1 files changed, 243 insertions, 68 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index e206951603c1..7f69cfeaadf7 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -195,20 +195,24 @@ void *ring_buffer_event_data(struct ring_buffer_event *event)
 #define TS_MASK         ((1ULL << TS_SHIFT) - 1)
 #define TS_DELTA_TEST   (~TS_MASK)
 
-/*
- * This hack stolen from mm/slob.c.
- * We can store per page timing information in the page frame of the page.
- * Thanks to Peter Zijlstra for suggesting this idea.
- */
-struct buffer_page {
+struct buffer_data_page {
         u64              time_stamp;    /* page time stamp */
-        local_t          write;         /* index for next write */
         local_t          commit;        /* write commited index */
+        unsigned char    data[];        /* data of buffer page */
+};
+
+struct buffer_page {
+        local_t          write;         /* index for next write */
         unsigned         read;          /* index for next read */
         struct list_head list;          /* list of free pages */
-        void *page;                     /* Actual data page */
+        struct buffer_data_page *page;  /* Actual data page */
 };
 
+static void rb_init_page(struct buffer_data_page *bpage)
+{
+        local_set(&bpage->commit, 0);
+}
+
 /*
  * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
  * this issue out.
@@ -230,7 +234,7 @@ static inline int test_time_stamp(u64 delta)
         return 0;
 }
 
-#define BUF_PAGE_SIZE PAGE_SIZE
+#define BUF_PAGE_SIZE (PAGE_SIZE - sizeof(struct buffer_data_page))
 
 /*
  * head_page == tail_page && head == tail then buffer is empty.
@@ -294,19 +298,19 @@ struct ring_buffer_iter {
 static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
 {
         struct list_head *head = &cpu_buffer->pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
 
         if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
                 return -1;
         if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
                 return -1;
 
-        list_for_each_entry_safe(page, tmp, head, list) {
+        list_for_each_entry_safe(bpage, tmp, head, list) {
                 if (RB_WARN_ON(cpu_buffer,
-                               page->list.next->prev != &page->list))
+                               bpage->list.next->prev != &bpage->list))
                         return -1;
                 if (RB_WARN_ON(cpu_buffer,
-                               page->list.prev->next != &page->list))
+                               bpage->list.prev->next != &bpage->list))
                         return -1;
         }
 
@@ -317,22 +321,23 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
                              unsigned nr_pages)
 {
         struct list_head *head = &cpu_buffer->pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
         unsigned long addr;
         LIST_HEAD(pages);
         unsigned i;
 
         for (i = 0; i < nr_pages; i++) {
-                page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
+                bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
                                     GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
-                if (!page)
+                if (!bpage)
                         goto free_pages;
-                list_add(&page->list, &pages);
+                list_add(&bpage->list, &pages);
 
                 addr = __get_free_page(GFP_KERNEL);
                 if (!addr)
                         goto free_pages;
-                page->page = (void *)addr;
+                bpage->page = (void *)addr;
+                rb_init_page(bpage->page);
         }
 
         list_splice(&pages, head);
@@ -342,9 +347,9 @@ static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
         return 0;
 
  free_pages:
-        list_for_each_entry_safe(page, tmp, &pages, list) {
-                list_del_init(&page->list);
-                free_buffer_page(page);
+        list_for_each_entry_safe(bpage, tmp, &pages, list) {
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
         return -ENOMEM;
 }
@@ -353,7 +358,7 @@ static struct ring_buffer_per_cpu *
 rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
-        struct buffer_page *page;
+        struct buffer_page *bpage;
         unsigned long addr;
         int ret;
 
@@ -368,16 +373,17 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
         cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
         INIT_LIST_HEAD(&cpu_buffer->pages);
 
-        page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
+        bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
                             GFP_KERNEL, cpu_to_node(cpu));
-        if (!page)
+        if (!bpage)
                 goto fail_free_buffer;
 
-        cpu_buffer->reader_page = page;
+        cpu_buffer->reader_page = bpage;
         addr = __get_free_page(GFP_KERNEL);
         if (!addr)
                 goto fail_free_reader;
-        page->page = (void *)addr;
+        bpage->page = (void *)addr;
+        rb_init_page(bpage->page);
 
         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
 
@@ -402,14 +408,14 @@ rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
 static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
 {
         struct list_head *head = &cpu_buffer->pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
 
         list_del_init(&cpu_buffer->reader_page->list);
         free_buffer_page(cpu_buffer->reader_page);
 
-        list_for_each_entry_safe(page, tmp, head, list) {
-                list_del_init(&page->list);
-                free_buffer_page(page);
+        list_for_each_entry_safe(bpage, tmp, head, list) {
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
         kfree(cpu_buffer);
 }
@@ -506,7 +512,7 @@ static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
 static void
 rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
 {
-        struct buffer_page *page;
+        struct buffer_page *bpage;
         struct list_head *p;
         unsigned i;
 
@@ -517,9 +523,9 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
                 if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
                         return;
                 p = cpu_buffer->pages.next;
-                page = list_entry(p, struct buffer_page, list);
-                list_del_init(&page->list);
-                free_buffer_page(page);
+                bpage = list_entry(p, struct buffer_page, list);
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
         if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
                 return;
@@ -536,7 +542,7 @@ static void
 rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
                 struct list_head *pages, unsigned nr_pages)
 {
-        struct buffer_page *page;
+        struct buffer_page *bpage;
         struct list_head *p;
         unsigned i;
 
@@ -547,9 +553,9 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
                 if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
                         return;
                 p = pages->next;
-                page = list_entry(p, struct buffer_page, list);
-                list_del_init(&page->list);
-                list_add_tail(&page->list, &cpu_buffer->pages);
+                bpage = list_entry(p, struct buffer_page, list);
+                list_del_init(&bpage->list);
+                list_add_tail(&bpage->list, &cpu_buffer->pages);
         }
         rb_reset_cpu(cpu_buffer);
 
@@ -576,7 +582,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
         unsigned nr_pages, rm_pages, new_pages;
-        struct buffer_page *page, *tmp;
+        struct buffer_page *bpage, *tmp;
         unsigned long buffer_size;
         unsigned long addr;
         LIST_HEAD(pages);
@@ -637,16 +643,17 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
 
         for_each_buffer_cpu(buffer, cpu) {
                 for (i = 0; i < new_pages; i++) {
-                        page = kzalloc_node(ALIGN(sizeof(*page),
+                        bpage = kzalloc_node(ALIGN(sizeof(*bpage),
                                                   cache_line_size()),
                                             GFP_KERNEL, cpu_to_node(cpu));
-                        if (!page)
+                        if (!bpage)
                                 goto free_pages;
-                        list_add(&page->list, &pages);
+                        list_add(&bpage->list, &pages);
                         addr = __get_free_page(GFP_KERNEL);
                         if (!addr)
                                 goto free_pages;
-                        page->page = (void *)addr;
+                        bpage->page = (void *)addr;
+                        rb_init_page(bpage->page);
                 }
         }
 
@@ -667,9 +674,9 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
         return size;
 
  free_pages:
-        list_for_each_entry_safe(page, tmp, &pages, list) {
-                list_del_init(&page->list);
-                free_buffer_page(page);
+        list_for_each_entry_safe(bpage, tmp, &pages, list) {
+                list_del_init(&bpage->list);
+                free_buffer_page(bpage);
         }
         mutex_unlock(&buffer->mutex);
         return -ENOMEM;
@@ -680,9 +687,15 @@ static inline int rb_null_event(struct ring_buffer_event *event)
         return event->type == RINGBUF_TYPE_PADDING;
 }
 
-static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
+static inline void *
+__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
 {
-        return page->page + index;
+        return bpage->data + index;
+}
+
+static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
+{
+        return bpage->page->data + index;
 }
 
 static inline struct ring_buffer_event *
@@ -712,7 +725,7 @@ static inline unsigned rb_page_write(struct buffer_page *bpage)
 
 static inline unsigned rb_page_commit(struct buffer_page *bpage)
 {
-        return local_read(&bpage->commit);
+        return local_read(&bpage->page->commit);
 }
 
 /* Size is determined by what has been commited */
@@ -758,14 +771,14 @@ static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
 }
 
 static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
-                               struct buffer_page **page)
+                               struct buffer_page **bpage)
 {
-        struct list_head *p = (*page)->list.next;
+        struct list_head *p = (*bpage)->list.next;
 
         if (p == &cpu_buffer->pages)
                 p = p->next;
 
-        *page = list_entry(p, struct buffer_page, list);
+        *bpage = list_entry(p, struct buffer_page, list);
 }
 
 static inline unsigned
@@ -804,14 +817,15 @@ rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
                 if (RB_WARN_ON(cpu_buffer,
                           cpu_buffer->commit_page == cpu_buffer->tail_page))
                         return;
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-                cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
+                cpu_buffer->write_stamp =
+                        cpu_buffer->commit_page->page->time_stamp;
         }
 
         /* Now set the commit to the event's index */
-        local_set(&cpu_buffer->commit_page->commit, index);
+        local_set(&cpu_buffer->commit_page->page->commit, index);
 }
 
 static inline void
@@ -826,16 +840,17 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
          * assign the commit to the tail.
          */
         while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-                cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
+                cpu_buffer->write_stamp =
+                        cpu_buffer->commit_page->page->time_stamp;
                 /* add barrier to keep gcc from optimizing too much */
                 barrier();
         }
         while (rb_commit_index(cpu_buffer) !=
                rb_page_write(cpu_buffer->commit_page)) {
-                cpu_buffer->commit_page->commit =
+                cpu_buffer->commit_page->page->commit =
                         cpu_buffer->commit_page->write;
                 barrier();
         }
@@ -843,7 +858,7 @@ rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
 
 static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
 {
-        cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
+        cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
         cpu_buffer->reader_page->read = 0;
 }
 
@@ -862,7 +877,7 @@ static inline void rb_inc_iter(struct ring_buffer_iter *iter)
         else
                 rb_inc_page(cpu_buffer, &iter->head_page);
 
-        iter->read_stamp = iter->head_page->time_stamp;
+        iter->read_stamp = iter->head_page->page->time_stamp;
         iter->head = 0;
 }
 
@@ -998,12 +1013,12 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                  */
                 if (tail_page == cpu_buffer->tail_page) {
                         local_set(&next_page->write, 0);
-                        local_set(&next_page->commit, 0);
+                        local_set(&next_page->page->commit, 0);
                         cpu_buffer->tail_page = next_page;
 
                         /* reread the time stamp */
                         *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
-                        cpu_buffer->tail_page->time_stamp = *ts;
+                        cpu_buffer->tail_page->page->time_stamp = *ts;
                 }
 
                 /*
@@ -1048,7 +1063,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
          * this page's time stamp.
          */
         if (!tail && rb_is_commit(cpu_buffer, event))
-                cpu_buffer->commit_page->time_stamp = *ts;
+                cpu_buffer->commit_page->page->time_stamp = *ts;
 
         return event;
 
@@ -1099,7 +1114,7 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
                         event->time_delta = *delta & TS_MASK;
                         event->array[0] = *delta >> TS_SHIFT;
                 } else {
-                        cpu_buffer->commit_page->time_stamp = *ts;
+                        cpu_buffer->commit_page->page->time_stamp = *ts;
                         event->time_delta = 0;
                         event->array[0] = 0;
                 }
@@ -1552,7 +1567,7 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
         if (iter->head)
                 iter->read_stamp = cpu_buffer->read_stamp;
         else
-                iter->read_stamp = iter->head_page->time_stamp;
+                iter->read_stamp = iter->head_page->page->time_stamp;
 }
 
 /**
@@ -1696,7 +1711,7 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
         cpu_buffer->reader_page->list.prev = reader->list.prev;
 
         local_set(&cpu_buffer->reader_page->write, 0);
-        local_set(&cpu_buffer->reader_page->commit, 0);
+        local_set(&cpu_buffer->reader_page->page->commit, 0);
 
         /* Make the reader page now replace the head */
         reader->list.prev->next = &cpu_buffer->reader_page->list;
@@ -2088,7 +2103,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
         cpu_buffer->head_page
                 = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
         local_set(&cpu_buffer->head_page->write, 0);
-        local_set(&cpu_buffer->head_page->commit, 0);
+        local_set(&cpu_buffer->head_page->page->commit, 0);
 
         cpu_buffer->head_page->read = 0;
 
@@ -2097,7 +2112,7 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
 
         INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
         local_set(&cpu_buffer->reader_page->write, 0);
-        local_set(&cpu_buffer->reader_page->commit, 0);
+        local_set(&cpu_buffer->reader_page->page->commit, 0);
         cpu_buffer->reader_page->read = 0;
 
         cpu_buffer->overrun = 0;
@@ -2223,6 +2238,166 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
         return 0;
 }
 
+static void rb_remove_entries(struct ring_buffer_per_cpu *cpu_buffer,
+                              struct buffer_data_page *bpage)
+{
+        struct ring_buffer_event *event;
+        unsigned long head;
+
+        __raw_spin_lock(&cpu_buffer->lock);
+        for (head = 0; head < local_read(&bpage->commit);
+             head += rb_event_length(event)) {
+
+                event = __rb_data_page_index(bpage, head);
+                if (RB_WARN_ON(cpu_buffer, rb_null_event(event)))
+                        return;
+                /* Only count data entries */
+                if (event->type != RINGBUF_TYPE_DATA)
+                        continue;
+                cpu_buffer->entries--;
+        }
+        __raw_spin_unlock(&cpu_buffer->lock);
+}
+
+/**
+ * ring_buffer_alloc_read_page - allocate a page to read from buffer
+ * @buffer: the buffer to allocate for.
+ *
+ * This function is used in conjunction with ring_buffer_read_page.
+ * When reading a full page from the ring buffer, these functions
+ * can be used to speed up the process. The calling function should
+ * allocate a few pages first with this function. Then when it
+ * needs to get pages from the ring buffer, it passes the result
+ * of this function into ring_buffer_read_page, which will swap
+ * the page that was allocated, with the read page of the buffer.
+ *
+ * Returns:
+ *  The page allocated, or NULL on error.
+ */
+void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
+{
+        unsigned long addr;
+        struct buffer_data_page *bpage;
+
+        addr = __get_free_page(GFP_KERNEL);
+        if (!addr)
+                return NULL;
+
+        bpage = (void *)addr;
+
+        return bpage;
+}
+
+/**
+ * ring_buffer_free_read_page - free an allocated read page
+ * @buffer: the buffer the page was allocate for
+ * @data: the page to free
+ *
+ * Free a page allocated from ring_buffer_alloc_read_page.
+ */
+void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
+{
+        free_page((unsigned long)data);
+}
+
+/**
+ * ring_buffer_read_page - extract a page from the ring buffer
+ * @buffer: buffer to extract from
+ * @data_page: the page to use allocated from ring_buffer_alloc_read_page
+ * @cpu: the cpu of the buffer to extract
+ * @full: should the extraction only happen when the page is full.
+ *
+ * This function will pull out a page from the ring buffer and consume it.
+ * @data_page must be the address of the variable that was returned
+ * from ring_buffer_alloc_read_page. This is because the page might be used
+ * to swap with a page in the ring buffer.
+ *
+ * for example:
+ *      rpage = ring_buffer_alloc_page(buffer);
+ *      if (!rpage)
+ *              return error;
+ *      ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);
+ *      if (ret)
+ *              process_page(rpage);
+ *
+ * When @full is set, the function will not return true unless
+ * the writer is off the reader page.
+ *
+ * Note: it is up to the calling functions to handle sleeps and wakeups.
+ *  The ring buffer can be used anywhere in the kernel and can not
+ *  blindly call wake_up. The layer that uses the ring buffer must be
+ *  responsible for that.
+ *
+ * Returns:
+ *  1 if data has been transferred
+ *  0 if no data has been transferred.
+ */
+int ring_buffer_read_page(struct ring_buffer *buffer,
+                            void **data_page, int cpu, int full)
+{
+        struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+        struct ring_buffer_event *event;
+        struct buffer_data_page *bpage;
+        unsigned long flags;
+        int ret = 0;
+
+        if (!data_page)
+                return 0;
+
+        bpage = *data_page;
+        if (!bpage)
+                return 0;
+
+        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+        /*
+         * rb_buffer_peek will get the next ring buffer if
+         * the current reader page is empty.
+         */
+        event = rb_buffer_peek(buffer, cpu, NULL);
+        if (!event)
+                goto out;
+
+        /* check for data */
+        if (!local_read(&cpu_buffer->reader_page->page->commit))
+                goto out;
+        /*
+         * If the writer is already off of the read page, then simply
+         * switch the read page with the given page. Otherwise
+         * we need to copy the data from the reader to the writer.
+         */
+        if (cpu_buffer->reader_page == cpu_buffer->commit_page) {
+                unsigned int read = cpu_buffer->reader_page->read;
+
+                if (full)
+                        goto out;
+                /* The writer is still on the reader page, we must copy */
+                bpage = cpu_buffer->reader_page->page;
+                memcpy(bpage->data,
+                       cpu_buffer->reader_page->page->data + read,
+                       local_read(&bpage->commit) - read);
+
+                /* consume what was read */
+                cpu_buffer->reader_page += read;
+
+        } else {
+                /* swap the pages */
+                rb_init_page(bpage);
+                bpage = cpu_buffer->reader_page->page;
+                cpu_buffer->reader_page->page = *data_page;
+                cpu_buffer->reader_page->read = 0;
+                *data_page = bpage;
+        }
+        ret = 1;
+
+        /* update the entry counter */
+        rb_remove_entries(cpu_buffer, bpage);
+ out:
+        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+        return ret;
+}
+
 static ssize_t
 rb_simple_read(struct file *filp, char __user *ubuf,
                size_t cnt, loff_t *ppos)