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relay: remove unused relay_late_setup_files

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The last use of relay_late_setup_files() was removed in 2018 by commit
2b47733045 ("drm/i915/guc: Merge log relay file and channel creation")

Remove it and the helper it used.

relay_late_setup_files() was used for eventually registering 'buffer only'
channels.  With it gone, delete the docs that explain how to do that. 
Which suggests it should be possible to lose the 'has_base_filename'
flags.

(Are there any other uses??)

Link: https://lkml.kernel.org/r/20250418234932.490863-1-linux@treblig.org
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Dr. David Alan Gilbert 2025-04-19 00:49:32 +01:00 • committed by Andrew Morton
parent ba8182d44b
commit 2a1c615813
3 changed files with 1 additions and 123 deletions
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10
Documentation/filesystems/relay.rst
View file

@ -301,16 +301,6 @@ user-defined data with a channel, and is immediately available
(including in create_buf_file()) via chan->private_data or
buf->chan->private_data.
Buffer-only channels
--------------------
These channels have no files associated and can be created with
relay_open(NULL, NULL, ...). Such channels are useful in scenarios such
as when doing early tracing in the kernel, before the VFS is up. In these
cases, one may open a buffer-only channel and then call
relay_late_setup_files() when the kernel is ready to handle files,
to expose the buffered data to the userspace.
Channel 'modes'
---------------

3
include/linux/relay.h
View file

@ -159,9 +159,6 @@ struct rchan *relay_open(const char *base_filename,
size_t n_subbufs,
const struct rchan_callbacks *cb,
void *private_data);
extern int relay_late_setup_files(struct rchan *chan,
const char *base_filename,
struct dentry *parent);
extern void relay_close(struct rchan *chan);
extern void relay_flush(struct rchan *chan);
extern void relay_subbufs_consumed(struct rchan *chan,

111
kernel/relay.c
View file

@ -452,7 +452,7 @@ int relay_prepare_cpu(unsigned int cpu)
/**
* relay_open - create a new relay channel
* @base_filename: base name of files to create, %NULL for buffering only
* @base_filename: base name of files to create
* @parent: dentry of parent directory, %NULL for root directory or buffer
* @subbuf_size: size of sub-buffers
* @n_subbufs: number of sub-buffers
@ -465,10 +465,6 @@ int relay_prepare_cpu(unsigned int cpu)
* 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,
@ -540,111 +536,6 @@ struct rchan_percpu_buf_dispatcher {
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