fsconnector.go 9.74 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416
package fuse

// This file contains the internal logic of the
// FileSystemConnector. The functions for satisfying the raw interface
// are in fsops.go

import (
	"log"
	"path/filepath"
	"strings"
	"sync/atomic"
	"time"
	"unsafe"

	"github.com/hanwen/go-fuse/raw"
)

// Tests should set to true.
var paranoia = false

// FilesystemConnector is a raw FUSE filesystem that manages
// in-process mounts and inodes.  Its job is twofold:
//
// * It translates between the raw kernel interface (padded structs of
// int32 and int64) and the more abstract Go-ish NodeFileSystem
// interface.
//
// * It manages mounting and unmounting of NodeFileSystems into the
// directory hierarchy
//
// To achieve this, the connector only needs a pointer to the root
// node.
type FileSystemConnector struct {
	DefaultRawFileSystem

	Debug bool

	// Callbacks for talking back to the kernel.
	fsInit RawFsInit

	nodeFs NodeFileSystem

	// Translate between uint64 handles and *Inode.
	inodeMap HandleMap

	// The root of the FUSE file system.
	rootNode *Inode

	// Used as the generation inodes.
	generation uint64
}

func NewFileSystemOptions() *FileSystemOptions {
	return &FileSystemOptions{
		NegativeTimeout: 0,
		AttrTimeout:     time.Second,
		EntryTimeout:    time.Second,
		Owner:           CurrentOwner(),
	}
}

func NewFileSystemConnector(nodeFs NodeFileSystem, opts *FileSystemOptions) (c *FileSystemConnector) {
	c = new(FileSystemConnector)
	if opts == nil {
		opts = NewFileSystemOptions()
	}
	c.nodeFs = nodeFs
	c.inodeMap = NewHandleMap(opts.PortableInodes)
	c.rootNode = newInode(true, nodeFs.Root())

	// Make sure we don't reuse generation numbers.
	c.generation = uint64(time.Now().UnixNano())

	c.verify()
	c.MountRoot(nodeFs, opts)

	// FUSE does not issue a LOOKUP for 1 (obviously), but it does
	// issue a forget.  This lookupUpdate is to make the counts match.
	c.lookupUpdate(c.rootNode)

	return c
}

func (c *FileSystemConnector) nextGeneration() uint64 {
	return atomic.AddUint64(&c.generation, 1)
}

// This verifies invariants of the data structure.  This routine
// acquires tree locks as it walks the inode tree.
func (c *FileSystemConnector) verify() {
	if !paranoia {
		return
	}
	root := c.rootNode
	root.verify(c.rootNode.mountPoint)
}

// Generate EntryOut and increase the lookup count for an inode.
func (c *FileSystemConnector) childLookup(out *raw.EntryOut, fsi FsNode) {
	n := fsi.Inode()
	fsi.GetAttr((*Attr)(&out.Attr), nil, nil)
	n.mount.fillEntry(out)
	out.Ino = c.lookupUpdate(n)
	out.NodeId = out.Ino
	if out.Nlink == 0 {
		// With Nlink == 0, newer kernels will refuse link
		// operations.
		out.Nlink = 1
	}
}

func (c *FileSystemConnector) toInode(nodeid uint64) *Inode {
	if nodeid == raw.FUSE_ROOT_ID {
		return c.rootNode
	}
	i := (*Inode)(unsafe.Pointer(c.inodeMap.Decode(nodeid)))
	return i
}

// Must run outside treeLock.  Returns the nodeId.
func (c *FileSystemConnector) lookupUpdate(node *Inode) (id uint64) {
	id = c.inodeMap.Register(&node.handled)
	c.verify()
	return id
}

// Must run outside treeLock.
func (c *FileSystemConnector) forgetUpdate(nodeID uint64, forgetCount int) {
	if nodeID == raw.FUSE_ROOT_ID {
		c.nodeFs.OnUnmount()
		
		// We never got a lookup for root, so don't try to
		// forget root.
		return
	}

	if forgotten, handled := c.inodeMap.Forget(nodeID, forgetCount); forgotten {
		node := (*Inode)(unsafe.Pointer(handled))
		node.mount.treeLock.Lock()
		c.recursiveConsiderDropInode(node)
		node.mount.treeLock.Unlock()
	}
	// TODO - try to drop children even forget was not successful.
	c.verify()
}

// InodeCount returns the number of inodes registered with the kernel.
func (c *FileSystemConnector) InodeHandleCount() int {
	return c.inodeMap.Count()
}

// Must hold treeLock.

func (c *FileSystemConnector) recursiveConsiderDropInode(n *Inode) (drop bool) {
	delChildren := []string{}
	for k, v := range n.children {
		// Only consider children from the same mount, or
		// already unmounted mountpoints.
		if v.mountPoint == nil && c.recursiveConsiderDropInode(v) {
			delChildren = append(delChildren, k)
		}
	}
	for _, k := range delChildren {
		ch := n.rmChild(k)
		if ch == nil {
			log.Panicf("trying to del child %q, but not present", k)
		}
		ch.fsInode.OnForget()
	}

	if len(n.children) > 0 || !n.FsNode().Deletable() {
		return false
	}
	if n == c.rootNode || n.mountPoint != nil {
		return false
	}

	n.openFilesMutex.Lock()
	ok := len(n.openFiles) == 0
	n.openFilesMutex.Unlock()

	return ok
}

// Finds a node within the currently known inodes, returns the last
// known node and the remaining unknown path components.  If parent is
// nil, start from FUSE mountpoint.
func (c *FileSystemConnector) Node(parent *Inode, fullPath string) (*Inode, []string) {
	if parent == nil {
		parent = c.rootNode
	}
	if fullPath == "" {
		return parent, nil
	}

	sep := string(filepath.Separator)
	fullPath = strings.TrimLeft(filepath.Clean(fullPath), sep)
	comps := strings.Split(fullPath, sep)

	node := parent
	if node.mountPoint == nil {
		node.mount.treeLock.RLock()
		defer node.mount.treeLock.RUnlock()
	}

	for i, component := range comps {
		if len(component) == 0 {
			continue
		}

		if node.mountPoint != nil {
			node.mount.treeLock.RLock()
			defer node.mount.treeLock.RUnlock()
		}

		next := node.children[component]
		if next == nil {
			return node, comps[i:]
		}
		node = next
	}

	return node, nil
}

func (c *FileSystemConnector) LookupNode(parent *Inode, path string) *Inode {
	if path == "" {
		return parent
	}
	components := strings.Split(path, "/")
	for _, r := range components {
		var a Attr
		child, _ := c.internalLookup(&a, parent, r, nil)
		if child == nil {
			return nil
		}

		parent = child
	}

	return parent
}

////////////////////////////////////////////////////////////////

func (c *FileSystemConnector) MountRoot(nodeFs NodeFileSystem, opts *FileSystemOptions) {
	c.rootNode.mountFs(nodeFs, opts)
	c.rootNode.mount.connector = c
	nodeFs.OnMount(c)
	c.verify()
}

// Mount() generates a synthetic directory node, and mounts the file
// system there.  If opts is nil, the mount options of the root file
// system are inherited.  The encompassing filesystem should pretend
// the mount point does not exist.  If it does, it will generate an
// Inode with the same, which will cause Mount() to return EBUSY.
//
// Return values:
//
// ENOENT: the directory containing the mount point does not exist.
//
// EBUSY: the intended mount point already exists.
func (c *FileSystemConnector) Mount(parent *Inode, name string, nodeFs NodeFileSystem, opts *FileSystemOptions) Status {
	defer c.verify()
	parent.mount.treeLock.Lock()
	defer parent.mount.treeLock.Unlock()
	node := parent.children[name]
	if node != nil {
		return EBUSY
	}

	node = newInode(true, nodeFs.Root())
	if opts == nil {
		opts = c.rootNode.mountPoint.options
	}

	node.mountFs(nodeFs, opts)
	node.mount.connector = c
	parent.addChild(name, node)

	node.mountPoint.parentInode = parent
	if c.Debug {
		log.Println("Mount: ", nodeFs, "on subdir", name,
			"parent", c.inodeMap.Handle(&parent.handled))
	}
	nodeFs.OnMount(c)
	return OK
}

// Unmount() tries to unmount the given inode.
//
// Returns the following error codes:
//
// EINVAL: path does not exist, or is not a mount point.
//
// EBUSY: there are open files, or submounts below this node.
func (c *FileSystemConnector) Unmount(node *Inode) Status {
	// TODO - racy.
	if node.mountPoint == nil {
		log.Println("not a mountpoint:", c.inodeMap.Handle(&node.handled))
		return EINVAL
	}

	nodeId := c.inodeMap.Handle(&node.handled)

	// Must lock parent to update tree structure.
	parentNode := node.mountPoint.parentInode
	parentNode.mount.treeLock.Lock()
	defer parentNode.mount.treeLock.Unlock()

	mount := node.mountPoint
	name := node.mountPoint.mountName()
	if mount.openFiles.Count() > 0 {
		return EBUSY
	}

	node.mount.treeLock.Lock()
	defer node.mount.treeLock.Unlock()

	if mount.mountInode != node {
		log.Panicf("got two different mount inodes %v vs %v",
			c.inodeMap.Handle(&mount.mountInode.handled),
			c.inodeMap.Handle(&node.handled))
	}

	if !node.canUnmount() {
		return EBUSY
	}

	delete(parentNode.children, name)
	mount.fs.OnUnmount()

	parentId := c.inodeMap.Handle(&parentNode.handled)
	if parentNode == c.rootNode {
		// TODO - test coverage. Currently covered by zipfs/multizip_test.go
		parentId = raw.FUSE_ROOT_ID
	}

	// We have to wait until the kernel has forgotten the
	// mountpoint, so the write to node.mountPoint is no longer
	// racy.
	code := c.fsInit.DeleteNotify(parentId, c.inodeMap.Handle(&node.handled), name)
	if code.Ok() {
		mount.treeLock.Unlock()
		parentNode.mount.treeLock.Unlock()
		delay := 100 * time.Microsecond
		for {
			// This operation is rare, so we kludge it to avoid
			// contention.
			time.Sleep(delay)
			delay = delay*2 + 1
			if !c.inodeMap.Has(nodeId) {
				break
			}
		}
		parentNode.mount.treeLock.Lock()
		mount.treeLock.Lock()
	}

	mount.mountInode = nil
	node.mountPoint = nil

	return OK
}

func (c *FileSystemConnector) FileNotify(node *Inode, off int64, length int64) Status {
	var nId uint64
	if node == c.rootNode {
		nId = raw.FUSE_ROOT_ID
	} else {
		nId = c.inodeMap.Handle(&node.handled)
	}

	if nId == 0 {
		return OK
	}
	out := raw.NotifyInvalInodeOut{
		Length: length,
		Off:    off,
		Ino:    nId,
	}
	return c.fsInit.InodeNotify(&out)
}

func (c *FileSystemConnector) EntryNotify(node *Inode, name string) Status {
	var nId uint64
	if node == c.rootNode {
		nId = raw.FUSE_ROOT_ID
	} else {
		nId = c.inodeMap.Handle(&node.handled)
	}

	if nId == 0 {
		return OK
	}
	return c.fsInit.EntryNotify(nId, name)
}

func (c *FileSystemConnector) DeleteNotify(dir *Inode, child *Inode, name string) Status {
	var nId uint64

	if dir == c.rootNode {
		nId = raw.FUSE_ROOT_ID
	} else {
		nId = c.inodeMap.Handle(&dir.handled)
	}

	if nId == 0 {
		return OK
	}

	chId := c.inodeMap.Handle(&child.handled)

	return c.fsInit.DeleteNotify(nId, chId, name)
}