[PATCH 37/38] vfs: Allow fsinfo() to query what's in an fs_context [ver #10]

[David Howells]

Allow fsinfo() to be used to query the filesystem attached to an fs_context
once a superblock has been created or if it comes from fspick().

This is done with something like:

        fd = fsopen("ext4", 0);
        ...
        fsconfig(fd, fsconfig_cmd_create, ...);
        fsinfo(fd, NULL, ...);

Signed-off-by: David Howells <dhowe...@redhat.com>
---

 fs/statfs.c |   29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/fs/statfs.c b/fs/statfs.c
index caf0773957e9..480ac4be8c2a 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c
@@ -669,13 +669,40 @@ static int vfs_fsinfo_path(int dfd, const char __user 
*filename,
        return ret;
 }
 
+static int vfs_fsinfo_fscontext(struct fs_context *fc,
+                               struct fsinfo_kparams *params)
+{
+       int ret;
+
+       if (fc->ops == &legacy_fs_context_ops)
+               return -EOPNOTSUPP;
+
+       ret = mutex_lock_interruptible(&fc->uapi_mutex);
+       if (ret < 0)
+               return ret;
+
+       ret = -EIO;
+       if (fc->root) {
+               struct path path = { .dentry = fc->root };
+
+               ret = vfs_fsinfo(&path, params);
+       }
+
+       mutex_unlock(&fc->uapi_mutex);
+       return ret;
+}
+
 static int vfs_fsinfo_fd(unsigned int fd, struct fsinfo_kparams *params)
 {
        struct fd f = fdget_raw(fd);
        int ret = -EBADF;
 
        if (f.file) {
-               ret = vfs_fsinfo(&f.file->f_path, params);
+               if (f.file->f_op == &fscontext_fops)
+                       ret = vfs_fsinfo_fscontext(f.file->private_data,
+                                                  params);
+               else
+                       ret = vfs_fsinfo(&f.file->f_path, params);
                fdput(f);
        }
        return ret;