[PATCH 02/25] vfs: Allow fsinfo() to query what's in an fs_context [ver #13]

[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/fsinfo.c |   30 +++++++++++++++++++++++++++++-
 fs/statfs.c |    2 +-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/fs/fsinfo.c b/fs/fsinfo.c
index f9a63410e9a2..14db881dd02d 100644
--- a/fs/fsinfo.c
+++ b/fs/fsinfo.c
@@ -8,6 +8,7 @@
 #include <linux/security.h>
 #include <linux/uaccess.h>
 #include <linux/fsinfo.h>
+#include <linux/fs_context.h>
 #include <uapi/linux/mount.h>
 #include "internal.h"
 
@@ -315,13 +316,40 @@ 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;
diff --git a/fs/statfs.c b/fs/statfs.c
index eea7af6f2f22..b9b63d9f4f24 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c
@@ -86,7 +86,7 @@ int vfs_statfs(const struct path *path, struct kstatfs *buf)
        int error;
 
        error = statfs_by_dentry(path->dentry, buf);
-       if (!error)
+       if (!error && path->mnt)
                buf->f_flags = calculate_f_flags(path->mnt);
        return error;
 }