From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:27347 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753014AbbLFS7m (ORCPT ); Sun, 6 Dec 2015 13:59:42 -0500 Date: Sun, 6 Dec 2015 10:59:39 -0800 From: Liu Bo To: Alex Lyakas Cc: linux-btrfs Subject: Re: [RFC PATCH] btrfs: flush_space: treat return value of do_chunk_alloc properly Message-ID: <20151206185939.GC3005@localhost.localdomain> Reply-To: bo.li.liu@oracle.com References: <20151203181428.GA19589@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Sun, Dec 06, 2015 at 12:32:31PM +0200, Alex Lyakas wrote: > do_chunk_alloc returns 1 when it succeeds to allocate a new chunk. > But flush_space will not convert this to 0, and will also return 1. > As a result, reserve_metadata_bytes will think that flush_space failed, > and may potentially return this value "1" to the caller (depends how > reserve_metadata_bytes was called). The caller will also treat this as an error. > For example, btrfs_block_rsv_refill does: > > int ret = -ENOSPC; > ... > ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush); > if (!ret) { > block_rsv_add_bytes(block_rsv, num_bytes, 0); > return 0; > } > > return ret; > > So it will return -ENOSPC. Reviewed-by: Liu Bo Thanks, -liubo > > Signed-off-by: Alex Lyakas > Reviewed-by: Josef Bacik > > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > index 4b89680..1ba3f0d 100644 > --- a/fs/btrfs/extent-tree.c > +++ b/fs/btrfs/extent-tree.c > @@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root, > btrfs_get_alloc_profile(root, 0), > CHUNK_ALLOC_NO_FORCE); > btrfs_end_transaction(trans, root); > - if (ret == -ENOSPC) > + if (ret > 0 || ret == -ENOSPC) > ret = 0; > break; > case COMMIT_TRANS: > > On Sun, Dec 6, 2015 at 12:19 PM, Alex Lyakas wrote: > > Hi Liu, > > I was studying on how block reservation works, and making some > > modifications in reserve_metadata_bytes to understand better what it > > does. Then suddenly I saw this problem. I guess it depends on which > > value of "flush" parameter is passed to reserve_metadata_bytes. > > > > Alex. > > > > > > On Thu, Dec 3, 2015 at 8:14 PM, Liu Bo wrote: > >> On Thu, Dec 03, 2015 at 06:51:03PM +0200, Alex Lyakas wrote: > >>> do_chunk_alloc returns 1 when it succeeds to allocate a new chunk. > >>> But flush_space will not convert this to 0, and will also return 1. > >>> As a result, reserve_metadata_bytes will think that flush_space failed, > >>> and may potentially return this value "1" to the caller (depends how > >>> reserve_metadata_bytes was called). The caller will also treat this as an error. > >>> For example, btrfs_block_rsv_refill does: > >>> > >>> int ret = -ENOSPC; > >>> ... > >>> ret = reserve_metadata_bytes(root, block_rsv, num_bytes, flush); > >>> if (!ret) { > >>> block_rsv_add_bytes(block_rsv, num_bytes, 0); > >>> return 0; > >>> } > >>> > >>> return ret; > >>> > >>> So it will return -ENOSPC. > >> > >> It will return 1 instead of -ENOSPC. > >> > >> The patch looks good, I noticed this before, but I didn't manage to trigger a error for this, did you catch a error like that? > >> > >> Thanks, > >> > >> -liubo > >> > >>> > >>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c > >>> index 4b89680..1ba3f0d 100644 > >>> --- a/fs/btrfs/extent-tree.c > >>> +++ b/fs/btrfs/extent-tree.c > >>> @@ -4727,7 +4727,7 @@ static int flush_space(struct btrfs_root *root, > >>> btrfs_get_alloc_profile(root, 0), > >>> CHUNK_ALLOC_NO_FORCE); > >>> btrfs_end_transaction(trans, root); > >>> - if (ret == -ENOSPC) > >>> + if (ret > 0 || ret == -ENOSPC) > >>> ret = 0; > >>> break; > >>> case COMMIT_TRANS: > >>> -- > >>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > >>> the body of a message to majordomo@vger.kernel.org > >>> More majordomo info at http://vger.kernel.org/majordomo-info.html