xfs: fix file_path handling in tracepoints

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.

Fixes: 3934e8e ("xfs: create a big array data structure")
Fixes: 5076a60 ("xfs: support in-memory buffer cache targets")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403290419.HPcyvqZu-lkp@intel.com/
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

Author: Darrick J. Wong

fs/xfs/scrub/trace.h

@@ -959,18 +959,16 @@ TRACE_EVENT(xfile_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;
 
 		__entry->ino = file_inode(xf->file)->i_ino;
-		memset(pathname, 0, sizeof(pathname));
-		path = file_path(xf->file, pathname, sizeof(pathname) - 1);
+		path = file_path(xf->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("xfino 0x%lx path '%s'",
 		  __entry->ino,

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),