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d391615618
Documentation/filesystems/relay.rst says to use
return debugfs_create_file(filename, mode, parent, buf,
&relay_file_operations);
and this is the only way relay_file_operations is used.
Thus: debugfs_create_file(&relay_file_operations)
-> __debugfs_create_file(&debugfs_full_proxy_file_operations,
&relay_file_operations)
-> dentry{inode: {i_fop: &debugfs_full_proxy_file_operations},
d_fsdata: &relay_file_operations
| DEBUGFS_FSDATA_IS_REAL_FOPS_BIT}
debugfs_full_proxy_file_operations.open is full_proxy_open, which extracts
the &relay_file_operations from the dentry, and allocates via
__full_proxy_fops_init() new fops, with trivial wrappers around release,
llseek, read, write, poll, and unlocked_ioctl, then replaces the fops on
the opened file therewith.
Naturally, all thusly-created debugfs files have .splice_read = NULL.
This was introduced in commit 49d200deaa
("debugfs: prevent access to
removed files' private data") from 2016-03-22.
AFAICT, relay_file_operations is the only struct file_operations used for
debugfs which defines a .splice_read callback. Hooking it up with
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> index 5063434be0fc..952fcf5b2afa 100644
> --- a/fs/debugfs/file.c
> +++ b/fs/debugfs/file.c
> @@ -328,6 +328,11 @@ FULL_PROXY_FUNC(write, ssize_t, filp,
> loff_t *ppos),
> ARGS(filp, buf, size, ppos));
>
> +FULL_PROXY_FUNC(splice_read, long, in,
> + PROTO(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe,
> + size_t len, unsigned int flags),
> + ARGS(in, ppos, pipe, len, flags));
> +
> FULL_PROXY_FUNC(unlocked_ioctl, long, filp,
> PROTO(struct file *filp, unsigned int cmd, unsigned long arg),
> ARGS(filp, cmd, arg));
> @@ -382,6 +387,8 @@ static void __full_proxy_fops_init(struct file_operations *proxy_fops,
> proxy_fops->write = full_proxy_write;
> if (real_fops->poll)
> proxy_fops->poll = full_proxy_poll;
> + if (real_fops->splice_read)
> + proxy_fops->splice_read = full_proxy_splice_read;
> if (real_fops->unlocked_ioctl)
> proxy_fops->unlocked_ioctl = full_proxy_unlocked_ioctl;
> }
shows it just doesn't work, and splicing always instantly returns empty
(subsequent reads actually return the contents).
No-one noticed it became dead code in 2016, who knows if it worked back
then. Clearly no-one cares; just delete it.
Link: https://lkml.kernel.org/r/dtexwpw6zcdx7dkx3xj5gyjp5syxmyretdcbcdtvrnukd4vvuh@tarta.nabijaczleweli.xyz
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Li kunyu <kunyu@nfschina.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zhang Zhengming <zhang.zhengming@h3c.com>
Cc: Zhao Lei <zhao_lei1@hoperun.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1086 lines
26 KiB
C
1086 lines
26 KiB
C
/*
|
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* Public API and common code for kernel->userspace relay file support.
|
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*
|
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* See Documentation/filesystems/relay.rst for an overview.
|
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*
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* Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
|
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* Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
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*
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* Moved to kernel/relay.c by Paul Mundt, 2006.
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* November 2006 - CPU hotplug support by Mathieu Desnoyers
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* (mathieu.desnoyers@polymtl.ca)
|
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*
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* This file is released under the GPL.
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*/
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#include <linux/errno.h>
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#include <linux/stddef.h>
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#include <linux/slab.h>
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#include <linux/export.h>
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#include <linux/string.h>
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#include <linux/relay.h>
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#include <linux/vmalloc.h>
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#include <linux/mm.h>
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#include <linux/cpu.h>
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#include <linux/splice.h>
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/* list of open channels, for cpu hotplug */
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static DEFINE_MUTEX(relay_channels_mutex);
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static LIST_HEAD(relay_channels);
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/*
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* fault() vm_op implementation for relay file mapping.
|
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*/
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static vm_fault_t relay_buf_fault(struct vm_fault *vmf)
|
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{
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struct page *page;
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struct rchan_buf *buf = vmf->vma->vm_private_data;
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pgoff_t pgoff = vmf->pgoff;
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if (!buf)
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return VM_FAULT_OOM;
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page = vmalloc_to_page(buf->start + (pgoff << PAGE_SHIFT));
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if (!page)
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return VM_FAULT_SIGBUS;
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get_page(page);
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vmf->page = page;
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return 0;
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}
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/*
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* vm_ops for relay file mappings.
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*/
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static const struct vm_operations_struct relay_file_mmap_ops = {
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.fault = relay_buf_fault,
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};
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/*
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* allocate an array of pointers of struct page
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*/
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static struct page **relay_alloc_page_array(unsigned int n_pages)
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{
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return kvcalloc(n_pages, sizeof(struct page *), GFP_KERNEL);
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}
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/*
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* free an array of pointers of struct page
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*/
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static void relay_free_page_array(struct page **array)
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{
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kvfree(array);
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}
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/**
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* relay_mmap_buf: - mmap channel buffer to process address space
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* @buf: relay channel buffer
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* @vma: vm_area_struct describing memory to be mapped
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*
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* Returns 0 if ok, negative on error
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*
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* Caller should already have grabbed mmap_lock.
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*/
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static int relay_mmap_buf(struct rchan_buf *buf, struct vm_area_struct *vma)
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{
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unsigned long length = vma->vm_end - vma->vm_start;
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if (!buf)
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return -EBADF;
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if (length != (unsigned long)buf->chan->alloc_size)
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return -EINVAL;
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vma->vm_ops = &relay_file_mmap_ops;
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vm_flags_set(vma, VM_DONTEXPAND);
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vma->vm_private_data = buf;
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return 0;
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}
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/**
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* relay_alloc_buf - allocate a channel buffer
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* @buf: the buffer struct
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* @size: total size of the buffer
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*
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* Returns a pointer to the resulting buffer, %NULL if unsuccessful. The
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* passed in size will get page aligned, if it isn't already.
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*/
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static void *relay_alloc_buf(struct rchan_buf *buf, size_t *size)
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{
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void *mem;
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unsigned int i, j, n_pages;
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*size = PAGE_ALIGN(*size);
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n_pages = *size >> PAGE_SHIFT;
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buf->page_array = relay_alloc_page_array(n_pages);
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if (!buf->page_array)
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return NULL;
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for (i = 0; i < n_pages; i++) {
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buf->page_array[i] = alloc_page(GFP_KERNEL);
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if (unlikely(!buf->page_array[i]))
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goto depopulate;
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set_page_private(buf->page_array[i], (unsigned long)buf);
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}
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mem = vmap(buf->page_array, n_pages, VM_MAP, PAGE_KERNEL);
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if (!mem)
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goto depopulate;
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memset(mem, 0, *size);
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buf->page_count = n_pages;
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return mem;
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depopulate:
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for (j = 0; j < i; j++)
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__free_page(buf->page_array[j]);
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relay_free_page_array(buf->page_array);
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return NULL;
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}
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/**
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* relay_create_buf - allocate and initialize a channel buffer
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* @chan: the relay channel
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*
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* Returns channel buffer if successful, %NULL otherwise.
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*/
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static struct rchan_buf *relay_create_buf(struct rchan *chan)
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{
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struct rchan_buf *buf;
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if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t))
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return NULL;
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buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);
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if (!buf)
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return NULL;
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buf->padding = kmalloc_array(chan->n_subbufs, sizeof(size_t),
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GFP_KERNEL);
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if (!buf->padding)
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goto free_buf;
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buf->start = relay_alloc_buf(buf, &chan->alloc_size);
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if (!buf->start)
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goto free_buf;
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buf->chan = chan;
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kref_get(&buf->chan->kref);
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return buf;
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free_buf:
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kfree(buf->padding);
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kfree(buf);
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return NULL;
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}
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/**
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* relay_destroy_channel - free the channel struct
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* @kref: target kernel reference that contains the relay channel
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*
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* Should only be called from kref_put().
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*/
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static void relay_destroy_channel(struct kref *kref)
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{
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struct rchan *chan = container_of(kref, struct rchan, kref);
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free_percpu(chan->buf);
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kfree(chan);
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}
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/**
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* relay_destroy_buf - destroy an rchan_buf struct and associated buffer
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* @buf: the buffer struct
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*/
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static void relay_destroy_buf(struct rchan_buf *buf)
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{
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struct rchan *chan = buf->chan;
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unsigned int i;
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if (likely(buf->start)) {
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vunmap(buf->start);
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for (i = 0; i < buf->page_count; i++)
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__free_page(buf->page_array[i]);
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relay_free_page_array(buf->page_array);
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}
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*per_cpu_ptr(chan->buf, buf->cpu) = NULL;
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kfree(buf->padding);
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kfree(buf);
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kref_put(&chan->kref, relay_destroy_channel);
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}
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/**
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* relay_remove_buf - remove a channel buffer
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* @kref: target kernel reference that contains the relay buffer
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*
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* Removes the file from the filesystem, which also frees the
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* rchan_buf_struct and the channel buffer. Should only be called from
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* kref_put().
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*/
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static void relay_remove_buf(struct kref *kref)
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{
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struct rchan_buf *buf = container_of(kref, struct rchan_buf, kref);
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relay_destroy_buf(buf);
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}
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/**
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* relay_buf_empty - boolean, is the channel buffer empty?
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* @buf: channel buffer
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*
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* Returns 1 if the buffer is empty, 0 otherwise.
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*/
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static int relay_buf_empty(struct rchan_buf *buf)
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{
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return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
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}
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/**
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* relay_buf_full - boolean, is the channel buffer full?
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* @buf: channel buffer
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*
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* Returns 1 if the buffer is full, 0 otherwise.
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*/
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int relay_buf_full(struct rchan_buf *buf)
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{
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size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
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return (ready >= buf->chan->n_subbufs) ? 1 : 0;
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}
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EXPORT_SYMBOL_GPL(relay_buf_full);
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/*
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* High-level relay kernel API and associated functions.
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*/
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static int relay_subbuf_start(struct rchan_buf *buf, void *subbuf,
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void *prev_subbuf, size_t prev_padding)
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{
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if (!buf->chan->cb->subbuf_start)
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return !relay_buf_full(buf);
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return buf->chan->cb->subbuf_start(buf, subbuf,
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prev_subbuf, prev_padding);
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}
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/**
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* wakeup_readers - wake up readers waiting on a channel
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* @work: contains the channel buffer
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*
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* This is the function used to defer reader waking
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*/
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static void wakeup_readers(struct irq_work *work)
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{
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struct rchan_buf *buf;
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buf = container_of(work, struct rchan_buf, wakeup_work);
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wake_up_interruptible(&buf->read_wait);
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}
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/**
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* __relay_reset - reset a channel buffer
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* @buf: the channel buffer
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* @init: 1 if this is a first-time initialization
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*
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* See relay_reset() for description of effect.
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*/
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static void __relay_reset(struct rchan_buf *buf, unsigned int init)
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{
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size_t i;
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if (init) {
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init_waitqueue_head(&buf->read_wait);
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kref_init(&buf->kref);
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init_irq_work(&buf->wakeup_work, wakeup_readers);
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} else {
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irq_work_sync(&buf->wakeup_work);
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}
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buf->subbufs_produced = 0;
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buf->subbufs_consumed = 0;
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buf->bytes_consumed = 0;
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buf->finalized = 0;
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buf->data = buf->start;
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buf->offset = 0;
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for (i = 0; i < buf->chan->n_subbufs; i++)
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buf->padding[i] = 0;
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relay_subbuf_start(buf, buf->data, NULL, 0);
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}
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/**
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* relay_reset - reset the channel
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* @chan: the channel
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*
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* This has the effect of erasing all data from all channel buffers
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* and restarting the channel in its initial state. The buffers
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* are not freed, so any mappings are still in effect.
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*
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* NOTE. Care should be taken that the channel isn't actually
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* being used by anything when this call is made.
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*/
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void relay_reset(struct rchan *chan)
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{
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struct rchan_buf *buf;
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unsigned int i;
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if (!chan)
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return;
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if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
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__relay_reset(buf, 0);
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return;
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}
|
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mutex_lock(&relay_channels_mutex);
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for_each_possible_cpu(i)
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if ((buf = *per_cpu_ptr(chan->buf, i)))
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__relay_reset(buf, 0);
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mutex_unlock(&relay_channels_mutex);
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}
|
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EXPORT_SYMBOL_GPL(relay_reset);
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|
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static inline void relay_set_buf_dentry(struct rchan_buf *buf,
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struct dentry *dentry)
|
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{
|
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buf->dentry = dentry;
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d_inode(buf->dentry)->i_size = buf->early_bytes;
|
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}
|
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|
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static struct dentry *relay_create_buf_file(struct rchan *chan,
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struct rchan_buf *buf,
|
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unsigned int cpu)
|
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{
|
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struct dentry *dentry;
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char *tmpname;
|
|
|
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tmpname = kzalloc(NAME_MAX + 1, GFP_KERNEL);
|
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if (!tmpname)
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return NULL;
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snprintf(tmpname, NAME_MAX, "%s%d", chan->base_filename, cpu);
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|
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/* Create file in fs */
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dentry = chan->cb->create_buf_file(tmpname, chan->parent,
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S_IRUSR, buf,
|
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&chan->is_global);
|
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if (IS_ERR(dentry))
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dentry = NULL;
|
|
|
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kfree(tmpname);
|
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|
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return dentry;
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}
|
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|
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/*
|
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* relay_open_buf - create a new relay channel buffer
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*
|
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* used by relay_open() and CPU hotplug.
|
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*/
|
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static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
|
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{
|
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struct rchan_buf *buf;
|
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struct dentry *dentry;
|
|
|
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if (chan->is_global)
|
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return *per_cpu_ptr(chan->buf, 0);
|
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|
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buf = relay_create_buf(chan);
|
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if (!buf)
|
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return NULL;
|
|
|
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if (chan->has_base_filename) {
|
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dentry = relay_create_buf_file(chan, buf, cpu);
|
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if (!dentry)
|
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goto free_buf;
|
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relay_set_buf_dentry(buf, dentry);
|
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} else {
|
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/* Only retrieve global info, nothing more, nothing less */
|
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dentry = chan->cb->create_buf_file(NULL, NULL,
|
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S_IRUSR, buf,
|
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&chan->is_global);
|
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if (IS_ERR_OR_NULL(dentry))
|
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goto free_buf;
|
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}
|
|
|
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buf->cpu = cpu;
|
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__relay_reset(buf, 1);
|
|
|
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if(chan->is_global) {
|
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*per_cpu_ptr(chan->buf, 0) = buf;
|
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buf->cpu = 0;
|
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}
|
|
|
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return buf;
|
|
|
|
free_buf:
|
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relay_destroy_buf(buf);
|
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return NULL;
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}
|
|
|
|
/**
|
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* relay_close_buf - close a channel buffer
|
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* @buf: channel buffer
|
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*
|
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* Marks the buffer finalized and restores the default callbacks.
|
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* The channel buffer and channel buffer data structure are then freed
|
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* automatically when the last reference is given up.
|
|
*/
|
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static void relay_close_buf(struct rchan_buf *buf)
|
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{
|
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buf->finalized = 1;
|
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irq_work_sync(&buf->wakeup_work);
|
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buf->chan->cb->remove_buf_file(buf->dentry);
|
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kref_put(&buf->kref, relay_remove_buf);
|
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}
|
|
|
|
int relay_prepare_cpu(unsigned int cpu)
|
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{
|
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struct rchan *chan;
|
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struct rchan_buf *buf;
|
|
|
|
mutex_lock(&relay_channels_mutex);
|
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list_for_each_entry(chan, &relay_channels, list) {
|
|
if (*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,
|
|
const 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;
|
|
if (!cb || !cb->create_buf_file || !cb->remove_buf_file)
|
|
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;
|
|
strscpy(chan->base_filename, base_filename, NAME_MAX);
|
|
}
|
|
chan->cb = 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;
|
|
|
|
strscpy(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 (!relay_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;
|
|
}
|
|
|
|
|
|
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,
|
|
};
|
|
EXPORT_SYMBOL_GPL(relay_file_operations);
|