Documentation/filesystems/relay.rst | 10 --- include/linux/relay.h | 3 - kernel/relay.c | 111 +--------------------------- 3 files changed, 1 insertion(+), 123 deletions(-)
From: "Dr. David Alan Gilbert" <linux@treblig.org>
The last use of relay_late_setup_files() was removed in 2018
by commit 2b47733045aa ("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??)
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
---
Documentation/filesystems/relay.rst | 10 ---
include/linux/relay.h | 3 -
kernel/relay.c | 111 +---------------------------
3 files changed, 1 insertion(+), 123 deletions(-)
diff --git a/Documentation/filesystems/relay.rst b/Documentation/filesystems/relay.rst
index 04ad083cfe62..292ba8492aeb 100644
--- a/Documentation/filesystems/relay.rst
+++ b/Documentation/filesystems/relay.rst
@@ -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'
---------------
diff --git a/include/linux/relay.h b/include/linux/relay.h
index 72b876dd5cb8..b3224111d074 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -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,
diff --git a/kernel/relay.c b/kernel/relay.c
index 5ac7e711e4b6..c0c93a04d4ce 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -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
--
2.49.0On Sat, 19 Apr 2025 00:49:32 +0100 linux@treblig.org wrote:
> From: "Dr. David Alan Gilbert" <linux@treblig.org>
>
> The last use of relay_late_setup_files() was removed in 2018
> by commit 2b47733045aa ("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??)
>
For some reason get_maintainer points at Al and Andy for relay.c but my
mental rolodex thinks "Axboe".
Jens, does this look OK?
> ---
> Documentation/filesystems/relay.rst | 10 ---
> include/linux/relay.h | 3 -
> kernel/relay.c | 111 +---------------------------
> 3 files changed, 1 insertion(+), 123 deletions(-)
>
> diff --git a/Documentation/filesystems/relay.rst b/Documentation/filesystems/relay.rst
> index 04ad083cfe62..292ba8492aeb 100644
> --- a/Documentation/filesystems/relay.rst
> +++ b/Documentation/filesystems/relay.rst
> @@ -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'
> ---------------
>
> diff --git a/include/linux/relay.h b/include/linux/relay.h
> index 72b876dd5cb8..b3224111d074 100644
> --- a/include/linux/relay.h
> +++ b/include/linux/relay.h
> @@ -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,
> diff --git a/kernel/relay.c b/kernel/relay.c
> index 5ac7e711e4b6..c0c93a04d4ce 100644
> --- a/kernel/relay.c
> +++ b/kernel/relay.c
> @@ -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
> --
> 2.49.0
On 4/20/25 3:07 PM, Andrew Morton wrote:
> On Sat, 19 Apr 2025 00:49:32 +0100 linux@treblig.org wrote:
>
>> From: "Dr. David Alan Gilbert" <linux@treblig.org>
>>
>> The last use of relay_late_setup_files() was removed in 2018
>> by commit 2b47733045aa ("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??)
>>
>
> For some reason get_maintainer points at Al and Andy for relay.c but my
> mental rolodex thinks "Axboe".
Heh, probably because I did dabble in it 20 YEARS AGO as we used it for
the original blktrace! I'm not saying we're both old, but...
> Jens, does this look OK?
Looks fine to me.
Reviewed-by: Jens Axboe <axboe@kernel.dk>
--
Jens Axboe
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