From 33c66f430bfa3a033e70470e4c93f967156b696d Mon Sep 17 00:00:00 2001 From: Yan Zheng Date: Wed, 22 Jul 2009 09:59:00 -0400 Subject: [PATCH] Btrfs: fix locking issue in btrfs_find_next_key When walking up the tree, btrfs_find_next_key assumes the upper level tree block is properly locked. This isn't always true even path->keep_locks is 1. This is because btrfs_find_next_key may advance path->slots[] several times instead of only once. When 'path->slots[level] >= btrfs_header_nritems(path->nodes[level])' is found, we can't guarantee the original value of 'path->slots[level]' is 'btrfs_header_nritems(path->nodes[level]) - 1'. If it's not, the tree block at 'level + 1' isn't locked. This patch fixes the issue by explicitly checking the locking state, re-searching the tree if it's not locked. Signed-off-by: Yan Zheng Signed-off-by: Chris Mason --- fs/btrfs/ctree.c | 95 ++++++++++++++++++++++++++++--------------- fs/btrfs/relocation.c | 3 ++ 2 files changed, 65 insertions(+), 33 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 7bb66c65ddfd..fdd423a550d6 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -1701,6 +1701,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root struct extent_buffer *b; int slot; int ret; + int err; int level; int lowest_unlock = 1; u8 lowest_level = 0; @@ -1737,8 +1738,6 @@ again: p->locks[level] = 1; if (cow) { - int wret; - /* * if we don't really need to cow this block * then we don't want to set the path blocking, @@ -1749,12 +1748,12 @@ again: btrfs_set_path_blocking(p); - wret = btrfs_cow_block(trans, root, b, - p->nodes[level + 1], - p->slots[level + 1], &b); - if (wret) { + err = btrfs_cow_block(trans, root, b, + p->nodes[level + 1], + p->slots[level + 1], &b); + if (err) { free_extent_buffer(b); - ret = wret; + ret = err; goto done; } } @@ -1793,41 +1792,45 @@ cow_done: ret = bin_search(b, key, level, &slot); if (level != 0) { - if (ret && slot > 0) + int dec = 0; + if (ret && slot > 0) { + dec = 1; slot -= 1; + } p->slots[level] = slot; - ret = setup_nodes_for_search(trans, root, p, b, level, + err = setup_nodes_for_search(trans, root, p, b, level, ins_len); - if (ret == -EAGAIN) + if (err == -EAGAIN) goto again; - else if (ret) + if (err) { + ret = err; goto done; + } b = p->nodes[level]; slot = p->slots[level]; unlock_up(p, level, lowest_unlock); - /* this is only true while dropping a snapshot */ if (level == lowest_level) { - ret = 0; + if (dec) + p->slots[level]++; goto done; } - ret = read_block_for_search(trans, root, p, + err = read_block_for_search(trans, root, p, &b, level, slot, key); - if (ret == -EAGAIN) + if (err == -EAGAIN) goto again; - - if (ret == -EIO) + if (err) { + ret = err; goto done; + } if (!p->skip_locking) { - int lret; - btrfs_clear_path_blocking(p, NULL); - lret = btrfs_try_spin_lock(b); + err = btrfs_try_spin_lock(b); - if (!lret) { + if (!err) { btrfs_set_path_blocking(p); btrfs_tree_lock(b); btrfs_clear_path_blocking(p, b); @@ -1837,16 +1840,14 @@ cow_done: p->slots[level] = slot; if (ins_len > 0 && btrfs_leaf_free_space(root, b) < ins_len) { - int sret; - btrfs_set_path_blocking(p); - sret = split_leaf(trans, root, key, - p, ins_len, ret == 0); + err = split_leaf(trans, root, key, + p, ins_len, ret == 0); btrfs_clear_path_blocking(p, NULL); - BUG_ON(sret > 0); - if (sret) { - ret = sret; + BUG_ON(err > 0); + if (err) { + ret = err; goto done; } } @@ -4042,10 +4043,9 @@ out: * calling this function. */ int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path, - struct btrfs_key *key, int lowest_level, + struct btrfs_key *key, int level, int cache_only, u64 min_trans) { - int level = lowest_level; int slot; struct extent_buffer *c; @@ -4058,11 +4058,40 @@ int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path, c = path->nodes[level]; next: if (slot >= btrfs_header_nritems(c)) { - level++; - if (level == BTRFS_MAX_LEVEL) + int ret; + int orig_lowest; + struct btrfs_key cur_key; + if (level + 1 >= BTRFS_MAX_LEVEL || + !path->nodes[level + 1]) return 1; - continue; + + if (path->locks[level + 1]) { + level++; + continue; + } + + slot = btrfs_header_nritems(c) - 1; + if (level == 0) + btrfs_item_key_to_cpu(c, &cur_key, slot); + else + btrfs_node_key_to_cpu(c, &cur_key, slot); + + orig_lowest = path->lowest_level; + btrfs_release_path(root, path); + path->lowest_level = level; + ret = btrfs_search_slot(NULL, root, &cur_key, path, + 0, 0); + path->lowest_level = orig_lowest; + if (ret < 0) + return ret; + + c = path->nodes[level]; + slot = path->slots[level]; + if (ret == 0) + slot++; + goto next; } + if (level == 0) btrfs_item_key_to_cpu(c, key, slot); else { diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 008397934778..e71264d1c2c9 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -670,6 +670,8 @@ again: err = ret; goto out; } + if (ret > 0 && path2->slots[level] > 0) + path2->slots[level]--; eb = path2->nodes[level]; WARN_ON(btrfs_node_blockptr(eb, path2->slots[level]) != @@ -1609,6 +1611,7 @@ static noinline_for_stack int merge_reloc_root(struct reloc_control *rc, BUG_ON(level == 0); path->lowest_level = level; ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0); + path->lowest_level = 0; if (ret < 0) { btrfs_free_path(path); return ret; -- 2.30.2