Repository navigation
Expand file tree
/
Copy pathfs-v1-rwpool.go
More file actions
227 lines (200 loc) · 6.14 KB
/
Copy pathfs-v1-rwpool.go
File metadata and controls
227 lines (200 loc) · 6.14 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
/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cmd
import (
"context"
"os"
pathutil "path"
"sync"
"github.com/minio/minio/cmd/logger"
"github.com/minio/minio/pkg/lock"
)
// fsIOPool represents a protected list to keep track of all
// the concurrent readers at a given path.
type fsIOPool struct {
sync.Mutex
readersMap map[string]*lock.RLockedFile
}
// lookupToRead - looks up an fd from readers map and
// returns read locked fd for caller to read from, if
// fd found increments the reference count. If the fd
// is found to be closed then purges it from the
// readersMap and returns nil instead.
//
// NOTE: this function is not protected and it is callers
// responsibility to lock this call to be thread safe. For
// implementation ideas look at the usage inside Open() call.
func (fsi *fsIOPool) lookupToRead(path string) (*lock.RLockedFile, bool) {
rlkFile, ok := fsi.readersMap[path]
// File reference exists on map, validate if its
// really closed and we are safe to purge it.
if ok && rlkFile != nil {
// If the file is closed and not removed from map is a bug.
if rlkFile.IsClosed() {
// Log this as an error.
reqInfo := (&logger.ReqInfo{}).AppendTags("path", path)
ctx := logger.SetReqInfo(context.Background(), reqInfo)
logger.LogIf(ctx, errUnexpected)
// Purge the cached lock path from map.
delete(fsi.readersMap, path)
// Indicate that we can populate the new fd.
ok = false
} else {
// Increment the lock ref, since the file is not closed yet
// and caller requested to read the file again.
rlkFile.IncLockRef()
}
}
return rlkFile, ok
}
// Open is a wrapper call to read locked file which
// returns a ReadAtCloser.
//
// ReaderAt is provided so that the fd is non seekable, since
// we are sharing fd's with concurrent threads, we don't want
// all readers to change offsets on each other during such
// concurrent operations. Using ReadAt allows us to read from
// any offsets.
//
// Closer is implemented to track total readers and to close
// only when there no more readers, the fd is purged if the lock
// count has reached zero.
func (fsi *fsIOPool) Open(path string) (*lock.RLockedFile, error) {
if err := checkPathLength(path); err != nil {
return nil, err
}
fsi.Lock()
rlkFile, ok := fsi.lookupToRead(path)
fsi.Unlock()
// Locked path reference doesn't exist, acquire a read lock again on the file.
if !ok {
// Open file for reading with read lock.
newRlkFile, err := lock.RLockedOpenFile(path)
if err != nil {
switch {
case os.IsNotExist(err):
return nil, errFileNotFound
case os.IsPermission(err):
return nil, errFileAccessDenied
case isSysErrIsDir(err):
return nil, errIsNotRegular
case isSysErrNotDir(err):
return nil, errFileAccessDenied
case isSysErrPathNotFound(err):
return nil, errFileNotFound
default:
return nil, err
}
}
/// Save new reader on the map.
// It is possible by this time due to concurrent
// i/o we might have another lock present. Lookup
// again to check for such a possibility. If no such
// file exists save the newly opened fd, if not
// reuse the existing fd and close the newly opened
// file
fsi.Lock()
rlkFile, ok = fsi.lookupToRead(path)
if ok {
// Close the new fd, since we already seem to have
// an active reference.
newRlkFile.Close()
} else {
// Save the new rlk file.
rlkFile = newRlkFile
}
// Save the new fd on the map.
fsi.readersMap[path] = rlkFile
fsi.Unlock()
}
// Success.
return rlkFile, nil
}
// Write - Attempt to lock the file if it exists,
// - if the file exists. Then we try to get a write lock this
// will block if we can't get a lock perhaps another write
// or read is in progress. Concurrent calls are protected
// by the global namspace lock within the same process.
func (fsi *fsIOPool) Write(path string) (wlk *lock.LockedFile, err error) {
if err = checkPathLength(path); err != nil {
return nil, err
}
wlk, err = lock.LockedOpenFile(path, os.O_RDWR, 0666)
if err != nil {
switch {
case os.IsNotExist(err):
return nil, errFileNotFound
case os.IsPermission(err):
return nil, errFileAccessDenied
case isSysErrIsDir(err):
return nil, errIsNotRegular
default:
return nil, err
}
}
return wlk, nil
}
// Create - creates a new write locked file instance.
// - if the file doesn't exist. We create the file and hold lock.
func (fsi *fsIOPool) Create(path string) (wlk *lock.LockedFile, err error) {
if err = checkPathLength(path); err != nil {
return nil, err
}
// Creates parent if missing.
if err = mkdirAll(pathutil.Dir(path), 0777); err != nil {
return nil, err
}
// Attempt to create the file.
wlk, err = lock.LockedOpenFile(path, os.O_RDWR|os.O_CREATE, 0666)
if err != nil {
switch {
case os.IsPermission(err):
return nil, errFileAccessDenied
case isSysErrIsDir(err):
return nil, errIsNotRegular
case isSysErrPathNotFound(err):
return nil, errFileAccessDenied
default:
return nil, err
}
}
// Success.
return wlk, nil
}
// Close implements closing the path referenced by the reader in such
// a way that it makes sure to remove entry from the map immediately
// if no active readers are present.
func (fsi *fsIOPool) Close(path string) error {
fsi.Lock()
defer fsi.Unlock()
if err := checkPathLength(path); err != nil {
return err
}
// Pop readers from path.
rlkFile, ok := fsi.readersMap[path]
if !ok {
return nil
}
// Close the reader.
rlkFile.Close()
// If the file is closed, remove it from the reader pool map.
if rlkFile.IsClosed() {
// Purge the cached lock path from map.
delete(fsi.readersMap, path)
}
// Success.
return nil
}