Merge branch 'irq' into release
[linux-2.6.git] / 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/timer.h>
16 #include <linux/wait.h>
17 #include <linux/list.h>
18 #include <linux/fs.h>
19 #include <linux/poll.h>
20 #include <linux/kref.h>
21
22 /* Needs a _much_ better name... */
23 #define FIX_SIZE(x) ((((x) - 1) & PAGE_MASK) + PAGE_SIZE)
24
25 /*
26  * Tracks changes to rchan/rchan_buf structs
27  */
28 #define RELAYFS_CHANNEL_VERSION         7
29
30 /*
31  * Per-cpu relay channel buffer
32  */
33 struct rchan_buf
34 {
35         void *start;                    /* start of channel buffer */
36         void *data;                     /* start of current sub-buffer */
37         size_t offset;                  /* current offset into sub-buffer */
38         size_t subbufs_produced;        /* count of sub-buffers produced */
39         size_t subbufs_consumed;        /* count of sub-buffers consumed */
40         struct rchan *chan;             /* associated channel */
41         wait_queue_head_t read_wait;    /* reader wait queue */
42         struct timer_list timer;        /* reader wake-up timer */
43         struct dentry *dentry;          /* channel file dentry */
44         struct kref kref;               /* channel buffer refcount */
45         struct page **page_array;       /* array of current buffer pages */
46         unsigned int page_count;        /* number of current buffer pages */
47         unsigned int finalized;         /* buffer has been finalized */
48         size_t *padding;                /* padding counts per sub-buffer */
49         size_t prev_padding;            /* temporary variable */
50         size_t bytes_consumed;          /* bytes consumed in cur read subbuf */
51         size_t early_bytes;             /* bytes consumed before VFS inited */
52         unsigned int cpu;               /* this buf's cpu */
53 } ____cacheline_aligned;
54
55 /*
56  * Relay channel data structure
57  */
58 struct rchan
59 {
60         u32 version;                    /* the version of this struct */
61         size_t subbuf_size;             /* sub-buffer size */
62         size_t n_subbufs;               /* number of sub-buffers per buffer */
63         size_t alloc_size;              /* total buffer size allocated */
64         struct rchan_callbacks *cb;     /* client callbacks */
65         struct kref kref;               /* channel refcount */
66         void *private_data;             /* for user-defined data */
67         size_t last_toobig;             /* tried to log event > subbuf size */
68         struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
69         int is_global;                  /* One global buffer ? */
70         struct list_head list;          /* for channel list */
71         struct dentry *parent;          /* parent dentry passed to open */
72         int has_base_filename;          /* has a filename associated? */
73         char base_filename[NAME_MAX];   /* saved base filename */
74 };
75
76 /*
77  * Relay channel client callbacks
78  */
79 struct rchan_callbacks
80 {
81         /*
82          * subbuf_start - called on buffer-switch to a new sub-buffer
83          * @buf: the channel buffer containing the new sub-buffer
84          * @subbuf: the start of the new sub-buffer
85          * @prev_subbuf: the start of the previous sub-buffer
86          * @prev_padding: unused space at the end of previous sub-buffer
87          *
88          * The client should return 1 to continue logging, 0 to stop
89          * logging.
90          *
91          * NOTE: subbuf_start will also be invoked when the buffer is
92          *       created, so that the first sub-buffer can be initialized
93          *       if necessary.  In this case, prev_subbuf will be NULL.
94          *
95          * NOTE: the client can reserve bytes at the beginning of the new
96          *       sub-buffer by calling subbuf_start_reserve() in this callback.
97          */
98         int (*subbuf_start) (struct rchan_buf *buf,
99                              void *subbuf,
100                              void *prev_subbuf,
101                              size_t prev_padding);
102
103         /*
104          * buf_mapped - relay buffer mmap notification
105          * @buf: the channel buffer
106          * @filp: relay file pointer
107          *
108          * Called when a relay file is successfully mmapped
109          */
110         void (*buf_mapped)(struct rchan_buf *buf,
111                            struct file *filp);
112
113         /*
114          * buf_unmapped - relay buffer unmap notification
115          * @buf: the channel buffer
116          * @filp: relay file pointer
117          *
118          * Called when a relay file is successfully unmapped
119          */
120         void (*buf_unmapped)(struct rchan_buf *buf,
121                              struct file *filp);
122         /*
123          * create_buf_file - create file to represent a relay channel buffer
124          * @filename: the name of the file to create
125          * @parent: the parent of the file to create
126          * @mode: the mode of the file to create
127          * @buf: the channel buffer
128          * @is_global: outparam - set non-zero if the buffer should be global
129          *
130          * Called during relay_open(), once for each per-cpu buffer,
131          * to allow the client to create a file to be used to
132          * represent the corresponding channel buffer.  If the file is
133          * created outside of relay, the parent must also exist in
134          * that filesystem.
135          *
136          * The callback should return the dentry of the file created
137          * to represent the relay buffer.
138          *
139          * Setting the is_global outparam to a non-zero value will
140          * cause relay_open() to create a single global buffer rather
141          * than the default set of per-cpu buffers.
142          *
143          * See Documentation/filesystems/relayfs.txt for more info.
144          */
145         struct dentry *(*create_buf_file)(const char *filename,
146                                           struct dentry *parent,
147                                           int mode,
148                                           struct rchan_buf *buf,
149                                           int *is_global);
150
151         /*
152          * remove_buf_file - remove file representing a relay channel buffer
153          * @dentry: the dentry of the file to remove
154          *
155          * Called during relay_close(), once for each per-cpu buffer,
156          * to allow the client to remove a file used to represent a
157          * channel buffer.
158          *
159          * The callback should return 0 if successful, negative if not.
160          */
161         int (*remove_buf_file)(struct dentry *dentry);
162 };
163
164 /*
165  * CONFIG_RELAY kernel API, kernel/relay.c
166  */
167
168 struct rchan *relay_open(const char *base_filename,
169                          struct dentry *parent,
170                          size_t subbuf_size,
171                          size_t n_subbufs,
172                          struct rchan_callbacks *cb,
173                          void *private_data);
174 extern int relay_late_setup_files(struct rchan *chan,
175                                   const char *base_filename,
176                                   struct dentry *parent);
177 extern void relay_close(struct rchan *chan);
178 extern void relay_flush(struct rchan *chan);
179 extern void relay_subbufs_consumed(struct rchan *chan,
180                                    unsigned int cpu,
181                                    size_t consumed);
182 extern void relay_reset(struct rchan *chan);
183 extern int relay_buf_full(struct rchan_buf *buf);
184
185 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
186                                   size_t length);
187
188 /**
189  *      relay_write - write data into the channel
190  *      @chan: relay channel
191  *      @data: data to be written
192  *      @length: number of bytes to write
193  *
194  *      Writes data into the current cpu's channel buffer.
195  *
196  *      Protects the buffer by disabling interrupts.  Use this
197  *      if you might be logging from interrupt context.  Try
198  *      __relay_write() if you know you won't be logging from
199  *      interrupt context.
200  */
201 static inline void relay_write(struct rchan *chan,
202                                const void *data,
203                                size_t length)
204 {
205         unsigned long flags;
206         struct rchan_buf *buf;
207
208         local_irq_save(flags);
209         buf = chan->buf[smp_processor_id()];
210         if (unlikely(buf->offset + length > chan->subbuf_size))
211                 length = relay_switch_subbuf(buf, length);
212         memcpy(buf->data + buf->offset, data, length);
213         buf->offset += length;
214         local_irq_restore(flags);
215 }
216
217 /**
218  *      __relay_write - write data into the channel
219  *      @chan: relay channel
220  *      @data: data to be written
221  *      @length: number of bytes to write
222  *
223  *      Writes data into the current cpu's channel buffer.
224  *
225  *      Protects the buffer by disabling preemption.  Use
226  *      relay_write() if you might be logging from interrupt
227  *      context.
228  */
229 static inline void __relay_write(struct rchan *chan,
230                                  const void *data,
231                                  size_t length)
232 {
233         struct rchan_buf *buf;
234
235         buf = chan->buf[get_cpu()];
236         if (unlikely(buf->offset + length > buf->chan->subbuf_size))
237                 length = relay_switch_subbuf(buf, length);
238         memcpy(buf->data + buf->offset, data, length);
239         buf->offset += length;
240         put_cpu();
241 }
242
243 /**
244  *      relay_reserve - reserve slot in channel buffer
245  *      @chan: relay channel
246  *      @length: number of bytes to reserve
247  *
248  *      Returns pointer to reserved slot, NULL if full.
249  *
250  *      Reserves a slot in the current cpu's channel buffer.
251  *      Does not protect the buffer at all - caller must provide
252  *      appropriate synchronization.
253  */
254 static inline void *relay_reserve(struct rchan *chan, size_t length)
255 {
256         void *reserved;
257         struct rchan_buf *buf = chan->buf[smp_processor_id()];
258
259         if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
260                 length = relay_switch_subbuf(buf, length);
261                 if (!length)
262                         return NULL;
263         }
264         reserved = buf->data + buf->offset;
265         buf->offset += length;
266
267         return reserved;
268 }
269
270 /**
271  *      subbuf_start_reserve - reserve bytes at the start of a sub-buffer
272  *      @buf: relay channel buffer
273  *      @length: number of bytes to reserve
274  *
275  *      Helper function used to reserve bytes at the beginning of
276  *      a sub-buffer in the subbuf_start() callback.
277  */
278 static inline void subbuf_start_reserve(struct rchan_buf *buf,
279                                         size_t length)
280 {
281         BUG_ON(length >= buf->chan->subbuf_size - 1);
282         buf->offset = length;
283 }
284
285 /*
286  * exported relay file operations, kernel/relay.c
287  */
288 extern const struct file_operations relay_file_operations;
289
290 #endif /* _LINUX_RELAY_H */
291