lttng lib: ring buffer

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/lttng/lib/ringbuffer/api.h

@@ -0,0 +1,25 @@
+#ifndef _LINUX_RING_BUFFER_API_H
+#define _LINUX_RING_BUFFER_API_H
+
+/*
+ * linux/ringbuffer/api.h
+ *
+ * Copyright (C) 2010 - Mathieu Desnoyers "mathieu.desnoyers@efficios.com"
+ *
+ * Ring Buffer API.
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include "../../wrapper/ringbuffer/backend.h"
+#include "../../wrapper/ringbuffer/frontend.h"
+#include "../../wrapper/ringbuffer/vfs.h"
+
+/*
+ * ring_buffer_frontend_api.h contains static inline functions that depend on
+ * client static inlines. Hence the inclusion of this "api" header only
+ * within the client.
+ */
+#include "../../wrapper/ringbuffer/frontend_api.h"
+
+#endif /* _LINUX_RING_BUFFER_API_H */

drivers/staging/lttng/lib/ringbuffer/backend.h

@@ -0,0 +1,250 @@
+#ifndef _LINUX_RING_BUFFER_BACKEND_H
+#define _LINUX_RING_BUFFER_BACKEND_H
+
+/*
+ * linux/ringbuffer/backend.h
+ *
+ * Copyright (C) 2008-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Ring buffer backend (API).
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ *
+ * Credits to Steven Rostedt for proposing to use an extra-subbuffer owned by
+ * the reader in flight recorder mode.
+ */
+
+#include <linux/types.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/wait.h>
+#include <linux/poll.h>
+#include <linux/list.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+
+/* Internal helpers */
+#include "../../wrapper/ringbuffer/backend_internal.h"
+#include "../../wrapper/ringbuffer/frontend_internal.h"
+
+/* Ring buffer backend API */
+
+/* Ring buffer backend access (read/write) */
+
+extern size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb,
+				   size_t offset, void *dest, size_t len);
+
+extern int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend *bufb,
+					  size_t offset, void __user *dest,
+					  size_t len);
+
+extern int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb,
+				     size_t offset, void *dest, size_t len);
+
+extern struct page **
+lib_ring_buffer_read_get_page(struct lib_ring_buffer_backend *bufb, size_t offset,
+			      void ***virt);
+
+/*
+ * Return the address where a given offset is located.
+ * Should be used to get the current subbuffer header pointer. Given we know
+ * it's never on a page boundary, it's safe to write directly to this address,
+ * as long as the write is never bigger than a page size.
+ */
+extern void *
+lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb,
+			       size_t offset);
+extern void *
+lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb,
+				    size_t offset);
+
+/**
+ * lib_ring_buffer_write - write data to a buffer backend
+ * @config : ring buffer instance configuration
+ * @ctx: ring buffer context. (input arguments only)
+ * @src : source pointer to copy from
+ * @len : length of data to copy
+ *
+ * This function copies "len" bytes of data from a source pointer to a buffer
+ * backend, at the current context offset. This is more or less a buffer
+ * backend-specific memcpy() operation. Calls the slow path (_ring_buffer_write)
+ * if copy is crossing a page boundary.
+ */
+static inline
+void lib_ring_buffer_write(const struct lib_ring_buffer_config *config,
+			   struct lib_ring_buffer_ctx *ctx,
+			   const void *src, size_t len)
+{
+	struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
+	struct channel_backend *chanb = &ctx->chan->backend;
+	size_t sbidx, index;
+	size_t offset = ctx->buf_offset;
+	ssize_t pagecpy;
+	struct lib_ring_buffer_backend_pages *rpages;
+	unsigned long sb_bindex, id;
+
+	offset &= chanb->buf_size - 1;
+	sbidx = offset >> chanb->subbuf_size_order;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+	id = bufb->buf_wsb[sbidx].id;
+	sb_bindex = subbuffer_id_get_index(config, id);
+	rpages = bufb->array[sb_bindex];
+	CHAN_WARN_ON(ctx->chan,
+		     config->mode == RING_BUFFER_OVERWRITE
+		     && subbuffer_id_is_noref(config, id));
+	if (likely(pagecpy == len))
+		lib_ring_buffer_do_copy(config,
+					rpages->p[index].virt
+					    + (offset & ~PAGE_MASK),
+					src, len);
+	else
+		_lib_ring_buffer_write(bufb, offset, src, len, 0);
+	ctx->buf_offset += len;
+}
+
+/**
+ * lib_ring_buffer_memset - write len bytes of c to a buffer backend
+ * @config : ring buffer instance configuration
+ * @bufb : ring buffer backend
+ * @offset : offset within the buffer
+ * @c : the byte to copy
+ * @len : number of bytes to copy
+ *
+ * This function writes "len" bytes of "c" to a buffer backend, at a specific
+ * offset. This is more or less a buffer backend-specific memset() operation.
+ * Calls the slow path (_ring_buffer_memset) if write is crossing a page
+ * boundary.
+ */
+static inline
+void lib_ring_buffer_memset(const struct lib_ring_buffer_config *config,
+			    struct lib_ring_buffer_ctx *ctx, int c, size_t len)
+{
+
+	struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
+	struct channel_backend *chanb = &ctx->chan->backend;
+	size_t sbidx, index;
+	size_t offset = ctx->buf_offset;
+	ssize_t pagecpy;
+	struct lib_ring_buffer_backend_pages *rpages;
+	unsigned long sb_bindex, id;
+
+	offset &= chanb->buf_size - 1;
+	sbidx = offset >> chanb->subbuf_size_order;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+	id = bufb->buf_wsb[sbidx].id;
+	sb_bindex = subbuffer_id_get_index(config, id);
+	rpages = bufb->array[sb_bindex];
+	CHAN_WARN_ON(ctx->chan,
+		     config->mode == RING_BUFFER_OVERWRITE
+		     && subbuffer_id_is_noref(config, id));
+	if (likely(pagecpy == len))
+		lib_ring_buffer_do_memset(rpages->p[index].virt
+					  + (offset & ~PAGE_MASK),
+					  c, len);
+	else
+		_lib_ring_buffer_memset(bufb, offset, c, len, 0);
+	ctx->buf_offset += len;
+}
+
+/**
+ * lib_ring_buffer_copy_from_user - write userspace data to a buffer backend
+ * @config : ring buffer instance configuration
+ * @ctx: ring buffer context. (input arguments only)
+ * @src : userspace source pointer to copy from
+ * @len : length of data to copy
+ *
+ * This function copies "len" bytes of data from a userspace pointer to a
+ * buffer backend, at the current context offset. This is more or less a buffer
+ * backend-specific memcpy() operation. Calls the slow path
+ * (_ring_buffer_write_from_user) if copy is crossing a page boundary.
+ */
+static inline
+void lib_ring_buffer_copy_from_user(const struct lib_ring_buffer_config *config,
+				    struct lib_ring_buffer_ctx *ctx,
+				    const void __user *src, size_t len)
+{
+	struct lib_ring_buffer_backend *bufb = &ctx->buf->backend;
+	struct channel_backend *chanb = &ctx->chan->backend;
+	size_t sbidx, index;
+	size_t offset = ctx->buf_offset;
+	ssize_t pagecpy;
+	struct lib_ring_buffer_backend_pages *rpages;
+	unsigned long sb_bindex, id;
+	unsigned long ret;
+
+	offset &= chanb->buf_size - 1;
+	sbidx = offset >> chanb->subbuf_size_order;
+	index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
+	pagecpy = min_t(size_t, len, (-offset) & ~PAGE_MASK);
+	id = bufb->buf_wsb[sbidx].id;
+	sb_bindex = subbuffer_id_get_index(config, id);
+	rpages = bufb->array[sb_bindex];
+	CHAN_WARN_ON(ctx->chan,
+		     config->mode == RING_BUFFER_OVERWRITE
+		     && subbuffer_id_is_noref(config, id));
+
+	if (unlikely(!access_ok(VERIFY_READ, src, len)))
+		goto fill_buffer;
+
+	if (likely(pagecpy == len)) {
+		ret = lib_ring_buffer_do_copy_from_user(
+			rpages->p[index].virt + (offset & ~PAGE_MASK),
+			src, len);
+		if (unlikely(ret > 0)) {
+			len -= (pagecpy - ret);
+			offset += (pagecpy - ret);
+			goto fill_buffer;
+		}
+	} else {
+		_lib_ring_buffer_copy_from_user(bufb, offset, src, len, 0);
+	}
+	ctx->buf_offset += len;
+
+	return;
+
+fill_buffer:
+	/*
+	 * In the error path we call the slow path version to avoid
+	 * the pollution of static inline code.
+	 */
+	_lib_ring_buffer_memset(bufb, offset, 0, len, 0);
+}
+
+/*
+ * This accessor counts the number of unread records in a buffer.
+ * It only provides a consistent value if no reads not writes are performed
+ * concurrently.
+ */
+static inline
+unsigned long lib_ring_buffer_get_records_unread(
+				const struct lib_ring_buffer_config *config,
+				struct lib_ring_buffer *buf)
+{
+	struct lib_ring_buffer_backend *bufb = &buf->backend;
+	struct lib_ring_buffer_backend_pages *pages;
+	unsigned long records_unread = 0, sb_bindex, id;
+	unsigned int i;
+
+	for (i = 0; i < bufb->chan->backend.num_subbuf; i++) {
+		id = bufb->buf_wsb[i].id;
+		sb_bindex = subbuffer_id_get_index(config, id);
+		pages = bufb->array[sb_bindex];
+		records_unread += v_read(config, &pages->records_unread);
+	}
+	if (config->mode == RING_BUFFER_OVERWRITE) {
+		id = bufb->buf_rsb.id;
+		sb_bindex = subbuffer_id_get_index(config, id);
+		pages = bufb->array[sb_bindex];
+		records_unread += v_read(config, &pages->records_unread);
+	}
+	return records_unread;
+}
+
+ssize_t lib_ring_buffer_file_splice_read(struct file *in, loff_t *ppos,
+					 struct pipe_inode_info *pipe,
+					 size_t len, unsigned int flags);
+loff_t lib_ring_buffer_no_llseek(struct file *file, loff_t offset, int origin);
+
+#endif /* _LINUX_RING_BUFFER_BACKEND_H */