On Tue, May 28, 2019 at 04:11:19PM +0100, David Howells wrote:
> 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 <[email protected]>
> ---
>
> 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);
You're using fdget_raw() which means you want to allow O_PATH fds but
below you're checking whether the f_ops correspond to
fscontext_fops. If it's an O_PATH f_ops will be set to empty_fops so
you'll always end up in the vfs_fsinfo branch. Is that your intention?
That means the new mount api doesn't support fsinfo() without using a
non-O_PATH fd, right? Why the fallback then?
Christian
> 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;
> }
>
