diff options
| author | Josef Bacik <josef@toxicpanda.com> | 2020-08-20 11:46:07 -0400 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2020-10-07 12:12:17 +0200 |
| commit | cf6f34aa3ada0be8c5f90fe93f48a75fea082c51 (patch) | |
| tree | eda9486b7532bda46f13e685536609de03b22592 | |
| parent | 4dff97e69005ea90266f3e3dda295264e854c15d (diff) | |
btrfs: introduce BTRFS_NESTING_NEW_ROOT for adding new roots
The way we add new roots is confusing from a locking perspective for
lockdep. We generally have the rule that we lock things in order from
highest level to lowest, but in the case of adding a new level to the
tree we actually allocate a new block for the root, which makes the
locking go in reverse. A similar issue exists for snapshotting, we cow
the original root for the root of a new tree, however they're at the
same level. Address this by using BTRFS_NESTING_NEW_ROOT for these
operations.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/ctree.c | 5 | ||||
| -rw-r--r-- | fs/btrfs/locking.h | 9 |
2 files changed, 12 insertions, 2 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 884c8b5a0e62..d61ea238ad8a 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -198,7 +198,8 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans, btrfs_node_key(buf, &disk_key, 0); cow = btrfs_alloc_tree_block(trans, root, 0, new_root_objectid, - &disk_key, level, buf->start, 0, BTRFS_NESTING_NORMAL); + &disk_key, level, buf->start, 0, + BTRFS_NESTING_NEW_ROOT); if (IS_ERR(cow)) return PTR_ERR(cow); @@ -3407,7 +3408,7 @@ static noinline int insert_new_root(struct btrfs_trans_handle *trans, c = alloc_tree_block_no_bg_flush(trans, root, 0, &lower_key, level, root->node->start, 0, - BTRFS_NESTING_NORMAL); + BTRFS_NESTING_NEW_ROOT); if (IS_ERR(c)) return PTR_ERR(c); diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h index a6b59808e046..3ea81ed3320b 100644 --- a/fs/btrfs/locking.h +++ b/fs/btrfs/locking.h @@ -62,6 +62,15 @@ enum btrfs_lock_nesting { BTRFS_NESTING_SPLIT, /* + * When promoting a new block to a root we need to have a special + * subclass so we don't confuse lockdep, as it will appear that we are + * locking a higher level node before a lower level one. Copying also + * has this problem as it appears we're locking the same block again + * when we make a snapshot of an existing root. + */ + BTRFS_NESTING_NEW_ROOT, + + /* * We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so * add this in here and add a static_assert to keep us from going over * the limit. As of this writing we're limited to 8, and we're |