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
|
/*
Copyright (c) 2013 Red Hat, Inc. <http://www.redhat.com>
This file is part of GlusterFS.
This file is licensed to you under your choice of the GNU Lesser
General Public License, version 3 or any later version (LGPLv3 or
later), or the GNU General Public License, version 2 (GPLv2), in all
cases as published by the Free Software Foundation.
*/
#include "afr.h"
#include "afr-transaction.h"
int
afr_read_txn_next_subvol (call_frame_t *frame, xlator_t *this)
{
afr_local_t *local = NULL;
afr_private_t *priv = NULL;
int i = 0;
int subvol = -1;
local = frame->local;
priv = this->private;
for (i = 0; i < priv->child_count; i++) {
if (!local->readable[i]) {
/* don't even bother trying here.
just mark as attempted and move on. */
local->read_attempted[i] = 1;
continue;
}
if (!local->read_attempted[i]) {
subvol = i;
break;
}
}
/* If no more subvols were available for reading, we leave
@subvol as -1, which is an indication we have run out of
readable subvols. */
if (subvol != -1)
local->read_attempted[subvol] = 1;
local->readfn (frame, this, subvol);
return 0;
}
#define AFR_READ_TXN_SET_ERROR_AND_GOTO(ret, errnum, index, label) \
do { \
local->op_ret = ret; \
local->op_errno = errnum; \
read_subvol = index; \
goto label; \
} while (0)
int
afr_read_txn_refresh_done (call_frame_t *frame, xlator_t *this, int err)
{
afr_local_t *local = NULL;
afr_private_t *priv = NULL;
int read_subvol = 0;
int event_generation = 0;
inode_t *inode = NULL;
int ret = -1;
int spb_choice = -1;
local = frame->local;
inode = local->inode;
priv = frame->this->private;
if (err)
AFR_READ_TXN_SET_ERROR_AND_GOTO (-1, -err, -1, readfn);
ret = afr_inode_read_subvol_type_get (inode, this, local->readable,
&event_generation,
local->transaction.type);
if (ret == -1 || !event_generation)
/* Even after refresh, we don't have a good
read subvolume. Time to bail */
AFR_READ_TXN_SET_ERROR_AND_GOTO (-1, EIO, -1, readfn);
/* For directories in split-brain, we need to allow all fops
* except (f)getxattr and access. */
if (!AFR_COUNT(local->readable, priv->child_count) &&
local->transaction.type == AFR_DATA_TRANSACTION &&
inode->ia_type == IA_IFDIR)
memcpy (local->readable, local->child_up, priv->child_count);
read_subvol = afr_read_subvol_select_by_policy (inode, this,
local->readable, NULL);
if (read_subvol == -1)
AFR_READ_TXN_SET_ERROR_AND_GOTO (-1, EIO, -1, readfn);
if (local->read_attempted[read_subvol]) {
afr_read_txn_next_subvol (frame, this);
return 0;
}
local->read_attempted[read_subvol] = 1;
readfn:
if (read_subvol == -1) {
ret = afr_inode_split_brain_choice_get (inode, this,
&spb_choice);
if ((ret == 0) && spb_choice >= 0)
read_subvol = spb_choice;
}
local->readfn (frame, this, read_subvol);
return 0;
}
int
afr_read_txn_continue (call_frame_t *frame, xlator_t *this, int subvol)
{
afr_local_t *local = NULL;
local = frame->local;
if (!local->refreshed) {
local->refreshed = _gf_true;
afr_inode_refresh (frame, this, local->inode,
afr_read_txn_refresh_done);
} else {
afr_read_txn_next_subvol (frame, this);
}
return 0;
}
/* afr_read_txn_wipe:
clean internal variables in @local in order to make
it possible to call afr_read_txn() multiple times from
the same frame
*/
void
afr_read_txn_wipe (call_frame_t *frame, xlator_t *this)
{
afr_local_t *local = NULL;
afr_private_t *priv = NULL;
int i = 0;
local = frame->local;
priv = this->private;
local->readfn = NULL;
if (local->inode)
inode_unref (local->inode);
for (i = 0; i < priv->child_count; i++) {
local->read_attempted[i] = 0;
local->readable[i] = 0;
}
}
/*
afr_read_txn:
This is the read transaction function. The way it works:
- Determine read-subvolume from inode ctx.
- If read-subvolume's generation was stale, refresh ctx once by
calling afr_inode_refresh()
Else make an attempt to read on read-subvolume.
- If attempted read on read-subvolume fails, refresh ctx once
by calling afr_inode_refresh()
- After ctx refresh, query read-subvolume freshly and attempt
read once.
- If read fails, try every other readable[] subvolume before
finally giving up. readable[] elements are set by afr_inode_refresh()
based on dirty and pending flags.
- If file is in split brain in the backend, generation will be
kept 0 by afr_inode_refresh() and readable[] will be set 0 for
all elements. Therefore reads always fail.
*/
int
afr_read_txn (call_frame_t *frame, xlator_t *this, inode_t *inode,
afr_read_txn_wind_t readfn, afr_transaction_type type)
{
afr_local_t *local = NULL;
afr_private_t *priv = NULL;
int read_subvol = -1;
int event_generation = 0;
int ret = -1;
priv = this->private;
local = frame->local;
afr_read_txn_wipe (frame, this);
local->readfn = readfn;
local->inode = inode_ref (inode);
if (priv->quorum_reads &&
priv->quorum_count && !afr_has_quorum (priv->child_up, this)) {
local->op_ret = -1;
local->op_errno = ENOTCONN;
read_subvol = -1;
goto read;
}
local->transaction.type = type;
ret = afr_inode_read_subvol_type_get (inode, this, local->readable,
&event_generation, type);
if (ret == -1)
/* very first transaction on this inode */
goto refresh;
gf_log (this->name, GF_LOG_DEBUG, "%s: generation now vs cached: %d, "
"%d", uuid_utoa (inode->gfid), local->event_generation,
event_generation);
if (local->event_generation != event_generation)
/* servers have disconnected / reconnected, and possibly
rebooted, very likely changing the state of freshness
of copies */
goto refresh;
read_subvol = afr_read_subvol_select_by_policy (inode, this,
local->readable, NULL);
if (read_subvol < 0 || read_subvol > priv->child_count) {
gf_msg (this->name, GF_LOG_WARNING, 0, AFR_MSG_SPLIT_BRAIN,
"Unreadable subvolume %d found with event generation "
"%d. (Possible split-brain)",
read_subvol, event_generation);
goto refresh;
}
if (!local->child_up[read_subvol]) {
/* should never happen, just in case */
gf_log (this->name, GF_LOG_WARNING, "subvolume %d is the "
"read subvolume in this generation, but is not up",
read_subvol);
goto refresh;
}
local->read_attempted[read_subvol] = 1;
read:
local->readfn (frame, this, read_subvol);
return 0;
refresh:
afr_inode_refresh (frame, this, inode, afr_read_txn_refresh_done);
return 0;
}
|
