On Wed, Jul 10, 2024 at 10:43:53PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>
> Since file_path() takes the output buffer as one of its arguments, we
> might as well have it format directly into the tracepoint's char array
> instead of wasting stack space.
This looks sensible to me, but..
The nicest way to format the interesting parts of a file path is to
simply use the magic %pD printk specificer, which removes the entire
need for an extra buffer. It would be kinda nice to use that for
tracing, but I can't see how to accomodate the users of the binary
trace buffer with that. Adding Steven and the trace list for
comments.
> - __array(char, pathname, 256)
> + __array(char, pathname, MAXNAMELEN)
> ),
> TP_fast_assign(
> - char pathname[257];
> char *path;
>
> __entry->ino = file_inode(xf->file)->i_ino;
> + path = file_path(xf->file, __entry->pathname, MAXNAMELEN);
> if (IS_ERR(path))
> + strncpy(__entry->pathname, "(unknown)",
> + sizeof(__entry->pathname));
> ),
> TP_printk("xfino 0x%lx path '%s'",
> __entry->ino,
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 56c8333a470bb..0dfb698a43aa4 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -4715,20 +4715,18 @@ TRACE_EVENT(xmbuf_create,
> TP_STRUCT__entry(
> __field(dev_t, dev)
> __field(unsigned long, ino)
> - __array(char, pathname, 256)
> + __array(char, pathname, MAXNAMELEN)
> ),
> TP_fast_assign(
> - char pathname[257];
> char *path;
> struct file *file = btp->bt_file;
>
> __entry->dev = btp->bt_mount->m_super->s_dev;
> __entry->ino = file_inode(file)->i_ino;
> - memset(pathname, 0, sizeof(pathname));
> - path = file_path(file, pathname, sizeof(pathname) - 1);
> + path = file_path(file, __entry->pathname, MAXNAMELEN);
> if (IS_ERR(path))
> - path = "(unknown)";
> - strncpy(__entry->pathname, path, sizeof(__entry->pathname));
> + strncpy(__entry->pathname, "(unknown)",
> + sizeof(__entry->pathname));
> ),
> TP_printk("dev %d:%d xmino 0x%lx path '%s'",
> MAJOR(__entry->dev), MINOR(__entry->dev),
---end quoted text---
----- End forwarded message -----
