On Fri, Sep 14, 2012 at 04:58:04PM +0800, Liu Bo wrote:
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -306,9 +306,17 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
> WARN_ON(type != TRANS_JOIN && type != TRANS_JOIN_NOLOCK &&
> type != TRANS_JOIN_ONLY);
> h = current->journal_info;
> - h->use_count++;
> - h->orig_rsv = h->block_rsv;
> + if (h->block_rsv) {
> + struct btrfs_trans_rsv_item *item;
> + item = kmalloc(sizeof(*item), GFP_NOFS);
I'd rather avoid the kmalloc here and add a list hook into
btrfs_block_rsv itself (used only for this purpose).
It also does not increase the failure surface and we don't have to
handle error conditions from deep callchains.
> + if (!item)
> + return ERR_PTR(-ENOMEM);
> + item->rsv = h->block_rsv;
> + INIT_LIST_HEAD(&item->list);
> + list_add(&item->list, &h->blk_rsv_list);
> + }
> h->block_rsv = NULL;
> + h->use_count++;
> goto got_it;
> } else if (type == TRANS_JOIN_ONLY) {
> return ERR_PTR(-ENOENT);
> --- a/fs/btrfs/transaction.h
> +++ b/fs/btrfs/transaction.h
> @@ -57,7 +57,6 @@ struct btrfs_trans_handle {
> unsigned long delayed_ref_updates;
> struct btrfs_transaction *transaction;
> struct btrfs_block_rsv *block_rsv;
> - struct btrfs_block_rsv *orig_rsv;
> int aborted;
> int adding_csums;
> /*
> @@ -68,6 +67,12 @@ struct btrfs_trans_handle {
> struct btrfs_root *root;
> struct seq_list delayed_ref_elem;
> struct list_head qgroup_ref_list;
> + struct list_head blk_rsv_list;
Does it refer to chain of orig_rsv's ? Ie. naming it orig_blk_rsv_list
> +};
> +
> +struct btrfs_trans_rsv_item {
> + struct btrfs_block_rsv *rsv;
> + struct list_head list;
Generally, for such 'list of single pointers' structs I'd evaluate the
possibility of embedding the hook inside the struct, the overhead
(memory, processing) is not desirable.
> };
>
> struct btrfs_pending_snapshot {
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