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SubjectRe: [RFC][PATCH 04/12 v3] tracing: Convert seq_buf_path() to be like seq_path()
On Tue 2014-11-04 10:52:41, Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
>
> Rewrite seq_buf_path() like it is done in seq_path() and allow
> it to accept any escape character instead of just "\n".
>
> Making seq_buf_path() like seq_path() will help prevent problems
> when converting seq_file to use the seq_buf logic.
>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> include/linux/seq_buf.h | 2 +-
> kernel/trace/seq_buf.c | 30 ++++++++++++++++--------------
> kernel/trace/trace_seq.c | 2 +-
> 3 files changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h
> index 97872154d51c..6d1c57d6073f 100644
> --- a/include/linux/seq_buf.h
> +++ b/include/linux/seq_buf.h
> @@ -64,7 +64,7 @@ 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);
> extern int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
> unsigned int len);
> -extern int seq_buf_path(struct seq_buf *s, const struct path *path);
> +extern int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc);
>
> extern int seq_buf_bitmask(struct seq_buf *s, const unsigned long *maskp,
> int nmaskbits);
> diff --git a/kernel/trace/seq_buf.c b/kernel/trace/seq_buf.c
> index 2bf582753902..243123b12d16 100644
> --- a/kernel/trace/seq_buf.c
> +++ b/kernel/trace/seq_buf.c
> @@ -272,28 +272,30 @@ int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
> * seq_buf_path - copy a path into the sequence buffer
> * @s: seq_buf descriptor
> * @path: path to write into the sequence buffer.
> + * @esc: set of characters to escape in the output
> *
> * Write a path name into the sequence buffer.
> *
> * Returns zero on success, -1 on overflow
>
> */
> -int seq_buf_path(struct seq_buf *s, const struct path *path)
> +int seq_buf_path(struct seq_buf *s, const struct path *path, const char *esc)
> {
> - unsigned int len = SEQ_BUF_LEFT(s);
> - unsigned char *p;
> -
> - WARN_ON(s->size == 0);

I would keep this check.

> - p = d_path(path, s->buffer + s->len, len);
> - if (!IS_ERR(p)) {
> - p = mangle_path(s->buffer + s->len, p, "\n");
> - if (p) {
> - s->len = p - s->buffer;
> - return 0;
> + char *buf = s->buffer + s->len;
> + size_t size = SEQ_BUF_LEFT(s);

I would use the variable name "len" to make it consistent with
the other fucntions in seq_buf.c.

> + int res = -1;
> +
> + if (size) {
> + char *p = d_path(path, buf, size);
> + if (!IS_ERR(p)) {
> + char *end = mangle_path(buf, p, esc);
> + if (end)
> + res = end - buf;
> }
> }
> - seq_buf_set_overflow(s);

We still should set overflow on failure.

> - return -1;
> + if (res > 0)
> + s->len += res;
> +
> + return res;

It returns -1 on failure and the number of written characters on
success. This is incompatible with the other seq_buf functions
and with the comment above this function. Also it changes the
return value from trace_seq_path().

I do not mind about the used scheme but I think that we should
make it consistent.

Best Regards,
Petr


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