Much work has recently gone into supporting block device integrity data (sometimes called "metadata") in Linux. Many NVMe devices these days support metadata transfers and/or automatic protection information generation and verification. However, ublk devices can't yet advertise integrity data capabilities. This patch series wires up support for integrity data in ublk. The ublk feature is referred to as "integrity" rather than "metadata" to match the block layer's name for it and to avoid confusion with the existing and unrelated UBLK_IO_F_META.
To advertise support for integrity data, a ublk server fills out the struct ublk_params's integrity field and sets UBLK_PARAM_TYPE_INTEGRITY. The struct ublk_param_integrity flags and csum_type fields use the existing LBMD_PI_* constants from the linux/fs.h UAPI header. The ublk driver fills out a corresponding struct blk_integrity.
When a request with integrity data is issued to the ublk device, the ublk driver sets UBLK_IO_F_INTEGRITY in struct ublksrv_io_desc's op_flags field. This is necessary for a ublk server for which bi_offload_capable() returns true to distinguish requests with integrity data from those without.
Integrity data transfers can currently only be performed via the ublk user copy mechanism. The overhead of zero-copy buffer registration makes it less appealing for the small transfers typical of integrity data. Additionally, neither io_uring NVMe passthru nor IORING_RW_ATTR_FLAG_PI currently allow an io_uring registered buffer for the integrity data. The ki_pos field of the struct kiocb passed to the user copy ->{read,write}_iter() callback gains a bit UBLKSRV_IO_INTEGRITY_FLAG for a ublk server to indicate whether to access the request's data or integrity data.
Not yet supported is an analogue for the IO_INTEGRITY_CHK_*/BIP_CHECK_* flags to ask the ublk server to verify the guard, reftag, and/or apptag of a request's protection information. The user copy mechanism currently forbids a ublk server from reading the data/integrity buffer of a read-direction request. We could potentially relax this restriction for integrity data on reads. Alternatively, the ublk driver could verify the requested fields as part of the user copy operation.
v4: - Add max_integrity_segments to struct ublk_param_integrity (Ming) - Move UBLKSRV_IO_INTEGRITY_FLAG to avoid overflow from QID + UBLKSRV_IO_BUF_OFFSET (Ming) - Check UBLK_F_INTEGRITY when UBLKSRV_IO_INTEGRITY_FLAG is used (Ming) - Initialize integrity backing file to disable integrity checks (Ming)
v3: - Drop support for communicating BIP_CHECK_* for now until the interface is decided - Add Reviewed-by tags
v2: - Communicate BIP_CHECK_* flags and expected reftag seed and app tag to ublk server - Add UBLK_F_INTEGRITY feature flag (Ming) - Don't change the definition of UBLKSRV_IO_BUF_TOTAL_BITS (Ming) - Drop patches already applied - Add Reviewed-by tags
Caleb Sander Mateos (16): blk-integrity: take const pointer in blk_integrity_rq() ublk: move ublk flag check functions earlier ublk: set UBLK_IO_F_INTEGRITY in ublksrv_io_desc ublk: split out ublk_copy_user_bvec() helper ublk: split out ublk_user_copy() helper ublk: inline ublk_check_and_get_req() into ublk_user_copy() ublk: move offset check out of __ublk_check_and_get_req() ublk: optimize ublk_user_copy() on daemon task selftests: ublk: display UBLK_F_INTEGRITY support selftests: ublk: add utility to get block device metadata size selftests: ublk: add kublk support for integrity params selftests: ublk: implement integrity user copy in kublk selftests: ublk: support non-O_DIRECT backing files selftests: ublk: add integrity data support to loop target selftests: ublk: add integrity params test selftests: ublk: add end-to-end integrity test
Stanley Zhang (3): ublk: support UBLK_PARAM_TYPE_INTEGRITY in device creation ublk: implement integrity user copy ublk: support UBLK_F_INTEGRITY
drivers/block/ublk_drv.c | 358 +++++++++++++------ include/linux/blk-integrity.h | 6 +- include/uapi/linux/ublk_cmd.h | 25 ++ tools/testing/selftests/ublk/Makefile | 7 +- tools/testing/selftests/ublk/common.c | 4 +- tools/testing/selftests/ublk/fault_inject.c | 1 + tools/testing/selftests/ublk/file_backed.c | 90 ++++- tools/testing/selftests/ublk/kublk.c | 90 ++++- tools/testing/selftests/ublk/kublk.h | 37 +- tools/testing/selftests/ublk/metadata_size.c | 36 ++ tools/testing/selftests/ublk/null.c | 1 + tools/testing/selftests/ublk/stripe.c | 6 +- tools/testing/selftests/ublk/test_common.sh | 10 + tools/testing/selftests/ublk/test_loop_08.sh | 111 ++++++ tools/testing/selftests/ublk/test_null_04.sh | 166 +++++++++ 15 files changed, 817 insertions(+), 131 deletions(-) create mode 100644 tools/testing/selftests/ublk/metadata_size.c create mode 100755 tools/testing/selftests/ublk/test_loop_08.sh create mode 100755 tools/testing/selftests/ublk/test_null_04.sh