On Thu, Nov 01, 2012 at 06:34:54AM -0600, Josef Bacik wrote:
> A user reported a problem where all of his block groups had invalid used
> counts in the block group item. This patch walks the extent tree and counts
> up the used amount for each block group. If the user specifies repair we
> can set the correct used value and when the transaction commits we're all
> set. This was reported and tested by a user and worked. Thanks,
Josef and I hashed this out a little bit on irc. My fsck repair code
already tries to fix the block group accounting, but I think there is a
key part his code does differently (correctly ;):
> +static int check_block_groups_used(struct btrfs_trans_handle *trans,
> + struct btrfs_root *root, int repair)
> +{
> + struct btrfs_block_group_cache *block_group;
> + struct btrfs_path *path;
> + u64 bytenr = 0;
> + int ret;
> + int err = 0;
> +
> + path = btrfs_alloc_path();
> + if (!path)
> + return -ENOMEM;
> +
> + path->reada = 2;
> + while ((block_group = btrfs_lookup_first_block_group(root->fs_info,
> + bytenr))) {
> + ret = check_block_group_used(trans, root, block_group, path,
> + repair);
> + if (ret && !err)
> + ret = err;
> + bytenr = block_group->key.objectid + block_group->key.offset;
> + }
> + btrfs_free_path(path);
> +
> + return err;
> +}
My code reuses btrfs_fix_block_group_acounting, which does this:
start = 0;
while(1) {
cache = btrfs_lookup_block_group(fs_info, start);
if (!cache)
break;
start = cache->key.objectid + cache->key.offset;
btrfs_set_block_group_used(&cache->item, 0);
cache->space_info->bytes_used = 0;
set_extent_bits(&root->fs_info->block_group_cache,
cache->key.objectid,
cache->key.objectid + cache->key.offset -1,
BLOCK_GROUP_DIRTY, GFP_NOFS);
}
Using btrfs_lookup_first_block_group here should fix things. It must be
breaking out too soon and so the accounting isn't updated properly.
-chris
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