Pull misc-for-upstream into release branch
[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         7
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         int is_global;                  /* One global buffer ? */
68         struct list_head list;          /* for channel list */
69         struct dentry *parent;          /* parent dentry passed to open */
70         char base_filename[NAME_MAX];   /* saved base filename */
71 };
72
73 /*
74  * Relay channel client callbacks
75  */
76 struct rchan_callbacks
77 {
78         /*
79          * subbuf_start - called on buffer-switch to a new sub-buffer
80          * @buf: the channel buffer containing the new sub-buffer
81          * @subbuf: the start of the new sub-buffer
82          * @prev_subbuf: the start of the previous sub-buffer
83          * @prev_padding: unused space at the end of previous sub-buffer
84          *
85          * The client should return 1 to continue logging, 0 to stop
86          * logging.
87          *
88          * NOTE: subbuf_start will also be invoked when the buffer is
89          *       created, so that the first sub-buffer can be initialized
90          *       if necessary.  In this case, prev_subbuf will be NULL.
91          *
92          * NOTE: the client can reserve bytes at the beginning of the new
93          *       sub-buffer by calling subbuf_start_reserve() in this callback.
94          */
95         int (*subbuf_start) (struct rchan_buf *buf,
96                              void *subbuf,
97                              void *prev_subbuf,
98                              size_t prev_padding);
99
100         /*
101          * buf_mapped - relay buffer mmap notification
102          * @buf: the channel buffer
103          * @filp: relay file pointer
104          *
105          * Called when a relay file is successfully mmapped
106          */
107         void (*buf_mapped)(struct rchan_buf *buf,
108                            struct file *filp);
109
110         /*
111          * buf_unmapped - relay buffer unmap notification
112          * @buf: the channel buffer
113          * @filp: relay file pointer
114          *
115          * Called when a relay file is successfully unmapped
116          */
117         void (*buf_unmapped)(struct rchan_buf *buf,
118                              struct file *filp);
119         /*
120          * create_buf_file - create file to represent a relay channel buffer
121          * @filename: the name of the file to create
122          * @parent: the parent of the file to create
123          * @mode: the mode of the file to create
124          * @buf: the channel buffer
125          * @is_global: outparam - set non-zero if the buffer should be global
126          *
127          * Called during relay_open(), once for each per-cpu buffer,
128          * to allow the client to create a file to be used to
129          * represent the corresponding channel buffer.  If the file is
130          * created outside of relay, the parent must also exist in
131          * that filesystem.
132          *
133          * The callback should return the dentry of the file created
134          * to represent the relay buffer.
135          *
136          * Setting the is_global outparam to a non-zero value will
137          * cause relay_open() to create a single global buffer rather
138          * than the default set of per-cpu buffers.
139          *
140          * See Documentation/filesystems/relayfs.txt for more info.
141          */
142         struct dentry *(*create_buf_file)(const char *filename,
143                                           struct dentry *parent,
144                                           int mode,
145                                           struct rchan_buf *buf,
146                                           int *is_global);
147
148         /*
149          * remove_buf_file - remove file representing a relay channel buffer
150          * @dentry: the dentry of the file to remove
151          *
152          * Called during relay_close(), once for each per-cpu buffer,
153          * to allow the client to remove a file used to represent a
154          * channel buffer.
155          *
156          * The callback should return 0 if successful, negative if not.
157          */
158         int (*remove_buf_file)(struct dentry *dentry);
159 };
160
161 /*
162  * CONFIG_RELAY kernel API, kernel/relay.c
163  */
164
165 struct rchan *relay_open(const char *base_filename,
166                          struct dentry *parent,
167                          size_t subbuf_size,
168                          size_t n_subbufs,
169                          struct rchan_callbacks *cb,
170                          void *private_data);
171 extern void relay_close(struct rchan *chan);
172 extern void relay_flush(struct rchan *chan);
173 extern void relay_subbufs_consumed(struct rchan *chan,
174                                    unsigned int cpu,
175                                    size_t consumed);
176 extern void relay_reset(struct rchan *chan);
177 extern int relay_buf_full(struct rchan_buf *buf);
178
179 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
180                                   size_t length);
181
182 /**
183  *      relay_write - write data into the channel
184  *      @chan: relay channel
185  *      @data: data to be written
186  *      @length: number of bytes to write
187  *
188  *      Writes data into the current cpu's channel buffer.
189  *
190  *      Protects the buffer by disabling interrupts.  Use this
191  *      if you might be logging from interrupt context.  Try
192  *      __relay_write() if you know you won't be logging from
193  *      interrupt context.
194  */
195 static inline void relay_write(struct rchan *chan,
196                                const void *data,
197                                size_t length)
198 {
199         unsigned long flags;
200         struct rchan_buf *buf;
201
202         local_irq_save(flags);
203         buf = chan->buf[smp_processor_id()];
204         if (unlikely(buf->offset + length > chan->subbuf_size))
205                 length = relay_switch_subbuf(buf, length);
206         memcpy(buf->data + buf->offset, data, length);
207         buf->offset += length;
208         local_irq_restore(flags);
209 }
210
211 /**
212  *      __relay_write - write data into the channel
213  *      @chan: relay channel
214  *      @data: data to be written
215  *      @length: number of bytes to write
216  *
217  *      Writes data into the current cpu's channel buffer.
218  *
219  *      Protects the buffer by disabling preemption.  Use
220  *      relay_write() if you might be logging from interrupt
221  *      context.
222  */
223 static inline void __relay_write(struct rchan *chan,
224                                  const void *data,
225                                  size_t length)
226 {
227         struct rchan_buf *buf;
228
229         buf = chan->buf[get_cpu()];
230         if (unlikely(buf->offset + length > buf->chan->subbuf_size))
231                 length = relay_switch_subbuf(buf, length);
232         memcpy(buf->data + buf->offset, data, length);
233         buf->offset += length;
234         put_cpu();
235 }
236
237 /**
238  *      relay_reserve - reserve slot in channel buffer
239  *      @chan: relay channel
240  *      @length: number of bytes to reserve
241  *
242  *      Returns pointer to reserved slot, NULL if full.
243  *
244  *      Reserves a slot in the current cpu's channel buffer.
245  *      Does not protect the buffer at all - caller must provide
246  *      appropriate synchronization.
247  */
248 static inline void *relay_reserve(struct rchan *chan, size_t length)
249 {
250         void *reserved;
251         struct rchan_buf *buf = chan->buf[smp_processor_id()];
252
253         if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
254                 length = relay_switch_subbuf(buf, length);
255                 if (!length)
256                         return NULL;
257         }
258         reserved = buf->data + buf->offset;
259         buf->offset += length;
260
261         return reserved;
262 }
263
264 /**
265  *      subbuf_start_reserve - reserve bytes at the start of a sub-buffer
266  *      @buf: relay channel buffer
267  *      @length: number of bytes to reserve
268  *
269  *      Helper function used to reserve bytes at the beginning of
270  *      a sub-buffer in the subbuf_start() callback.
271  */
272 static inline void subbuf_start_reserve(struct rchan_buf *buf,
273                                         size_t length)
274 {
275         BUG_ON(length >= buf->chan->subbuf_size - 1);
276         buf->offset = length;
277 }
278
279 /*
280  * exported relay file operations, kernel/relay.c
281  */
282 extern const struct file_operations relay_file_operations;
283
284 #endif /* _LINUX_RELAY_H */
285