Re: [PATCH] Btrfs: hold enough space for global_rsv

[Johannes Hirte <johannes.hirte@fem.tu-ilmenau.de>]

Am Tue, 17 Jan 2012 17:51:59 +0800
schrieb Liu Bo <liubo2009@cn.fujitsu.com>:

> I've kept hitting enospc warnings of global_rsv while running
> defragment on files:
> btrfs: block rsv returned -28
> WARNING: at fs/btrfs/extent-tree.c:5984
> btrfs_alloc_free_block+0x333/0x340 [btrfs]() ...
> 
> I used a fio jobs to create a file with lots of fragments:
> $ filefrag /mnt/btrfs/foobar
> /mnt/btrfs/foobar: 66964 extents found
> 
> and then "btrfs fi defrag /mnt/btrfs/foobar && sync" would pop the
> warnings.
> 
> I found that the global_rsv size is just not enough for defragment,
> and didn't find any space leak in using global_rsv, so double it and
> go ahead.
> 
> Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
> ---
>  fs/btrfs/extent-tree.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 8603ee4..77ea23c 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -3979,7 +3979,7 @@ static u64 calc_global_metadata_size(struct
> btrfs_fs_info *fs_info) num_bytes += div64_u64(data_used + meta_used,
> 50); 
>  	if (num_bytes * 3 > meta_used)
> -		num_bytes = div64_u64(meta_used, 3);
> +		num_bytes = div64_u64(meta_used, 3) * 2;
>  
>  	return ALIGN(num_bytes, fs_info->extent_root->leafsize <<
> 10); }

This patch breakes my system. With this applied all services fail on
boot with "no space left" messages.