include/linux/relayfs_fs.h

   1 /*
   2  * linux/include/linux/relayfs_fs.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  * RelayFS definitions and declarations
   8  */
   9
  10 #ifndef _LINUX_RELAYFS_FS_H
  11 #define _LINUX_RELAYFS_FS_H
  12
  13 #include <linux/config.h>
  14 #include <linux/types.h>
  15 #include <linux/sched.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 /*
  23  * Tracks changes to rchan_buf struct
  24  */
  25 #define RELAYFS_CHANNEL_VERSION         5
  26
  27 /*
  28  * Per-cpu relay channel buffer
  29  */
  30 struct rchan_buf
  31 {
  32         void *start;                    /* start of channel buffer */
  33         void *data;                     /* start of current sub-buffer */
  34         size_t offset;                  /* current offset into sub-buffer */
  35         size_t subbufs_produced;        /* count of sub-buffers produced */
  36         size_t subbufs_consumed;        /* count of sub-buffers consumed */
  37         struct rchan *chan;             /* associated channel */
  38         wait_queue_head_t read_wait;    /* reader wait queue */
  39         struct work_struct wake_readers; /* reader wake-up work struct */
  40         struct dentry *dentry;          /* channel file dentry */
  41         struct kref kref;               /* channel buffer refcount */
  42         struct page **page_array;       /* array of current buffer pages */
  43         unsigned int page_count;        /* number of current buffer pages */
  44         unsigned int finalized;         /* buffer has been finalized */
  45         size_t *padding;                /* padding counts per sub-buffer */
  46         size_t prev_padding;            /* temporary variable */
  47         size_t bytes_consumed;          /* bytes consumed in cur read subbuf */
  48         unsigned int cpu;               /* this buf's cpu */
  49 } ____cacheline_aligned;
  50
  51 /*
  52  * Relay channel data structure
  53  */
  54 struct rchan
  55 {
  56         u32 version;                    /* the version of this struct */
  57         size_t subbuf_size;             /* sub-buffer size */
  58         size_t n_subbufs;               /* number of sub-buffers per buffer */
  59         size_t alloc_size;              /* total buffer size allocated */
  60         struct rchan_callbacks *cb;     /* client callbacks */
  61         struct kref kref;               /* channel refcount */
  62         void *private_data;             /* for user-defined data */
  63         struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
  64 };
  65
  66 /*
  67  * Relayfs inode
  68  */
  69 struct relayfs_inode_info
  70 {
  71         struct inode vfs_inode;
  72         struct rchan_buf *buf;
  73 };
  74
  75 static inline struct relayfs_inode_info *RELAYFS_I(struct inode *inode)
  76 {
  77         return container_of(inode, struct relayfs_inode_info, vfs_inode);
  78 }
  79
  80 /*
  81  * Relay channel client callbacks
  82  */
  83 struct rchan_callbacks
  84 {
  85         /*
  86          * subbuf_start - called on buffer-switch to a new sub-buffer
  87          * @buf: the channel buffer containing the new sub-buffer
  88          * @subbuf: the start of the new sub-buffer
  89          * @prev_subbuf: the start of the previous sub-buffer
  90          * @prev_padding: unused space at the end of previous sub-buffer
  91          *
  92          * The client should return 1 to continue logging, 0 to stop
  93          * logging.
  94          *
  95          * NOTE: subbuf_start will also be invoked when the buffer is
  96          *       created, so that the first sub-buffer can be initialized
  97          *       if necessary.  In this case, prev_subbuf will be NULL.
  98          *
  99          * NOTE: the client can reserve bytes at the beginning of the new
 100          *       sub-buffer by calling subbuf_start_reserve() in this callback.
 101          */
 102         int (*subbuf_start) (struct rchan_buf *buf,
 103                              void *subbuf,
 104                              void *prev_subbuf,
 105                              size_t prev_padding);
 106
 107         /*
 108          * buf_mapped - relayfs buffer mmap notification
 109          * @buf: the channel buffer
 110          * @filp: relayfs file pointer
 111          *
 112          * Called when a relayfs file is successfully mmapped
 113          */
 114         void (*buf_mapped)(struct rchan_buf *buf,
 115                            struct file *filp);
 116
 117         /*
 118          * buf_unmapped - relayfs buffer unmap notification
 119          * @buf: the channel buffer
 120          * @filp: relayfs file pointer
 121          *
 122          * Called when a relayfs file is successfully unmapped
 123          */
 124         void (*buf_unmapped)(struct rchan_buf *buf,
 125                              struct file *filp);
 126 };
 127
 128 /*
 129  * relayfs kernel API, fs/relayfs/relay.c
 130  */
 131
 132 struct rchan *relay_open(const char *base_filename,
 133                          struct dentry *parent,
 134                          size_t subbuf_size,
 135                          size_t n_subbufs,
 136                          struct rchan_callbacks *cb);
 137 extern void relay_close(struct rchan *chan);
 138 extern void relay_flush(struct rchan *chan);
 139 extern void relay_subbufs_consumed(struct rchan *chan,
 140                                    unsigned int cpu,
 141                                    size_t consumed);
 142 extern void relay_reset(struct rchan *chan);
 143 extern int relay_buf_full(struct rchan_buf *buf);
 144
 145 extern size_t relay_switch_subbuf(struct rchan_buf *buf,
 146                                   size_t length);
 147 extern struct dentry *relayfs_create_dir(const char *name,
 148                                          struct dentry *parent);
 149 extern int relayfs_remove_dir(struct dentry *dentry);
 150
 151 /**
 152  *      relay_write - write data into the channel
 153  *      @chan: relay channel
 154  *      @data: data to be written
 155  *      @length: number of bytes to write
 156  *
 157  *      Writes data into the current cpu's channel buffer.
 158  *
 159  *      Protects the buffer by disabling interrupts.  Use this
 160  *      if you might be logging from interrupt context.  Try
 161  *      __relay_write() if you know you won't be logging from
 162  *      interrupt context.
 163  */
 164 static inline void relay_write(struct rchan *chan,
 165                                const void *data,
 166                                size_t length)
 167 {
 168         unsigned long flags;
 169         struct rchan_buf *buf;
 170
 171         local_irq_save(flags);
 172         buf = chan->buf[smp_processor_id()];
 173         if (unlikely(buf->offset + length > chan->subbuf_size))
 174                 length = relay_switch_subbuf(buf, length);
 175         memcpy(buf->data + buf->offset, data, length);
 176         buf->offset += length;
 177         local_irq_restore(flags);
 178 }
 179
 180 /**
 181  *      __relay_write - write data into the channel
 182  *      @chan: relay channel
 183  *      @data: data to be written
 184  *      @length: number of bytes to write
 185  *
 186  *      Writes data into the current cpu's channel buffer.
 187  *
 188  *      Protects the buffer by disabling preemption.  Use
 189  *      relay_write() if you might be logging from interrupt
 190  *      context.
 191  */
 192 static inline void __relay_write(struct rchan *chan,
 193                                  const void *data,
 194                                  size_t length)
 195 {
 196         struct rchan_buf *buf;
 197
 198         buf = chan->buf[get_cpu()];
 199         if (unlikely(buf->offset + length > buf->chan->subbuf_size))
 200                 length = relay_switch_subbuf(buf, length);
 201         memcpy(buf->data + buf->offset, data, length);
 202         buf->offset += length;
 203         put_cpu();
 204 }
 205
 206 /**
 207  *      relay_reserve - reserve slot in channel buffer
 208  *      @chan: relay channel
 209  *      @length: number of bytes to reserve
 210  *
 211  *      Returns pointer to reserved slot, NULL if full.
 212  *
 213  *      Reserves a slot in the current cpu's channel buffer.
 214  *      Does not protect the buffer at all - caller must provide
 215  *      appropriate synchronization.
 216  */
 217 static inline void *relay_reserve(struct rchan *chan, size_t length)
 218 {
 219         void *reserved;
 220         struct rchan_buf *buf = chan->buf[smp_processor_id()];
 221
 222         if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
 223                 length = relay_switch_subbuf(buf, length);
 224                 if (!length)
 225                         return NULL;
 226         }
 227         reserved = buf->data + buf->offset;
 228         buf->offset += length;
 229
 230         return reserved;
 231 }
 232
 233 /**
 234  *      subbuf_start_reserve - reserve bytes at the start of a sub-buffer
 235  *      @buf: relay channel buffer
 236  *      @length: number of bytes to reserve
 237  *
 238  *      Helper function used to reserve bytes at the beginning of
 239  *      a sub-buffer in the subbuf_start() callback.
 240  */
 241 static inline void subbuf_start_reserve(struct rchan_buf *buf,
 242                                         size_t length)
 243 {
 244         BUG_ON(length >= buf->chan->subbuf_size - 1);
 245         buf->offset = length;
 246 }
 247
 248 /*
 249  * exported relayfs file operations, fs/relayfs/inode.c
 250  */
 251
 252 extern struct file_operations relayfs_file_operations;
 253
 254 #endif /* _LINUX_RELAYFS_FS_H */
 255