Btrfs: fix locking on ROOT_REPLACE operations in tree mod log

To resolve backrefs, ROOT_REPLACE operations in the tree mod log are
required to be tied to at least one KEY_REMOVE_WHILE_FREEING operation.
Therefore, those operations must be enclosed by tree_mod_log_write_lock()
and tree_mod_log_write_unlock() calls.

Those calls are private to the tree_mod_log_* functions, which means that
removal of the elements of an old root node must be logged from
tree_mod_log_insert_root. This partly reverts and corrects commit ba1bfbd5
(Btrfs: fix a tree mod logging issue for root replacement operations).

This fixes the brand-new version of xfstest 276 as of commit cfe73f71.

Cc: stable@vger.kernel.org
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index ecd25a1..ca9d8f1 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -651,6 +651,8 @@ tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
        if (tree_mod_dont_log(fs_info, NULL))
                return 0;
 
+       __tree_mod_log_free_eb(fs_info, old_root);
+
        ret = tree_mod_alloc(fs_info, flags, &tm);
        if (ret < 0)
                goto out;
@@ -736,7 +738,7 @@ tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq)
 static noinline void
 tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
                     struct extent_buffer *src, unsigned long dst_offset,
-                    unsigned long src_offset, int nr_items)
+                    unsigned long src_offset, int nr_items, int log_removal)
 {
        int ret;
        int i;
@@ -750,10 +752,12 @@ tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
        }
 
        for (i = 0; i < nr_items; i++) {
-               ret = tree_mod_log_insert_key_locked(fs_info, src,
-                                                    i + src_offset,
-                                                    MOD_LOG_KEY_REMOVE);
-               BUG_ON(ret < 0);
+               if (log_removal) {
+                       ret = tree_mod_log_insert_key_locked(fs_info, src,
+                                                       i + src_offset,
+                                                       MOD_LOG_KEY_REMOVE);
+                       BUG_ON(ret < 0);
+               }
                ret = tree_mod_log_insert_key_locked(fs_info, dst,
                                                     i + dst_offset,
                                                     MOD_LOG_KEY_ADD);
@@ -927,7 +931,6 @@ static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
                        ret = btrfs_dec_ref(trans, root, buf, 1, 1);
                        BUG_ON(ret); /* -ENOMEM */
                }
-               tree_mod_log_free_eb(root->fs_info, buf);
                clean_tree_block(trans, root, buf);
                *last_ref = 1;
        }
@@ -1046,6 +1049,7 @@ static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
                btrfs_set_node_ptr_generation(parent, parent_slot,
                                              trans->transid);
                btrfs_mark_buffer_dirty(parent);
+               tree_mod_log_free_eb(root->fs_info, buf);
                btrfs_free_tree_block(trans, root, buf, parent_start,
                                      last_ref);
        }
@@ -1750,7 +1754,6 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
                        goto enospc;
                }
 
-               tree_mod_log_free_eb(root->fs_info, root->node);
                tree_mod_log_set_root_pointer(root, child);
                rcu_assign_pointer(root->node, child);
 
@@ -2995,7 +2998,7 @@ static int push_node_left(struct btrfs_trans_handle *trans,
                push_items = min(src_nritems - 8, push_items);
 
        tree_mod_log_eb_copy(root->fs_info, dst, src, dst_nritems, 0,
-                            push_items);
+                            push_items, 1);
        copy_extent_buffer(dst, src,
                           btrfs_node_key_ptr_offset(dst_nritems),
                           btrfs_node_key_ptr_offset(0),
@@ -3066,7 +3069,7 @@ static int balance_node_right(struct btrfs_trans_handle *trans,
                                      sizeof(struct btrfs_key_ptr));
 
        tree_mod_log_eb_copy(root->fs_info, dst, src, 0,
-                            src_nritems - push_items, push_items);
+                            src_nritems - push_items, push_items, 1);
        copy_extent_buffer(dst, src,
                           btrfs_node_key_ptr_offset(0),
                           btrfs_node_key_ptr_offset(src_nritems - push_items),
@@ -3218,12 +3221,18 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
        int mid;
        int ret;
        u32 c_nritems;
+       int tree_mod_log_removal = 1;
 
        c = path->nodes[level];
        WARN_ON(btrfs_header_generation(c) != trans->transid);
        if (c == root->node) {
                /* trying to split the root, lets make a new one */
                ret = insert_new_root(trans, root, path, level + 1);
+               /*
+                * removal of root nodes has been logged by
+                * tree_mod_log_set_root_pointer due to locking
+                */
+               tree_mod_log_removal = 0;
                if (ret)
                        return ret;
        } else {
@@ -3261,7 +3270,8 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
                            (unsigned long)btrfs_header_chunk_tree_uuid(split),
                            BTRFS_UUID_SIZE);
 
-       tree_mod_log_eb_copy(root->fs_info, split, c, 0, mid, c_nritems - mid);
+       tree_mod_log_eb_copy(root->fs_info, split, c, 0, mid, c_nritems - mid,
+                            tree_mod_log_removal);
        copy_extent_buffer(split, c,
                           btrfs_node_key_ptr_offset(0),
                           btrfs_node_key_ptr_offset(mid),