[bug report] bcachefs: Add an ioctl for resizing journal on a device

[Dan Carpenter]

Hello Kent Overstreet,

The patch f9e4304e0562: "bcachefs: Add an ioctl for resizing journal
on a device" from Nov 16, 2020 (linux-next), leads to the following
(unpublished) Smatch static checker warning:

        fs/bcachefs/chardev.c:624 bch2_ioctl_disk_resize_journal()
        warn: truncating user data 'arg.nbuckets' '0-u64max'

fs/bcachefs/chardev.c
    607 static long bch2_ioctl_disk_resize_journal(struct bch_fs *c,
    608                                    struct bch_ioctl_disk_resize_journal 
arg)
    609 {
    610         struct bch_dev *ca;
    611         int ret;
    612 
    613         if (!capable(CAP_SYS_ADMIN))
    614                 return -EPERM;
    615 
    616         if ((arg.flags & ~BCH_BY_INDEX) ||
    617             arg.pad)
    618                 return -EINVAL;
    619 
    620         ca = bch2_device_lookup(c, arg.dev, arg.flags);
    621         if (IS_ERR(ca))
    622                 return PTR_ERR(ca);
    623 
--> 624         ret = bch2_set_nr_journal_buckets(c, ca, arg.nbuckets);

This is harmless.  arg.nbuckets is a u64 and bch2_set_nr_journal_buckets()
takes a u32.  However this u32 vs u64 inconsistency with ->nbuckets is
not just here but also in other places.  (struct journal_device)->nr is
a u32 for example.  It would be better if it were consistent everywhere.

    625 
    626         percpu_ref_put(&ca->ref);
    627         return ret;
    628 }

regards,
dan carpenter