/* * 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);