diff mbox series

[for-next,5/6] tracing: Move readpos from seq_buf to trace_seq

Message ID 20231020222740.632819967@goodmis.org
State New
Headers
Series tracing: Updates for 6.7 |

Commit Message

Steven Rostedt Oct. 20, 2023, 10:27 p.m. UTC 
  From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

To make seq_buf more lightweight as a string buf, move the readpos member
from seq_buf to its container, trace_seq.  That puts the responsibility
of maintaining the readpos entirely in the tracing code.  If some future
users want to package up the readpos with a seq_buf, we can define a
new struct then.

Link: https://lore.kernel.org/linux-trace-kernel/20231020033545.2587554-2-willy@infradead.org

Cc: Kees Cook <keescook@chromium.org>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 include/linux/seq_buf.h   |  5 +----
 include/linux/trace_seq.h |  2 ++
 kernel/trace/trace.c      | 10 +++++-----
 kernel/trace/trace_seq.c  |  6 +++++-
 lib/seq_buf.c             | 22 ++++++++++------------
 5 files changed, 23 insertions(+), 22 deletions(-)

Comments

Andy Shevchenko Oct. 23, 2023, 9:57 a.m. UTC | #1 
On Fri, Oct 20, 2023 at 06:27:18PM -0400, Steven Rostedt wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> 
> To make seq_buf more lightweight as a string buf, move the readpos member
> from seq_buf to its container, trace_seq.  That puts the responsibility
> of maintaining the readpos entirely in the tracing code.  If some future
> users want to package up the readpos with a seq_buf, we can define a
> new struct then.

> Link: https://lore.kernel.org/linux-trace-kernel/20231020033545.2587554-2-willy@infradead.org
> 

If we want Link: to be recognized as a tag, we probably should remove the blank
line. Maybe new versions of b4 support that, but not all maintainers use it and
AFAIK the convention was to have no blank lines in the tag block.

> Cc: Kees Cook <keescook@chromium.org>
> Cc: Justin Stitt <justinstitt@google.com>
> Cc: Kent Overstreet <kent.overstreet@linux.dev>
> Cc: Petr Mladek <pmladek@suse.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Steven Rostedt Oct. 23, 2023, 2:43 p.m. UTC | #2 
On Mon, 23 Oct 2023 12:57:53 +0300
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Fri, Oct 20, 2023 at 06:27:18PM -0400, Steven Rostedt wrote:
> > From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> > 
> > To make seq_buf more lightweight as a string buf, move the readpos member
> > from seq_buf to its container, trace_seq.  That puts the responsibility
> > of maintaining the readpos entirely in the tracing code.  If some future
> > users want to package up the readpos with a seq_buf, we can define a
> > new struct then.  
> 
> > Link: https://lore.kernel.org/linux-trace-kernel/20231020033545.2587554-2-willy@infradead.org
> >   
> 
> If we want Link: to be recognized as a tag, we probably should remove the blank
> line. Maybe new versions of b4 support that, but not all maintainers use it and
> AFAIK the convention was to have no blank lines in the tag block.
> 

So I've been using Link tags for over a decade. I originally had it as
part of the tag block, but realized that it's more for humans than bots,
and purposely separated it out. What Link tags are good for IMO is for
humans that are looking at git blame and want to know more content. I
prefer the Link tag to stand out so that it's easier for humans to go back
to the archive and see if there was more discussions about why the change
was made.

Hence, I don't really care if Link tags are "recognized" by anything but
humans. It's actually one of the first tags to show up after Signed-off-by:
Cc: and Acked-by:. I believe it even predates "Fixes". At least the new
format for the Fixes tag.

-- Steve
diff mbox series

Patch

diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
index 515d7fcb9634..a0fb013cebdf 100644
--- a/include/linux/seq_buf.h
+++ b/include/linux/seq_buf.h
@@ -14,19 +14,16 @@ 
  * @buffer:	pointer to the buffer
  * @size:	size of the buffer
  * @len:	the amount of data inside the buffer
- * @readpos:	The next position to read in the buffer.
  */
 struct seq_buf {
 	char			*buffer;
 	size_t			size;
 	size_t			len;
-	loff_t			readpos;
 };
 
 static inline void seq_buf_clear(struct seq_buf *s)
 {
 	s->len = 0;
-	s->readpos = 0;
 }
 
 static inline void
@@ -143,7 +140,7 @@  extern __printf(2, 0)
 int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args);
 extern int seq_buf_print_seq(struct seq_file *m, struct seq_buf *s);
 extern int seq_buf_to_user(struct seq_buf *s, char __user *ubuf,
-			   int cnt);
+			   size_t start, int cnt);
 extern int seq_buf_puts(struct seq_buf *s, const char *str);
 extern int seq_buf_putc(struct seq_buf *s, unsigned char c);
 extern int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len);
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 6be92bf559fe..3691e0e76a1a 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -14,6 +14,7 @@ 
 struct trace_seq {
 	char			buffer[PAGE_SIZE];
 	struct seq_buf		seq;
+	size_t			readpos;
 	int			full;
 };
 
@@ -22,6 +23,7 @@  trace_seq_init(struct trace_seq *s)
 {
 	seq_buf_init(&s->seq, s->buffer, PAGE_SIZE);
 	s->full = 0;
+	s->readpos = 0;
 }
 
 /**
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4383be8fa1b0..d629065c2383 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1731,15 +1731,15 @@  static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 {
 	int len;
 
-	if (trace_seq_used(s) <= s->seq.readpos)
+	if (trace_seq_used(s) <= s->readpos)
 		return -EBUSY;
 
-	len = trace_seq_used(s) - s->seq.readpos;
+	len = trace_seq_used(s) - s->readpos;
 	if (cnt > len)
 		cnt = len;
-	memcpy(buf, s->buffer + s->seq.readpos, cnt);
+	memcpy(buf, s->buffer + s->readpos, cnt);
 
-	s->seq.readpos += cnt;
+	s->readpos += cnt;
 	return cnt;
 }
 
@@ -7008,7 +7008,7 @@  tracing_read_pipe(struct file *filp, char __user *ubuf,
 
 	/* Now copy what we have to the user */
 	sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
-	if (iter->seq.seq.readpos >= trace_seq_used(&iter->seq))
+	if (iter->seq.readpos >= trace_seq_used(&iter->seq))
 		trace_seq_init(&iter->seq);
 
 	/*
diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c
index bac06ee3b98b..7be97229ddf8 100644
--- a/kernel/trace/trace_seq.c
+++ b/kernel/trace/trace_seq.c
@@ -370,8 +370,12 @@  EXPORT_SYMBOL_GPL(trace_seq_path);
  */
 int trace_seq_to_user(struct trace_seq *s, char __user *ubuf, int cnt)
 {
+	int ret;
 	__trace_seq_init(s);
-	return seq_buf_to_user(&s->seq, ubuf, cnt);
+	ret = seq_buf_to_user(&s->seq, ubuf, s->readpos, cnt);
+	if (ret > 0)
+		s->readpos += ret;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(trace_seq_to_user);
 
diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index 45c450f423fa..b7477aefff53 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -324,23 +324,24 @@  int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
  * seq_buf_to_user - copy the sequence buffer to user space
  * @s: seq_buf descriptor
  * @ubuf: The userspace memory location to copy to
+ * @start: The first byte in the buffer to copy
  * @cnt: The amount to copy
  *
  * Copies the sequence buffer into the userspace memory pointed to
- * by @ubuf. It starts from the last read position (@s->readpos)
- * and writes up to @cnt characters or till it reaches the end of
- * the content in the buffer (@s->len), which ever comes first.
+ * by @ubuf. It starts from @start and writes up to @cnt characters
+ * or until it reaches the end of the content in the buffer (@s->len),
+ * whichever comes first.
  *
  * On success, it returns a positive number of the number of bytes
  * it copied.
  *
  * On failure it returns -EBUSY if all of the content in the
  * sequence has been already read, which includes nothing in the
- * sequence (@s->len == @s->readpos).
+ * sequence (@s->len == @start).
  *
  * Returns -EFAULT if the copy to userspace fails.
  */
-int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
+int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, size_t start, int cnt)
 {
 	int len;
 	int ret;
@@ -350,20 +351,17 @@  int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
 
 	len = seq_buf_used(s);
 
-	if (len <= s->readpos)
+	if (len <= start)
 		return -EBUSY;
 
-	len -= s->readpos;
+	len -= start;
 	if (cnt > len)
 		cnt = len;
-	ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);
+	ret = copy_to_user(ubuf, s->buffer + start, cnt);
 	if (ret == cnt)
 		return -EFAULT;
 
-	cnt -= ret;
-
-	s->readpos += cnt;
-	return cnt;
+	return cnt - ret;
 }
 
 /**