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btrfs: qgroup: Introduce function to find all new tree blocks of reloc tree

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Introduce new function, qgroup_trace_new_subtree_blocks(), to iterate
all new tree blocks in a reloc tree.
So that qgroup could skip unrelated tree blocks during balance, which
should hugely speedup balance speed when quota is enabled.

The function qgroup_trace_new_subtree_blocks() itself only cares about
new tree blocks in reloc tree.

All its main works are:

1) Read out tree blocks according to parent pointers

2) Do recursive depth-first search
   Will call the same function on all its children tree blocks, with
   search level set to current level -1.
   And will also skip all children whose generation is smaller than
   @last_snapshot.

3) Call qgroup_trace_extent_swap() to trace tree blocks

So although we have parameter list related to source file tree, it's not
used at all, but only passed to qgroup_trace_extent_swap().
Thus despite the tree read code, the core should be pretty short and all
about recursive depth-first search.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2018-09-27 14:42:31 +08:00 committed by David Sterba
parent 25982561db
commit ea49f3e73c
1 changed files with 135 additions and 0 deletions
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135
fs/btrfs/qgroup.c
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@ -1874,6 +1874,141 @@ out:
return ret;
}
/*
* Helper function to do recursive generation-aware depth-first search, to
* locate all new tree blocks in a subtree of reloc tree.
*
* E.g. (OO = Old tree blocks, NN = New tree blocks, whose gen == last_snapshot)
* reloc tree
* L2 NN (a)
* / \
* L1 OO NN (b)
* / \ / \
* L0 OO OO OO NN
* (c) (d)
* If we pass:
* @dst_path = [ nodes[1] = NN(b), nodes[0] = NULL ],
* @cur_level = 1
* @root_level = 1
*
* We will iterate through tree blocks NN(b), NN(d) and info qgroup to trace
* above tree blocks along with their counter parts in file tree.
* While during search, old tree blocsk OO(c) will be skiped as tree block swap
* won't affect OO(c).
*/
static int qgroup_trace_new_subtree_blocks(struct btrfs_trans_handle* trans,
struct extent_buffer *src_eb,
struct btrfs_path *dst_path,
int cur_level, int root_level,
u64 last_snapshot)
{
struct btrfs_fs_info *fs_info = trans->fs_info;
struct extent_buffer *eb;
bool need_cleanup = false;
int ret = 0;
int i;
/* Level sanity check */
if (cur_level < 0 || cur_level >= BTRFS_MAX_LEVEL ||
root_level < 0 || root_level >= BTRFS_MAX_LEVEL ||
root_level < cur_level) {
btrfs_err_rl(fs_info,
"%s: bad levels, cur_level=%d root_level=%d",
__func__, cur_level, root_level);
return -EUCLEAN;
}
/* Read the tree block if needed */
if (dst_path->nodes[cur_level] == NULL) {
struct btrfs_key first_key;
int parent_slot;
u64 child_gen;
u64 child_bytenr;
/*
* dst_path->nodes[root_level] must be initialized before
* calling this function.
*/
if (cur_level == root_level) {
btrfs_err_rl(fs_info,
"%s: dst_path->nodes[%d] not initialized, root_level=%d cur_level=%d",
__func__, root_level, root_level, cur_level);
return -EUCLEAN;
}
/*
* We need to get child blockptr/gen from parent before we can
* read it.
*/
eb = dst_path->nodes[cur_level + 1];
parent_slot = dst_path->slots[cur_level + 1];
child_bytenr = btrfs_node_blockptr(eb, parent_slot);
child_gen = btrfs_node_ptr_generation(eb, parent_slot);
btrfs_node_key_to_cpu(eb, &first_key, parent_slot);
/* This node is old, no need to trace */
if (child_gen < last_snapshot)
goto out;
eb = read_tree_block(fs_info, child_bytenr, child_gen,
cur_level, &first_key);
if (IS_ERR(eb)) {
ret = PTR_ERR(eb);
goto out;
} else if (!extent_buffer_uptodate(eb)) {
free_extent_buffer(eb);
ret = -EIO;
goto out;
}
dst_path->nodes[cur_level] = eb;
dst_path->slots[cur_level] = 0;
btrfs_tree_read_lock(eb);
btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
dst_path->locks[cur_level] = BTRFS_READ_LOCK_BLOCKING;
need_cleanup = true;
}
/* Now record this tree block and its counter part for qgroups */
ret = qgroup_trace_extent_swap(trans, src_eb, dst_path, cur_level,
root_level);
if (ret < 0)
goto cleanup;
eb = dst_path->nodes[cur_level];
if (cur_level > 0) {
/* Iterate all child tree blocks */
for (i = 0; i < btrfs_header_nritems(eb); i++) {
/* Skip old tree blocks as they won't be swapped */
if (btrfs_node_ptr_generation(eb, i) < last_snapshot)
continue;
dst_path->slots[cur_level] = i;
/* Recursive call (at most 7 times) */
ret = qgroup_trace_new_subtree_blocks(trans, src_eb,
dst_path, cur_level - 1, root_level,
last_snapshot);
if (ret < 0)
goto cleanup;
}
}
cleanup:
if (need_cleanup) {
/* Clean up */
btrfs_tree_unlock_rw(dst_path->nodes[cur_level],
dst_path->locks[cur_level]);
free_extent_buffer(dst_path->nodes[cur_level]);
dst_path->nodes[cur_level] = NULL;
dst_path->slots[cur_level] = 0;
dst_path->locks[cur_level] = 0;
}
out:
return ret;
}
int btrfs_qgroup_trace_subtree(struct btrfs_trans_handle *trans,
struct extent_buffer *root_eb,
u64 root_gen, int root_level)