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authorJosef Bacik <josef@toxicpanda.com>2020-08-20 11:46:06 -0400
committerDavid Sterba <dsterba@suse.com>2020-10-07 12:12:16 +0200
commit4dff97e69005ea90266f3e3dda295264e854c15d (patch)
tree6f2cc1bb65ab472f6cec7106c7b3fa2c04277163 /fs
parentbf59a5a21604ef79da9105bef1bae817fd053e75 (diff)
btrfs: introduce BTRFS_NESTING_SPLIT for split blocks
If we are splitting a leaf/node, we could do something like the following lock(leaf) BTRFS_NESTING_NORMAL lock(left) BTRFS_NESTING_LEFT + BTRFS_NESTING_COW push from leaf -> left reset path to point to left split left allocate new block, lock block BTRFS_NESTING_SPLIT at the new block point we need to have a different nesting level, because we have already used either BTRFS_NESTING_LEFT or BTRFS_NESTING_RIGHT when pushing items from the original leaf into the adjacent leaves. Signed-off-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/ctree.c4
-rw-r--r--fs/btrfs/locking.h9
2 files changed, 11 insertions, 2 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index ecf8bf240d73..884c8b5a0e62 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -3537,7 +3537,7 @@ static noinline int split_node(struct btrfs_trans_handle *trans,
btrfs_node_key(c, &disk_key, mid);
split = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, level,
- c->start, 0, BTRFS_NESTING_NORMAL);
+ c->start, 0, BTRFS_NESTING_SPLIT);
if (IS_ERR(split))
return PTR_ERR(split);
@@ -4324,7 +4324,7 @@ again:
btrfs_item_key(l, &disk_key, mid);
right = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, 0,
- l->start, 0, BTRFS_NESTING_NORMAL);
+ l->start, 0, BTRFS_NESTING_SPLIT);
if (IS_ERR(right))
return PTR_ERR(right);
diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h
index 16563bc486c7..a6b59808e046 100644
--- a/fs/btrfs/locking.h
+++ b/fs/btrfs/locking.h
@@ -53,6 +53,15 @@ enum btrfs_lock_nesting {
BTRFS_NESTING_RIGHT_COW,
/*
+ * When splitting we may push nodes to the left or right, but still use
+ * the subsequent nodes in our path, keeping our locks on those adjacent
+ * blocks. Thus when we go to allocate a new split block we've already
+ * used up all of our available subclasses, so this subclass exists to
+ * handle this case where we need to allocate a new split block.
+ */
+ BTRFS_NESTING_SPLIT,
+
+ /*
* 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