mm: bdi: allow setting a minimum for the bdi dirty limit
[linux-2.6.git] / mm / backing-dev.c
1
2 #include <linux/wait.h>
3 #include <linux/backing-dev.h>
4 #include <linux/fs.h>
5 #include <linux/sched.h>
6 #include <linux/module.h>
7 #include <linux/writeback.h>
8 #include <linux/device.h>
9
10
11 static struct class *bdi_class;
12
13 static ssize_t read_ahead_kb_store(struct device *dev,
14                                   struct device_attribute *attr,
15                                   const char *buf, size_t count)
16 {
17         struct backing_dev_info *bdi = dev_get_drvdata(dev);
18         char *end;
19         unsigned long read_ahead_kb;
20         ssize_t ret = -EINVAL;
21
22         read_ahead_kb = simple_strtoul(buf, &end, 10);
23         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
24                 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
25                 ret = count;
26         }
27         return ret;
28 }
29
30 #define K(pages) ((pages) << (PAGE_SHIFT - 10))
31
32 #define BDI_SHOW(name, expr)                                            \
33 static ssize_t name##_show(struct device *dev,                          \
34                            struct device_attribute *attr, char *page)   \
35 {                                                                       \
36         struct backing_dev_info *bdi = dev_get_drvdata(dev);            \
37                                                                         \
38         return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);  \
39 }
40
41 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
42
43 BDI_SHOW(reclaimable_kb, K(bdi_stat(bdi, BDI_RECLAIMABLE)))
44 BDI_SHOW(writeback_kb, K(bdi_stat(bdi, BDI_WRITEBACK)))
45
46 static inline unsigned long get_dirty(struct backing_dev_info *bdi, int i)
47 {
48         unsigned long thresh[3];
49
50         get_dirty_limits(&thresh[0], &thresh[1], &thresh[2], bdi);
51
52         return thresh[i];
53 }
54
55 BDI_SHOW(dirty_kb, K(get_dirty(bdi, 1)))
56 BDI_SHOW(bdi_dirty_kb, K(get_dirty(bdi, 2)))
57
58 static ssize_t min_ratio_store(struct device *dev,
59                 struct device_attribute *attr, const char *buf, size_t count)
60 {
61         struct backing_dev_info *bdi = dev_get_drvdata(dev);
62         char *end;
63         unsigned int ratio;
64         ssize_t ret = -EINVAL;
65
66         ratio = simple_strtoul(buf, &end, 10);
67         if (*buf && (end[0] == '\0' || (end[0] == '\n' && end[1] == '\0'))) {
68                 ret = bdi_set_min_ratio(bdi, ratio);
69                 if (!ret)
70                         ret = count;
71         }
72         return ret;
73 }
74 BDI_SHOW(min_ratio, bdi->min_ratio)
75
76 #define __ATTR_RW(attr) __ATTR(attr, 0644, attr##_show, attr##_store)
77
78 static struct device_attribute bdi_dev_attrs[] = {
79         __ATTR_RW(read_ahead_kb),
80         __ATTR_RO(reclaimable_kb),
81         __ATTR_RO(writeback_kb),
82         __ATTR_RO(dirty_kb),
83         __ATTR_RO(bdi_dirty_kb),
84         __ATTR_RW(min_ratio),
85         __ATTR_NULL,
86 };
87
88 static __init int bdi_class_init(void)
89 {
90         bdi_class = class_create(THIS_MODULE, "bdi");
91         bdi_class->dev_attrs = bdi_dev_attrs;
92         return 0;
93 }
94
95 core_initcall(bdi_class_init);
96
97 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
98                 const char *fmt, ...)
99 {
100         char *name;
101         va_list args;
102         int ret = 0;
103         struct device *dev;
104
105         va_start(args, fmt);
106         name = kvasprintf(GFP_KERNEL, fmt, args);
107         va_end(args);
108
109         if (!name)
110                 return -ENOMEM;
111
112         dev = device_create(bdi_class, parent, MKDEV(0, 0), name);
113         if (IS_ERR(dev)) {
114                 ret = PTR_ERR(dev);
115                 goto exit;
116         }
117
118         bdi->dev = dev;
119         dev_set_drvdata(bdi->dev, bdi);
120
121 exit:
122         kfree(name);
123         return ret;
124 }
125 EXPORT_SYMBOL(bdi_register);
126
127 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
128 {
129         return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
130 }
131 EXPORT_SYMBOL(bdi_register_dev);
132
133 void bdi_unregister(struct backing_dev_info *bdi)
134 {
135         if (bdi->dev) {
136                 device_unregister(bdi->dev);
137                 bdi->dev = NULL;
138         }
139 }
140 EXPORT_SYMBOL(bdi_unregister);
141
142 int bdi_init(struct backing_dev_info *bdi)
143 {
144         int i;
145         int err;
146
147         bdi->dev = NULL;
148
149         bdi->min_ratio = 0;
150
151         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
152                 err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
153                 if (err)
154                         goto err;
155         }
156
157         bdi->dirty_exceeded = 0;
158         err = prop_local_init_percpu(&bdi->completions);
159
160         if (err) {
161 err:
162                 while (i--)
163                         percpu_counter_destroy(&bdi->bdi_stat[i]);
164         }
165
166         return err;
167 }
168 EXPORT_SYMBOL(bdi_init);
169
170 void bdi_destroy(struct backing_dev_info *bdi)
171 {
172         int i;
173
174         bdi_unregister(bdi);
175
176         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
177                 percpu_counter_destroy(&bdi->bdi_stat[i]);
178
179         prop_local_destroy_percpu(&bdi->completions);
180 }
181 EXPORT_SYMBOL(bdi_destroy);
182
183 static wait_queue_head_t congestion_wqh[2] = {
184                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
185                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
186         };
187
188
189 void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
190 {
191         enum bdi_state bit;
192         wait_queue_head_t *wqh = &congestion_wqh[rw];
193
194         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
195         clear_bit(bit, &bdi->state);
196         smp_mb__after_clear_bit();
197         if (waitqueue_active(wqh))
198                 wake_up(wqh);
199 }
200 EXPORT_SYMBOL(clear_bdi_congested);
201
202 void set_bdi_congested(struct backing_dev_info *bdi, int rw)
203 {
204         enum bdi_state bit;
205
206         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
207         set_bit(bit, &bdi->state);
208 }
209 EXPORT_SYMBOL(set_bdi_congested);
210
211 /**
212  * congestion_wait - wait for a backing_dev to become uncongested
213  * @rw: READ or WRITE
214  * @timeout: timeout in jiffies
215  *
216  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
217  * write congestion.  If no backing_devs are congested then just wait for the
218  * next write to be completed.
219  */
220 long congestion_wait(int rw, long timeout)
221 {
222         long ret;
223         DEFINE_WAIT(wait);
224         wait_queue_head_t *wqh = &congestion_wqh[rw];
225
226         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
227         ret = io_schedule_timeout(timeout);
228         finish_wait(wqh, &wait);
229         return ret;
230 }
231 EXPORT_SYMBOL(congestion_wait);
232