ClabureDB: Classified Bug-Reports Database

   /*
    * Public API and common code for kernel->userspace relay file support.
    *
    * See Documentation/filesystems/relay.txt for an overview.
    *
    * Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
    * Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
    *
    * Moved to kernel/relay.c by Paul Mundt, 2006.
   * November 2006 - CPU hotplug support by Mathieu Desnoyers
   *         (mathieu.desnoyers@polymtl.ca)
   *
   * This file is released under the GPL.
   */
  #include <linux/errno.h>
  #include <linux/stddef.h>
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/string.h>
  #include <linux/relay.h>
  #include <linux/vmalloc.h>
  #include <linux/mm.h>
  #include <linux/cpu.h>
  #include <linux/splice.h>
  
  /* list of open channels, for cpu hotplug */
  static DEFINE_MUTEX(relay_channels_mutex);
  static LIST_HEAD(relay_channels);
  
  /*
   * close() vm_op implementation for relay file mapping.
   */
  static void relay_file_mmap_close(struct vm_area_struct *vma)
  {
          struct rchan_buf *buf = vma->vm_private_data;
          buf->chan->cb->buf_unmapped(buf, vma->vm_file);
  }
  
  /*
   * fault() vm_op implementation for relay file mapping.
   */
  static int relay_buf_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
  {
          struct page *page;
          struct rchan_buf *buf = vma->vm_private_data;
          pgoff_t pgoff = vmf->pgoff;
  
          if (!buf)
                  return VM_FAULT_OOM;
  
          page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
          if (!page)
                  return VM_FAULT_SIGBUS;
          get_page(page);
          vmf->page = page;
  
          return 0;
  }
  
  /*
   * vm_ops for relay file mappings.
   */
  static struct vm_operations_struct relay_file_mmap_ops = {
          .fault = relay_buf_fault,
          .close = relay_file_mmap_close,
  };
  
  /*
   * allocate an array of pointers of struct page
   */
  static struct page **relay_alloc_page_array(unsigned int n_pages)
  {
          struct page **array;
          size_t pa_size = n_pages * sizeof(struct page *);
  
          if (pa_size > PAGE_SIZE) {
                  array = vmalloc(pa_size);
                  if (array)
                          memset(array, 0, pa_size);
          } else {
                  array = kzalloc(pa_size, GFP_KERNEL);
          }
          return array;
  }
  
  /*
   * free an array of pointers of struct page
   */
  static void relay_free_page_array(struct page **array)
  {
          if (is_vmalloc_addr(array))
                  vfree(array);
          else
                  kfree(array);
  }
  
  /**
   *        relay_mmap_buf: - mmap channel buffer to process address space
   *        @buf: relay channel buffer
  *        @vma: vm_area_struct describing memory to be mapped
  *
  *        Returns 0 if ok, negative on error
  *
  *        Caller should already have grabbed mmap_sem.
  */
 static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
 {
         unsigned long length = vma->vm_end - vma->vm_start;
         struct file *filp = vma->vm_file;
 
         if (!buf)
                 return -EBADF;
 
         if (length != (unsigned long)buf->chan->alloc_size)
                 return -EINVAL;
 
         vma->vm_ops = &relay_file_mmap_ops;
         vma->vm_flags |= VM_DONTEXPAND;
         vma->vm_private_data = buf;
         buf->chan->cb->buf_mapped(buf, filp);
 
         return 0;
 }
 
 /**
  *        relay_alloc_buf - allocate a channel buffer
  *        @buf: the buffer struct
  *        @size: total size of the buffer
  *
  *        Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
  *        passed in size will get page aligned, if it isn't already.
  */
 static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
 {
         void *mem;
         unsigned int i, j, n_pages;
 
         *size = PAGE_ALIGN(*size);
         n_pages = *size >> PAGE_SHIFT;
 
         buf->page_array = relay_alloc_page_array(n_pages);
         if (!buf->page_array)
                 return NULL;
 
         for (i = 0; i < n_pages; i++) {
                 buf->page_array[i] = alloc_page(GFP_KERNEL);
                 if (unlikely(!buf->page_array[i]))
                         goto depopulate;
                 set_page_private(buf->page_array[i], (unsigned long)buf);
         }
         mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
         if (!mem)
                 goto depopulate;
 
         memset(mem, 0, *size);
         buf->page_count = n_pages;
         return mem;
 
 depopulate:
         for (j = 0; j < i; j++)
                 __free_page(buf->page_array[j]);
         relay_free_page_array(buf->page_array);
         return NULL;
 }
 
 /**
  *        relay_create_buf - allocate and initialize a channel buffer
  *        @chan: the relay channel
  *
  *        Returns channel buffer if successful, %NULL otherwise.
  */
 static struct rchan_buf *relay_create_buf(struct rchan *chan)
 {
         struct rchan_buf *buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
         if (!buf)
                 return NULL;
 
         buf->padding = kmalloc(chan->n_subbufs * sizeof(size_t *), GFP_KERNEL);
         if (!buf->padding)
                 goto free_buf;
 
         buf->start = relay_alloc_buf(buf, &chan->alloc_size);
         if (!buf->start)
                 goto free_buf;
 
         buf->chan = chan;
         kref_get(&buf->chan->kref);
         return buf;
 
 free_buf:
         kfree(buf->padding);
         kfree(buf);
         return NULL;
 }
 
 /**
  *        relay_destroy_channel - free the channel struct
  *        @kref: target kernel reference that contains the relay channel
  *
  *        Should only be called from kref_put().
  */
 static void relay_destroy_channel(struct kref *kref)
 {
         struct rchan *chan = container_of(kref, struct rchan, kref);
         kfree(chan);
 }
 
 /**
  *        relay_destroy_buf - destroy an rchan_buf struct and associated buffer
  *        @buf: the buffer struct
  */
 static void relay_destroy_buf(struct rchan_buf *buf)
 {
         struct rchan *chan = buf->chan;
         unsigned int i;
 
         if (likely(buf->start)) {
                 vunmap(buf->start);
                 for (i = 0; i < buf->page_count; i++)
                         __free_page(buf->page_array[i]);
                 relay_free_page_array(buf->page_array);
         }
         chan->buf[buf->cpu] = NULL;
         kfree(buf->padding);
         kfree(buf);
         kref_put(&chan->kref, relay_destroy_channel);
 }
 
 /**
  *        relay_remove_buf - remove a channel buffer
  *        @kref: target kernel reference that contains the relay buffer
  *
  *        Removes the file from the fileystem, which also frees the
  *        rchan_buf_struct and the channel buffer.  Should only be called from
  *        kref_put().
  */
 static void relay_remove_buf(struct kref *kref)
 {
         struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
         buf->chan->cb->remove_buf_file(buf->dentry);
         relay_destroy_buf(buf);
 }
 
 /**
  *        relay_buf_empty - boolean, is the channel buffer empty?
  *        @buf: channel buffer
  *
  *        Returns 1 if the buffer is empty, 0 otherwise.
  */
 static int relay_buf_empty(struct rchan_buf *buf)
 {
         return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
 }
 
 /**
  *        relay_buf_full - boolean, is the channel buffer full?
  *        @buf: channel buffer
  *
  *        Returns 1 if the buffer is full, 0 otherwise.
  */
 int relay_buf_full(struct rchan_buf *buf)
 {
         size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
         return (ready >= buf->chan->n_subbufs) ? 1 : 0;
 }
 EXPORT_SYMBOL_GPL(relay_buf_full);
 
 /*
  * High-level relay kernel API and associated functions.
  */
 
 /*
  * rchan_callback implementations defining default channel behavior.  Used
  * in place of corresponding NULL values in client callback struct.
  */
 
 /*
  * subbuf_start() default callback.  Does nothing.
  */
 static int subbuf_start_default_callback (struct rchan_buf *buf,
                                           void *subbuf,
                                           void *prev_subbuf,
                                           size_t prev_padding)
 {
         if (relay_buf_full(buf))
                 return 0;
 
         return 1;
 }
 
 /*
  * buf_mapped() default callback.  Does nothing.
  */
 static void buf_mapped_default_callback(struct rchan_buf *buf,
                                         struct file *filp)
 {
 }
 
 /*
  * buf_unmapped() default callback.  Does nothing.
  */
 static void buf_unmapped_default_callback(struct rchan_buf *buf,
                                           struct file *filp)
 {
 }
 
 /*
  * create_buf_file_create() default callback.  Does nothing.
  */
 static struct dentry *create_buf_file_default_callback(const char *filename,
                                                        struct dentry *parent,
                                                        int mode,
                                                        struct rchan_buf *buf,
                                                        int *is_global)
 {
         return NULL;
 }
 
 /*
  * remove_buf_file() default callback.  Does nothing.
  */
 static int remove_buf_file_default_callback(struct dentry *dentry)
 {
         return -EINVAL;
 }
 
 /* relay channel default callbacks */
 static struct rchan_callbacks default_channel_callbacks = {
         .subbuf_start = subbuf_start_default_callback,
         .buf_mapped = buf_mapped_default_callback,
         .buf_unmapped = buf_unmapped_default_callback,
         .create_buf_file = create_buf_file_default_callback,
         .remove_buf_file = remove_buf_file_default_callback,
 };
 
 /**
  *        wakeup_readers - wake up readers waiting on a channel
  *        @data: contains the channel buffer
  *
  *        This is the timer function used to defer reader waking.
  */
 static void wakeup_readers(unsigned long data)
 {
         struct rchan_buf *buf = (struct rchan_buf *)data;
         wake_up_interruptible(&buf->read_wait);
 }
 
 /**
  *        __relay_reset - reset a channel buffer
  *        @buf: the channel buffer
  *        @init: 1 if this is a first-time initialization
  *
  *        See relay_reset() for description of effect.
  */
 static void __relay_reset(struct rchan_buf *buf, unsigned int init)
 {
         size_t i;
 
         if (init) {
                 init_waitqueue_head(&buf->read_wait);
                 kref_init(&buf->kref);
                 setup_timer(&buf->timer, wakeup_readers, (unsigned long)buf);
         } else
                 del_timer_sync(&buf->timer);
 
         buf->subbufs_produced = 0;
         buf->subbufs_consumed = 0;
         buf->bytes_consumed = 0;
         buf->finalized = 0;
         buf->data = buf->start;
         buf->offset = 0;
 
         for (i = 0; i < buf->chan->n_subbufs; i++)
                 buf->padding[i] = 0;
 
         buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
 }
 
 /**
  *        relay_reset - reset the channel
  *        @chan: the channel
  *
  *        This has the effect of erasing all data from all channel buffers
  *        and restarting the channel in its initial state.  The buffers
  *        are not freed, so any mappings are still in effect.
  *
  *        NOTE. Care should be taken that the channel isn't actually
  *        being used by anything when this call is made.
  */
 void relay_reset(struct rchan *chan)
 {
         unsigned int i;
 
         if (!chan)
                 return;
 
         if (chan->is_global && chan->buf[0]) {
                 __relay_reset(chan->buf[0], 0);
                 return;
         }
 
         mutex_lock(&relay_channels_mutex);
         for_each_possible_cpu(i)
                 if (chan->buf[i])
                         __relay_reset(chan->buf[i], 0);
         mutex_unlock(&relay_channels_mutex);
 }
 EXPORT_SYMBOL_GPL(relay_reset);
 
 static inline void relay_set_buf_dentry(struct rchan_buf *buf,
                                         struct dentry *dentry)
 {
         buf->dentry = dentry;
         buf->dentry->d_inode->i_size = buf->early_bytes;
 }
 
 static struct dentry *relay_create_buf_file(struct rchan *chan,
                                             struct rchan_buf *buf,
                                             unsigned int cpu)
 {
         struct dentry *dentry;
         char *tmpname;
 
         tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
         if (!tmpname)
                 return NULL;
         snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
 
         /* Create file in fs */
         dentry = chan->cb->create_buf_file(tmpname, chan->parent,
                                            S_IRUSR, buf,
                                            &chan->is_global);
 
         kfree(tmpname);
 
         return dentry;
 }
 
 /*
  *        relay_open_buf - create a new relay channel buffer
  *
  *        used by relay_open() and CPU hotplug.
  */
 static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
 {
          struct rchan_buf *buf = NULL;
         struct dentry *dentry;
 
          if (chan->is_global)
                 return chan->buf[0];
 
         buf = relay_create_buf(chan);
         if (!buf)
                 return NULL;
 
         if (chan->has_base_filename) {
                 dentry = relay_create_buf_file(chan, buf, cpu);
                 if (!dentry)
                         goto free_buf;
                 relay_set_buf_dentry(buf, dentry);
         }
 
          buf->cpu = cpu;
          __relay_reset(buf, 1);
 
          if(chan->is_global) {
                  chan->buf[0] = buf;
                  buf->cpu = 0;
           }
 
         return buf;
 
 free_buf:
          relay_destroy_buf(buf);
         return NULL;
 }
 
 /**
  *        relay_close_buf - close a channel buffer
  *        @buf: channel buffer
  *
  *        Marks the buffer finalized and restores the default callbacks.
  *        The channel buffer and channel buffer data structure are then freed
  *        automatically when the last reference is given up.
  */
 static void relay_close_buf(struct rchan_buf *buf)
 {
         buf->finalized = 1;
         del_timer_sync(&buf->timer);
         kref_put(&buf->kref, relay_remove_buf);
 }
 
 static void setup_callbacks(struct rchan *chan,
                                    struct rchan_callbacks *cb)
 {
         if (!cb) {
                 chan->cb = &default_channel_callbacks;
                 return;
         }
 
         if (!cb->subbuf_start)
                 cb->subbuf_start = subbuf_start_default_callback;
         if (!cb->buf_mapped)
                 cb->buf_mapped = buf_mapped_default_callback;
         if (!cb->buf_unmapped)
                 cb->buf_unmapped = buf_unmapped_default_callback;
         if (!cb->create_buf_file)
                 cb->create_buf_file = create_buf_file_default_callback;
         if (!cb->remove_buf_file)
                 cb->remove_buf_file = remove_buf_file_default_callback;
         chan->cb = cb;
 }
 
 /**
  *         relay_hotcpu_callback - CPU hotplug callback
  *         @nb: notifier block
  *         @action: hotplug action to take
  *         @hcpu: CPU number
  *
  *         Returns the success/failure of the operation. (%NOTIFY_OK, %NOTIFY_BAD)
  */
 static int __cpuinit relay_hotcpu_callback(struct notifier_block *nb,
                                 unsigned long action,
                                 void *hcpu)
 {
         unsigned int hotcpu = (unsigned long)hcpu;
         struct rchan *chan;
 
         switch(action) {
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
                 mutex_lock(&relay_channels_mutex);
                 list_for_each_entry(chan, &relay_channels, list) {
                         if (chan->buf[hotcpu])
                                 continue;
                         chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
                         if(!chan->buf[hotcpu]) {
                                 printk(KERN_ERR
                                         "relay_hotcpu_callback: cpu %d buffer "
                                         "creation failed\n", hotcpu);
                                 mutex_unlock(&relay_channels_mutex);
                                 return NOTIFY_BAD;
                         }
                 }
                 mutex_unlock(&relay_channels_mutex);
                 break;
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
                 /* No need to flush the cpu : will be flushed upon
                  * final relay_flush() call. */
                 break;
         }
         return NOTIFY_OK;
 }
 
 /**
  *        relay_open - create a new relay channel
  *        @base_filename: base name of files to create, %NULL for buffering only
  *        @parent: dentry of parent directory, %NULL for root directory or buffer
  *        @subbuf_size: size of sub-buffers
  *        @n_subbufs: number of sub-buffers
  *        @cb: client callback functions
  *        @private_data: user-defined data
  *
  *        Returns channel pointer if successful, %NULL otherwise.
  *
  *        Creates a channel buffer for each cpu using the sizes and
  *        attributes specified.  The created channel buffer files
  *        will be named base_filename0...base_filenameN-1.  File
  *        permissions will be %S_IRUSR.
  */
 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)
 {
         unsigned int i;
         struct rchan *chan;
 
         if (!(subbuf_size && n_subbufs))
                 return NULL;
 
         chan = kzalloc(sizeof(struct rchan), GFP_KERNEL);
         if (!chan)
                 return NULL;
 
         chan->version = RELAYFS_CHANNEL_VERSION;
         chan->n_subbufs = n_subbufs;
         chan->subbuf_size = subbuf_size;
         chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
         chan->parent = parent;
         chan->private_data = private_data;
         if (base_filename) {
                 chan->has_base_filename = 1;
                 strlcpy(chan->base_filename, base_filename, NAME_MAX);
         }
         setup_callbacks(chan, cb);
         kref_init(&chan->kref);
 
         mutex_lock(&relay_channels_mutex);
         for_each_online_cpu(i) {
                 chan->buf[i] = relay_open_buf(chan, i);
                 if (!chan->buf[i])
                         goto free_bufs;
         }
         list_add(&chan->list, &relay_channels);
         mutex_unlock(&relay_channels_mutex);
 
         return chan;
 
 free_bufs:
         for_each_possible_cpu(i) {
                 if (chan->buf[i])
                         relay_close_buf(chan->buf[i]);
         }
 
         kref_put(&chan->kref, relay_destroy_channel);
         mutex_unlock(&relay_channels_mutex);
         return NULL;
 }
 EXPORT_SYMBOL_GPL(relay_open);
 
 struct rchan_percpu_buf_dispatcher {
         struct rchan_buf *buf;
         struct dentry *dentry;
 };
 
 /* Called in atomic context. */
 static void __relay_set_buf_dentry(void *info)
 {
         struct rchan_percpu_buf_dispatcher *p = info;
 
         relay_set_buf_dentry(p->buf, p->dentry);
 }
 
 /**
  *        relay_late_setup_files - triggers file creation
  *        @chan: channel to operate on
  *        @base_filename: base name of files to create
  *        @parent: dentry of parent directory, %NULL for root directory
  *
  *        Returns 0 if successful, non-zero otherwise.
  *
  *        Use to setup files for a previously buffer-only channel.
  *        Useful to do early tracing in kernel, before VFS is up, for example.
  */
 int relay_late_setup_files(struct rchan *chan,
                            const char *base_filename,
                            struct dentry *parent)
 {
         int err = 0;
         unsigned int i, curr_cpu;
         unsigned long flags;
         struct dentry *dentry;
         struct rchan_percpu_buf_dispatcher disp;
 
         if (!chan || !base_filename)
                 return -EINVAL;
 
         strlcpy(chan->base_filename, base_filename, NAME_MAX);
 
         mutex_lock(&relay_channels_mutex);
         /* Is chan already set up? */
         if (unlikely(chan->has_base_filename))
                 return -EEXIST;
         chan->has_base_filename = 1;
         chan->parent = parent;
         curr_cpu = get_cpu();
         /*
          * The CPU hotplug notifier ran before us and created buffers with
          * no files associated. So it's safe to call relay_setup_buf_file()
          * on all currently online CPUs.
          */
         for_each_online_cpu(i) {
                 if (unlikely(!chan->buf[i])) {
                         printk(KERN_ERR "relay_late_setup_files: CPU %u "
                                         "has no buffer, it must have!\n", i);
                         BUG();
                         err = -EINVAL;
                         break;
                 }
 
                 dentry = relay_create_buf_file(chan, chan->buf[i], i);
                 if (unlikely(!dentry)) {
                         err = -EINVAL;
                         break;
                 }
 
                 if (curr_cpu == i) {
                         local_irq_save(flags);
                         relay_set_buf_dentry(chan->buf[i], dentry);
                         local_irq_restore(flags);
                 } else {
                         disp.buf = chan->buf[i];
                         disp.dentry = dentry;
                         smp_mb();
                         /* relay_channels_mutex must be held, so wait. */
                         err = smp_call_function_single(i,
                                                        __relay_set_buf_dentry,
                                                        &disp, 1);
                 }
                 if (unlikely(err))
                         break;
         }
         put_cpu();
         mutex_unlock(&relay_channels_mutex);
 
         return err;
 }
 
 /**
  *        relay_switch_subbuf - switch to a new sub-buffer
  *        @buf: channel buffer
  *        @length: size of current event
  *
  *        Returns either the length passed in or 0 if full.
  *
  *        Performs sub-buffer-switch tasks such as invoking callbacks,
  *        updating padding counts, waking up readers, etc.
  */
 size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
 {
         void *old, *new;
         size_t old_subbuf, new_subbuf;
 
         if (unlikely(length > buf->chan->subbuf_size))
                 goto toobig;
 
         if (buf->offset != buf->chan->subbuf_size + 1) {
                 buf->prev_padding = buf->chan->subbuf_size - buf->offset;
                 old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
                 buf->padding[old_subbuf] = buf->prev_padding;
                 buf->subbufs_produced++;
                 if (buf->dentry)
                         buf->dentry->d_inode->i_size +=
                                 buf->chan->subbuf_size -
                                 buf->padding[old_subbuf];
                 else
                         buf->early_bytes += buf->chan->subbuf_size -
                                             buf->padding[old_subbuf];
                 smp_mb();
                 if (waitqueue_active(&buf->read_wait))
                         /*
                          * Calling wake_up_interruptible() from here
                          * will deadlock if we happen to be logging
                          * from the scheduler (trying to re-grab
                          * rq->lock), so defer it.
                          */
                         __mod_timer(&buf->timer, jiffies + 1);
         }
 
         old = buf->data;
         new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
         new = buf->start + new_subbuf * buf->chan->subbuf_size;
         buf->offset = 0;
         if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
                 buf->offset = buf->chan->subbuf_size + 1;
                 return 0;
         }
         buf->data = new;
         buf->padding[new_subbuf] = 0;
 
         if (unlikely(length + buf->offset > buf->chan->subbuf_size))
                 goto toobig;
 
         return length;
 
 toobig:
         buf->chan->last_toobig = length;
         return 0;
 }
 EXPORT_SYMBOL_GPL(relay_switch_subbuf);
 
 /**
  *        relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
  *        @chan: the channel
  *        @cpu: the cpu associated with the channel buffer to update
  *        @subbufs_consumed: number of sub-buffers to add to current buf's count
  *
  *        Adds to the channel buffer's consumed sub-buffer count.
  *        subbufs_consumed should be the number of sub-buffers newly consumed,
  *        not the total consumed.
  *
  *        NOTE. Kernel clients don't need to call this function if the channel
  *        mode is 'overwrite'.
  */
 void relay_subbufs_consumed(struct rchan *chan,
                             unsigned int cpu,
                             size_t subbufs_consumed)
 {
         struct rchan_buf *buf;
 
         if (!chan)
                 return;
 
         if (cpu >= NR_CPUS || !chan->buf[cpu])
                 return;
 
         buf = chan->buf[cpu];
         buf->subbufs_consumed += subbufs_consumed;
         if (buf->subbufs_consumed > buf->subbufs_produced)
                 buf->subbufs_consumed = buf->subbufs_produced;
 }
 EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
 
 /**
  *        relay_close - close the channel
  *        @chan: the channel
  *
  *        Closes all channel buffers and frees the channel.
  */
 void relay_close(struct rchan *chan)
 {
         unsigned int i;
 
         if (!chan)
                 return;
 
         mutex_lock(&relay_channels_mutex);
         if (chan->is_global && chan->buf[0])
                 relay_close_buf(chan->buf[0]);
         else
                 for_each_possible_cpu(i)
                         if (chan->buf[i])
                                 relay_close_buf(chan->buf[i]);
 
         if (chan->last_toobig)
                 printk(KERN_WARNING "relay: one or more items not logged "
                        "[item size (%Zd) > sub-buffer size (%Zd)]\n",
                        chan->last_toobig, chan->subbuf_size);
 
         list_del(&chan->list);
         kref_put(&chan->kref, relay_destroy_channel);
         mutex_unlock(&relay_channels_mutex);
 }
 EXPORT_SYMBOL_GPL(relay_close);
 
 /**
  *        relay_flush - close the channel
  *        @chan: the channel
  *
  *        Flushes all channel buffers, i.e. forces buffer switch.
  */
 void relay_flush(struct rchan *chan)
 {
         unsigned int i;
 
         if (!chan)
                 return;
 
         if (chan->is_global && chan->buf[0]) {
                 relay_switch_subbuf(chan->buf[0], 0);
                 return;
         }
 
         mutex_lock(&relay_channels_mutex);
         for_each_possible_cpu(i)
                 if (chan->buf[i])
                         relay_switch_subbuf(chan->buf[i], 0);
         mutex_unlock(&relay_channels_mutex);
 }
 EXPORT_SYMBOL_GPL(relay_flush);
 
 /**
  *        relay_file_open - open file op for relay files
  *        @inode: the inode
  *        @filp: the file
  *
  *        Increments the channel buffer refcount.
  */
 static int relay_file_open(struct inode *inode, struct file *filp)
 {
         struct rchan_buf *buf = inode->i_private;
         kref_get(&buf->kref);
         filp->private_data = buf;
 
         return nonseekable_open(inode, filp);
 }
 
 /**
  *        relay_file_mmap - mmap file op for relay files
  *        @filp: the file
  *        @vma: the vma describing what to map
  *
  *        Calls upon relay_mmap_buf() to map the file into user space.
  */
 static int relay_file_mmap(struct file *filp, struct vm_area_struct *vma)
 {
         struct rchan_buf *buf = filp->private_data;
         return relay_mmap_buf(buf, vma);
 }
 
 /**
  *        relay_file_poll - poll file op for relay files
  *        @filp: the file
  *        @wait: poll table
  *
  *        Poll implemention.
  */
 static unsigned int relay_file_poll(struct file *filp, poll_table *wait)
 {
         unsigned int mask = 0;
         struct rchan_buf *buf = filp->private_data;
 
         if (buf->finalized)
                 return POLLERR;
 
         if (filp->f_mode & FMODE_READ) {
                 poll_wait(filp, &buf->read_wait, wait);
                 if (!relay_buf_empty(buf))
                         mask |= POLLIN | POLLRDNORM;
         }
 
         return mask;
 }
 
 /**
  *        relay_file_release - release file op for relay files
  *        @inode: the inode
  *        @filp: the file
  *
  *        Decrements the channel refcount, as the filesystem is
  *        no longer using it.
  */
 static int relay_file_release(struct inode *inode, struct file *filp)
 {
         struct rchan_buf *buf = filp->private_data;
         kref_put(&buf->kref, relay_remove_buf);
 
         return 0;
 }
 
 /*
  *        relay_file_read_consume - update the consumed count for the buffer
  */
 static void relay_file_read_consume(struct rchan_buf *buf,
                                     size_t read_pos,
                                     size_t bytes_consumed)
 {
         size_t subbuf_size = buf->chan->subbuf_size;
         size_t n_subbufs = buf->chan->n_subbufs;
         size_t read_subbuf;
 
         if (buf->subbufs_produced == buf->subbufs_consumed &&
             buf->offset == buf->bytes_consumed)
                 return;
 
         if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
                 buf->bytes_consumed = 0;
         }
 
         buf->bytes_consumed += bytes_consumed;
         if (!read_pos)
                 read_subbuf = buf->subbufs_consumed % n_subbufs;
         else
                 read_subbuf = read_pos / buf->chan->subbuf_size;
         if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
                 if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
                     (buf->offset == subbuf_size))
                         return;
                 relay_subbufs_consumed(buf->chan, buf->cpu, 1);
                 buf->bytes_consumed = 0;
         }
 }
 
 /*
  *        relay_file_read_avail - boolean, are there unconsumed bytes available?
  */
 static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
 {
         size_t subbuf_size = buf->chan->subbuf_size;
         size_t n_subbufs = buf->chan->n_subbufs;
         size_t produced = buf->subbufs_produced;
         size_t consumed = buf->subbufs_consumed;
 
         relay_file_read_consume(buf, read_pos, 0);
 
         consumed = buf->subbufs_consumed;
 
         if (unlikely(buf->offset > subbuf_size)) {
                 if (produced == consumed)
                         return 0;
                 return 1;
         }
 
         if (unlikely(produced - consumed >= n_subbufs)) {
                 consumed = produced - n_subbufs + 1;
                 buf->subbufs_consumed = consumed;
                 buf->bytes_consumed = 0;
         }
 
         produced = (produced % n_subbufs) * subbuf_size + buf->offset;
         consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
 
         if (consumed > produced)
                 produced += n_subbufs * subbuf_size;

        if (consumed == produced) {
                if (buf->offset == subbuf_size &&
                    buf->subbufs_produced > buf->subbufs_consumed)
                        return 1;
                return 0;
        }

        return 1;
}

/**
 *        relay_file_read_subbuf_avail - return bytes available in sub-buffer
 *        @read_pos: file read position
 *        @buf: relay channel buffer
 */
static size_t relay_file_read_subbuf_avail(size_t read_pos,
                                           struct rchan_buf *buf)
{
        size_t padding, avail = 0;
        size_t read_subbuf, read_offset, write_subbuf, write_offset;
        size_t subbuf_size = buf->chan->subbuf_size;

        write_subbuf = (buf->data - buf->start) / subbuf_size;
        write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
        read_subbuf = read_pos / subbuf_size;
        read_offset = read_pos % subbuf_size;
        padding = buf->padding[read_subbuf];

        if (read_subbuf == write_subbuf) {
                if (read_offset + padding < write_offset)
                        avail = write_offset - (read_offset + padding);
        } else
                avail = (subbuf_size - padding) - read_offset;

        return avail;
}

/**
 *        relay_file_read_start_pos - find the first available byte to read
 *        @read_pos: file read position
 *        @buf: relay channel buffer
 *
 *        If the @read_pos is in the middle of padding, return the
 *        position of the first actually available byte, otherwise
 *        return the original value.
 */
static size_t relay_file_read_start_pos(size_t read_pos,
                                        struct rchan_buf *buf)
{
        size_t read_subbuf, padding, padding_start, padding_end;
        size_t subbuf_size = buf->chan->subbuf_size;
        size_t n_subbufs = buf->chan->n_subbufs;
        size_t consumed = buf->subbufs_consumed % n_subbufs;

        if (!read_pos)
                read_pos = consumed * subbuf_size + buf->bytes_consumed;
        read_subbuf = read_pos / subbuf_size;
        padding = buf->padding[read_subbuf];
        padding_start = (read_subbuf + 1) * subbuf_size - padding;
        padding_end = (read_subbuf + 1) * subbuf_size;
        if (read_pos >= padding_start && read_pos < padding_end) {
                read_subbuf = (read_subbuf + 1) % n_subbufs;
                read_pos = read_subbuf * subbuf_size;
        }

        return read_pos;
}

/**
 *        relay_file_read_end_pos - return the new read position
 *        @read_pos: file read position
 *        @buf: relay channel buffer
 *        @count: number of bytes to be read
 */
static size_t relay_file_read_end_pos(struct rchan_buf *buf,
                                      size_t read_pos,
                                      size_t count)
{
        size_t read_subbuf, padding, end_pos;
        size_t subbuf_size = buf->chan->subbuf_size;
        size_t n_subbufs = buf->chan->n_subbufs;

        read_subbuf = read_pos / subbuf_size;
        padding = buf->padding[read_subbuf];
        if (read_pos % subbuf_size + count + padding == subbuf_size)
                end_pos = (read_subbuf + 1) * subbuf_size;
        else
                end_pos = read_pos + count;
        if (end_pos >= subbuf_size * n_subbufs)
                end_pos = 0;

        return end_pos;
}

/*
 *        subbuf_read_actor - read up to one subbuf's worth of data
 */
static int subbuf_read_actor(size_t read_start,
                             struct rchan_buf *buf,
                             size_t avail,
                             read_descriptor_t *desc,
                             read_actor_t actor)
{
        void *from;
        int ret = 0;

        from = buf->start + read_start;
        ret = avail;
        if (copy_to_user(desc->arg.buf, from, avail)) {
                desc->error = -EFAULT;
                ret = 0;
        }
        desc->arg.data += ret;
        desc->written += ret;
        desc->count -= ret;

        return ret;
}

typedef int (*subbuf_actor_t) (size_t read_start,
                               struct rchan_buf *buf,
                               size_t avail,
                               read_descriptor_t *desc,
                               read_actor_t actor);

/*
 *        relay_file_read_subbufs - read count bytes, bridging subbuf boundaries
 */
static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
                                        subbuf_actor_t subbuf_actor,
                                        read_actor_t actor,
                                        read_descriptor_t *desc)
{
        struct rchan_buf *buf = filp->private_data;
        size_t read_start, avail;
        int ret;

        if (!desc->count)
                return 0;

        mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
        do {
                if (!relay_file_read_avail(buf, *ppos))
                        break;

                read_start = relay_file_read_start_pos(*ppos, buf);
                avail = relay_file_read_subbuf_avail(read_start, buf);
                if (!avail)
                        break;

                avail = min(desc->count, avail);
                ret = subbuf_actor(read_start, buf, avail, desc, actor);
                if (desc->error < 0)
                        break;

                if (ret) {
                        relay_file_read_consume(buf, read_start, ret);
                        *ppos = relay_file_read_end_pos(buf, read_start, ret);
                }
        } while (desc->count && ret);
        mutex_unlock(&filp->f_path.dentry->d_inode->i_mutex);

        return desc->written;
}

static ssize_t relay_file_read(struct file *filp,
                               char __user *buffer,
                               size_t count,
                               loff_t *ppos)
{
        read_descriptor_t desc;
        desc.written = 0;
        desc.count = count;
        desc.arg.buf = buffer;
        desc.error = 0;
        return relay_file_read_subbufs(filp, ppos, subbuf_read_actor,
                                       NULL, &desc);
}

static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
{
        rbuf->bytes_consumed += bytes_consumed;

        if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
                relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
                rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
        }
}

static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
                                   struct pipe_buffer *buf)
{
        struct rchan_buf *rbuf;

        rbuf = (struct rchan_buf *)page_private(buf->page);
        relay_consume_bytes(rbuf, buf->private);
}

static struct pipe_buf_operations relay_pipe_buf_ops = {
        .can_merge = 0,
        .map = generic_pipe_buf_map,
        .unmap = generic_pipe_buf_unmap,
        .confirm = generic_pipe_buf_confirm,
        .release = relay_pipe_buf_release,
        .steal = generic_pipe_buf_steal,
        .get = generic_pipe_buf_get,
};

static void relay_page_release(struct splice_pipe_desc *spd, unsigned int i)
{
}

/*
 *        subbuf_splice_actor - splice up to one subbuf's worth of data
 */
static int subbuf_splice_actor(struct file *in,
                               loff_t *ppos,
                               struct pipe_inode_info *pipe,
                               size_t len,
                               unsigned int flags,
                               int *nonpad_ret)
{
        unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret;
        struct rchan_buf *rbuf = in->private_data;
        unsigned int subbuf_size = rbuf->chan->subbuf_size;
        uint64_t pos = (uint64_t) *ppos;
        uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
        size_t read_start = (size_t) do_div(pos, alloc_size);
        size_t read_subbuf = read_start / subbuf_size;
        size_t padding = rbuf->padding[read_subbuf];
        size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
        struct page *pages[PIPE_BUFFERS];
        struct partial_page partial[PIPE_BUFFERS];
        struct splice_pipe_desc spd = {
                .pages = pages,
                .nr_pages = 0,
                .partial = partial,
                .flags = flags,
                .ops = &relay_pipe_buf_ops,
                .spd_release = relay_page_release,
        };

        if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
                return 0;

        /*
         * Adjust read len, if longer than what is available
         */
        if (len > (subbuf_size - read_start % subbuf_size))
                len = subbuf_size - read_start % subbuf_size;

        subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
        pidx = (read_start / PAGE_SIZE) % subbuf_pages;
        poff = read_start & ~PAGE_MASK;
        nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS);

        for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
                unsigned int this_len, this_end, private;
                unsigned int cur_pos = read_start + total_len;

                if (!len)
                        break;

                this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
                private = this_len;

                spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
                spd.partial[spd.nr_pages].offset = poff;

                this_end = cur_pos + this_len;
                if (this_end >= nonpad_end) {
                        this_len = nonpad_end - cur_pos;
                        private = this_len + padding;
                }
                spd.partial[spd.nr_pages].len = this_len;
                spd.partial[spd.nr_pages].private = private;

                len -= this_len;
                total_len += this_len;
                poff = 0;
                pidx = (pidx + 1) % subbuf_pages;

                if (this_end >= nonpad_end) {
                        spd.nr_pages++;
                        break;
                }
        }

        if (!spd.nr_pages)
                return 0;

        ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
        if (ret < 0 || ret < total_len)
                return ret;

        if (read_start + ret == nonpad_end)
                ret += padding;

        return ret;
}

static ssize_t relay_file_splice_read(struct file *in,
                                      loff_t *ppos,
                                      struct pipe_inode_info *pipe,
                                      size_t len,
                                      unsigned int flags)
{
        ssize_t spliced;
        int ret;
        int nonpad_ret = 0;

        ret = 0;
        spliced = 0;

        while (len && !spliced) {
                ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
                if (ret < 0)
                        break;
                else if (!ret) {
                        if (flags & SPLICE_F_NONBLOCK)
                                ret = -EAGAIN;
                        break;
                }

                *ppos += ret;
                if (ret > len)
                        len = 0;
                else
                        len -= ret;
                spliced += nonpad_ret;
                nonpad_ret = 0;
        }

        if (spliced)
                return spliced;

        return ret;
}

const struct file_operations relay_file_operations = {
        .open                = relay_file_open,
        .poll                = relay_file_poll,
        .mmap                = relay_file_mmap,
        .read                = relay_file_read,
        .llseek                = no_llseek,
        .release        = relay_file_release,
        .splice_read        = relay_file_splice_read,
};
EXPORT_SYMBOL_GPL(relay_file_operations);

static __init int relay_init(void)
{

        hotcpu_notifier(relay_hotcpu_callback, 0);
        return 0;
}

early_initcall(relay_init);