[PATCH 23/25] fsinfo: bpf - add sb operation fsinfo() [ver #13]

[David Howells]

From: Ian Kent <ra...@themaw.net>

The new fsinfo() system call adds a new super block operation
->fsinfo() which is used by file systems to provide file
system specific information for fsinfo() requests.

The fsinfo() request FSINFO_ATTR_PARAMETERS provides the same
function as sb operation ->show_options() so it needs to be
implemented by any file system that provides ->show_options()
as a minimum.

Signed-off-by: Ian Kent <ra...@themaw.net>
Signed-off-by: David Howells <dhowe...@redhat.com>
---

 kernel/bpf/inode.c |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 6e22363054b1..49ac30424dd1 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -23,6 +23,7 @@
 #include <linux/filter.h>
 #include <linux/bpf.h>
 #include <linux/bpf_trace.h>
+#include <linux/fsinfo.h>
 
 enum bpf_type {
        BPF_TYPE_UNSPEC = 0,
@@ -567,6 +568,26 @@ static int bpf_show_options(struct seq_file *m, struct 
dentry *root)
        return 0;
 }
 
+#ifdef CONFIG_FSINFO
+/*
+ * Get filesystem information.
+ */
+static int bpf_fsinfo(struct path *path, struct fsinfo_kparams *params)
+{
+       umode_t mode = d_inode(path->dentry)->i_mode & S_IALLUGO & ~S_ISVTX;
+
+       switch (params->request) {
+       case FSINFO_ATTR_PARAMETERS:
+               if (mode != S_IRWXUGO)
+                       fsinfo_note_paramf(params, "mode", "%o", mode);
+               return params->usage;
+
+       default:
+               return generic_fsinfo(path, params);
+       }
+}
+#endif /* CONFIG_FSINFO */
+
 static void bpf_free_inode(struct inode *inode)
 {
        enum bpf_type type;
@@ -583,6 +604,9 @@ static const struct super_operations bpf_super_ops = {
        .drop_inode     = generic_delete_inode,
        .show_options   = bpf_show_options,
        .free_inode     = bpf_free_inode,
+#ifdef CONFIG_FSINFO
+       .fsinfo         = bpf_fsinfo,
+#endif
 };
 
 enum {