Re: [PATCH v4] btrfs: add BTRFS_IOC_GET_CSUMS ioctl

[David Sterba <dsterba@suse.cz>]

On Wed, Apr 15, 2026 at 06:46:46PM +0100, Filipe Manana wrote:
> > @@ -5140,6 +5141,344 @@ static int btrfs_ioctl_shutdown(struct btrfs_fs_info *fs_info, unsigned long arg
> >         return ret;
> >  }
> >
> > +#define GET_CSUMS_BUF_MAX      SZ_16M
> > +
> > +static int copy_csums_to_user(struct btrfs_fs_info *fs_info, u64 disk_bytenr,
> > +                             u64 len, u8 __user *buf)
> > +{
> > +       struct btrfs_root *csum_root;
> > +       struct btrfs_ordered_sum *sums;
> > +       LIST_HEAD(list);
> > +       const u32 csum_size = fs_info->csum_size;
> > +       int ret;
> > +
> > +       csum_root = btrfs_csum_root(fs_info, disk_bytenr);
> 
> Please, check that the root is not null; if it is null, log an error
> message and return an error.
> We found many missing instances that sometimes triggered null pointer
> dereferences when the file system was corrupted or mounted with the
> rescue option, among other issues.

We can start adding the __must_check annotations.