diff options
Diffstat (limited to 'fs/btrfs/ctree.c')
-rw-r--r-- | fs/btrfs/ctree.c | 98 |
1 files changed, 74 insertions, 24 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 95a6a63caf04..899f85445925 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -1566,32 +1566,13 @@ static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root, struct btrfs_path *p, int write_lock_level) { - struct btrfs_fs_info *fs_info = root->fs_info; struct extent_buffer *b; int root_lock = 0; int level = 0; if (p->search_commit_root) { - /* - * The commit roots are read only so we always do read locks, - * and we always must hold the commit_root_sem when doing - * searches on them, the only exception is send where we don't - * want to block transaction commits for a long time, so - * we need to clone the commit root in order to avoid races - * with transaction commits that create a snapshot of one of - * the roots used by a send operation. - */ - if (p->need_commit_sem) { - down_read(&fs_info->commit_root_sem); - b = btrfs_clone_extent_buffer(root->commit_root); - up_read(&fs_info->commit_root_sem); - if (!b) - return ERR_PTR(-ENOMEM); - - } else { - b = root->commit_root; - atomic_inc(&b->refs); - } + b = root->commit_root; + atomic_inc(&b->refs); level = btrfs_header_level(b); /* * Ensure that all callers have set skip_locking when @@ -1657,6 +1638,42 @@ out: return b; } +/* + * Replace the extent buffer at the lowest level of the path with a cloned + * version. The purpose is to be able to use it safely, after releasing the + * commit root semaphore, even if relocation is happening in parallel, the + * transaction used for relocation is committed and the extent buffer is + * reallocated in the next transaction. + * + * This is used in a context where the caller does not prevent transaction + * commits from happening, either by holding a transaction handle or holding + * some lock, while it's doing searches through a commit root. + * At the moment it's only used for send operations. + */ +static int finish_need_commit_sem_search(struct btrfs_path *path) +{ + const int i = path->lowest_level; + const int slot = path->slots[i]; + struct extent_buffer *lowest = path->nodes[i]; + struct extent_buffer *clone; + + ASSERT(path->need_commit_sem); + + if (!lowest) + return 0; + + lockdep_assert_held_read(&lowest->fs_info->commit_root_sem); + + clone = btrfs_clone_extent_buffer(lowest); + if (!clone) + return -ENOMEM; + + btrfs_release_path(path); + path->nodes[i] = clone; + path->slots[i] = slot; + + return 0; +} /* * btrfs_search_slot - look for a key in a tree and perform necessary @@ -1693,6 +1710,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, const struct btrfs_key *key, struct btrfs_path *p, int ins_len, int cow) { + struct btrfs_fs_info *fs_info = root->fs_info; struct extent_buffer *b; int slot; int ret; @@ -1734,6 +1752,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root, min_write_lock_level = write_lock_level; + if (p->need_commit_sem) { + ASSERT(p->search_commit_root); + down_read(&fs_info->commit_root_sem); + } + again: prev_cmp = -1; b = btrfs_search_slot_get_root(root, p, write_lock_level); @@ -1928,6 +1951,16 @@ cow_done: done: if (ret < 0 && !p->skip_release_on_error) btrfs_release_path(p); + + if (p->need_commit_sem) { + int ret2; + + ret2 = finish_need_commit_sem_search(p); + up_read(&fs_info->commit_root_sem); + if (ret2) + ret = ret2; + } + return ret; } ALLOW_ERROR_INJECTION(btrfs_search_slot, ERRNO); @@ -4396,7 +4429,9 @@ int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path, int level; struct extent_buffer *c; struct extent_buffer *next; + struct btrfs_fs_info *fs_info = root->fs_info; struct btrfs_key key; + bool need_commit_sem = false; u32 nritems; int ret; int i; @@ -4413,14 +4448,20 @@ again: path->keep_locks = 1; - if (time_seq) + if (time_seq) { ret = btrfs_search_old_slot(root, &key, path, time_seq); - else + } else { + if (path->need_commit_sem) { + path->need_commit_sem = 0; + need_commit_sem = true; + down_read(&fs_info->commit_root_sem); + } ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + } path->keep_locks = 0; if (ret < 0) - return ret; + goto done; nritems = btrfs_header_nritems(path->nodes[0]); /* @@ -4543,6 +4584,15 @@ again: ret = 0; done: unlock_up(path, 0, 1, 0, NULL); + if (need_commit_sem) { + int ret2; + + path->need_commit_sem = 1; + ret2 = finish_need_commit_sem_search(path); + up_read(&fs_info->commit_root_sem); + if (ret2) + ret = ret2; + } return ret; } |