| /* |
| * Public API and common code for kernel->userspace relay file support. |
| * |
| * See Documentation/filesystems/relayfs.txt for an overview of relayfs. |
| * |
| * 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. |
| * |
| * 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> |
| |
| /* |
| * 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); |
| } |
| |
| /* |
| * nopage() vm_op implementation for relay file mapping. |
| */ |
| static struct page *relay_buf_nopage(struct vm_area_struct *vma, |
| unsigned long address, |
| int *type) |
| { |
| struct page *page; |
| struct rchan_buf *buf = vma->vm_private_data; |
| unsigned long offset = address - vma->vm_start; |
| |
| if (address > vma->vm_end) |
| return NOPAGE_SIGBUS; /* Disallow mremap */ |
| if (!buf) |
| return NOPAGE_OOM; |
| |
| page = vmalloc_to_page(buf->start + offset); |
| if (!page) |
| return NOPAGE_OOM; |
| get_page(page); |
| |
| if (type) |
| *type = VM_FAULT_MINOR; |
| |
| return page; |
| } |
| |
| /* |
| * vm_ops for relay file mappings. |
| */ |
| static struct vm_operations_struct relay_file_mmap_ops = { |
| .nopage = relay_buf_nopage, |
| .close = relay_file_mmap_close, |
| }; |
| |
| /** |
| * 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. |
| */ |
| 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_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 = kcalloc(n_pages, sizeof(struct page *), GFP_KERNEL); |
| 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; |
| } |
| 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]); |
| kfree(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. |
| */ |
| struct rchan_buf *relay_create_buf(struct rchan *chan) |
| { |
| struct rchan_buf *buf = kcalloc(1, 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(). |
| */ |
| 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 |
| */ |
| 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]); |
| kfree(buf->page_array); |
| } |
| 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(). |
| */ |
| 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. |
| */ |
| int relay_buf_empty(struct rchan_buf *buf) |
| { |
| return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1; |
| } |
| EXPORT_SYMBOL_GPL(relay_buf_empty); |
| |
| /** |
| * 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 |
| * @private: the channel buffer |
| * |
| * This is the work function used to defer reader waking. The |
| * reason waking is deferred is that calling directly from write |
| * causes problems if you're writing from say the scheduler. |
| */ |
| static void wakeup_readers(void *private) |
| { |
| struct rchan_buf *buf = private; |
| 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 inline 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); |
| INIT_WORK(&buf->wake_readers, NULL, NULL); |
| } else { |
| cancel_delayed_work(&buf->wake_readers); |
| flush_scheduled_work(); |
| } |
| |
| 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; |
| struct rchan_buf *prev = NULL; |
| |
| if (!chan) |
| return; |
| |
| for (i = 0; i < NR_CPUS; i++) { |
| if (!chan->buf[i] || chan->buf[i] == prev) |
| break; |
| __relay_reset(chan->buf[i], 0); |
| prev = chan->buf[i]; |
| } |
| } |
| EXPORT_SYMBOL_GPL(relay_reset); |
| |
| /* |
| * relay_open_buf - create a new relay channel buffer |
| * |
| * Internal - used by relay_open(). |
| */ |
| static struct rchan_buf *relay_open_buf(struct rchan *chan, |
| const char *filename, |
| struct dentry *parent, |
| int *is_global) |
| { |
| struct rchan_buf *buf; |
| struct dentry *dentry; |
| |
| if (*is_global) |
| return chan->buf[0]; |
| |
| buf = relay_create_buf(chan); |
| if (!buf) |
| return NULL; |
| |
| /* Create file in fs */ |
| dentry = chan->cb->create_buf_file(filename, parent, S_IRUSR, |
| buf, is_global); |
| if (!dentry) { |
| relay_destroy_buf(buf); |
| return NULL; |
| } |
| |
| buf->dentry = dentry; |
| __relay_reset(buf, 1); |
| |
| return buf; |
| } |
| |
| /** |
| * 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 inline void relay_close_buf(struct rchan_buf *buf) |
| { |
| buf->finalized = 1; |
| cancel_delayed_work(&buf->wake_readers); |
| flush_scheduled_work(); |
| kref_put(&buf->kref, relay_remove_buf); |
| } |
| |
| static inline 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_open - create a new relay channel |
| * @base_filename: base name of files to create |
| * @parent: dentry of parent directory, %NULL for root directory |
| * @subbuf_size: size of sub-buffers |
| * @n_subbufs: number of sub-buffers |
| * @cb: client callback functions |
| * |
| * 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) |
| { |
| unsigned int i; |
| struct rchan *chan; |
| char *tmpname; |
| int is_global = 0; |
| |
| if (!base_filename) |
| return NULL; |
| |
| if (!(subbuf_size && n_subbufs)) |
| return NULL; |
| |
| chan = kcalloc(1, 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); |
| setup_callbacks(chan, cb); |
| kref_init(&chan->kref); |
| |
| tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL); |
| if (!tmpname) |
| goto free_chan; |
| |
| for_each_online_cpu(i) { |
| sprintf(tmpname, "%s%d", base_filename, i); |
| chan->buf[i] = relay_open_buf(chan, tmpname, parent, |
| &is_global); |
| if (!chan->buf[i]) |
| goto free_bufs; |
| |
| chan->buf[i]->cpu = i; |
| } |
| |
| kfree(tmpname); |
| return chan; |
| |
| free_bufs: |
| for (i = 0; i < NR_CPUS; i++) { |
| if (!chan->buf[i]) |
| break; |
| relay_close_buf(chan->buf[i]); |
| if (is_global) |
| break; |
| } |
| kfree(tmpname); |
| |
| free_chan: |
| kref_put(&chan->kref, relay_destroy_channel); |
| return NULL; |
| } |
| EXPORT_SYMBOL_GPL(relay_open); |
| |
| /** |
| * 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++; |
| buf->dentry->d_inode->i_size += buf->chan->subbuf_size - |
| buf->padding[old_subbuf]; |
| smp_mb(); |
| if (waitqueue_active(&buf->read_wait)) { |
| PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf); |
| schedule_delayed_work(&buf->wake_readers, 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; |
| struct rchan_buf *prev = NULL; |
| |
| if (!chan) |
| return; |
| |
| for (i = 0; i < NR_CPUS; i++) { |
| if (!chan->buf[i] || chan->buf[i] == prev) |
| break; |
| relay_close_buf(chan->buf[i]); |
| prev = 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); |
| |
| kref_put(&chan->kref, relay_destroy_channel); |
| } |
| 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; |
| struct rchan_buf *prev = NULL; |
| |
| if (!chan) |
| return; |
| |
| for (i = 0; i < NR_CPUS; i++) { |
| if (!chan->buf[i] || chan->buf[i] == prev) |
| break; |
| relay_switch_subbuf(chan->buf[i], 0); |
| prev = chan->buf[i]; |
| } |
| } |
| 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 0; |
| } |
| |
| /** |
| * 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->bytes_consumed + bytes_consumed > subbuf_size) { |
| relay_subbufs_consumed(buf->chan, buf->cpu, 1); |
| buf->bytes_consumed = 0; |
| } |
| |
| buf->bytes_consumed += bytes_consumed; |
| 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); |
| |
| if (unlikely(buf->offset > subbuf_size)) { |
| if (produced == consumed) |
| return 0; |
| return 1; |
| } |
| |
| if (unlikely(produced - consumed >= n_subbufs)) { |
| consumed = (produced / n_subbufs) * n_subbufs; |
| buf->subbufs_consumed = consumed; |
| } |
| |
| 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) |
| 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; |
| |
| 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; |
| } |
| |
| /* |
| * subbuf_send_actor - send up to one subbuf's worth of data |
| */ |
| static int subbuf_send_actor(size_t read_start, |
| struct rchan_buf *buf, |
| size_t avail, |
| read_descriptor_t *desc, |
| read_actor_t actor) |
| { |
| unsigned long pidx, poff; |
| unsigned int subbuf_pages; |
| int ret = 0; |
| |
| subbuf_pages = buf->chan->alloc_size >> PAGE_SHIFT; |
| pidx = (read_start / PAGE_SIZE) % subbuf_pages; |
| poff = read_start & ~PAGE_MASK; |
| while (avail) { |
| struct page *p = buf->page_array[pidx]; |
| unsigned int len; |
| |
| len = PAGE_SIZE - poff; |
| if (len > avail) |
| len = avail; |
| |
| len = actor(desc, p, poff, len); |
| if (desc->error) |
| break; |
| |
| avail -= len; |
| ret += len; |
| poff = 0; |
| pidx = (pidx + 1) % subbuf_pages; |
| } |
| |
| 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 inline 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_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_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 ssize_t relay_file_sendfile(struct file *filp, |
| loff_t *ppos, |
| size_t count, |
| read_actor_t actor, |
| void *target) |
| { |
| read_descriptor_t desc; |
| desc.written = 0; |
| desc.count = count; |
| desc.arg.data = target; |
| desc.error = 0; |
| return relay_file_read_subbufs(filp, ppos, subbuf_send_actor, |
| actor, &desc); |
| } |
| |
| 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, |
| .sendfile = relay_file_sendfile, |
| }; |
| EXPORT_SYMBOL_GPL(relay_file_operations); |