blob: 9d834aa4b9795264d87eef283c2492a99d67597b (
plain) (
blame)
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
|
/*
* mm/pdflush.c - worker threads for writing back filesystem data
*
* Copyright (C) 2002, Linus Torvalds.
*
* 09Apr2002 akpm@zip.com.au
* Initial version
* 29Feb2004 kaos@sgi.com
* Move worker thread creation to kthread to avoid chewing
* up stack space with nested calls to kernel_thread.
*/
#include <linux/sched.h>
#include <linux/list.h>
#include <linux/signal.h>
#include <linux/spinlock.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h> /* Needed by writeback.h */
#include <linux/writeback.h> /* Prototypes pdflush_operation() */
#include <linux/kthread.h>
#include <linux/cpuset.h>
#include <linux/freezer.h>
/*
* Minimum and maximum number of pdflush instances
*/
#define MIN_PDFLUSH_THREADS 2
#define MAX_PDFLUSH_THREADS 8
static void start_one_pdflush_thread(void);
/*
* The pdflush threads are worker threads for writing back dirty data.
* Ideally, we'd like one thread per active disk spindle. But the disk
* topology is very hard to divine at this level. Instead, we take
* care in various places to prevent more than one pdflush thread from
* performing writeback against a single filesystem. pdflush threads
* have the PF_FLUSHER flag set in current->flags to aid in this.
*/
/*
* All the pdflush threads. Protected by pdflush_lock
*/
static LIST_HEAD(pdflush_list);
static DEFINE_SPINLOCK(pdflush_lock);
/*
* The count of currently-running pdflush threads. Protected
* by pdflush_lock.
*
* Readable by sysctl, but not writable. Published to userspace at
* /proc/sys/vm/nr_pdflush_threads.
*/
int nr_pdflush_threads = 0;
/*
* The time at which the pdflush thread pool last went empty
*/
static unsigned long last_empty_jifs;
/*
* The pdflush thread.
*
* Thread pool management algorithm:
*
* - The minimum and maximum number of pdflush instances are bound
* by MIN_PDFLUSH_THREADS and MAX_PDFLUSH_THREADS.
*
* - If there have been no idle pdflush instances for 1 second, create
* a new one.
*
* - If the least-recently-went-to-sleep pdflush thread has been asleep
* for more than one second, terminate a thread.
*/
/*
* A structure for passing work to a pdflush thread. Also for passing
* state information between pdflush threads. Protected by pdflush_lock.
*/
struct pdflush_work {
struct task_struct *who; /* The thread */
void (*fn)(unsigned long); /* A callback function */
unsigned long arg0; /* An argument to the callback */
struct list_head list; /* On pdflush_list, when idle */
unsigned long when_i_went_to_sleep;
};
static int __pdflush(struct pdflush_work *my_work)
{
current->flags |= PF_FLUSHER | PF_SWAPWRITE;
set_freezable();
my_work->fn = NULL;
my_work->who = current;
INIT_LIST_HEAD(&my_work->list);
spin_lock_irq(&pdflush_lock);
nr_pdflush_threads++;
for ( ; ; ) {
struct pdflush_work *pdf;
|
