include/linux/relay.h: fix percpu annotation in struct rchan
[muen/linux.git] / include / linux / relay.h
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * linux/include/linux/relay.h
4  *
5  * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
6  * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
7  *
8  * CONFIG_RELAY definitions and declarations
9  */
10
11 #ifndef _LINUX_RELAY_H
12 #define _LINUX_RELAY_H
13
14 #include <linux/types.h>
15 #include <linux/sched.h>
16 #include <linux/timer.h>
17 #include <linux/wait.h>
18 #include <linux/list.h>
19 #include <linux/irq_work.h>
20 #include <linux/bug.h>
21 #include <linux/fs.h>
22 #include <linux/poll.h>
23 #include <linux/kref.h>
24 #include <linux/percpu.h>
25
26 /*
27  * Tracks changes to rchan/rchan_buf structs
28  */
29 #define RELAYFS_CHANNEL_VERSION         7
30
31 /*
32  * Per-cpu relay channel buffer
33  */
34 struct rchan_buf
35 {
36         void *start;                    /* start of channel buffer */
37         void *data;                     /* start of current sub-buffer */
38         size_t offset;                  /* current offset into sub-buffer */
39         size_t subbufs_produced;        /* count of sub-buffers produced */
40         size_t subbufs_consumed;        /* count of sub-buffers consumed */
41         struct rchan *chan;             /* associated channel */
42         wait_queue_head_t read_wait;    /* reader wait queue */
43         struct irq_work wakeup_work;    /* reader wakeup */
44         struct dentry *dentry;          /* channel file dentry */
45         struct kref kref;               /* channel buffer refcount */
46         struct page **page_array;       /* array of current buffer pages */
47         unsigned int page_count;        /* number of current buffer pages */
48         unsigned int finalized;         /* buffer has been finalized */
49         size_t *padding;                /* padding counts per sub-buffer */
50         size_t prev_padding;            /* temporary variable */
51         size_t bytes_consumed;          /* bytes consumed in cur read subbuf */
52         size_t early_bytes;             /* bytes consumed before VFS inited */
53         unsigned int cpu;               /* this buf's cpu */
54 } ____cacheline_aligned;
55
56 /*
57  * Relay channel data structure
58  */
59 struct rchan
60 {
61         u32 version;                    /* the version of this struct */
62         size_t subbuf_size;             /* sub-buffer size */
63         size_t n_subbufs;               /* number of sub-buffers per buffer */
64         size_t alloc_size;              /* total buffer size allocated */
65         struct rchan_callbacks *cb;     /* client callbacks */
66         struct kref kref;               /* channel refcount */
67         void *private_data;             /* for user-defined data */
68         size_t last_toobig;             /* tried to log event > subbuf size */
69         struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */
70         int is_global;                  /* One global buffer ? */
71         struct list_head list;          /* for channel list */
72         struct dentry *parent;          /* parent dentry passed to open */
73         int has_base_filename;          /* has a filename associated? */
74         char base_filename[NAME_MAX];   /* saved base filename */
75 };
76
77 /*
78  * Relay channel client callbacks
79  */
80 struct rchan_callbacks
81 {
82         /*
83          * subbuf_start - called on buffer-switch to a new sub-buffer
84          * @buf: the channel buffer containing the new sub-buffer
85          * @subbuf: the start of the new sub-buffer
86          * @prev_subbuf: the start of the previous sub-buffer
87          * @prev_padding: unused space at the end of previous sub-buffer
88          *
89          * The client should return 1 to continue logging, 0 to stop
90          * logging.
91          *
92          * NOTE: subbuf_start will also be invoked when the buffer is
93          *       created, so that the first sub-buffer can be initialized
94          *       if necessary.  In this case, prev_subbuf will be NULL.
95          *
96          * NOTE: the client can reserve bytes at the beginning of the new
97          *       sub-buffer by calling subbuf_start_reserve() in this callback.
98          */
99         int (*subbuf_start) (struct rchan_buf *buf,
100                              void *subbuf,
101                              void *prev_subbuf,
102                              size_t prev_padding);
103
104         /*
105          * buf_mapped - relay buffer mmap notification
106          * @buf: the channel buffer
107          * @filp: relay file pointer
108          *
109          * Called when a relay file is successfully mmapped
110          */
111         void (*buf_mapped)(struct rchan_buf *buf,
112                            struct file *filp);
113
114         /*
115          * buf_unmapped - relay buffer unmap notification
116          * @buf: the channel buffer
117          * @filp: relay file pointer
118          *
119          * Called when a relay file is successfully unmapped
120          */
121         void (*buf_unmapped)(struct rchan_buf *buf,
122                              struct file *filp);
123         /*
124          * create_buf_file - create file to represent a relay channel buffer
125          * @filename: the name of the file to create
126          * @parent: the parent of the file to create
127          * @mode: the mode of the file to create
128          * @buf: the channel buffer
129          * @is_global: outparam - set non-zero if the buffer should be global
130          *
131          * Called during relay_open(), once for each per-cpu buffer,
132          * to allow the client to create a file to be used to
133          * represent the corresponding channel buffer.  If the file is
134          * created outside of relay, the parent must also exist in
135          * that filesystem.
136          *
137          * The callback should return the dentry of the file created
138          * to represent the relay buffer.
139          *
140          * Setting the is_global outparam to a non-zero value will
141          * cause relay_open() to create a single global buffer rather
142          * than the default set of per-cpu buffers.
143          *
144          * See Documentation/filesystems/relay.txt for more info.
145          */
146         struct dentry *(*create_buf_file)(const char *filename,
147                                           struct dentry *parent,
148                                           umode_t mode,
149                                           struct rchan_buf *buf,
150                                           int *is_global);
151
152         /*
153          * remove_buf_file - remove file representing a relay channel buffer
154          * @dentry: the dentry of the file to remove
155          *
156          * Called during relay_close(), once for each per-cpu buffer,
157          * to allow the client to remove a file used to represent a
158          * channel buffer.
159          *
160          * The callback should return 0 if successful, negative if not.
161          */
162         int (*remove_buf_file)(struct dentry *dentry);
163 };
164
165 /*
166  * CONFIG_RELAY kernel API, kernel/relay.c
167  */
168
169 struct rchan *relay_open(const char *base_filename,
170                          struct dentry *parent,
171                          size_t subbuf_size,
172                          size_t n_subbufs,
173                          struct rchan_callbacks *cb,
174                          void *private_data);
175 extern int relay_late_setup_files(struct rchan *chan,
176                                   const char *base_filename,
177                                   struct dentry *parent);
178 extern void relay_close(struct rchan *chan);
179 extern void relay_flush(struct rchan *chan);
180 extern void relay_subbufs_consumed(struct rchan *chan,
181                                    unsigned int cpu,
182                                    size_t consumed);
183 extern void relay_reset(struct rchan *chan);
184 extern int relay_buf_full(struct rchan_buf *buf);
185
186 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
187                                   size_t length);
188
189 /**
190  *      relay_write - write data into the channel
191  *      @chan: relay channel
192  *      @data: data to be written
193  *      @length: number of bytes to write
194  *
195  *      Writes data into the current cpu's channel buffer.
196  *
197  *      Protects the buffer by disabling interrupts.  Use this
198  *      if you might be logging from interrupt context.  Try
199  *      __relay_write() if you know you won't be logging from
200  *      interrupt context.
201  */
202 static inline void relay_write(struct rchan *chan,
203                                const void *data,
204                                size_t length)
205 {
206         unsigned long flags;
207         struct rchan_buf *buf;
208
209         local_irq_save(flags);
210         buf = *this_cpu_ptr(chan->buf);
211         if (unlikely(buf->offset + length > chan->subbuf_size))
212                 length = relay_switch_subbuf(buf, length);
213         memcpy(buf->data + buf->offset, data, length);
214         buf->offset += length;
215         local_irq_restore(flags);
216 }
217
218 /**
219  *      __relay_write - write data into the channel
220  *      @chan: relay channel
221  *      @data: data to be written
222  *      @length: number of bytes to write
223  *
224  *      Writes data into the current cpu's channel buffer.
225  *
226  *      Protects the buffer by disabling preemption.  Use
227  *      relay_write() if you might be logging from interrupt
228  *      context.
229  */
230 static inline void __relay_write(struct rchan *chan,
231                                  const void *data,
232                                  size_t length)
233 {
234         struct rchan_buf *buf;
235
236         buf = *get_cpu_ptr(chan->buf);
237         if (unlikely(buf->offset + length > buf->chan->subbuf_size))
238                 length = relay_switch_subbuf(buf, length);
239         memcpy(buf->data + buf->offset, data, length);
240         buf->offset += length;
241         put_cpu_ptr(chan->buf);
242 }
243
244 /**
245  *      relay_reserve - reserve slot in channel buffer
246  *      @chan: relay channel
247  *      @length: number of bytes to reserve
248  *
249  *      Returns pointer to reserved slot, NULL if full.
250  *
251  *      Reserves a slot in the current cpu's channel buffer.
252  *      Does not protect the buffer at all - caller must provide
253  *      appropriate synchronization.
254  */
255 static inline void *relay_reserve(struct rchan *chan, size_t length)
256 {
257         void *reserved = NULL;
258         struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
259
260         if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
261                 length = relay_switch_subbuf(buf, length);
262                 if (!length)
263                         goto end;
264         }
265         reserved = buf->data + buf->offset;
266         buf->offset += length;
267
268 end:
269         put_cpu_ptr(chan->buf);
270         return reserved;
271 }
272
273 /**
274  *      subbuf_start_reserve - reserve bytes at the start of a sub-buffer
275  *      @buf: relay channel buffer
276  *      @length: number of bytes to reserve
277  *
278  *      Helper function used to reserve bytes at the beginning of
279  *      a sub-buffer in the subbuf_start() callback.
280  */
281 static inline void subbuf_start_reserve(struct rchan_buf *buf,
282                                         size_t length)
283 {
284         BUG_ON(length >= buf->chan->subbuf_size - 1);
285         buf->offset = length;
286 }
287
288 /*
289  * exported relay file operations, kernel/relay.c
290  */
291 extern const struct file_operations relay_file_operations;
292
293 #ifdef CONFIG_RELAY
294 int relay_prepare_cpu(unsigned int cpu);
295 #else
296 #define relay_prepare_cpu     NULL
297 #endif
298
299 #endif /* _LINUX_RELAY_H */
300