ContractManager race condition

[ChrisSchinnerl]

I was debugging an NDF in skyd and ran into the following race condition while running commit 7df49efeb198ce8d27d7ac5a91ce1c4da9cf7311.

I haven't looked into it any further yet because it only happend once so far but there might be something wrong in managedAddPhysicalSector since we are calling defer sf.mu.RUnlock suggesting that we only have a read lock on the storage folder while calling setUsage.

WARNING: DATA RACE
Read at 0x00c000784090 by goroutine 225:
  go.sia.tech/siad/modules/host/contractmanager.(*ContractManager).StorageFolders()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/contractmanager/storagefolder.go:439 +0x45c
  go.sia.tech/siad/modules/host.(*Host).capacity()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/negotiatesettings.go:19 +0x6f
  go.sia.tech/siad/modules/host.(*Host).externalSettings()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/negotiatesettings.go:32 +0xf3
  go.sia.tech/siad/modules/host.(*Host).managedUpdatePriceTable()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/host.go:334 +0xfa
  go.sia.tech/siad/modules/host.(*Host).managedPriceTableForRenter()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/rpcupdatepricetable.go:96 +0x4a
  go.sia.tech/siad/modules/host.(*Host).managedRPCUpdatePriceTable()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/rpcupdatepricetable.go:115 +0x64
  go.sia.tech/siad/modules/host.(*Host).threadedHandleStream()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/network.go:415 +0x19a7
  go.sia.tech/siad/modules/host.(*Host).threadedHandleStream-fm()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/network.go:349 +0x4d
  gitlab.com/NebulousLabs/siamux.(*Handler).threadedHandleNext()
      /Users/cschinnerl/go/pkg/mod/gitlab.com/!nebulous!labs/siamux@v0.0.0-20210824082138-a4ebafe4b9d9/listener.go:82 +0x4a3
  gitlab.com/NebulousLabs/siamux.(*SiaMux).threadedAccept.func2()
      /Users/cschinnerl/go/pkg/mod/gitlab.com/!nebulous!labs/siamux@v0.0.0-20210824082138-a4ebafe4b9d9/listener.go:280 +0x85

Previous write at 0x00c000784090 by goroutine 87:
  go.sia.tech/siad/modules/host/contractmanager.(*storageFolder).setUsage()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/contractmanager/storagefolder.go:276 +0x317
  go.sia.tech/siad/modules/host/contractmanager.(*writeAheadLog).managedAddPhysicalSector.func1()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/contractmanager/sectorupdate.go:93 +0x260
  go.sia.tech/siad/modules/host/contractmanager.(*writeAheadLog).managedAddPhysicalSector()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/contractmanager/sectorupdate.go:148 +0x31e
  go.sia.tech/siad/modules/host/contractmanager.(*ContractManager).AddSector()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/contractmanager/sectorupdate.go:460 +0x484
  go.sia.tech/siad/modules/host.(*Host).managedModifyStorageObligation()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/storageobligations.go:889 +0xa71
  go.sia.tech/siad/modules/host.(*Host).managedRPCLoopWrite()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/newrpc.go:389 +0x4b44
  go.sia.tech/siad/modules/host.(*Host).managedRPCLoopWrite-fm()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/newrpc.go:162 +0x44
  go.sia.tech/siad/modules/host.(*Host).managedRPCLoop()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/rpcloop.go:145 +0x1875
  go.sia.tech/siad/modules/host.(*Host).threadedHandleConn()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/network.go:321 +0x23ba
  go.sia.tech/siad/modules/host.(*Host).threadedListen·dwrap·63()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/network.go:452 +0x58

Goroutine 225 (running) created at:
  gitlab.com/NebulousLabs/siamux.(*SiaMux).threadedAccept()
      /Users/cschinnerl/go/pkg/mod/gitlab.com/!nebulous!labs/siamux@v0.0.0-20210824082138-a4ebafe4b9d9/listener.go:278 +0x804
  gitlab.com/NebulousLabs/siamux.(*SiaMux).managedUpgradeConn.func3()
      /Users/cschinnerl/go/pkg/mod/gitlab.com/!nebulous!labs/siamux@v0.0.0-20210824082138-a4ebafe4b9d9/siamux.go:608 +0x3e

Goroutine 87 (running) created at:
  go.sia.tech/siad/modules/host.(*Host).threadedListen()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/network.go:452 +0x284
  go.sia.tech/siad/modules/host.(*Host).initNetworking·dwrap·54()
      /Users/cschinnerl/go/src/github.com/ChrisSchinnerl/siad/modules/host/network.go:246 +0x47
==================