btrfs: trimming some start_transaction() code away

Just call kmem_cache_zalloc() instead of calling kmem_cache_alloc().
We're just initializing most fields to 0, false and NULL later on
_anyway_, so to make the code mode readable and potentially gain
a bit of performance (completely untested claim), we should fill our
btrfs_trans_handle with zeros on allocation then just initialize
those five remaining fields (not counting the list_heads) as normal.

Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Alexandru Moise <00moses.alexander00@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Alexandru Moise 2015-08-27 23:53:45 +00:00 committed by David Sterba
parent 0412e58c6d
commit f2f767e734

View file

@ -502,7 +502,7 @@ start_transaction(struct btrfs_root *root, u64 num_items, unsigned int type,
goto reserve_fail;
}
again:
h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
h = kmem_cache_zalloc(btrfs_trans_handle_cachep, GFP_NOFS);
if (!h) {
ret = -ENOMEM;
goto alloc_fail;
@ -543,23 +543,10 @@ again:
h->transid = cur_trans->transid;
h->transaction = cur_trans;
h->blocks_used = 0;
h->bytes_reserved = 0;
h->chunk_bytes_reserved = 0;
h->root = root;
h->delayed_ref_updates = 0;
h->use_count = 1;
h->adding_csums = 0;
h->block_rsv = NULL;
h->orig_rsv = NULL;
h->aborted = 0;
h->qgroup_reserved = 0;
h->delayed_ref_elem.seq = 0;
h->type = type;
h->allocating_chunk = false;
h->can_flush_pending_bgs = true;
h->reloc_reserved = false;
h->sync = false;
INIT_LIST_HEAD(&h->qgroup_ref_list);
INIT_LIST_HEAD(&h->new_bgs);
INIT_LIST_HEAD(&h->ordered);