On Fri, Aug 02, 2019 at 12:09:53PM -0400, Josef Bacik wrote:
> Sometimes when messing with the chunk allocator code we can end up
> over-allocating chunks. Generally speaking I'll notice this when a
> random xfstest fails with ENOSPC when it shouldn't, but I'm super
> worried that I won't catch a problem until somebody has a fs completely
> filled up with empty block groups. Add a fsck option to check for too
> many empty block groups. This way I can set FSCK_OPTIONS="-B" to catch
> cases where we're too aggressive with the chunk allocator but not so
> aggressive that it causes problems in xfstests.
>
> Thankfully this doesn't trip up currently, so this will just keep me
> from regressing us. Thanks,
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> ---
> v1->v2:
> - tested with my alloc chunk ioctl, realized the chunk checker removes the bg
> recs from the list, so this wasn't actually doing anything. Moved the check
> so now it properly fails on a bad fs.
I sent some comments to v1 that seem to apply to v2 as well.
> static int is_free_space_tree = 0;
> int init_extent_tree = 0;
> int check_data_csum = 0;
> +int check_bg_usage = 0;
> struct btrfs_fs_info *global_info;
> struct task_ctx ctx = { 0 };
> struct cache_tree *roots_info_cache = NULL;
> @@ -5126,6 +5127,7 @@ btrfs_new_block_group_record(struct extent_buffer *leaf, struct btrfs_key *key,
>
> ptr = btrfs_item_ptr(leaf, slot, struct btrfs_block_group_item);
> rec->flags = btrfs_disk_block_group_flags(leaf, ptr);
> + rec->used = btrfs_disk_block_group_used(leaf, ptr);
>
> INIT_LIST_HEAD(&rec->list);
>
> @@ -8522,6 +8524,41 @@ out:
> return ret;
> }
>
> +static int check_block_group_usage(struct block_group_tree *block_group_cache)
> +{
> + struct block_group_record *bg_rec;
> + int empty_data = 0, empty_metadata = 0, empty_system = 0;
> + int ret = 0;
> +
> + list_for_each_entry(bg_rec, &block_group_cache->block_groups, list) {
> + if (bg_rec->used)
> + continue;
> + if (bg_rec->flags & BTRFS_BLOCK_GROUP_DATA)
> + empty_data++;
> + else if (bg_rec->flags & BTRFS_BLOCK_GROUP_METADATA)
> + empty_metadata++;
> + else
> + empty_system++;
> + }
> +
> + if (empty_data > 1) {
> + ret = -EINVAL;
> + fprintf(stderr, "Too many empty data block groups: %d\n",
> + empty_data);
> + }
> + if (empty_metadata > 1) {
> + ret = -EINVAL;
> + fprintf(stderr, "Too many empty metadata block groups: %d\n",
> + empty_metadata);
> + }
> + if (empty_system > 1) {
> + ret = -EINVAL;
> + fprintf(stderr, "Too many empty system block groups: %d\n",
> + empty_system);
Can you please add images that trigger each of the above problems?
> + }
> + return ret;
> +}
> +
> static int check_chunks_and_extents(struct btrfs_fs_info *fs_info)
> {
> struct rb_root dev_cache;
> @@ -8622,6 +8659,13 @@ again:
> goto out;
> }
>
> + if (check_bg_usage) {
> + ret = check_block_group_usage(&block_group_cache);
> + if (ret)
> + err = ret;
> + goto out;
> + }
> +
> ret = check_chunks(&chunk_cache, &block_group_cache,
> &dev_extent_cache, NULL, NULL, NULL, 0);
> if (ret) {
> @@ -9810,6 +9854,7 @@ static const char * const cmd_check_usage[] = {
> " -E|--subvol-extents <subvolid>",
> " print subvolume extents and sharing state",
> " -p|--progress indicate progress",
> + " -B|--check-bg-usage check for too many empty block groups",
> NULL
> };
>
> @@ -9841,7 +9886,7 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
> GETOPT_VAL_INIT_EXTENT, GETOPT_VAL_CHECK_CSUM,
> GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE,
> GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE,
> - GETOPT_VAL_FORCE };
> + GETOPT_VAL_FORCE};
> static const struct option long_options[] = {
> { "super", required_argument, NULL, 's' },
> { "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
> @@ -9864,10 +9909,11 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
> { "clear-space-cache", required_argument, NULL,
> GETOPT_VAL_CLEAR_SPACE_CACHE},
> { "force", no_argument, NULL, GETOPT_VAL_FORCE },
> + { "check-bg-usage", no_argument, NULL, 'B' },
The option name does not match the description, it could be something
like --check-empty-bg-count and certainly should not use the short
option. That are reserved for most common usecases, I don't think
this is the case.
