From 80ff385665b7fca29fefe358a60ab0d09f9b8e87 Mon Sep 17 00:00:00 2001 From: Yan Zheng Date: Thu, 30 Oct 2008 14:20:02 -0400 Subject: Btrfs: update nodatacow code v2 This patch simplifies the nodatacow checker. If all references were created after the latest snapshot, then we can avoid COW safely. This patch also updates run_delalloc_nocow to do more fine-grained checking. Signed-off-by: Yan Zheng --- fs/btrfs/extent-tree.c | 131 +++++++------------------------------------------ 1 file changed, 18 insertions(+), 113 deletions(-) (limited to 'fs/btrfs/extent-tree.c') diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 535cee47fcfb..1eb69a91b727 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -848,9 +848,8 @@ out: return 0; } -static int get_reference_status(struct btrfs_root *root, u64 bytenr, - u64 parent_gen, u64 ref_objectid, - u64 *min_generation, u32 *ref_count) +int btrfs_cross_ref_exist(struct btrfs_trans_handle *trans, + struct btrfs_root *root, u64 bytenr) { struct btrfs_root *extent_root = root->fs_info->extent_root; struct btrfs_path *path; @@ -858,8 +857,8 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr, struct btrfs_extent_ref *ref_item; struct btrfs_key key; struct btrfs_key found_key; - u64 root_objectid = root->root_key.objectid; - u64 ref_generation; + u64 ref_root; + u64 last_snapshot; u32 nritems; int ret; @@ -872,7 +871,9 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr, if (ret < 0) goto out; BUG_ON(ret == 0); - if (ret < 0 || path->slots[0] == 0) + + ret = -ENOENT; + if (path->slots[0] == 0) goto out; path->slots[0]--; @@ -880,14 +881,10 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr, btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]); if (found_key.objectid != bytenr || - found_key.type != BTRFS_EXTENT_ITEM_KEY) { - ret = 1; + found_key.type != BTRFS_EXTENT_ITEM_KEY) goto out; - } - - *ref_count = 0; - *min_generation = (u64)-1; + last_snapshot = btrfs_root_last_snapshot(&root->root_item); while (1) { leaf = path->nodes[0]; nritems = btrfs_header_nritems(leaf); @@ -910,114 +907,22 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr, ref_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_ref); - ref_generation = btrfs_ref_generation(leaf, ref_item); - /* - * For (parent_gen > 0 && parent_gen > ref_generation): - * - * we reach here through the oldest root, therefore - * all other reference from same snapshot should have - * a larger generation. - */ - if ((root_objectid != btrfs_ref_root(leaf, ref_item)) || - (parent_gen > 0 && parent_gen > ref_generation) || - (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID && - ref_objectid != btrfs_ref_objectid(leaf, ref_item))) { - *ref_count = 2; - break; - } - - *ref_count = 1; - if (*min_generation > ref_generation) - *min_generation = ref_generation; - - path->slots[0]++; - } - ret = 0; -out: - btrfs_free_path(path); - return ret; -} - -int btrfs_cross_ref_exists(struct btrfs_trans_handle *trans, - struct btrfs_root *root, - struct btrfs_key *key, u64 bytenr) -{ - struct btrfs_root *old_root; - struct btrfs_path *path = NULL; - struct extent_buffer *eb; - struct btrfs_file_extent_item *item; - u64 ref_generation; - u64 min_generation; - u64 extent_start; - u32 ref_count; - int level; - int ret; - - BUG_ON(trans == NULL); - BUG_ON(key->type != BTRFS_EXTENT_DATA_KEY); - ret = get_reference_status(root, bytenr, 0, key->objectid, - &min_generation, &ref_count); - if (ret) - return ret; - - if (ref_count != 1) - return 1; - - old_root = root->dirty_root->root; - ref_generation = old_root->root_key.offset; - - /* all references are created in running transaction */ - if (min_generation > ref_generation) { - ret = 0; - goto out; - } - - path = btrfs_alloc_path(); - if (!path) { - ret = -ENOMEM; - goto out; - } - - path->skip_locking = 1; - /* if no item found, the extent is referenced by other snapshot */ - ret = btrfs_search_slot(NULL, old_root, key, path, 0, 0); - if (ret) - goto out; - - eb = path->nodes[0]; - item = btrfs_item_ptr(eb, path->slots[0], - struct btrfs_file_extent_item); - if (btrfs_file_extent_type(eb, item) != BTRFS_FILE_EXTENT_REG || - btrfs_file_extent_disk_bytenr(eb, item) != bytenr) { - ret = 1; - goto out; - } - - for (level = BTRFS_MAX_LEVEL - 1; level >= -1; level--) { - if (level >= 0) { - eb = path->nodes[level]; - if (!eb) - continue; - extent_start = eb->start; - } else - extent_start = bytenr; - - ret = get_reference_status(root, extent_start, ref_generation, - 0, &min_generation, &ref_count); - if (ret) + ref_root = btrfs_ref_root(leaf, ref_item); + if (ref_root != root->root_key.objectid && + ref_root != BTRFS_TREE_LOG_OBJECTID) { + ret = 1; goto out; - - if (ref_count != 1) { + } + if (btrfs_ref_generation(leaf, ref_item) <= last_snapshot) { ret = 1; goto out; } - if (level >= 0) - ref_generation = btrfs_header_generation(eb); + + path->slots[0]++; } ret = 0; out: - if (path) - btrfs_free_path(path); + btrfs_free_path(path); return ret; } -- cgit v1.2.2