Hi Jens, The patches in this series are what I came up with as the result of analyzing Alexander Potapenko's report about reading from null_blk. Please consider these patches for kernel v5.8. Thanks, Bart. Changes compared to v1: - Adjusted the comments added by patch "Document the bio_vec properties" as requested by Christoph. - Left out the patch "Fix zero_fill_bio()" since it is not necessary. - Moved zero_fill_bvec() from patch "Fix zero_fill_bio()" into patch "null_blk: Zero-initialize read buffers in non-memory-backed mode". Bart Van Assche (4): block: Fix type of first compat_put_{,u}long() argument bio.h: Declare the arguments of the bio iteration functions const block: Document the bio_vec properties null_blk: Zero-initialize read buffers in non-memory-backed mode block/ioctl.c | 4 +-- drivers/block/null_blk_main.c | 50 +++++++++++++++++++++++++++++++++++ include/linux/bio.h | 6 ++--- include/linux/bvec.h | 13 +++++++-- 4 files changed, 66 insertions(+), 7 deletions(-)