--- /dev/null
+/*
+ * linux/include/linux/relay.h
+ *
+ * Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
+ * Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
+ *
+ * CONFIG_RELAY definitions and declarations
+ */
+
+#ifndef _LINUX_RELAY_H
+#define _LINUX_RELAY_H
+
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/wait.h>
+#include <linux/list.h>
+#include <linux/bug.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/kref.h>
+
+/*
+ * Tracks changes to rchan/rchan_buf structs
+ */
+#define RELAYFS_CHANNEL_VERSION 7
+
+/*
+ * Per-cpu relay channel buffer
+ */
+struct rchan_buf
+{
+ void *start; /* start of channel buffer */
+ void *data; /* start of current sub-buffer */
+ size_t offset; /* current offset into sub-buffer */
+ size_t subbufs_produced; /* count of sub-buffers produced */
+ size_t subbufs_consumed; /* count of sub-buffers consumed */
+ struct rchan *chan; /* associated channel */
+ wait_queue_head_t read_wait; /* reader wait queue */
+ struct timer_list timer; /* reader wake-up timer */
+ struct dentry *dentry; /* channel file dentry */
+ struct kref kref; /* channel buffer refcount */
+ struct page **page_array; /* array of current buffer pages */
+ unsigned int page_count; /* number of current buffer pages */
+ unsigned int finalized; /* buffer has been finalized */
+ size_t *padding; /* padding counts per sub-buffer */
+ size_t prev_padding; /* temporary variable */
+ size_t bytes_consumed; /* bytes consumed in cur read subbuf */
+ size_t early_bytes; /* bytes consumed before VFS inited */
+ unsigned int cpu; /* this buf's cpu */
+} ____cacheline_aligned;
+
+/*
+ * Relay channel data structure
+ */
+struct rchan
+{
+ u32 version; /* the version of this struct */
+ size_t subbuf_size; /* sub-buffer size */
+ size_t n_subbufs; /* number of sub-buffers per buffer */
+ size_t alloc_size; /* total buffer size allocated */
+ struct rchan_callbacks *cb; /* client callbacks */
+ struct kref kref; /* channel refcount */
+ void *private_data; /* for user-defined data */
+ size_t last_toobig; /* tried to log event > subbuf size */
+ struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+ int is_global; /* One global buffer ? */
+ struct list_head list; /* for channel list */
+ struct dentry *parent; /* parent dentry passed to open */
+ int has_base_filename; /* has a filename associated? */
+ char base_filename[NAME_MAX]; /* saved base filename */
+};
+
+/*
+ * Relay channel client callbacks
+ */
+struct rchan_callbacks
+{
+ /*
+ * subbuf_start - called on buffer-switch to a new sub-buffer
+ * @buf: the channel buffer containing the new sub-buffer
+ * @subbuf: the start of the new sub-buffer
+ * @prev_subbuf: the start of the previous sub-buffer
+ * @prev_padding: unused space at the end of previous sub-buffer
+ *
+ * The client should return 1 to continue logging, 0 to stop
+ * logging.
+ *
+ * NOTE: subbuf_start will also be invoked when the buffer is
+ * created, so that the first sub-buffer can be initialized
+ * if necessary. In this case, prev_subbuf will be NULL.
+ *
+ * NOTE: the client can reserve bytes at the beginning of the new
+ * sub-buffer by calling subbuf_start_reserve() in this callback.
+ */
+ int (*subbuf_start) (struct rchan_buf *buf,
+ void *subbuf,
+ void *prev_subbuf,
+ size_t prev_padding);
+
+ /*
+ * buf_mapped - relay buffer mmap notification
+ * @buf: the channel buffer
+ * @filp: relay file pointer
+ *
+ * Called when a relay file is successfully mmapped
+ */
+ void (*buf_mapped)(struct rchan_buf *buf,
+ struct file *filp);
+
+ /*
+ * buf_unmapped - relay buffer unmap notification
+ * @buf: the channel buffer
+ * @filp: relay file pointer
+ *
+ * Called when a relay file is successfully unmapped
+ */
+ void (*buf_unmapped)(struct rchan_buf *buf,
+ struct file *filp);
+ /*
+ * create_buf_file - create file to represent a relay channel buffer
+ * @filename: the name of the file to create
+ * @parent: the parent of the file to create
+ * @mode: the mode of the file to create
+ * @buf: the channel buffer
+ * @is_global: outparam - set non-zero if the buffer should be global
+ *
+ * Called during relay_open(), once for each per-cpu buffer,
+ * to allow the client to create a file to be used to
+ * represent the corresponding channel buffer. If the file is
+ * created outside of relay, the parent must also exist in
+ * that filesystem.
+ *
+ * The callback should return the dentry of the file created
+ * to represent the relay buffer.
+ *
+ * Setting the is_global outparam to a non-zero value will
+ * cause relay_open() to create a single global buffer rather
+ * than the default set of per-cpu buffers.
+ *
+ * See Documentation/filesystems/relay.txt for more info.
+ */
+ struct dentry *(*create_buf_file)(const char *filename,
+ struct dentry *parent,
+ umode_t mode,
+ struct rchan_buf *buf,
+ int *is_global);
+
+ /*
+ * remove_buf_file - remove file representing a relay channel buffer
+ * @dentry: the dentry of the file to remove
+ *
+ * Called during relay_close(), once for each per-cpu buffer,
+ * to allow the client to remove a file used to represent a
+ * channel buffer.
+ *
+ * The callback should return 0 if successful, negative if not.
+ */
+ int (*remove_buf_file)(struct dentry *dentry);
+};
+
+/*
+ * CONFIG_RELAY kernel API, kernel/relay.c
+ */
+
+struct rchan *relay_open(const char *base_filename,
+ struct dentry *parent,
+ size_t subbuf_size,
+ size_t n_subbufs,
+ struct rchan_callbacks *cb,
+ void *private_data);
+extern int relay_late_setup_files(struct rchan *chan,
+ const char *base_filename,
+ struct dentry *parent);
+extern void relay_close(struct rchan *chan);
+extern void relay_flush(struct rchan *chan);
+extern void relay_subbufs_consumed(struct rchan *chan,
+ unsigned int cpu,
+ size_t consumed);
+extern void relay_reset(struct rchan *chan);
+extern int relay_buf_full(struct rchan_buf *buf);
+
+extern size_t relay_switch_subbuf(struct rchan_buf *buf,
+ size_t length);
+
+/**
+ * relay_write - write data into the channel
+ * @chan: relay channel
+ * @data: data to be written
+ * @length: number of bytes to write
+ *
+ * Writes data into the current cpu's channel buffer.
+ *
+ * Protects the buffer by disabling interrupts. Use this
+ * if you might be logging from interrupt context. Try
+ * __relay_write() if you know you won't be logging from
+ * interrupt context.
+ */
+static inline void relay_write(struct rchan *chan,
+ const void *data,
+ size_t length)
+{
+ unsigned long flags;
+ struct rchan_buf *buf;
+
+ local_irq_save(flags);
+ buf = chan->buf[smp_processor_id()];
+ if (unlikely(buf->offset + length > chan->subbuf_size))
+ length = relay_switch_subbuf(buf, length);
+ memcpy(buf->data + buf->offset, data, length);
+ buf->offset += length;
+ local_irq_restore(flags);
+}
+
+/**
+ * __relay_write - write data into the channel
+ * @chan: relay channel
+ * @data: data to be written
+ * @length: number of bytes to write
+ *
+ * Writes data into the current cpu's channel buffer.
+ *
+ * Protects the buffer by disabling preemption. Use
+ * relay_write() if you might be logging from interrupt
+ * context.
+ */
+static inline void __relay_write(struct rchan *chan,
+ const void *data,
+ size_t length)
+{
+ struct rchan_buf *buf;
+
+ buf = chan->buf[get_cpu()];
+ if (unlikely(buf->offset + length > buf->chan->subbuf_size))
+ length = relay_switch_subbuf(buf, length);
+ memcpy(buf->data + buf->offset, data, length);
+ buf->offset += length;
+ put_cpu();
+}
+
+/**
+ * relay_reserve - reserve slot in channel buffer
+ * @chan: relay channel
+ * @length: number of bytes to reserve
+ *
+ * Returns pointer to reserved slot, NULL if full.
+ *
+ * Reserves a slot in the current cpu's channel buffer.
+ * Does not protect the buffer at all - caller must provide
+ * appropriate synchronization.
+ */
+static inline void *relay_reserve(struct rchan *chan, size_t length)
+{
+ void *reserved;
+ struct rchan_buf *buf = chan->buf[smp_processor_id()];
+
+ if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
+ length = relay_switch_subbuf(buf, length);
+ if (!length)
+ return NULL;
+ }
+ reserved = buf->data + buf->offset;
+ buf->offset += length;
+
+ return reserved;
+}
+
+/**
+ * subbuf_start_reserve - reserve bytes at the start of a sub-buffer
+ * @buf: relay channel buffer
+ * @length: number of bytes to reserve
+ *
+ * Helper function used to reserve bytes at the beginning of
+ * a sub-buffer in the subbuf_start() callback.
+ */
+static inline void subbuf_start_reserve(struct rchan_buf *buf,
+ size_t length)
+{
+ BUG_ON(length >= buf->chan->subbuf_size - 1);
+ buf->offset = length;
+}
+
+/*
+ * exported relay file operations, kernel/relay.c
+ */
+extern const struct file_operations relay_file_operations;
+
+#endif /* _LINUX_RELAY_H */
+
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