calc_inode_res(mp, 1) + > > > xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK), > > > - XFS_FSB_TO_B(mp, 1)) + > > > + blksz) + > > > xfs_calc_buf_res(3, mp->m_sb.sb_sectsize) + > > > - xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), > > > - XFS_FSB_TO_B(mp, 1))), > > > - (xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) + > > > - xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), > > > - XFS_FSB_TO_B(mp, 1)))); > > > + xfs_calc_buf_res(xfs_rtalloc_log_count(mp, 1), blksz) + > > > + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 1), blksz); > > > + } else { > > > + t2 = 0; > > > + } > > > + > > > + t3 = xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) + > > > + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz); > > > + > > > + return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3); > > > } > > > > > > /* > > > - * In truncating a file we free up to two extents at once. We can modify: > > > + * In truncating a file we free up to two extents at once. We can modify (t1): > > > * the inode being truncated: inode size > > > * the inode's bmap btree: (max depth + 1) * block size > > > - * And the bmap_finish transaction can free the blocks and bmap blocks: > > > + * And the bmap_finish transaction can free the blocks and bmap blocks (t2): > > > * the agf for each of the ags: 4 * sector size > > > * the agfl for each of the ags: 4 * sector size > > > * the super block to reflect the freed blocks: sector size > > > * worst case split in allocation btrees per extent assuming 4 extents: > > > * 4 exts * 2 trees * (2 * max depth - 1) * block size > > > + * Or, if it's a realtime file (t3): > > > + * the agf for each of the ags: 2 * sector size > > > + * the agfl for each of the ags: 2 * sector size > > > + * the super block to reflect the freed blocks: sector size > > > + * the realtime bitmap: 2 exts * ((MAXEXTLEN / rtextsize) / NBBY) bytes > > > + * the realtime summary: 2 exts * 1 block > > > + * worst case split in allocation btrees per extent assuming 2 extents: > > > + * 2 exts * 2 trees * (2 * max depth - 1) * block size > > > */ > > > STATIC uint > > > xfs_calc_itruncate_reservation( > > > struct xfs_mount *mp) > > > { > > > - return XFS_DQUOT_LOGRES(mp) + > > > - max((xfs_calc_inode_res(mp, 1) + > > > - xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1, > > > - XFS_FSB_TO_B(mp, 1))), > > > - (xfs_calc_buf_res(9, mp->m_sb.sb_sectsize) + > > > - xfs_calc_buf_res(xfs_allocfree_log_count(mp, 4), > > > - XFS_FSB_TO_B(mp, 1)))); > > > + unsigned int t1, t2, t3; > > > + unsigned int blksz = XFS_FSB_TO_B(mp, 1); > > > + > > > + t1 = xfs_calc_inode_res(mp, 1) + > > > + xfs_calc_buf_res(XFS_BM_MAXLEVELS(mp, XFS_DATA_FORK) + 1, blksz); > > > + > > > + t2 = xfs_calc_buf_res(9, mp->m_sb.sb_sectsize) + > > > + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 4), blksz); > > > + > > > + if (xfs_sb_version_hasrealtime(&mp->m_sb)) { > > > + t3 = xfs_calc_buf_res(5, mp->m_sb.sb_sectsize) + > > > + xfs_calc_buf_res(xfs_rtalloc_log_count(mp, 2), blksz) + > > > + xfs_calc_buf_res(xfs_allocfree_log_count(mp, 2), blksz); > > > + } else { > > > + t3 = 0; > > > + } > > > + > > > + return XFS_DQUOT_LOGRES(mp) + max3(t1, t2, t3); > > > } > > > > > > /* > > > > > >