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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfsutil
import (
"fmt"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfstree"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
"git.lukeshu.com/btrfs-progs-ng/lib/containers"
"git.lukeshu.com/btrfs-progs-ng/lib/diskio"
)
type skinnyItem struct {
Node btrfsvol.LogicalAddr
Item int
}
type SkinnyPath struct {
Root btrfsvol.LogicalAddr
Items []int
}
type SkinnyPathArena struct {
FS diskio.File[btrfsvol.LogicalAddr]
SB btrfstree.Superblock
fatRoots map[btrfsvol.LogicalAddr]btrfstree.TreePathElem
fatItems *containers.LRUCache[skinnyItem, btrfstree.TreePathElem]
}
func (a *SkinnyPathArena) init() {
if a.fatRoots == nil {
a.fatRoots = make(map[btrfsvol.LogicalAddr]btrfstree.TreePathElem)
// This cache size is sorta arbitrary. At first I figured
// "let's allow 1GB of cached items", and figured 67bytes per
// item, that's about 16M items. But with overhead of the
// LRUCache, it's actually a lot higher than that. So then I
// cut it to .5M, and that cut my total memory use to ~8GB,
// which is a good number for me. Then I tought it to do a
// better job of recovering trees, and so the memory grew, and I
// cut it to 64K. Then to 8K. Then grew it to 128K.
a.fatItems = containers.NewLRUCache[skinnyItem, btrfstree.TreePathElem](128 * 1024)
}
}
func (a *SkinnyPathArena) getItem(parent btrfstree.TreePath, itemIdx int) (btrfstree.TreePathElem, error) {
if itemIdx < 0 {
panic("should not happen")
}
a.init()
ret, ok := a.fatItems.Get(skinnyItem{
Node: parent.Node(-1).ToNodeAddr,
Item: itemIdx,
})
if ok {
return ret, nil
}
node, err := btrfstree.ReadNode(a.FS, a.SB, parent.Node(-1).ToNodeAddr, btrfstree.NodeExpectations{})
if err != nil {
return btrfstree.TreePathElem{}, err
}
if node.Data.Head.Level > 0 {
if itemIdx >= len(node.Data.BodyInternal) {
panic("should not happen")
}
for i, item := range node.Data.BodyInternal {
toMaxKey := parent.Node(-1).ToMaxKey
if i+1 < len(node.Data.BodyInternal) {
toMaxKey = node.Data.BodyInternal[i+1].Key.Mm()
}
elem := btrfstree.TreePathElem{
FromTree: node.Data.Head.Owner,
FromItemIdx: i,
ToNodeAddr: item.BlockPtr,
ToNodeGeneration: item.Generation,
ToNodeLevel: node.Data.Head.Level - 1,
ToKey: item.Key,
ToMaxKey: toMaxKey,
}
a.fatItems.Add(skinnyItem{Node: parent.Node(-1).ToNodeAddr, Item: i}, elem)
if i == itemIdx {
ret = elem
}
}
} else {
if itemIdx >= len(node.Data.BodyLeaf) {
panic("should not happen")
}
for i, item := range node.Data.BodyLeaf {
elem := btrfstree.TreePathElem{
FromTree: node.Data.Head.Owner,
FromItemIdx: i,
ToKey: item.Key,
ToMaxKey: item.Key,
}
a.fatItems.Add(skinnyItem{Node: parent.Node(-1).ToNodeAddr, Item: i}, elem)
if i == itemIdx {
ret = elem
}
}
}
return ret, nil
}
func (a *SkinnyPathArena) Deflate(fat btrfstree.TreePath) SkinnyPath {
a.init()
var ret SkinnyPath
var prevNode btrfsvol.LogicalAddr
for i, elem := range fat {
if i == 0 {
a.fatRoots[elem.ToNodeAddr] = elem
ret.Root = elem.ToNodeAddr
} else {
a.fatItems.Add(skinnyItem{Node: prevNode, Item: elem.FromItemIdx}, elem)
ret.Items = append(ret.Items, elem.FromItemIdx)
}
prevNode = elem.ToNodeAddr
}
return ret
}
func (a *SkinnyPathArena) Inflate(skinny SkinnyPath) btrfstree.TreePath {
a.init()
ret := make(btrfstree.TreePath, 0, 1+len(skinny.Items))
root, ok := a.fatRoots[skinny.Root]
if !ok {
panic(fmt.Errorf("SkinnyPathArena.Inflate: no stored TreePathElem for root->%v",
skinny.Root))
}
ret = append(ret, root)
for _, itemIdx := range skinny.Items {
elem, err := a.getItem(ret, itemIdx)
if err != nil {
panic(err)
}
ret = append(ret, elem)
}
return ret
}
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