diff options
Diffstat (limited to 'fs/btrfs/tree-mod-log.c')
| -rw-r--r-- | fs/btrfs/tree-mod-log.c | 929 |
1 files changed, 929 insertions, 0 deletions
diff --git a/fs/btrfs/tree-mod-log.c b/fs/btrfs/tree-mod-log.c new file mode 100644 index 000000000..8a3a14686 --- /dev/null +++ b/fs/btrfs/tree-mod-log.c @@ -0,0 +1,929 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "tree-mod-log.h" +#include "disk-io.h" + +struct tree_mod_root { + u64 logical; + u8 level; +}; + +struct tree_mod_elem { + struct rb_node node; + u64 logical; + u64 seq; + enum btrfs_mod_log_op op; + + /* + * This is used for BTRFS_MOD_LOG_KEY_* and BTRFS_MOD_LOG_MOVE_KEYS + * operations. + */ + int slot; + + /* This is used for BTRFS_MOD_LOG_KEY* and BTRFS_MOD_LOG_ROOT_REPLACE. */ + u64 generation; + + /* Those are used for op == BTRFS_MOD_LOG_KEY_{REPLACE,REMOVE}. */ + struct btrfs_disk_key key; + u64 blockptr; + + /* This is used for op == BTRFS_MOD_LOG_MOVE_KEYS. */ + struct { + int dst_slot; + int nr_items; + } move; + + /* This is used for op == BTRFS_MOD_LOG_ROOT_REPLACE. */ + struct tree_mod_root old_root; +}; + +/* + * Pull a new tree mod seq number for our operation. + */ +static inline u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info) +{ + return atomic64_inc_return(&fs_info->tree_mod_seq); +} + +/* + * This adds a new blocker to the tree mod log's blocker list if the @elem + * passed does not already have a sequence number set. So when a caller expects + * to record tree modifications, it should ensure to set elem->seq to zero + * before calling btrfs_get_tree_mod_seq. + * Returns a fresh, unused tree log modification sequence number, even if no new + * blocker was added. + */ +u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info, + struct btrfs_seq_list *elem) +{ + write_lock(&fs_info->tree_mod_log_lock); + if (!elem->seq) { + elem->seq = btrfs_inc_tree_mod_seq(fs_info); + list_add_tail(&elem->list, &fs_info->tree_mod_seq_list); + set_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags); + } + write_unlock(&fs_info->tree_mod_log_lock); + + return elem->seq; +} + +void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info, + struct btrfs_seq_list *elem) +{ + struct rb_root *tm_root; + struct rb_node *node; + struct rb_node *next; + struct tree_mod_elem *tm; + u64 min_seq = BTRFS_SEQ_LAST; + u64 seq_putting = elem->seq; + + if (!seq_putting) + return; + + write_lock(&fs_info->tree_mod_log_lock); + list_del(&elem->list); + elem->seq = 0; + + if (list_empty(&fs_info->tree_mod_seq_list)) { + clear_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags); + } else { + struct btrfs_seq_list *first; + + first = list_first_entry(&fs_info->tree_mod_seq_list, + struct btrfs_seq_list, list); + if (seq_putting > first->seq) { + /* + * Blocker with lower sequence number exists, we cannot + * remove anything from the log. + */ + write_unlock(&fs_info->tree_mod_log_lock); + return; + } + min_seq = first->seq; + } + + /* + * Anything that's lower than the lowest existing (read: blocked) + * sequence number can be removed from the tree. + */ + tm_root = &fs_info->tree_mod_log; + for (node = rb_first(tm_root); node; node = next) { + next = rb_next(node); + tm = rb_entry(node, struct tree_mod_elem, node); + if (tm->seq >= min_seq) + continue; + rb_erase(node, tm_root); + kfree(tm); + } + write_unlock(&fs_info->tree_mod_log_lock); +} + +/* + * Key order of the log: + * node/leaf start address -> sequence + * + * The 'start address' is the logical address of the *new* root node for root + * replace operations, or the logical address of the affected block for all + * other operations. + */ +static noinline int tree_mod_log_insert(struct btrfs_fs_info *fs_info, + struct tree_mod_elem *tm) +{ + struct rb_root *tm_root; + struct rb_node **new; + struct rb_node *parent = NULL; + struct tree_mod_elem *cur; + + lockdep_assert_held_write(&fs_info->tree_mod_log_lock); + + tm->seq = btrfs_inc_tree_mod_seq(fs_info); + + tm_root = &fs_info->tree_mod_log; + new = &tm_root->rb_node; + while (*new) { + cur = rb_entry(*new, struct tree_mod_elem, node); + parent = *new; + if (cur->logical < tm->logical) + new = &((*new)->rb_left); + else if (cur->logical > tm->logical) + new = &((*new)->rb_right); + else if (cur->seq < tm->seq) + new = &((*new)->rb_left); + else if (cur->seq > tm->seq) + new = &((*new)->rb_right); + else + return -EEXIST; + } + + rb_link_node(&tm->node, parent, new); + rb_insert_color(&tm->node, tm_root); + return 0; +} + +/* + * Determines if logging can be omitted. Returns true if it can. Otherwise, it + * returns false with the tree_mod_log_lock acquired. The caller must hold + * this until all tree mod log insertions are recorded in the rb tree and then + * write unlock fs_info::tree_mod_log_lock. + */ +static inline bool tree_mod_dont_log(struct btrfs_fs_info *fs_info, + struct extent_buffer *eb) +{ + if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags)) + return true; + if (eb && btrfs_header_level(eb) == 0) + return true; + + write_lock(&fs_info->tree_mod_log_lock); + if (list_empty(&(fs_info)->tree_mod_seq_list)) { + write_unlock(&fs_info->tree_mod_log_lock); + return true; + } + + return false; +} + +/* Similar to tree_mod_dont_log, but doesn't acquire any locks. */ +static inline bool tree_mod_need_log(const struct btrfs_fs_info *fs_info, + struct extent_buffer *eb) +{ + if (!test_bit(BTRFS_FS_TREE_MOD_LOG_USERS, &fs_info->flags)) + return false; + if (eb && btrfs_header_level(eb) == 0) + return false; + + return true; +} + +static struct tree_mod_elem *alloc_tree_mod_elem(struct extent_buffer *eb, + int slot, + enum btrfs_mod_log_op op, + gfp_t flags) +{ + struct tree_mod_elem *tm; + + tm = kzalloc(sizeof(*tm), flags); + if (!tm) + return NULL; + + tm->logical = eb->start; + if (op != BTRFS_MOD_LOG_KEY_ADD) { + btrfs_node_key(eb, &tm->key, slot); + tm->blockptr = btrfs_node_blockptr(eb, slot); + } + tm->op = op; + tm->slot = slot; + tm->generation = btrfs_node_ptr_generation(eb, slot); + RB_CLEAR_NODE(&tm->node); + + return tm; +} + +int btrfs_tree_mod_log_insert_key(struct extent_buffer *eb, int slot, + enum btrfs_mod_log_op op, gfp_t flags) +{ + struct tree_mod_elem *tm; + int ret; + + if (!tree_mod_need_log(eb->fs_info, eb)) + return 0; + + tm = alloc_tree_mod_elem(eb, slot, op, flags); + if (!tm) + return -ENOMEM; + + if (tree_mod_dont_log(eb->fs_info, eb)) { + kfree(tm); + return 0; + } + + ret = tree_mod_log_insert(eb->fs_info, tm); + write_unlock(&eb->fs_info->tree_mod_log_lock); + if (ret) + kfree(tm); + + return ret; +} + +int btrfs_tree_mod_log_insert_move(struct extent_buffer *eb, + int dst_slot, int src_slot, + int nr_items) +{ + struct tree_mod_elem *tm = NULL; + struct tree_mod_elem **tm_list = NULL; + int ret = 0; + int i; + bool locked = false; + + if (!tree_mod_need_log(eb->fs_info, eb)) + return 0; + + tm_list = kcalloc(nr_items, sizeof(struct tree_mod_elem *), GFP_NOFS); + if (!tm_list) + return -ENOMEM; + + tm = kzalloc(sizeof(*tm), GFP_NOFS); + if (!tm) { + ret = -ENOMEM; + goto free_tms; + } + + tm->logical = eb->start; + tm->slot = src_slot; + tm->move.dst_slot = dst_slot; + tm->move.nr_items = nr_items; + tm->op = BTRFS_MOD_LOG_MOVE_KEYS; + + for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) { + tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot, + BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING, GFP_NOFS); + if (!tm_list[i]) { + ret = -ENOMEM; + goto free_tms; + } + } + + if (tree_mod_dont_log(eb->fs_info, eb)) + goto free_tms; + locked = true; + + /* + * When we override something during the move, we log these removals. + * This can only happen when we move towards the beginning of the + * buffer, i.e. dst_slot < src_slot. + */ + for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) { + ret = tree_mod_log_insert(eb->fs_info, tm_list[i]); + if (ret) + goto free_tms; + } + + ret = tree_mod_log_insert(eb->fs_info, tm); + if (ret) + goto free_tms; + write_unlock(&eb->fs_info->tree_mod_log_lock); + kfree(tm_list); + + return 0; + +free_tms: + for (i = 0; i < nr_items; i++) { + if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node)) + rb_erase(&tm_list[i]->node, &eb->fs_info->tree_mod_log); + kfree(tm_list[i]); + } + if (locked) + write_unlock(&eb->fs_info->tree_mod_log_lock); + kfree(tm_list); + kfree(tm); + + return ret; +} + +static inline int tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, + struct tree_mod_elem **tm_list, + int nritems) +{ + int i, j; + int ret; + + for (i = nritems - 1; i >= 0; i--) { + ret = tree_mod_log_insert(fs_info, tm_list[i]); + if (ret) { + for (j = nritems - 1; j > i; j--) + rb_erase(&tm_list[j]->node, + &fs_info->tree_mod_log); + return ret; + } + } + + return 0; +} + +int btrfs_tree_mod_log_insert_root(struct extent_buffer *old_root, + struct extent_buffer *new_root, + bool log_removal) +{ + struct btrfs_fs_info *fs_info = old_root->fs_info; + struct tree_mod_elem *tm = NULL; + struct tree_mod_elem **tm_list = NULL; + int nritems = 0; + int ret = 0; + int i; + + if (!tree_mod_need_log(fs_info, NULL)) + return 0; + + if (log_removal && btrfs_header_level(old_root) > 0) { + nritems = btrfs_header_nritems(old_root); + tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *), + GFP_NOFS); + if (!tm_list) { + ret = -ENOMEM; + goto free_tms; + } + for (i = 0; i < nritems; i++) { + tm_list[i] = alloc_tree_mod_elem(old_root, i, + BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS); + if (!tm_list[i]) { + ret = -ENOMEM; + goto free_tms; + } + } + } + + tm = kzalloc(sizeof(*tm), GFP_NOFS); + if (!tm) { + ret = -ENOMEM; + goto free_tms; + } + + tm->logical = new_root->start; + tm->old_root.logical = old_root->start; + tm->old_root.level = btrfs_header_level(old_root); + tm->generation = btrfs_header_generation(old_root); + tm->op = BTRFS_MOD_LOG_ROOT_REPLACE; + + if (tree_mod_dont_log(fs_info, NULL)) + goto free_tms; + + if (tm_list) + ret = tree_mod_log_free_eb(fs_info, tm_list, nritems); + if (!ret) + ret = tree_mod_log_insert(fs_info, tm); + + write_unlock(&fs_info->tree_mod_log_lock); + if (ret) + goto free_tms; + kfree(tm_list); + + return ret; + +free_tms: + if (tm_list) { + for (i = 0; i < nritems; i++) + kfree(tm_list[i]); + kfree(tm_list); + } + kfree(tm); + + return ret; +} + +static struct tree_mod_elem *__tree_mod_log_search(struct btrfs_fs_info *fs_info, + u64 start, u64 min_seq, + bool smallest) +{ + struct rb_root *tm_root; + struct rb_node *node; + struct tree_mod_elem *cur = NULL; + struct tree_mod_elem *found = NULL; + + read_lock(&fs_info->tree_mod_log_lock); + tm_root = &fs_info->tree_mod_log; + node = tm_root->rb_node; + while (node) { + cur = rb_entry(node, struct tree_mod_elem, node); + if (cur->logical < start) { + node = node->rb_left; + } else if (cur->logical > start) { + node = node->rb_right; + } else if (cur->seq < min_seq) { + node = node->rb_left; + } else if (!smallest) { + /* We want the node with the highest seq */ + if (found) + BUG_ON(found->seq > cur->seq); + found = cur; + node = node->rb_left; + } else if (cur->seq > min_seq) { + /* We want the node with the smallest seq */ + if (found) + BUG_ON(found->seq < cur->seq); + found = cur; + node = node->rb_right; + } else { + found = cur; + break; + } + } + read_unlock(&fs_info->tree_mod_log_lock); + + return found; +} + +/* + * This returns the element from the log with the smallest time sequence + * value that's in the log (the oldest log item). Any element with a time + * sequence lower than min_seq will be ignored. + */ +static struct tree_mod_elem *tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info, + u64 start, u64 min_seq) +{ + return __tree_mod_log_search(fs_info, start, min_seq, true); +} + +/* + * This returns the element from the log with the largest time sequence + * value that's in the log (the most recent log item). Any element with + * a time sequence lower than min_seq will be ignored. + */ +static struct tree_mod_elem *tree_mod_log_search(struct btrfs_fs_info *fs_info, + u64 start, u64 min_seq) +{ + return __tree_mod_log_search(fs_info, start, min_seq, false); +} + +int btrfs_tree_mod_log_eb_copy(struct extent_buffer *dst, + struct extent_buffer *src, + unsigned long dst_offset, + unsigned long src_offset, + int nr_items) +{ + struct btrfs_fs_info *fs_info = dst->fs_info; + int ret = 0; + struct tree_mod_elem **tm_list = NULL; + struct tree_mod_elem **tm_list_add, **tm_list_rem; + int i; + bool locked = false; + + if (!tree_mod_need_log(fs_info, NULL)) + return 0; + + if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0) + return 0; + + tm_list = kcalloc(nr_items * 2, sizeof(struct tree_mod_elem *), + GFP_NOFS); + if (!tm_list) + return -ENOMEM; + + tm_list_add = tm_list; + tm_list_rem = tm_list + nr_items; + for (i = 0; i < nr_items; i++) { + tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset, + BTRFS_MOD_LOG_KEY_REMOVE, GFP_NOFS); + if (!tm_list_rem[i]) { + ret = -ENOMEM; + goto free_tms; + } + + tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset, + BTRFS_MOD_LOG_KEY_ADD, GFP_NOFS); + if (!tm_list_add[i]) { + ret = -ENOMEM; + goto free_tms; + } + } + + if (tree_mod_dont_log(fs_info, NULL)) + goto free_tms; + locked = true; + + for (i = 0; i < nr_items; i++) { + ret = tree_mod_log_insert(fs_info, tm_list_rem[i]); + if (ret) + goto free_tms; + ret = tree_mod_log_insert(fs_info, tm_list_add[i]); + if (ret) + goto free_tms; + } + + write_unlock(&fs_info->tree_mod_log_lock); + kfree(tm_list); + + return 0; + +free_tms: + for (i = 0; i < nr_items * 2; i++) { + if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node)) + rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log); + kfree(tm_list[i]); + } + if (locked) + write_unlock(&fs_info->tree_mod_log_lock); + kfree(tm_list); + + return ret; +} + +int btrfs_tree_mod_log_free_eb(struct extent_buffer *eb) +{ + struct tree_mod_elem **tm_list = NULL; + int nritems = 0; + int i; + int ret = 0; + + if (!tree_mod_need_log(eb->fs_info, eb)) + return 0; + + nritems = btrfs_header_nritems(eb); + tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *), GFP_NOFS); + if (!tm_list) + return -ENOMEM; + + for (i = 0; i < nritems; i++) { + tm_list[i] = alloc_tree_mod_elem(eb, i, + BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS); + if (!tm_list[i]) { + ret = -ENOMEM; + goto free_tms; + } + } + + if (tree_mod_dont_log(eb->fs_info, eb)) + goto free_tms; + + ret = tree_mod_log_free_eb(eb->fs_info, tm_list, nritems); + write_unlock(&eb->fs_info->tree_mod_log_lock); + if (ret) + goto free_tms; + kfree(tm_list); + + return 0; + +free_tms: + for (i = 0; i < nritems; i++) + kfree(tm_list[i]); + kfree(tm_list); + + return ret; +} + +/* + * Returns the logical address of the oldest predecessor of the given root. + * Entries older than time_seq are ignored. + */ +static struct tree_mod_elem *tree_mod_log_oldest_root(struct extent_buffer *eb_root, + u64 time_seq) +{ + struct tree_mod_elem *tm; + struct tree_mod_elem *found = NULL; + u64 root_logical = eb_root->start; + bool looped = false; + + if (!time_seq) + return NULL; + + /* + * The very last operation that's logged for a root is the replacement + * operation (if it is replaced at all). This has the logical address + * of the *new* root, making it the very first operation that's logged + * for this root. + */ + while (1) { + tm = tree_mod_log_search_oldest(eb_root->fs_info, root_logical, + time_seq); + if (!looped && !tm) + return NULL; + /* + * If there are no tree operation for the oldest root, we simply + * return it. This should only happen if that (old) root is at + * level 0. + */ + if (!tm) + break; + + /* + * If there's an operation that's not a root replacement, we + * found the oldest version of our root. Normally, we'll find a + * BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here. + */ + if (tm->op != BTRFS_MOD_LOG_ROOT_REPLACE) + break; + + found = tm; + root_logical = tm->old_root.logical; + looped = true; + } + + /* If there's no old root to return, return what we found instead */ + if (!found) + found = tm; + + return found; +} + + +/* + * tm is a pointer to the first operation to rewind within eb. Then, all + * previous operations will be rewound (until we reach something older than + * time_seq). + */ +static void tree_mod_log_rewind(struct btrfs_fs_info *fs_info, + struct extent_buffer *eb, + u64 time_seq, + struct tree_mod_elem *first_tm) +{ + u32 n; + struct rb_node *next; + struct tree_mod_elem *tm = first_tm; + unsigned long o_dst; + unsigned long o_src; + unsigned long p_size = sizeof(struct btrfs_key_ptr); + + n = btrfs_header_nritems(eb); + read_lock(&fs_info->tree_mod_log_lock); + while (tm && tm->seq >= time_seq) { + /* + * All the operations are recorded with the operator used for + * the modification. As we're going backwards, we do the + * opposite of each operation here. + */ + switch (tm->op) { + case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING: + BUG_ON(tm->slot < n); + fallthrough; + case BTRFS_MOD_LOG_KEY_REMOVE_WHILE_MOVING: + case BTRFS_MOD_LOG_KEY_REMOVE: + btrfs_set_node_key(eb, &tm->key, tm->slot); + btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr); + btrfs_set_node_ptr_generation(eb, tm->slot, + tm->generation); + n++; + break; + case BTRFS_MOD_LOG_KEY_REPLACE: + BUG_ON(tm->slot >= n); + btrfs_set_node_key(eb, &tm->key, tm->slot); + btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr); + btrfs_set_node_ptr_generation(eb, tm->slot, + tm->generation); + break; + case BTRFS_MOD_LOG_KEY_ADD: + /* if a move operation is needed it's in the log */ + n--; + break; + case BTRFS_MOD_LOG_MOVE_KEYS: + o_dst = btrfs_node_key_ptr_offset(tm->slot); + o_src = btrfs_node_key_ptr_offset(tm->move.dst_slot); + memmove_extent_buffer(eb, o_dst, o_src, + tm->move.nr_items * p_size); + break; + case BTRFS_MOD_LOG_ROOT_REPLACE: + /* + * This operation is special. For roots, this must be + * handled explicitly before rewinding. + * For non-roots, this operation may exist if the node + * was a root: root A -> child B; then A gets empty and + * B is promoted to the new root. In the mod log, we'll + * have a root-replace operation for B, a tree block + * that is no root. We simply ignore that operation. + */ + break; + } + next = rb_next(&tm->node); + if (!next) + break; + tm = rb_entry(next, struct tree_mod_elem, node); + if (tm->logical != first_tm->logical) + break; + } + read_unlock(&fs_info->tree_mod_log_lock); + btrfs_set_header_nritems(eb, n); +} + +/* + * Called with eb read locked. If the buffer cannot be rewound, the same buffer + * is returned. If rewind operations happen, a fresh buffer is returned. The + * returned buffer is always read-locked. If the returned buffer is not the + * input buffer, the lock on the input buffer is released and the input buffer + * is freed (its refcount is decremented). + */ +struct extent_buffer *btrfs_tree_mod_log_rewind(struct btrfs_fs_info *fs_info, + struct btrfs_path *path, + struct extent_buffer *eb, + u64 time_seq) +{ + struct extent_buffer *eb_rewin; + struct tree_mod_elem *tm; + + if (!time_seq) + return eb; + + if (btrfs_header_level(eb) == 0) + return eb; + + tm = tree_mod_log_search(fs_info, eb->start, time_seq); + if (!tm) + return eb; + + if (tm->op == BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) { + BUG_ON(tm->slot != 0); + eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start); + if (!eb_rewin) { + btrfs_tree_read_unlock(eb); + free_extent_buffer(eb); + return NULL; + } + btrfs_set_header_bytenr(eb_rewin, eb->start); + btrfs_set_header_backref_rev(eb_rewin, + btrfs_header_backref_rev(eb)); + btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb)); + btrfs_set_header_level(eb_rewin, btrfs_header_level(eb)); + } else { + eb_rewin = btrfs_clone_extent_buffer(eb); + if (!eb_rewin) { + btrfs_tree_read_unlock(eb); + free_extent_buffer(eb); + return NULL; + } + } + + btrfs_tree_read_unlock(eb); + free_extent_buffer(eb); + + btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb_rewin), + eb_rewin, btrfs_header_level(eb_rewin)); + btrfs_tree_read_lock(eb_rewin); + tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm); + WARN_ON(btrfs_header_nritems(eb_rewin) > + BTRFS_NODEPTRS_PER_BLOCK(fs_info)); + + return eb_rewin; +} + +/* + * Rewind the state of @root's root node to the given @time_seq value. + * If there are no changes, the current root->root_node is returned. If anything + * changed in between, there's a fresh buffer allocated on which the rewind + * operations are done. In any case, the returned buffer is read locked. + * Returns NULL on error (with no locks held). + */ +struct extent_buffer *btrfs_get_old_root(struct btrfs_root *root, u64 time_seq) +{ + struct btrfs_fs_info *fs_info = root->fs_info; + struct tree_mod_elem *tm; + struct extent_buffer *eb = NULL; + struct extent_buffer *eb_root; + u64 eb_root_owner = 0; + struct extent_buffer *old; + struct tree_mod_root *old_root = NULL; + u64 old_generation = 0; + u64 logical; + int level; + + eb_root = btrfs_read_lock_root_node(root); + tm = tree_mod_log_oldest_root(eb_root, time_seq); + if (!tm) + return eb_root; + + if (tm->op == BTRFS_MOD_LOG_ROOT_REPLACE) { + old_root = &tm->old_root; + old_generation = tm->generation; + logical = old_root->logical; + level = old_root->level; + } else { + logical = eb_root->start; + level = btrfs_header_level(eb_root); + } + + tm = tree_mod_log_search(fs_info, logical, time_seq); + if (old_root && tm && tm->op != BTRFS_MOD_LOG_KEY_REMOVE_WHILE_FREEING) { + btrfs_tree_read_unlock(eb_root); + free_extent_buffer(eb_root); + old = read_tree_block(fs_info, logical, root->root_key.objectid, + 0, level, NULL); + if (WARN_ON(IS_ERR(old) || !extent_buffer_uptodate(old))) { + if (!IS_ERR(old)) + free_extent_buffer(old); + btrfs_warn(fs_info, + "failed to read tree block %llu from get_old_root", + logical); + } else { + struct tree_mod_elem *tm2; + + btrfs_tree_read_lock(old); + eb = btrfs_clone_extent_buffer(old); + /* + * After the lookup for the most recent tree mod operation + * above and before we locked and cloned the extent buffer + * 'old', a new tree mod log operation may have been added. + * So lookup for a more recent one to make sure the number + * of mod log operations we replay is consistent with the + * number of items we have in the cloned extent buffer, + * otherwise we can hit a BUG_ON when rewinding the extent + * buffer. + */ + tm2 = tree_mod_log_search(fs_info, logical, time_seq); + btrfs_tree_read_unlock(old); + free_extent_buffer(old); + ASSERT(tm2); + ASSERT(tm2 == tm || tm2->seq > tm->seq); + if (!tm2 || tm2->seq < tm->seq) { + free_extent_buffer(eb); + return NULL; + } + tm = tm2; + } + } else if (old_root) { + eb_root_owner = btrfs_header_owner(eb_root); + btrfs_tree_read_unlock(eb_root); + free_extent_buffer(eb_root); + eb = alloc_dummy_extent_buffer(fs_info, logical); + } else { + eb = btrfs_clone_extent_buffer(eb_root); + btrfs_tree_read_unlock(eb_root); + free_extent_buffer(eb_root); + } + + if (!eb) + return NULL; + if (old_root) { + btrfs_set_header_bytenr(eb, eb->start); + btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV); + btrfs_set_header_owner(eb, eb_root_owner); + btrfs_set_header_level(eb, old_root->level); + btrfs_set_header_generation(eb, old_generation); + } + btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb), eb, + btrfs_header_level(eb)); + btrfs_tree_read_lock(eb); + if (tm) + tree_mod_log_rewind(fs_info, eb, time_seq, tm); + else + WARN_ON(btrfs_header_level(eb) != 0); + WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(fs_info)); + + return eb; +} + +int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq) +{ + struct tree_mod_elem *tm; + int level; + struct extent_buffer *eb_root = btrfs_root_node(root); + + tm = tree_mod_log_oldest_root(eb_root, time_seq); + if (tm && tm->op == BTRFS_MOD_LOG_ROOT_REPLACE) + level = tm->old_root.level; + else + level = btrfs_header_level(eb_root); + + free_extent_buffer(eb_root); + + return level; +} + +/* + * Return the lowest sequence number in the tree modification log. + * + * Return the sequence number of the oldest tree modification log user, which + * corresponds to the lowest sequence number of all existing users. If there are + * no users it returns 0. + */ +u64 btrfs_tree_mod_log_lowest_seq(struct btrfs_fs_info *fs_info) +{ + u64 ret = 0; + + read_lock(&fs_info->tree_mod_log_lock); + if (!list_empty(&fs_info->tree_mod_seq_list)) { + struct btrfs_seq_list *elem; + + elem = list_first_entry(&fs_info->tree_mod_seq_list, + struct btrfs_seq_list, list); + ret = elem->seq; + } + read_unlock(&fs_info->tree_mod_log_lock); + + return ret; +} |