From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([59.151.112.132]:49498 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752509AbcAGBIt (ORCPT ); Wed, 6 Jan 2016 20:08:49 -0500 Received: from G08CNEXCHPEKD02.g08.fujitsu.local (unknown [10.167.33.83]) by cn.fujitsu.com (Postfix) with ESMTP id 1D64D45DEE17 for ; Thu, 7 Jan 2016 09:08:23 +0800 (CST) From: Qu Wenruo To: CC: Wang Xiaoguang Subject: [PATCH v3 07/16] btrfs: dedup: Introduce function to search for an existing hash Date: Thu, 7 Jan 2016 09:08:08 +0800 Message-ID: <1452128897-5433-8-git-send-email-quwenruo@cn.fujitsu.com> In-Reply-To: <1452128897-5433-1-git-send-email-quwenruo@cn.fujitsu.com> References: <1452128897-5433-1-git-send-email-quwenruo@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-btrfs-owner@vger.kernel.org List-ID: From: Wang Xiaoguang Introduce static function inmem_search() to handle the job for in-memory hash tree. The trick is, we must ensure the delayed ref head is not being run at the time we search the for the hash. With inmem_search(), we can implement the btrfs_dedup_search() interface. Signed-off-by: Qu Wenruo Signed-off-by: Wang Xiaoguang --- v3: Use struct inmem_hash instead of struct btrfs_dedup_hash. --- fs/btrfs/dedup.c | 163 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 163 insertions(+) diff --git a/fs/btrfs/dedup.c b/fs/btrfs/dedup.c index 0272411..4863cf2 100644 --- a/fs/btrfs/dedup.c +++ b/fs/btrfs/dedup.c @@ -336,3 +336,166 @@ int btrfs_dedup_disable(struct btrfs_fs_info *fs_info) inmem_destroy(fs_info); return 0; } + +/* + * Caller must ensure the corresponding ref head is not being run. + */ +static struct inmem_hash * +inmem_search_hash(struct btrfs_dedup_info *dedup_info, u8 *hash) +{ + struct rb_node **p = &dedup_info->hash_root.rb_node; + struct rb_node *parent = NULL; + struct inmem_hash *entry = NULL; + u16 hash_type = dedup_info->hash_type; + int hash_len = btrfs_dedup_sizes[hash_type]; + + while (*p) { + parent = *p; + entry = rb_entry(parent, struct inmem_hash, hash_node); + + if (memcmp(hash, entry->hash, hash_len) < 0) { + p = &(*p)->rb_left; + } else if (memcmp(hash, entry->hash, hash_len) > 0) { + p = &(*p)->rb_right; + } else { + /* Found, need to re-add it to LRU list head */ + list_del(&entry->lru_list); + list_add(&entry->lru_list, &dedup_info->lru_list); + return entry; + } + } + return NULL; +} + +static int inmem_search(struct inode *inode, u64 file_pos, + struct btrfs_dedup_hash *hash) +{ + int ret; + struct btrfs_root *root = BTRFS_I(inode)->root; + struct btrfs_fs_info *fs_info = root->fs_info; + struct btrfs_trans_handle *trans; + struct btrfs_delayed_ref_root *delayed_refs; + struct btrfs_delayed_ref_head *head; + struct inmem_hash *found_hash; + struct btrfs_dedup_info *dedup_info = fs_info->dedup_info; + u64 bytenr, num_bytes; + + spin_lock(&dedup_info->lock); + found_hash = inmem_search_hash(dedup_info, hash->hash); + /* If we don't find a duplicated extent, just return. */ + if (!found_hash) { + spin_unlock(&dedup_info->lock); + return 0; + } + bytenr = found_hash->bytenr; + num_bytes = found_hash->num_bytes; + spin_unlock(&dedup_info->lock); + + trans = btrfs_join_transaction(root); + if (IS_ERR(trans)) + return PTR_ERR(trans); + +again: + delayed_refs = &trans->transaction->delayed_refs; + + spin_lock(&delayed_refs->lock); + head = btrfs_find_delayed_ref_head(trans, bytenr); + if (!head) { + /* + * We can safely insert a new delayed_ref as long as we + * hold delayed_refs->lock. + * Only need to use atomic inc_extent_ref() + */ + ret = btrfs_inc_extent_ref_atomic(trans, root, bytenr, + num_bytes, 0, root->root_key.objectid, + btrfs_ino(inode), file_pos); + spin_unlock(&delayed_refs->lock); + btrfs_end_transaction(trans, root); + + if (ret == 0) { + hash->bytenr = bytenr; + hash->num_bytes = num_bytes; + ret = 1; + } + return ret; + } + + /* + * we may have dropped the delayed_refs->lock to get the head mutex + * lock, and that might have given someone else time to free the head. + * If that's true, it has been removed from our list and we can move on. + */ + ret = btrfs_delayed_ref_lock(trans, head); + spin_unlock(&delayed_refs->lock); + if (ret == -EAGAIN) { + spin_lock(&dedup_info->lock); + found_hash = inmem_search_hash(dedup_info, hash->hash); + if (!found_hash) { + spin_unlock(&dedup_info->lock); + goto out; + } + bytenr = found_hash->bytenr; + num_bytes = found_hash->num_bytes; + spin_unlock(&dedup_info->lock); + goto again; + } + + /* We still need to look up the hash again... */ + spin_lock(&dedup_info->lock); + found_hash = inmem_search_hash(dedup_info, hash->hash); + if (!found_hash) { + spin_unlock(&dedup_info->lock); + mutex_unlock(&head->mutex); + goto out; + } + + /* The bytenr has changed, we need to re-lock the delayed_ref head */ + if (found_hash->bytenr != bytenr) { + bytenr = found_hash->bytenr; + num_bytes = found_hash->num_bytes; + spin_unlock(&dedup_info->lock); + mutex_unlock(&head->mutex); + goto again; + } + + hash->bytenr = bytenr; + hash->num_bytes = num_bytes; + spin_unlock(&dedup_info->lock); + + /* + * Increase the extent ref right now, to avoid delayed ref run + * Or we may increase ref on non-exist extent. + */ + btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, 0, + root->root_key.objectid, + btrfs_ino(inode), file_pos); + mutex_unlock(&head->mutex); + btrfs_end_transaction(trans, root); + + return 1; + +out: + btrfs_end_transaction(trans, root); + return 0; +} + +int btrfs_dedup_search(struct inode *inode, u64 file_pos, + struct btrfs_dedup_hash *hash) +{ + struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info; + struct btrfs_dedup_info *dedup_info = fs_info->dedup_info; + int ret = 0; + + if (WARN_ON(!dedup_info || !hash)) + return 0; + + if (dedup_info->backend == BTRFS_DEDUP_BACKEND_INMEMORY) + ret = inmem_search(inode, file_pos, hash); + + /* It's possible hash->bytenr/num_bytenr already changed */ + if (ret == 0) { + hash->num_bytes = 0; + hash->bytenr = 0; + } + return ret; +} -- 2.6.4