Hi Jason,
On Mon, 12 May 2025 10:49:32 +0800
Jason Xing <kerneljasonxing@xxxxxxxxx> wrote:
> From: Jason Xing <kernelxing@xxxxxxxxxxx>
>
> In this version, only support dumping the counter for buffer full and
> implement the framework of how it works. Users MUST pass a valid @buf
> with a valid @len that is required to be larger than RELAY_DUMP_BUF_MAX_LEN
> to acquire which information indicated by @flags to dump.
>
> RELAY_DUMP_BUF_MAX_LEN shows the maximum len of the buffer if users
> choose to dump all the values.
>
> Users can use this buffer to do whatever they expect in their own kernel
> module, say, print to console/dmesg or write them into the relay buffer.
>
> Reviewed-by: Yushan Zhou <katrinzhou@xxxxxxxxxxx>
> Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx>
> ---
> include/linux/relay.h | 10 ++++++++++
> kernel/relay.c | 35 +++++++++++++++++++++++++++++++++++
> 2 files changed, 45 insertions(+)
>
> diff --git a/include/linux/relay.h b/include/linux/relay.h
> index 022cf11e5a92..7a442c4cbead 100644
> --- a/include/linux/relay.h
> +++ b/include/linux/relay.h
> @@ -31,6 +31,15 @@
> /*
> * Relay buffer error statistics dump
> */
> +enum {
> + RELAY_DUMP_BUF_FULL = (1 << 0),
> +
> + RELAY_DUMP_LAST = RELAY_DUMP_BUF_FULL,
> + RELAY_DUMP_MASK = (RELAY_DUMP_LAST - 1) | RELAY_DUMP_LAST
> +};
> +
> +#define RELAY_DUMP_BUF_MAX_LEN 32
> +
> struct rchan_buf_error_stats
> {
> unsigned int full; /* counter for buffer full */
> @@ -170,6 +179,7 @@ extern int relay_late_setup_files(struct rchan *chan,
> struct dentry *parent);
> extern void relay_close(struct rchan *chan);
> extern void relay_flush(struct rchan *chan);
> +extern void relay_dump(struct rchan *chan, char *buf, int len, int flags);
> extern void relay_subbufs_consumed(struct rchan *chan,
> unsigned int cpu,
> size_t consumed);
> diff --git a/kernel/relay.c b/kernel/relay.c
> index b5db4aa60da1..0e675a77285c 100644
> --- a/kernel/relay.c
> +++ b/kernel/relay.c
> @@ -810,6 +810,41 @@ void relay_flush(struct rchan *chan)
> }
> EXPORT_SYMBOL_GPL(relay_flush);
>
> +/**
> + * relay_dump - dump statistics of the specified channel buffer
> + * @chan: the channel
> + * @buf: buf to store statistics
> + * @len: len of buf to check
> + * @flags: select particular information to dump
> + */
> +void relay_dump(struct rchan *chan, char *buf, int len, int flags)
> +{
> + unsigned int i, full_counter = 0;
> + struct rchan_buf *rbuf;
> + int offset = 0;
> +
> + if (!chan || !buf || flags & ~RELAY_DUMP_MASK)
> + return;
> +
> + if (len < RELAY_DUMP_BUF_MAX_LEN)
> + return;
> +
> + if (chan->is_global) {
> + rbuf = *per_cpu_ptr(chan->buf, 0);
> + full_counter = rbuf->stats.full;
> + } else {
> + for_each_possible_cpu(i) {
> + if ((rbuf = *per_cpu_ptr(chan->buf, i)))
> + full_counter += rbuf->stats.full;
> + }
> +
> + if (flags & RELAY_DUMP_BUF_FULL)
> + offset += snprintf(buf, sizeof(unsigned int), "%u", full_counter);
> +
> + snprintf(buf + offset, 1, "\n");
Is there any reason to return the value as string?
If it returns a digit value and the caller makes it a string,
it could be more flexible for other use cases.
Thank you,
> +}
> +EXPORT_SYMBOL_GPL(relay_dump);
> +
> /**
> * relay_file_open - open file op for relay files
> * @inode: the inode
> --
> 2.43.5
>
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
