SIGSEGV from pathInode.GetAttr() on ESTALE

[charles-dyfis-net]

ENOSYS and EBADF are both handled in the pathfs GetAttr implementation, but the Linux-kernel NFS server can return ESTALE as well.

This would explain fi not being set, and causing a nil pointer exception on line 619 below:

go-fuse/fuse/pathfs/pathfs.go

Lines 606 to 619 in 509d146

	if file == nil || code == fuse.ENOSYS || code == fuse.EBADF {
	fi, code = n.fs.GetAttr(n.GetPath(), context)
	if !code.Ok() {
	return code
	}
	// This is a bug in the filesystem implementation, but let's not
	// crash.
	if fi == nil {
	log.Printf("Bug: fs.GetAttr returned OK with nil data")
	return fuse.EINVAL
	}
	}
	// Set inode number (unless already set or disabled).
	n.setClientInode(fi.Ino)

...as seen in the following stack trace (which is from 291273c; filed here, however, as the codepath appears to still be accessible in master):

github.com/hanwen/go-fuse/fuse/pathfs.(*pathInode).GetAttr(0xc421652660, 0xc421f00598, 0x7b16e0, 0x0, 0xc421f00618, 0xc4200b2360)
        /tmp/build/src/GO/src/github.com/hanwen/go-fuse/fuse/pathfs/pathfs.go:615 +0x9b
github.com/hanwen/go-fuse/fuse/nodefs.(*FileSystemConnector).internalLookup(0xc4241fc510, 0xc421f00598, 0xc421671f10, 0xc420a50060, 0x2b, 0xc421f00600, 0x60000000008, 0x8)
        /tmp/build/src/GO/src/github.com/hanwen/go-fuse/fuse/nodefs/fsops.go:89 +0x11d
github.com/hanwen/go-fuse/fuse/nodefs.(*rawBridge).Lookup(0xc4241fc510, 0xc421f00600, 0xc420a50060, 0x2b, 0xc421f00570, 0x0)
        /tmp/build/src/GO/src/github.com/hanwen/go-fuse/fuse/nodefs/fsops.go:104 +0xb7
github.com/hanwen/go-fuse/fuse.doLookup(0xc420138000, 0xc421f00480)
        /tmp/build/src/GO/src/github.com/hanwen/go-fuse/fuse/opcode.go:287 +0x86
github.com/hanwen/go-fuse/fuse.(*Server).handleRequest(0xc420138000, 0xc421f00480, 0xc421f00480)
        /tmp/build/src/GO/src/github.com/hanwen/go-fuse/fuse/server.go:404 +0x296
github.com/hanwen/go-fuse/fuse.(*Server).loop(0xc420138000, 0xc422217d01)
        /tmp/build/src/GO/src/github.com/hanwen/go-fuse/fuse/server.go:376 +0x162
created by github.com/hanwen/go-fuse/fuse.(*Server).readRequest
        /tmp/build/src/GO/src/github.com/hanwen/go-fuse/fuse/server.go:284 +0x2be