On Tue, 2 Apr 2013 09:46:26 -0400 Josef Bacik <jba...@fusionio.com> wrote:
> On Tue, Apr 02, 2013 at 02:04:52AM -0600, Roman Mamedov wrote:
> > Hello,
> >
> > With kernel 3.7.10 patched with "Btrfs: limit the global reserve to 512mb".
> > (the problem was occuring also without this patch, but seemed to be even
> > worse).
> >
> > At the start of balance:
> >
> > Data: total=31.85GB, used=9.96GB
> > System: total=4.00MB, used=16.00KB
> > Metadata: total=1.01GB, used=696.17MB
> >
> > "btrfs balance start -musage=5 -dusage=5" is going on for about 50 minutes
> >
> > Current situation:
> >
> > Balance on '/mnt/r1/' is running
> > 1 out of about 2 chunks balanced (20 considered), 50% left
> >
> > Data: total=30.85GB, used=10.04GB
> > System: total=4.00MB, used=16.00KB
> > Metadata: total=1.01GB, used=851.69MB
> >
> > And a constant stream of these in dmesg:
> >
>
> Can you try this out and see if it helps? Thanks,
Hello,
Well that balance has now completed, and unfortunately I don't have a complete
image of the filesystem from before, to apply the patch and check if the same
operation goes better this time.
I'll keep it in mind and will try to test it out if I will get a similar
situation again on some filesystem.
Generally what seems to make me run into various problems with balance, is the
following usage scenario: On an active filesystem (used as /home and root FS),
a snapshot is made every 30 minutes with an unique (timestamped) name; and once
a day snapshots from more than two days ago are purged. And it goes like this
for months.
Another variant of this, a backup partition, where snapshots are made every six
hours, and all snapshots are kept for 1-3 months before getting purged.
I guess this kind of usage causes a lot of internal fragmentation or
something, which makes it difficult for a balance to find enough free space to
work with.
>
> Josef
>
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 0d89ff0..9830e86 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -2548,6 +2548,13 @@ static int do_relocation(struct btrfs_trans_handle
> *trans,
> list_for_each_entry(edge, &node->upper, list[LOWER]) {
> cond_resched();
>
> + ret = btrfs_block_rsv_refill(rc->extent_root, rc->block_rsv,
> + rc->extent_root->leafsize,
> + BTRFS_RESERVE_FLUSH_ALL);
> + if (ret) {
> + err = ret;
> + break;
> + }
> upper = edge->node[UPPER];
> root = select_reloc_root(trans, rc, upper, edges, &nr);
> BUG_ON(!root);
> --
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--
With respect,
Roman
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