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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 780B7C169C4 for ; Wed, 6 Feb 2019 18:21:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 50E7220823 for ; Wed, 6 Feb 2019 18:21:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728120AbfBFSVD (ORCPT ); Wed, 6 Feb 2019 13:21:03 -0500 Received: from mx2.suse.de ([195.135.220.15]:52490 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727129AbfBFSVD (ORCPT ); Wed, 6 Feb 2019 13:21:03 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 47312B6F4; Wed, 6 Feb 2019 18:21:01 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 4C674DA823; Wed, 6 Feb 2019 19:20:21 +0100 (CET) Date: Wed, 6 Feb 2019 19:20:20 +0100 From: David Sterba To: Nikolay Borisov Cc: Josef Bacik , linux-btrfs@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 6/8] btrfs: loop in inode_rsv_refill Message-ID: <20190206182020.GF2900@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Nikolay Borisov , Josef Bacik , linux-btrfs@vger.kernel.org, kernel-team@fb.com References: <20181203152459.21630-1-josef@toxicpanda.com> <20181203152459.21630-7-josef@toxicpanda.com> <6a7a6a50-9a58-032e-e62a-c551b257b0ac@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6a7a6a50-9a58-032e-e62a-c551b257b0ac@suse.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, Dec 12, 2018 at 06:01:57PM +0200, Nikolay Borisov wrote: > > > On 3.12.18 г. 17:24 ч., Josef Bacik wrote: > > With severe fragmentation we can end up with our inode rsv size being > > huge during writeout, which would cause us to need to make very large > > metadata reservations. However we may not actually need that much once > > The sentence beginning with "However" needs more information, why might > we not need that much once writeout is complete? Updated in changelog > > writeout is complete. So instead try to make our reservation, and if we > > couldn't make it re-calculate our new reservation size and try again. > > Why do you think that recalculating the requested bytes will be > different the 2nd time ? Partly answered in the comment in the code > > > If our reservation size doesn't change between tries then we know we are > > actually out of space and can error out. > > > > Signed-off-by: Josef Bacik > > --- > > fs/btrfs/extent-tree.c | 58 +++++++++++++++++++++++++++++++++++++------------- > > 1 file changed, 43 insertions(+), 15 deletions(-) > > > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > > index 0ee77a98f867..0e1a499035ac 100644 > > --- a/fs/btrfs/extent-tree.c > > +++ b/fs/btrfs/extent-tree.c > > @@ -5787,6 +5787,21 @@ int btrfs_block_rsv_refill(struct btrfs_root *root, > > return ret; > > } > > > > +static inline void __get_refill_bytes(struct btrfs_block_rsv *block_rsv, > > + u64 *metadata_bytes, u64 *qgroup_bytes) > > This function needs a better name. Something like calc_required_bytes or > calc_refill_bytes renamed to calc_refill_bytes > > > +{ > > + *metadata_bytes = 0; > > + *qgroup_bytes = 0; > > + > > + spin_lock(&block_rsv->lock); > > + if (block_rsv->reserved < block_rsv->size) > > + *metadata_bytes = block_rsv->size - block_rsv->reserved; > > + if (block_rsv->qgroup_rsv_reserved < block_rsv->qgroup_rsv_size) > > + *qgroup_bytes = block_rsv->qgroup_rsv_size - > > + block_rsv->qgroup_rsv_reserved; > > + spin_unlock(&block_rsv->lock); > > +} > > + > > /** > > * btrfs_inode_rsv_refill - refill the inode block rsv. > > * @inode - the inode we are refilling. > > @@ -5802,25 +5817,39 @@ static int btrfs_inode_rsv_refill(struct btrfs_inode *inode, > > { > > struct btrfs_root *root = inode->root; > > struct btrfs_block_rsv *block_rsv = &inode->block_rsv; > > - u64 num_bytes = 0; > > + u64 num_bytes = 0, last = 0; > > u64 qgroup_num_bytes = 0; > > int ret = -ENOSPC; > > > > - spin_lock(&block_rsv->lock); > > - if (block_rsv->reserved < block_rsv->size) > > - num_bytes = block_rsv->size - block_rsv->reserved; > > - if (block_rsv->qgroup_rsv_reserved < block_rsv->qgroup_rsv_size) > > - qgroup_num_bytes = block_rsv->qgroup_rsv_size - > > - block_rsv->qgroup_rsv_reserved; > > - spin_unlock(&block_rsv->lock); > > - > > + __get_refill_bytes(block_rsv, &num_bytes, &qgroup_num_bytes); > > if (num_bytes == 0) > > return 0; > > > > - ret = btrfs_qgroup_reserve_meta_prealloc(root, qgroup_num_bytes, true); > > - if (ret) > > - return ret; > > - ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush); > > + do { > > + ret = btrfs_qgroup_reserve_meta_prealloc(root, qgroup_num_bytes, true); > > + if (ret) > > + return ret; > > + ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush); > > + if (ret) { > > + btrfs_qgroup_free_meta_prealloc(root, qgroup_num_bytes); > > + last = num_bytes; > > + /* > > + * If we are fragmented we can end up with a lot of > > + * outstanding extents which will make our size be much > > + * larger than our reserved amount. If we happen to > > + * try to do a reservation here that may result in us > > + * trying to do a pretty hefty reservation, which we may > > + * not need once delalloc flushing happens. If this is > > The "If we happen" sentence needs to be reworded because it's -ENOPARSE. > Perhaps one of the "to do a reservation" should go away? Reworded