diff options
| -rw-r--r-- | fs/btrfs/ctree.c | 39 | ||||
| -rw-r--r-- | fs/btrfs/ctree.h | 2 | ||||
| -rw-r--r-- | fs/btrfs/locking.c | 25 | ||||
| -rw-r--r-- | fs/btrfs/locking.h | 1 |
4 files changed, 64 insertions, 3 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index ebfa35fe1c38..84548b4074f7 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -1447,6 +1447,11 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p, return 0; } + if (p->nowait) { + free_extent_buffer(tmp); + return -EAGAIN; + } + if (unlock_up) btrfs_unlock_up_safe(p, level + 1); @@ -1467,6 +1472,8 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p, ret = -EAGAIN; goto out; + } else if (p->nowait) { + return -EAGAIN; } if (unlock_up) { @@ -1634,7 +1641,13 @@ static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root, * We don't know the level of the root node until we actually * have it read locked */ - b = btrfs_read_lock_root_node(root); + if (p->nowait) { + b = btrfs_try_read_lock_root_node(root); + if (IS_ERR(b)) + return b; + } else { + b = btrfs_read_lock_root_node(root); + } level = btrfs_header_level(b); if (level > write_lock_level) goto out; @@ -1910,6 +1923,13 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, WARN_ON(p->nodes[0] != NULL); BUG_ON(!cow && ins_len); + /* + * For now only allow nowait for read only operations. There's no + * strict reason why we can't, we just only need it for reads so it's + * only implemented for reads. + */ + ASSERT(!p->nowait || !cow); + if (ins_len < 0) { lowest_unlock = 2; @@ -1936,7 +1956,12 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, if (p->need_commit_sem) { ASSERT(p->search_commit_root); - down_read(&fs_info->commit_root_sem); + if (p->nowait) { + if (!down_read_trylock(&fs_info->commit_root_sem)) + return -EAGAIN; + } else { + down_read(&fs_info->commit_root_sem); + } } again: @@ -2082,7 +2107,15 @@ cow_done: btrfs_tree_lock(b); p->locks[level] = BTRFS_WRITE_LOCK; } else { - btrfs_tree_read_lock(b); + if (p->nowait) { + if (!btrfs_try_tree_read_lock(b)) { + free_extent_buffer(b); + ret = -EAGAIN; + goto done; + } + } else { + btrfs_tree_read_lock(b); + } p->locks[level] = BTRFS_READ_LOCK; } p->nodes[level] = b; diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 38c4c4fa2762..17af7e317e8e 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -443,6 +443,8 @@ struct btrfs_path { * header (ie. sizeof(struct btrfs_item) is not included). */ unsigned int search_for_extension:1; + /* Stop search if any locks need to be taken (for read) */ + unsigned int nowait:1; }; struct btrfs_dev_replace { diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c index 9063072b399b..0eab3cb274a1 100644 --- a/fs/btrfs/locking.c +++ b/fs/btrfs/locking.c @@ -286,6 +286,31 @@ struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root) } /* + * Loop around taking references on and locking the root node of the tree in + * nowait mode until we end up with a lock on the root node or returning to + * avoid blocking. + * + * Return: root extent buffer with read lock held or -EAGAIN. + */ +struct extent_buffer *btrfs_try_read_lock_root_node(struct btrfs_root *root) +{ + struct extent_buffer *eb; + + while (1) { + eb = btrfs_root_node(root); + if (!btrfs_try_tree_read_lock(eb)) { + free_extent_buffer(eb); + return ERR_PTR(-EAGAIN); + } + if (eb == root->node) + break; + btrfs_tree_read_unlock(eb); + free_extent_buffer(eb); + } + return eb; +} + +/* * DREW locks * ========== * diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h index ab268be09bb5..490c7a79e995 100644 --- a/fs/btrfs/locking.h +++ b/fs/btrfs/locking.h @@ -94,6 +94,7 @@ int btrfs_try_tree_read_lock(struct extent_buffer *eb); int btrfs_try_tree_write_lock(struct extent_buffer *eb); struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root); struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root); +struct extent_buffer *btrfs_try_read_lock_root_node(struct btrfs_root *root); #ifdef CONFIG_BTRFS_DEBUG static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb) |