From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f45.google.com ([74.125.83.45]:35141 "EHLO mail-pg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751012AbdGNVgr (ORCPT ); Fri, 14 Jul 2017 17:36:47 -0400 Received: by mail-pg0-f45.google.com with SMTP id j186so51099777pge.2 for ; Fri, 14 Jul 2017 14:36:47 -0700 (PDT) Date: Fri, 14 Jul 2017 14:36:45 -0700 From: Omar Sandoval To: linux-btrfs@vger.kernel.org, Jeff Mahoney , Nikolay Borisov Cc: kernel-team@fb.com Subject: Re: [PATCH] Btrfs: fix early ENOSPC due to delalloc Message-ID: <20170714213645.GC13690@vader.DHCP.thefacebook.com> References: <0cf8577381f6ebe99b584ca60f920c630000c343.1499407060.git.osandov@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <0cf8577381f6ebe99b584ca60f920c630000c343.1499407060.git.osandov@fb.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Thu, Jul 06, 2017 at 10:59:27PM -0700, Omar Sandoval wrote: > From: Omar Sandoval > > If a lot of metadata is reserved for outstanding delayed allocations, we > rely on shrink_delalloc() to reclaim metadata space in order to fulfill > reservation tickets. However, shrink_delalloc() has a shortcut where if > it determines that space can be overcommitted, it will stop early. This > made sense before the ticketed enospc system, but now it means that > shrink_delalloc() will often not reclaim enough space to fulfill any > tickets, leading to an early ENOSPC. (Reservation tickets don't care > about being able to overcommit, they need every byte accounted for.) > > Fix it by getting rid of the shortcut so that shrink_delalloc() reclaims > all of the metadata it is supposed to. This fixes early ENOSPCs we were > seeing when doing a btrfs receive to populate a new filesystem. Jeff, Nikolay, did either of you get a chance to test this yet? > Signed-off-by: Omar Sandoval > --- > I don't have a good reproducer for this except for the btrfs send stream > I was given by someone internally, unfortunately. > > fs/btrfs/extent-tree.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index 33d979e9ea2a..83eecd33ad96 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -4776,10 +4776,6 @@ static void shrink_delalloc(struct btrfs_root *root, u64 to_reclaim, u64 orig, > else > flush = BTRFS_RESERVE_NO_FLUSH; > spin_lock(&space_info->lock); > - if (can_overcommit(root, space_info, orig, flush)) { > - spin_unlock(&space_info->lock); > - break; > - } > if (list_empty(&space_info->tickets) && > list_empty(&space_info->priority_tickets)) { > spin_unlock(&space_info->lock); > -- > 2.13.2 >