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btrfs: use BTRFS_NESTED_NEW_ROOT for double splits

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I've made this change separate since it requires both of the newly added
NESTED flags and I didn't want to slip it into one of those changes.

If we do a double split of a node we can end up doing a
BTRFS_NESTED_SPLIT on level 0, which throws lockdep off because it
appears as a double lock.  Since we're maxed out on subclasses, use
BTRFS_NESTED_NEW_ROOT if we had to do a double split.  This is OK
because we won't have to do a double split if we had to insert a new
root, and the new root would be at a higher level anyway.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2020-08-20 11:46:08 -04:00 committed by David Sterba
parent cf6f34aa3a
commit ca9d473a3e
1 changed files with 11 additions and 1 deletions
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12
fs/btrfs/ctree.c
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@ -4324,8 +4324,18 @@ again:
else
btrfs_item_key(l, &disk_key, mid);
/*
* We have to about BTRFS_NESTING_NEW_ROOT here if we've done a double
* split, because we're only allowed to have MAX_LOCKDEP_SUBCLASSES
* subclasses, which is 8 at the time of this patch, and we've maxed it
* out. In the future we could add a
* BTRFS_NESTING_SPLIT_THE_SPLITTENING if we need to, but for now just
* use BTRFS_NESTING_NEW_ROOT.
*/
right = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, 0,
l->start, 0, BTRFS_NESTING_SPLIT);
l->start, 0, num_doubles ?
BTRFS_NESTING_NEW_ROOT :
BTRFS_NESTING_SPLIT);
if (IS_ERR(right))
return PTR_ERR(right);