Re: [PATCHv2 perf/core 5/7] tools lib bpf: Add bpf_program__pin()

[Wangnan (F)]

On 2017/1/23 9:11, Joe Stringer wrote:
Add a new API to pin a BPF program to the filesystem. The user can
specify the path full path within a BPF filesystem to pin the program.
Programs with multiple instances are pinned as 'foo', 'foo_1', 'foo_2',
and so on.

Signed-off-by: Joe Stringer <j...@ovn.org>
---
v2: Don't automount BPF filesystem
     Split program, map, object pinning into separate APIs and separate
     patches.
---
  tools/lib/bpf/libbpf.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++
  tools/lib/bpf/libbpf.h |  1 +
  2 files changed, 77 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e6cd62b1264b..eea5c74808f7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4,6 +4,7 @@
   * Copyright (C) 2013-2015 Alexei Starovoitov <a...@kernel.org>
   * Copyright (C) 2015 Wang Nan <wangn...@huawei.com>
   * Copyright (C) 2015 Huawei Inc.
+ * Copyright (C) 2017 Nicira, Inc.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
@@ -22,6 +23,7 @@
  #include <stdlib.h>
  #include <stdio.h>
  #include <stdarg.h>
+#include <libgen.h>
  #include <inttypes.h>
  #include <string.h>
  #include <unistd.h>
@@ -31,7 +33,10 @@
  #include <linux/err.h>
  #include <linux/kernel.h>
  #include <linux/bpf.h>
+#include <linux/magic.h>
  #include <linux/list.h>
+#include <linux/limits.h>
+#include <sys/vfs.h>
  #include <libelf.h>
  #include <gelf.h>
  
@@ -1237,6 +1242,77 @@ int bpf_object__load(struct bpf_object *obj)
        return err;
  }
  
+static int check_path(const char *path)
+{
+       struct statfs st_fs;
+       char *dname, *dir;
+       int err = 0;
+
+       if (path == NULL)
+               return -EINVAL;
+
+       dname = strdup(path);
+       dir = dirname(dname);
+       if (statfs(dir, &st_fs)) {
+               pr_warning("failed to statfs %s: %s\n", dir, strerror(errno));
+               err = -errno;
+       }
+       free(dname);
+
+       if (!err && st_fs.f_type != BPF_FS_MAGIC) {
+               pr_warning("specified path %s is not on BPF FS\n", path);
+               err = -EINVAL;
+       }
+
+       return err;
+}
+
+int bpf_program__pin(struct bpf_program *prog, const char *path)

In your next patch please let caller select one instance:

int bpf_program__pin(struct bpf_program *prog, int instance, const char 
*path)
(please choose a better name)

Then your can wrap it with another function to pin all instances, implement
naming schema (%s_%d) there.

Then implement naming schema in bpf_object__pin like:

%s/objectname_mapname
%s/objectname_progname_%d

and make a bpf_{map,program}__pin the raw pinning functions with no 
naming schema.

Thank you.