Re: [PATCH v3 2/3] btrfs: block-group: Refactor btrfs_read_block_groups()

Qu WenRuo
2019-10-30T05:17:44Z

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On 2019/10/10 上午10:39, Qu Wenruo wrote:
> Refactor the work inside the loop of btrfs_read_block_groups() into one
> separate function, read_one_block_group().
>
> This allows read_one_block_group to be reused for later BG_TREE feature.
>
> The refactor does the following extra fix:
> - Use btrfs_fs_incompat() to replace open-coded feature check
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
> Reviewed-by: Anand Jain <anand.jain@oracle.com>

Hi David,

Mind to add this patch to for-next branch?

Considering the recent changes to struct btrfs_block_group_cache, there
is some considerable conflicts.

It would be much easier to solve them sooner than later.
If needed I could send a newer version based on latest for-next branch.

Thanks,
Qu

> ---
> fs/btrfs/block-group.c | 215 +++++++++++++++++++++--------------------
> 1 file changed, 108 insertions(+), 107 deletions(-)
>
> diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
> index c906a2b6c2cf..0c5eef0610fa 100644
> --- a/fs/btrfs/block-group.c
> +++ b/fs/btrfs/block-group.c
> @@ -1687,6 +1687,109 @@ static int check_chunk_block_group_mappings(struct btrfs_fs_info *fs_info)
> return ret;
> }
>
> +static int read_one_block_group(struct btrfs_fs_info *info,
> + struct btrfs_path *path,
> + int need_clear)
> +{
> + struct extent_buffer *leaf = path->nodes[0];
> + struct btrfs_block_group_cache *cache;
> + struct btrfs_space_info *space_info;
> + struct btrfs_key key;
> + int mixed = btrfs_fs_incompat(info, MIXED_GROUPS);
> + int slot = path->slots[0];
> + int ret;
> +
> + btrfs_item_key_to_cpu(leaf, &key, slot);
> + ASSERT(key.type == BTRFS_BLOCK_GROUP_ITEM_KEY);
> +
> + cache = btrfs_create_block_group_cache(info, key.objectid,
> + key.offset);
> + if (!cache)
> + return -ENOMEM;
> +
> + if (need_clear) {
> + /*
> + * When we mount with old space cache, we need to
> + * set BTRFS_DC_CLEAR and set dirty flag.
> + *
> + * a) Setting 'BTRFS_DC_CLEAR' makes sure that we
> + * truncate the old free space cache inode and
> + * setup a new one.
> + * b) Setting 'dirty flag' makes sure that we flush
> + * the new space cache info onto disk.
> + */
> + if (btrfs_test_opt(info, SPACE_CACHE))
> + cache->disk_cache_state = BTRFS_DC_CLEAR;
> + }
> + read_extent_buffer(leaf, &cache->item,
> + btrfs_item_ptr_offset(leaf, slot),
> + sizeof(cache->item));
> + cache->flags = btrfs_block_group_flags(&cache->item);
> + if (!mixed && ((cache->flags & BTRFS_BLOCK_GROUP_METADATA) &&
> + (cache->flags & BTRFS_BLOCK_GROUP_DATA))) {
> + btrfs_err(info,
> +"bg %llu is a mixed block group but filesystem hasn't enabled mixed block groups",
> + cache->key.objectid);
> + ret = -EINVAL;
> + goto error;
> + }
> +
> + /*
> + * We need to exclude the super stripes now so that the space info has
> + * super bytes accounted for, otherwise we'll think we have more space
> + * than we actually do.
> + */
> + ret = exclude_super_stripes(cache);
> + if (ret) {
> + /* We may have excluded something, so call this just in case. */
> + btrfs_free_excluded_extents(cache);
> + goto error;
> + }
> +
> + /*
> + * Check for two cases, either we are full, and therefore don't need
> + * to bother with the caching work since we won't find any space, or we
> + * are empty, and we can just add all the space in and be done with it.
> + * This saves us _a_lot_ of time, particularly in the full case.
> + */
> + if (key.offset == btrfs_block_group_used(&cache->item)) {
> + cache->last_byte_to_unpin = (u64)-1;
> + cache->cached = BTRFS_CACHE_FINISHED;
> + btrfs_free_excluded_extents(cache);
> + } else if (btrfs_block_group_used(&cache->item) == 0) {
> + cache->last_byte_to_unpin = (u64)-1;
> + cache->cached = BTRFS_CACHE_FINISHED;
> + add_new_free_space(cache, key.objectid,
> + key.objectid + key.offset);
> + btrfs_free_excluded_extents(cache);
> + }
> + ret = btrfs_add_block_group_cache(info, cache);
> + if (ret) {
> + btrfs_remove_free_space_cache(cache);
> + goto error;
> + }
> + trace_btrfs_add_block_group(info, cache, 0);
> + btrfs_update_space_info(info, cache->flags, key.offset,
> + btrfs_block_group_used(&cache->item),
> + cache->bytes_super, &space_info);
> +
> + cache->space_info = space_info;
> +
> + link_block_group(cache);
> +
> + set_avail_alloc_bits(info, cache->flags);
> + if (btrfs_chunk_readonly(info, cache->key.objectid)) {
> + inc_block_group_ro(cache, 1);
> + } else if (btrfs_block_group_used(&cache->item) == 0) {
> + ASSERT(list_empty(&cache->bg_list));
> + btrfs_mark_bg_unused(cache);
> + }
> + return 0;
> +error:
> + btrfs_put_block_group(cache);
> + return ret;
> +}
> +
> int btrfs_read_block_groups(struct btrfs_fs_info *info)
> {
> struct btrfs_path *path;
> @@ -1694,15 +1797,8 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
> struct btrfs_block_group_cache *cache;
> struct btrfs_space_info *space_info;
> struct btrfs_key key;
> - struct btrfs_key found_key;
> - struct extent_buffer *leaf;
> int need_clear = 0;
> u64 cache_gen;
> - u64 feature;
> - int mixed;
> -
> - feature = btrfs_super_incompat_flags(info->super_copy);
> - mixed = !!(feature & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS);
>
> key.objectid = 0;
> key.offset = 0;
> @@ -1726,108 +1822,13 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
> if (ret != 0)
> goto error;
>
> - leaf = path->nodes[0];
> - btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
> -
> - cache = btrfs_create_block_group_cache(info, found_key.objectid,
> - found_key.offset);
> - if (!cache) {
> - ret = -ENOMEM;
> - goto error;
> - }
> -
> - if (need_clear) {
> - /*
> - * When we mount with old space cache, we need to
> - * set BTRFS_DC_CLEAR and set dirty flag.
> - *
> - * a) Setting 'BTRFS_DC_CLEAR' makes sure that we
> - * truncate the old free space cache inode and
> - * setup a new one.
> - * b) Setting 'dirty flag' makes sure that we flush
> - * the new space cache info onto disk.
> - */
> - if (btrfs_test_opt(info, SPACE_CACHE))
> - cache->disk_cache_state = BTRFS_DC_CLEAR;
> - }
> -
> - read_extent_buffer(leaf, &cache->item,
> - btrfs_item_ptr_offset(leaf, path->slots[0]),
> - sizeof(cache->item));
> - cache->flags = btrfs_block_group_flags(&cache->item);
> - if (!mixed &&
> - ((cache->flags & BTRFS_BLOCK_GROUP_METADATA) &&
> - (cache->flags & BTRFS_BLOCK_GROUP_DATA))) {
> - btrfs_err(info,
> -"bg %llu is a mixed block group but filesystem hasn't enabled mixed block groups",
> - cache->key.objectid);
> - ret = -EINVAL;
> - btrfs_put_block_group(cache);
> + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
> + ret = read_one_block_group(info, path, need_clear);
> + if (ret < 0)
> goto error;
> - }
> -
> - key.objectid = found_key.objectid + found_key.offset;
> + key.objectid += key.offset;
> + key.offset = 0;
> btrfs_release_path(path);
> -
> - /*
> - * We need to exclude the super stripes now so that the space
> - * info has super bytes accounted for, otherwise we'll think
> - * we have more space than we actually do.
> - */
> - ret = exclude_super_stripes(cache);
> - if (ret) {
> - /*
> - * We may have excluded something, so call this just in
> - * case.
> - */
> - btrfs_free_excluded_extents(cache);
> - btrfs_put_block_group(cache);
> - goto error;
> - }
> -
> - /*
> - * Check for two cases, either we are full, and therefore
> - * don't need to bother with the caching work since we won't
> - * find any space, or we are empty, and we can just add all
> - * the space in and be done with it. This saves us _a_lot_ of
> - * time, particularly in the full case.
> - */
> - if (found_key.offset == btrfs_block_group_used(&cache->item)) {
> - cache->last_byte_to_unpin = (u64)-1;
> - cache->cached = BTRFS_CACHE_FINISHED;
> - btrfs_free_excluded_extents(cache);
> - } else if (btrfs_block_group_used(&cache->item) == 0) {
> - cache->last_byte_to_unpin = (u64)-1;
> - cache->cached = BTRFS_CACHE_FINISHED;
> - add_new_free_space(cache, found_key.objectid,
> - found_key.objectid +
> - found_key.offset);
> - btrfs_free_excluded_extents(cache);
> - }
> -
> - ret = btrfs_add_block_group_cache(info, cache);
> - if (ret) {
> - btrfs_remove_free_space_cache(cache);
> - btrfs_put_block_group(cache);
> - goto error;
> - }
> -
> - trace_btrfs_add_block_group(info, cache, 0);
> - btrfs_update_space_info(info, cache->flags, found_key.offset,
> - btrfs_block_group_used(&cache->item),
> - cache->bytes_super, &space_info);
> -
> - cache->space_info = space_info;
> -
> - link_block_group(cache);
> -
> - set_avail_alloc_bits(info, cache->flags);
> - if (btrfs_chunk_readonly(info, cache->key.objectid)) {
> - inc_block_group_ro(cache, 1);
> - } else if (btrfs_block_group_used(&cache->item) == 0) {
> - ASSERT(list_empty(&cache->bg_list));
> - btrfs_mark_bg_unused(cache);
> - }
> }
>
> list_for_each_entry_rcu(space_info, &info->space_info, list) {
>

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