/* SPDX-License-Identifier: GPL-2.0 */ /* * 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/irq_work.h> #include <linux/bug.h> #include <linux/fs.h> #include <linux/poll.h> #include <linux/kref.h> #include <linux/percpu.h> /* * Tracks changes to rchan/rchan_buf structs */ #define RELAYFS_CHANNEL_VERSION 7 /* * Relay buffer statistics */ enum { RELAY_STATS_BUF_FULL = (1 << 0), RELAY_STATS_WRT_BIG = (1 << 1), RELAY_STATS_LAST = RELAY_STATS_WRT_BIG, }; struct rchan_buf_stats { unsigned int full_count; /* counter for buffer full */ unsigned int big_count; /* counter for too big to write */ }; /* * 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 irq_work wakeup_work; /* reader wakeup */ struct dentry *dentry; /* channel file dentry */ struct kref kref; /* channel buffer refcount */ struct rchan_buf_stats stats; /* buffer stats */ 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 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 */ const struct rchan_callbacks *cb; /* client callbacks */ struct kref kref; /* channel refcount */ void *private_data; /* for user-defined data */ struct rchan_buf * __percpu *buf; /* 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 * * The client should return 1 to continue logging, 0 to stop * logging. * * This callback is optional. * * 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); /* * 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. * * This callback is mandatory. * * See Documentation/filesystems/relay.rst 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. * * This callback is mandatory. */ 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, const struct rchan_callbacks *cb, void *private_data); extern void relay_close(struct rchan *chan); extern void relay_flush(struct rchan *chan); size_t relay_stats(struct rchan *chan, int flags); 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 = *this_cpu_ptr(chan->buf); 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 = *get_cpu_ptr(chan->buf); 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_ptr(chan->buf); } /** * 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 = NULL; struct rchan_buf *buf = *get_cpu_ptr(chan->buf); if (unlikely(buf->offset + length > buf->chan->subbuf_size)) { length = relay_switch_subbuf(buf, length); if (!length) goto end; } reserved = buf->data + buf->offset; buf->offset += length; end: put_cpu_ptr(chan->buf); 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; #ifdef CONFIG_RELAY int relay_prepare_cpu(unsigned int cpu); #else #define relay_prepare_cpu NULL #endif #endif /* _LINUX_RELAY_H */
