On Mon, Dec 22, 2025 at 9:26 AM Ming Lei ming.lei@redhat.com wrote:
On Tue, Dec 16, 2025 at 10:34:38PM -0700, Caleb Sander Mateos wrote:
From: Stanley Zhang stazhang@purestorage.com
Add UAPI definitions for metadata/integrity support in ublk. UBLK_PARAM_TYPE_INTEGRITY and struct ublk_param_integrity allow a ublk server to specify the integrity params of a ublk device. The ublk driver will set UBLK_IO_F_INTEGRITY in the op_flags field of struct ublksrv_io_desc for requests with integrity data. The ublk server uses user copy with UBLKSRV_IO_INTEGRITY_FLAG set in the offset parameter to access a request's integrity buffer.
Signed-off-by: Stanley Zhang stazhang@purestorage.com [csander: drop feature flag and redundant pi_tuple_size field, add io_desc flag, use block metadata UAPI constants] Signed-off-by: Caleb Sander Mateos csander@purestorage.com
include/uapi/linux/ublk_cmd.h | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index ec77dabba45b..5bfb9a0521c3 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -129,11 +129,15 @@ #define UBLK_QID_BITS 12 #define UBLK_QID_BITS_MASK ((1ULL << UBLK_QID_BITS) - 1)
#define UBLK_MAX_NR_QUEUES (1U << UBLK_QID_BITS)
-#define UBLKSRV_IO_BUF_TOTAL_BITS (UBLK_QID_OFF + UBLK_QID_BITS) +/* Copy to/from request integrity buffer instead of data buffer */ +#define UBLK_INTEGRITY_FLAG_OFF (UBLK_QID_OFF + UBLK_QID_BITS) +#define UBLKSRV_IO_INTEGRITY_FLAG (1ULL << UBLK_INTEGRITY_FLAG_OFF)
I feel it is more readable to move the definition into the patch which uses them.
Sure, I can do that.
+#define UBLKSRV_IO_BUF_TOTAL_BITS (UBLK_INTEGRITY_FLAG_OFF + 1)
It is UAPI, UBLKSRV_IO_BUF_TOTAL_BITS shouldn't be changed, or can you explain this way is safe?
It's not clear to me how userspace is expected to use UBLKSRV_IO_BUF_TOTAL_BITS. (Our ublk server, for one, doesn't use it.) Can you provide an example? It looks to me like the purpose is to communicate the number of bits needed to represent a user copy offset value, in which case it makes sense to include the integrity flag now that that bit is being used.
#define UBLKSRV_IO_BUF_TOTAL_SIZE (1ULL << UBLKSRV_IO_BUF_TOTAL_BITS)
/*
- ublk server can register data buffers for incoming I/O requests with a sparse
- io_uring buffer table. The request buffer can then be used as the data buffer
@@ -406,10 +410,12 @@ struct ublksrv_ctrl_dev_info {
- ublk server has to check this flag if UBLK_AUTO_BUF_REG_FALLBACK is
- passed in.
*/ #define UBLK_IO_F_NEED_REG_BUF (1U << 17) +/* Request has an integrity data buffer */ +#define UBLK_IO_F_INTEGRITY (1U << 18)
/*
- io cmd is described by this structure, and stored in share memory, indexed
- by request tag.
@@ -598,10 +604,20 @@ struct ublk_param_segment { __u32 max_segment_size; __u16 max_segments; __u8 pad[2]; };
+struct ublk_param_integrity {
__u32 flags; /* LBMD_PI_CAP_* from linux/fs.h */__u8 interval_exp;__u8 metadata_size;__u8 pi_offset;__u8 csum_type; /* LBMD_PI_CSUM_* from linux/fs.h */__u8 tag_size;__u8 pad[7];+};
Just be curious, `pi_tuple_size` isn't defined, instead it is hard-coded in ublk_integrity_pi_tuple_size().
However, both scsi and nvme sets `pi_tuple_size`, so it means that ublk PI supports one `subset` or scsi/nvme `pi_tuple_size` can be removed too?
blk_validate_integrity_limits() validates that pi_tuple_size matches the expected PI size for each csum_type value. So it looks like these fields are redundant. Yes, pi_tuple_size could probably be removed from the scsi/nvme block drivers too. But maybe there's value in having the drivers explicitly specify both values?
Thanks, Caleb