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
|
package fusefrontend
import (
"fmt"
"log"
"sync"
"syscall"
"time"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
const (
// Number of entries in the dirCache. Three entries work well for two
// (probably also three) parallel tar extracts (hit rate around 92%).
dirCacheSize = 3
// Enable Lookup/Store/Clear debug messages
enableDebugMessages = false
// Enable hit rate statistics printing
enableStats = false
)
type dirCacheEntryStruct struct {
// relative plaintext path to the directory
dirRelPath string
// fd to the directory (opened with O_PATH!)
fd int
// content of gocryptfs.diriv in this directory
iv []byte
}
func (e *dirCacheEntryStruct) Clear() {
// An earlier clear may have already closed the fd, or the cache
// has never been filled (fd is 0 in that case).
if e.fd > 0 {
err := syscall.Close(e.fd)
if err != nil {
tlog.Warn.Printf("dirCache.Clear: Close failed: %v", err)
}
}
e.fd = -1
e.dirRelPath = ""
e.iv = nil
}
type dirCacheStruct struct {
sync.Mutex
// Cache entries
entries [dirCacheSize]dirCacheEntryStruct
// Where to store the next entry (index into entries)
nextIndex int
// On the first Lookup(), the expire thread is stared, and this flag is set
// to true.
expireThreadRunning bool
// Hit rate stats. Evaluated and reset by the expire thread.
lookups uint64
hits uint64
}
// Clear clears the cache contents.
func (d *dirCacheStruct) Clear() {
d.Lock()
defer d.Unlock()
for i := range d.entries {
d.entries[i].Clear()
}
}
// Store the entry in the cache. The passed "fd" will be Dup()ed, and the caller
// can close their copy at will.
func (d *dirCacheStruct) Store(dirRelPath string, fd int, iv []byte) {
if fd <= 0 || len(iv) != nametransform.DirIVLen {
log.Panicf("Store sanity check failed: fd=%d len=%d", fd, len(iv))
}
d.Lock()
defer d.Unlock()
e := &d.entries[d.nextIndex]
// Round-robin works well enough
d.nextIndex = (d.nextIndex + 1) % dirCacheSize
// Close the old fd
e.Clear()
fd2, err := syscall.Dup(fd)
if err != nil {
tlog.Warn.Printf("dirCache.Store: Dup failed: %v", err)
return
}
d.dbg("Store: %q %d %x\n", dirRelPath, fd2, iv)
e.fd = fd2
e.dirRelPath = dirRelPath
e.iv = iv
// expireThread is started on the first Lookup()
if !d.expireThreadRunning {
d.expireThreadRunning = true
go d.expireThread()
}
}
// Lookup checks if relPath is in the cache, and returns an (fd, iv) pair.
// It returns (-1, nil) if not found. The fd is internally Dup()ed and the
// caller must close it when done.
func (d *dirCacheStruct) Lookup(dirRelPath string) (fd int, iv []byte) {
d.Lock()
defer d.Unlock()
if enableStats {
d.lookups++
}
for i := range d.entries {
e := &d.entries[i]
if e.fd <= 0 {
// Cache slot is empty
continue
}
if dirRelPath != e.dirRelPath {
// Not the right path
continue
}
var err error
fd, err = syscall.Dup(e.fd)
if err != nil {
tlog.Warn.Printf("dirCache.Lookup: Dup failed: %v", err)
return -1, nil
}
iv = e.iv
}
if fd == 0 {
d.dbg("Lookup %q: miss\n", dirRelPath)
return -1, nil
}
if enableStats {
d.hits++
}
if fd <= 0 || len(iv) != nametransform.DirIVLen {
log.Panicf("Lookup sanity check failed: fd=%d len=%d", fd, len(iv))
}
d.dbg("Lookup %q: hit %d %x\n", dirRelPath, fd, iv)
return fd, iv
}
// expireThread is started on the first Lookup()
func (d *dirCacheStruct) expireThread() {
for {
time.Sleep(1 * time.Second)
d.Clear()
if enableStats {
d.Lock()
lookups := d.lookups
hits := d.hits
d.lookups = 0
d.hits = 0
d.Unlock()
if lookups > 0 {
fmt.Printf("dirCache: hits=%3d lookups=%3d, rate=%3d%%\n", hits, lookups, (hits*100)/lookups)
}
}
}
}
// dbg prints a debug message. Usually disabled.
func (d *dirCacheStruct) dbg(format string, a ...interface{}) {
if enableDebugMessages {
fmt.Printf(format, a...)
}
}
|
