Merge branch 'upstream-linus' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik...
[linux-2.6] / include / linux / relay.h
1 /*
2  * linux/include/linux/relay.h
3  *
4  * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
5  * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
6  *
7  * CONFIG_RELAY definitions and declarations
8  */
9
10 #ifndef _LINUX_RELAY_H
11 #define _LINUX_RELAY_H
12
13 #include <linux/types.h>
14 #include <linux/sched.h>
15 #include <linux/wait.h>
16 #include <linux/list.h>
17 #include <linux/fs.h>
18 #include <linux/poll.h>
19 #include <linux/kref.h>
20
21 /* Needs a _much_ better name... */
22 #define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)
23
24 /*
25  * Tracks changes to rchan/rchan_buf structs
26  */
27 #define RELAYFS_CHANNEL_VERSION         6
28
29 /*
30  * Per-cpu relay channel buffer
31  */
32 struct rchan_buf
33 {
34         void *start;                    /* start of channel buffer */
35         void *data;                     /* start of current sub-buffer */
36         size_t offset;                  /* current offset into sub-buffer */
37         size_t subbufs_produced;        /* count of sub-buffers produced */
38         size_t subbufs_consumed;        /* count of sub-buffers consumed */
39         struct rchan *chan;             /* associated channel */
40         wait_queue_head_t read_wait;    /* reader wait queue */
41         struct delayed_work wake_readers; /* reader wake-up work struct */
42         struct dentry *dentry;          /* channel file dentry */
43         struct kref kref;               /* channel buffer refcount */
44         struct page **page_array;       /* array of current buffer pages */
45         unsigned int page_count;        /* number of current buffer pages */
46         unsigned int finalized;         /* buffer has been finalized */
47         size_t *padding;                /* padding counts per sub-buffer */
48         size_t prev_padding;            /* temporary variable */
49         size_t bytes_consumed;          /* bytes consumed in cur read subbuf */
50         unsigned int cpu;               /* this buf's cpu */
51 } ____cacheline_aligned;
52
53 /*
54  * Relay channel data structure
55  */
56 struct rchan
57 {
58         u32 version;                    /* the version of this struct */
59         size_t subbuf_size;             /* sub-buffer size */
60         size_t n_subbufs;               /* number of sub-buffers per buffer */
61         size_t alloc_size;              /* total buffer size allocated */
62         struct rchan_callbacks *cb;     /* client callbacks */
63         struct kref kref;               /* channel refcount */
64         void *private_data;             /* for user-defined data */
65         size_t last_toobig;             /* tried to log event > subbuf size */
66         struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
67 };
68
69 /*
70  * Relay channel client callbacks
71  */
72 struct rchan_callbacks
73 {
74         /*
75          * subbuf_start - called on buffer-switch to a new sub-buffer
76          * @buf: the channel buffer containing the new sub-buffer
77          * @subbuf: the start of the new sub-buffer
78          * @prev_subbuf: the start of the previous sub-buffer
79          * @prev_padding: unused space at the end of previous sub-buffer
80          *
81          * The client should return 1 to continue logging, 0 to stop
82          * logging.
83          *
84          * NOTE: subbuf_start will also be invoked when the buffer is
85          *       created, so that the first sub-buffer can be initialized
86          *       if necessary.  In this case, prev_subbuf will be NULL.
87          *
88          * NOTE: the client can reserve bytes at the beginning of the new
89          *       sub-buffer by calling subbuf_start_reserve() in this callback.
90          */
91         int (*subbuf_start) (struct rchan_buf *buf,
92                              void *subbuf,
93                              void *prev_subbuf,
94                              size_t prev_padding);
95
96         /*
97          * buf_mapped - relay buffer mmap notification
98          * @buf: the channel buffer
99          * @filp: relay file pointer
100          *
101          * Called when a relay file is successfully mmapped
102          */
103         void (*buf_mapped)(struct rchan_buf *buf,
104                            struct file *filp);
105
106         /*
107          * buf_unmapped - relay buffer unmap notification
108          * @buf: the channel buffer
109          * @filp: relay file pointer
110          *
111          * Called when a relay file is successfully unmapped
112          */
113         void (*buf_unmapped)(struct rchan_buf *buf,
114                              struct file *filp);
115         /*
116          * create_buf_file - create file to represent a relay channel buffer
117          * @filename: the name of the file to create
118          * @parent: the parent of the file to create
119          * @mode: the mode of the file to create
120          * @buf: the channel buffer
121          * @is_global: outparam - set non-zero if the buffer should be global
122          *
123          * Called during relay_open(), once for each per-cpu buffer,
124          * to allow the client to create a file to be used to
125          * represent the corresponding channel buffer.  If the file is
126          * created outside of relay, the parent must also exist in
127          * that filesystem.
128          *
129          * The callback should return the dentry of the file created
130          * to represent the relay buffer.
131          *
132          * Setting the is_global outparam to a non-zero value will
133          * cause relay_open() to create a single global buffer rather
134          * than the default set of per-cpu buffers.
135          *
136          * See Documentation/filesystems/relayfs.txt for more info.
137          */
138         struct dentry *(*create_buf_file)(const char *filename,
139                                           struct dentry *parent,
140                                           int mode,
141                                           struct rchan_buf *buf,
142                                           int *is_global);
143
144         /*
145          * remove_buf_file - remove file representing a relay channel buffer
146          * @dentry: the dentry of the file to remove
147          *
148          * Called during relay_close(), once for each per-cpu buffer,
149          * to allow the client to remove a file used to represent a
150          * channel buffer.
151          *
152          * The callback should return 0 if successful, negative if not.
153          */
154         int (*remove_buf_file)(struct dentry *dentry);
155 };
156
157 /*
158  * CONFIG_RELAY kernel API, kernel/relay.c
159  */
160
161 struct rchan *relay_open(const char *base_filename,
162                          struct dentry *parent,
163                          size_t subbuf_size,
164                          size_t n_subbufs,
165                          struct rchan_callbacks *cb);
166 extern void relay_close(struct rchan *chan);
167 extern void relay_flush(struct rchan *chan);
168 extern void relay_subbufs_consumed(struct rchan *chan,
169                                    unsigned int cpu,
170                                    size_t consumed);
171 extern void relay_reset(struct rchan *chan);
172 extern int relay_buf_full(struct rchan_buf *buf);
173
174 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
175                                   size_t length);
176
177 /**
178  *      relay_write - write data into the channel
179  *      @chan: relay channel
180  *      @data: data to be written
181  *      @length: number of bytes to write
182  *
183  *      Writes data into the current cpu's channel buffer.
184  *
185  *      Protects the buffer by disabling interrupts.  Use this
186  *      if you might be logging from interrupt context.  Try
187  *      __relay_write() if you know you won't be logging from
188  *      interrupt context.
189  */
190 static inline void relay_write(struct rchan *chan,
191                                const void *data,
192                                size_t length)
193 {
194         unsigned long flags;
195         struct rchan_buf *buf;
196
197         local_irq_save(flags);
198         buf = chan->buf[smp_processor_id()];
199         if (unlikely(buf->offset + length > chan->subbuf_size))
200                 length = relay_switch_subbuf(buf, length);
201         memcpy(buf->data + buf->offset, data, length);
202         buf->offset += length;
203         local_irq_restore(flags);
204 }
205
206 /**
207  *      __relay_write - write data into the channel
208  *      @chan: relay channel
209  *      @data: data to be written
210  *      @length: number of bytes to write
211  *
212  *      Writes data into the current cpu's channel buffer.
213  *
214  *      Protects the buffer by disabling preemption.  Use
215  *      relay_write() if you might be logging from interrupt
216  *      context.
217  */
218 static inline void __relay_write(struct rchan *chan,
219                                  const void *data,
220                                  size_t length)
221 {
222         struct rchan_buf *buf;
223
224         buf = chan->buf[get_cpu()];
225         if (unlikely(buf->offset + length > buf->chan->subbuf_size))
226                 length = relay_switch_subbuf(buf, length);
227         memcpy(buf->data + buf->offset, data, length);
228         buf->offset += length;
229         put_cpu();
230 }
231
232 /**
233  *      relay_reserve - reserve slot in channel buffer
234  *      @chan: relay channel
235  *      @length: number of bytes to reserve
236  *
237  *      Returns pointer to reserved slot, NULL if full.
238  *
239  *      Reserves a slot in the current cpu's channel buffer.
240  *      Does not protect the buffer at all - caller must provide
241  *      appropriate synchronization.
242  */
243 static inline void *relay_reserve(struct rchan *chan, size_t length)
244 {
245         void *reserved;
246         struct rchan_buf *buf = chan->buf[smp_processor_id()];
247
248         if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
249                 length = relay_switch_subbuf(buf, length);
250                 if (!length)
251                         return NULL;
252         }
253         reserved = buf->data + buf->offset;
254         buf->offset += length;
255
256         return reserved;
257 }
258
259 /**
260  *      subbuf_start_reserve - reserve bytes at the start of a sub-buffer
261  *      @buf: relay channel buffer
262  *      @length: number of bytes to reserve
263  *
264  *      Helper function used to reserve bytes at the beginning of
265  *      a sub-buffer in the subbuf_start() callback.
266  */
267 static inline void subbuf_start_reserve(struct rchan_buf *buf,
268                                         size_t length)
269 {
270         BUG_ON(length >= buf->chan->subbuf_size - 1);
271         buf->offset = length;
272 }
273
274 /*
275  * exported relay file operations, kernel/relay.c
276  */
277 extern const struct file_operations relay_file_operations;
278
279 #endif /* _LINUX_RELAY_H */
280