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relayfs: abolish prev_padding

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Patch series "relayfs: misc changes", v5.

The series mostly focuses on the error counters which helps every user
debug their own kernel module.


This patch (of 5):

prev_padding represents the unused space of certain subbuffer.  If the
content of a call of relay_write() exceeds the limit of the remainder of
this subbuffer, it will skip storing in the rest space and record the
start point as buf->prev_padding in relay_switch_subbuf().  Since the buf
is a per-cpu big buffer, the point of prev_padding as a global value for
the whole buffer instead of a single subbuffer (whose padding info is
stored in buf->padding[]) seems meaningless from the real use cases, so we
don't bother to record it any more.

Link: https://lkml.kernel.org/r/20250612061201.34272-1-kerneljasonxing@gmail.com
Link: https://lkml.kernel.org/r/20250612061201.34272-2-kerneljasonxing@gmail.com
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Yushan Zhou <katrinzhou@tencent.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jason Xing
2025-07-09 22:57:51 -07:00
committed by Andrew Morton
parent c9e3fb050e
commit 2489e95812
6 changed files with 13 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/relay.c
+8 -6
View File
@@ -249,13 +249,13 @@ EXPORT_SYMBOL_GPL(relay_buf_full);
*/
static int relay_subbuf_start(struct rchan_buf *buf, void *subbuf,
void *prev_subbuf, size_t prev_padding)
void *prev_subbuf)
{
if (!buf->chan->cb->subbuf_start)
return !relay_buf_full(buf);
return buf->chan->cb->subbuf_start(buf, subbuf,
prev_subbuf, prev_padding);
prev_subbuf);
}
/**
@@ -301,7 +301,7 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
for (i = 0; i < buf->chan->n_subbufs; i++)
buf->padding[i] = 0;
relay_subbuf_start(buf, buf->data, NULL, 0);
relay_subbuf_start(buf, buf->data, NULL);
}
/**
@@ -554,9 +554,11 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
goto toobig;
if (buf->offset != buf->chan->subbuf_size + 1) {
buf->prev_padding = buf->chan->subbuf_size - buf->offset;
size_t prev_padding;
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->padding[old_subbuf] = prev_padding;
buf->subbufs_produced++;
if (buf->dentry)
d_inode(buf->dentry)->i_size +=
@@ -581,7 +583,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
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)) {
if (!relay_subbuf_start(buf, new, old)) {
buf->offset = buf->chan->subbuf_size + 1;
return 0;
}
kernel/trace/blktrace.c
+1 -1
View File
@@ -461,7 +461,7 @@ static const struct file_operations blk_msg_fops = {
* the user space app in telling how many lost events there were.
*/
static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
void *prev_subbuf, size_t prev_padding)
void *prev_subbuf)
{
struct blk_trace *bt;