nilfs2: switch WARN_ONs to warning output in nilfs_sufile_do_free()

nilfs_sufile_do_free(), which is called when log write fails or during GC,
uses WARN_ONs to check for abnormal status of metadata.  In the former
case, these WARN_ONs will not be fired, but in the latter case they don't
"never-happen".  It is possible to trigger these by intentionally
modifying the userland GC library to release segments that are not in the
expected state.

So, replace them with warning output using the dedicated macro
nilfs_warn().

This replaces two potentially triggered WARN_ONs with ones that use a
warning output macro.

Link: https://lkml.kernel.org/r/20231207045730.5205-1-konishi.ryusuke@gmail.comSigned-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/sufile.c

@@ -471,10 +471,15 @@ void nilfs_sufile_do_free(struct inode *sufile, __u64 segnum,
 		kunmap_atomic(kaddr);
 		return;
 	}
-	WARN_ON(nilfs_segment_usage_error(su));
-	WARN_ON(!nilfs_segment_usage_dirty(su));
+	if (unlikely(nilfs_segment_usage_error(su)))
+		nilfs_warn(sufile->i_sb, "free segment %llu marked in error",
+			   (unsigned long long)segnum);
 
 	sudirty = nilfs_segment_usage_dirty(su);
+	if (unlikely(!sudirty))
+		nilfs_warn(sufile->i_sb, "free unallocated segment %llu",
+			   (unsigned long long)segnum);
+
 	nilfs_segment_usage_set_clean(su);
 	kunmap_atomic(kaddr);
 	mark_buffer_dirty(su_bh);