From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C4CFC18E5B for ; Tue, 17 Mar 2020 08:11:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F1C6B20674 for ; Tue, 17 Mar 2020 08:11:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725995AbgCQILl (ORCPT ); Tue, 17 Mar 2020 04:11:41 -0400 Received: from mx2.suse.de ([195.135.220.15]:42248 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725837AbgCQILl (ORCPT ); Tue, 17 Mar 2020 04:11:41 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id C509CAB95; Tue, 17 Mar 2020 08:11:38 +0000 (UTC) From: Qu Wenruo To: linux-btrfs@vger.kernel.org Cc: Johannes Thumshirn Subject: [PATCH RFC 01/39] btrfs: backref: Introduce the skeleton of btrfs_backref_iter Date: Tue, 17 Mar 2020 16:10:47 +0800 Message-Id: <20200317081125.36289-2-wqu@suse.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200317081125.36289-1-wqu@suse.com> References: <20200317081125.36289-1-wqu@suse.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Due to the complex nature of btrfs extent tree, when we want to iterate all backrefs of one extent, it involves quite a lot of work, like searching the EXTENT_ITEM/METADATA_ITEM, iteration through inline and keyed backrefs. Normally this would result pretty complex code, something like: btrfs_search_slot() /* Ensure we are at EXTENT_ITEM/METADATA_ITEM */ while (1) { /* Loop for extent tree items */ while (ptr < end) { /* Loop for inlined items */ /* REAL WORK HERE */ } next: ret = btrfs_next_item() /* Ensure we're still at keyed item for specified bytenr */ } The idea of btrfs_backref_iter is to avoid such complex and hard to read code structure, but something like the following: iter = btrfs_backref_iter_alloc(); ret = btrfs_backref_iter_start(iter, bytenr); if (ret < 0) goto out; for (; ; ret = btrfs_backref_iter_next(iter)) { /* REAL WORK HERE */ } out: btrfs_backref_iter_free(iter); This patch is just the skeleton + btrfs_backref_iter_start() code. Signed-off-by: Qu Wenruo Reviewed-by: Johannes Thumshirn --- fs/btrfs/backref.c | 111 +++++++++++++++++++++++++++++++++++++++++++++ fs/btrfs/backref.h | 39 ++++++++++++++++ 2 files changed, 150 insertions(+) diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 327e4480957b..33fec39bf5ef 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -2299,3 +2299,114 @@ void free_ipath(struct inode_fs_paths *ipath) kvfree(ipath->fspath); kfree(ipath); } + +struct btrfs_backref_iter *btrfs_backref_iter_alloc( + struct btrfs_fs_info *fs_info, gfp_t gfp_flag) +{ + struct btrfs_backref_iter *ret; + + ret = kzalloc(sizeof(*ret), gfp_flag); + if (!ret) + return NULL; + + ret->path = btrfs_alloc_path(); + if (!ret) { + kfree(ret); + return NULL; + } + + /* Current backref iterator only supports iteration in commit root */ + ret->path->search_commit_root = 1; + ret->path->skip_locking = 1; + ret->path->reada = READA_FORWARD; + ret->fs_info = fs_info; + + return ret; +} + +int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr) +{ + struct btrfs_fs_info *fs_info = iter->fs_info; + struct btrfs_path *path = iter->path; + struct btrfs_extent_item *ei; + struct btrfs_key key; + int ret; + + key.objectid = bytenr; + key.type = BTRFS_METADATA_ITEM_KEY; + key.offset = (u64)-1; + iter->bytenr = bytenr; + + ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0); + if (ret < 0) + return ret; + if (ret == 0) { + ret = -EUCLEAN; + goto release; + } + if (path->slots[0] == 0) { + WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG)); + ret = -EUCLEAN; + goto release; + } + path->slots[0]--; + + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + if ((key.type != BTRFS_EXTENT_ITEM_KEY && + key.type != BTRFS_METADATA_ITEM_KEY) || key.objectid != bytenr) { + ret = -ENOENT; + goto release; + } + memcpy(&iter->cur_key, &key, sizeof(key)); + iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0], + path->slots[0]); + iter->end_ptr = (u32)(iter->item_ptr + + btrfs_item_size_nr(path->nodes[0], path->slots[0])); + ei = btrfs_item_ptr(path->nodes[0], path->slots[0], + struct btrfs_extent_item); + + /* + * Only support iteration on tree backref yet. + * + * This is extra precaustion for non skinny-metadata, where + * EXTENT_ITEM is also used for tree blocks, that we can only use + * extent flags to determine if it's a tree block. + */ + if (btrfs_extent_flags(path->nodes[0], ei) & BTRFS_EXTENT_FLAG_DATA) { + ret = -ENOTSUPP; + goto release; + } + iter->cur_ptr = (u32)(iter->item_ptr + sizeof(*ei)); + + /* If there is no inline backref, go search for keyed backref */ + if (iter->cur_ptr >= iter->end_ptr) { + ret = btrfs_next_item(fs_info->extent_root, path); + + /* No inline nor keyed ref */ + if (ret > 0) { + ret = -ENOENT; + goto release; + } + if (ret < 0) + goto release; + + btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key, + path->slots[0]); + if (iter->cur_key.objectid != bytenr || + (iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY && + iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY)) { + ret = -ENOENT; + goto release; + } + iter->cur_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0], + path->slots[0]); + iter->item_ptr = iter->cur_ptr; + iter->end_ptr = (u32)(iter->item_ptr + btrfs_item_size_nr( + path->nodes[0], path->slots[0])); + } + + return 0; +release: + btrfs_backref_iter_release(iter); + return ret; +} diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h index 777f61dc081e..3ca9604981f8 100644 --- a/fs/btrfs/backref.h +++ b/fs/btrfs/backref.h @@ -74,4 +74,43 @@ struct prelim_ref { u64 wanted_disk_byte; }; +/* + * Helper structure to help iterate backrefs of one extent. + * + * Now it only supports iteration for tree block in commit root. + */ +struct btrfs_backref_iter { + u64 bytenr; + struct btrfs_path *path; + struct btrfs_fs_info *fs_info; + struct btrfs_key cur_key; + u32 item_ptr; + u32 cur_ptr; + u32 end_ptr; +}; + +struct btrfs_backref_iter *btrfs_backref_iter_alloc( + struct btrfs_fs_info *fs_info, gfp_t gfp_flag); + +static inline void btrfs_backref_iter_free(struct btrfs_backref_iter *iter) +{ + if (!iter) + return; + btrfs_free_path(iter->path); + kfree(iter); +} + +int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr); + +static inline void +btrfs_backref_iter_release(struct btrfs_backref_iter *iter) +{ + iter->bytenr = 0; + iter->item_ptr = 0; + iter->cur_ptr = 0; + iter->end_ptr = 0; + btrfs_release_path(iter->path); + memset(&iter->cur_key, 0, sizeof(iter->cur_key)); +} + #endif -- 2.25.1