diff options
Diffstat (limited to 'kernel/relay.c')
| -rw-r--r-- | kernel/relay.c | 1335 |
1 files changed, 1335 insertions, 0 deletions
diff --git a/kernel/relay.c b/kernel/relay.c new file mode 100644 index 000000000..f6826dec2 --- /dev/null +++ b/kernel/relay.c @@ -0,0 +1,1335 @@ +/* + * Public API and common code for kernel->userspace relay file support. + * + * See Documentation/filesystems/relay.rst 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/export.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 vm_fault_t relay_buf_fault(struct vm_fault *vmf) +{ + struct page *page; + struct rchan_buf *buf = vmf->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 const 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) +{ + const size_t pa_size = n_pages * sizeof(struct page *); + if (pa_size > PAGE_SIZE) + return vzalloc(pa_size); + return kzalloc(pa_size, GFP_KERNEL); +} + +/* + * free an array of pointers of struct page + */ +static void relay_free_page_array(struct page **array) +{ + kvfree(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_lock. + */ +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; + + if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t)) + return NULL; + + buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL); + if (!buf) + return NULL; + buf->padding = kmalloc_array(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); + free_percpu(chan->buf); + 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); + } + *per_cpu_ptr(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 filesystem, 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); + 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, + umode_t 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 + * @work: contains the channel buffer + * + * This is the function used to defer reader waking + */ +static void wakeup_readers(struct irq_work *work) +{ + struct rchan_buf *buf; + + buf = container_of(work, struct rchan_buf, wakeup_work); + 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); + init_irq_work(&buf->wakeup_work, wakeup_readers); + } else { + irq_work_sync(&buf->wakeup_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) +{ + struct rchan_buf *buf; + unsigned int i; + + if (!chan) + return; + + if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) { + __relay_reset(buf, 0); + return; + } + + mutex_lock(&relay_channels_mutex); + for_each_possible_cpu(i) + if ((buf = *per_cpu_ptr(chan->buf, i))) + __relay_reset(buf, 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; + d_inode(buf->dentry)->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); + if (IS_ERR(dentry)) + dentry = NULL; + + 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 *per_cpu_ptr(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); + } else { + /* Only retrieve global info, nothing more, nothing less */ + dentry = chan->cb->create_buf_file(NULL, NULL, + S_IRUSR, buf, + &chan->is_global); + if (IS_ERR_OR_NULL(dentry)) + goto free_buf; + } + + buf->cpu = cpu; + __relay_reset(buf, 1); + + if(chan->is_global) { + *per_cpu_ptr(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; + irq_work_sync(&buf->wakeup_work); + buf->chan->cb->remove_buf_file(buf->dentry); + 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; +} + +int relay_prepare_cpu(unsigned int cpu) +{ + struct rchan *chan; + struct rchan_buf *buf; + + mutex_lock(&relay_channels_mutex); + list_for_each_entry(chan, &relay_channels, list) { + if ((buf = *per_cpu_ptr(chan->buf, cpu))) + continue; + buf = relay_open_buf(chan, cpu); + if (!buf) { + pr_err("relay: cpu %d buffer creation failed\n", cpu); + mutex_unlock(&relay_channels_mutex); + return -ENOMEM; + } + *per_cpu_ptr(chan->buf, cpu) = buf; + } + mutex_unlock(&relay_channels_mutex); + return 0; +} + +/** + * 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. + * + * If opening a buffer (@parent = NULL) that you later wish to register + * in a filesystem, call relay_late_setup_files() once the @parent dentry + * is available. + */ +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; + struct rchan_buf *buf; + + if (!(subbuf_size && n_subbufs)) + return NULL; + if (subbuf_size > UINT_MAX / n_subbufs) + return NULL; + + chan = kzalloc(sizeof(struct rchan), GFP_KERNEL); + if (!chan) + return NULL; + + chan->buf = alloc_percpu(struct rchan_buf *); + if (!chan->buf) { + kfree(chan); + return NULL; + } + + chan->version = RELAYFS_CHANNEL_VERSION; + chan->n_subbufs = n_subbufs; + chan->subbuf_size = subbuf_size; + chan->alloc_size = PAGE_ALIGN(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) { + buf = relay_open_buf(chan, i); + if (!buf) + goto free_bufs; + *per_cpu_ptr(chan->buf, i) = buf; + } + list_add(&chan->list, &relay_channels); + mutex_unlock(&relay_channels_mutex); + + return chan; + +free_bufs: + for_each_possible_cpu(i) { + if ((buf = *per_cpu_ptr(chan->buf, i))) + relay_close_buf(buf); + } + + 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 created + * by relay_open() with a NULL parent dentry. + * + * For example, this is useful for perfomring early tracing in kernel, + * before VFS is up and then exposing the early results once the dentry + * is available. + */ +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_buf *buf; + 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)) { + mutex_unlock(&relay_channels_mutex); + return -EEXIST; + } + chan->has_base_filename = 1; + chan->parent = parent; + + if (chan->is_global) { + err = -EINVAL; + buf = *per_cpu_ptr(chan->buf, 0); + if (!WARN_ON_ONCE(!buf)) { + dentry = relay_create_buf_file(chan, buf, 0); + if (dentry && !WARN_ON_ONCE(!chan->is_global)) { + relay_set_buf_dentry(buf, dentry); + err = 0; + } + } + mutex_unlock(&relay_channels_mutex); + return err; + } + + 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) { + buf = *per_cpu_ptr(chan->buf, i); + if (unlikely(!buf)) { + WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n"); + err = -EINVAL; + break; + } + + dentry = relay_create_buf_file(chan, buf, i); + if (unlikely(!dentry)) { + err = -EINVAL; + break; + } + + if (curr_cpu == i) { + local_irq_save(flags); + relay_set_buf_dentry(buf, dentry); + local_irq_restore(flags); + } else { + disp.buf = buf; + 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; +} +EXPORT_SYMBOL_GPL(relay_late_setup_files); + +/** + * 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) + d_inode(buf->dentry)->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. + */ + irq_work_queue(&buf->wakeup_work); + } + } + + 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 || cpu >= NR_CPUS) + return; + + buf = *per_cpu_ptr(chan->buf, cpu); + if (!buf || subbufs_consumed > chan->n_subbufs) + return; + + if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed) + buf->subbufs_consumed = buf->subbufs_produced; + else + buf->subbufs_consumed += subbufs_consumed; +} +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) +{ + struct rchan_buf *buf; + unsigned int i; + + if (!chan) + return; + + mutex_lock(&relay_channels_mutex); + if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) + relay_close_buf(buf); + else + for_each_possible_cpu(i) + if ((buf = *per_cpu_ptr(chan->buf, i))) + relay_close_buf(buf); + + 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) +{ + struct rchan_buf *buf; + unsigned int i; + + if (!chan) + return; + + if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) { + relay_switch_subbuf(buf, 0); + return; + } + + mutex_lock(&relay_channels_mutex); + for_each_possible_cpu(i) + if ((buf = *per_cpu_ptr(chan->buf, i))) + relay_switch_subbuf(buf, 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 __poll_t relay_file_poll(struct file *filp, poll_table *wait) +{ + __poll_t mask = 0; + struct rchan_buf *buf = filp->private_data; + + if (buf->finalized) + return EPOLLERR; + + if (filp->f_mode & FMODE_READ) { + poll_wait(filp, &buf->read_wait, wait); + if (!relay_buf_empty(buf)) + mask |= EPOLLIN | EPOLLRDNORM; + } + + 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 subbuf_size = buf->chan->subbuf_size; + size_t n_subbufs = buf->chan->n_subbufs; + size_t produced = buf->subbufs_produced; + size_t consumed; + + relay_file_read_consume(buf, 0, 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 + * @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(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; + size_t read_pos = (consumed * subbuf_size + buf->bytes_consumed) + % (n_subbufs * subbuf_size); + + 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; +} + +static ssize_t relay_file_read(struct file *filp, + char __user *buffer, + size_t count, + loff_t *ppos) +{ + struct rchan_buf *buf = filp->private_data; + size_t read_start, avail; + size_t written = 0; + int ret; + + if (!count) + return 0; + + inode_lock(file_inode(filp)); + do { + void *from; + + if (!relay_file_read_avail(buf)) + break; + + read_start = relay_file_read_start_pos(buf); + avail = relay_file_read_subbuf_avail(read_start, buf); + if (!avail) + break; + + avail = min(count, avail); + from = buf->start + read_start; + ret = avail; + if (copy_to_user(buffer, from, avail)) + break; + + buffer += ret; + written += ret; + count -= ret; + + relay_file_read_consume(buf, read_start, ret); + *ppos = relay_file_read_end_pos(buf, read_start, ret); + } while (count); + inode_unlock(file_inode(filp)); + + return written; +} + +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 const struct pipe_buf_operations relay_pipe_buf_ops = { + .release = relay_pipe_buf_release, + .try_steal = generic_pipe_buf_try_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 ssize_t 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; + 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_DEF_BUFFERS]; + struct partial_page partial[PIPE_DEF_BUFFERS]; + struct splice_pipe_desc spd = { + .pages = pages, + .nr_pages = 0, + .nr_pages_max = PIPE_DEF_BUFFERS, + .partial = partial, + .ops = &relay_pipe_buf_ops, + .spd_release = relay_page_release, + }; + ssize_t ret; + + if (rbuf->subbufs_produced == rbuf->subbufs_consumed) + return 0; + if (splice_grow_spd(pipe, &spd)) + return -ENOMEM; + + /* + * 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, spd.nr_pages_max); + + 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; + } + } + + ret = 0; + if (!spd.nr_pages) + goto out; + + ret = *nonpad_ret = splice_to_pipe(pipe, &spd); + if (ret < 0 || ret < total_len) + goto out; + + if (read_start + ret == nonpad_end) + ret += padding; + +out: + splice_shrink_spd(&spd); + 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); |