On Tue, Jan 6, 2026 at 5:34 AM Ming Lei <[email protected]> wrote:
>
> On Mon, Jan 05, 2026 at 05:57:41PM -0700, Caleb Sander Mateos wrote:
> > From: Stanley Zhang <[email protected]>
> >
> > Add a function ublk_copy_user_integrity() to copy integrity information
> > between a request and a user iov_iter. This mirrors the existing
> > ublk_copy_user_pages() but operates on request integrity data instead of
> > regular data. Check UBLKSRV_IO_INTEGRITY_FLAG in iocb->ki_pos in
> > ublk_user_copy() to choose between copying data or integrity data.
> >
> > Signed-off-by: Stanley Zhang <[email protected]>
> > [csander: change offset units from data bytes to integrity data bytes,
> > test UBLKSRV_IO_INTEGRITY_FLAG after subtracting UBLKSRV_IO_BUF_OFFSET,
> > fix CONFIG_BLK_DEV_INTEGRITY=n build,
> > rebase on ublk user copy refactor]
> > Signed-off-by: Caleb Sander Mateos <[email protected]>
> > ---
> > drivers/block/ublk_drv.c | 52 +++++++++++++++++++++++++++++++++--
> > include/uapi/linux/ublk_cmd.h | 4 +++
> > 2 files changed, 53 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> > index e44ab9981ef4..9694a4c1caa7 100644
> > --- a/drivers/block/ublk_drv.c
> > +++ b/drivers/block/ublk_drv.c
> > @@ -621,10 +621,15 @@ static inline unsigned ublk_pos_to_tag(loff_t pos)
> > {
> > return ((pos - UBLKSRV_IO_BUF_OFFSET) >> UBLK_TAG_OFF) &
> > UBLK_TAG_BITS_MASK;
> > }
> >
> > +static inline bool ublk_pos_is_integrity(loff_t pos)
> > +{
> > + return !!((pos - UBLKSRV_IO_BUF_OFFSET) & UBLKSRV_IO_INTEGRITY_FLAG);
> > +}
> > +
>
> It could be more readable to check UBLKSRV_IO_INTEGRITY_FLAG only.
That's assuming that UBLK_TAG_BITS = 16 has more bits than are
strictly required by UBLK_MAX_QUEUE_DEPTH = 4096? Otherwise, adding
UBLKSRV_IO_BUF_OFFSET = 1 << 31 to tag << UBLK_TAG_OFF could overflow
into the QID bits, which could then overflow into
UBLKSRV_IO_INTEGRITY_FLAG. That seems like a very fragile assumption.
And if you want to rely on this assumption, why bother subtracting
UBLKSRV_IO_BUF_OFFSET in ublk_pos_to_hwq() either? The compiler should
easily be able to deduplicate the iocb->ki_pos - UBLKSRV_IO_BUF_OFFSET
computations, so I can't imagine it matters for performance.
>
> > static void ublk_dev_param_basic_apply(struct ublk_device *ub)
> > {
> > const struct ublk_param_basic *p = &ub->params.basic;
> >
> > if (p->attrs & UBLK_ATTR_READ_ONLY)
> > @@ -1047,10 +1052,37 @@ static size_t ublk_copy_user_pages(const struct
> > request *req,
> > break;
> > }
> > return done;
> > }
> >
> > +#ifdef CONFIG_BLK_DEV_INTEGRITY
> > +static size_t ublk_copy_user_integrity(const struct request *req,
> > + unsigned offset, struct iov_iter *uiter, int dir)
> > +{
> > + size_t done = 0;
> > + struct bio *bio = req->bio;
> > + struct bvec_iter iter;
> > + struct bio_vec iv;
> > +
> > + if (!blk_integrity_rq(req))
> > + return 0;
> > +
> > + bio_for_each_integrity_vec(iv, bio, iter) {
> > + if (!ublk_copy_user_bvec(&iv, &offset, uiter, dir, &done))
> > + break;
> > + }
> > +
> > + return done;
> > +}
> > +#else /* #ifdef CONFIG_BLK_DEV_INTEGRITY */
> > +static size_t ublk_copy_user_integrity(const struct request *req,
> > + unsigned offset, struct iov_iter *uiter, int dir)
> > +{
> > + return 0;
> > +}
> > +#endif /* #ifdef CONFIG_BLK_DEV_INTEGRITY */
> > +
> > static inline bool ublk_need_map_req(const struct request *req)
> > {
> > return ublk_rq_has_data(req) && req_op(req) == REQ_OP_WRITE;
> > }
> >
> > @@ -2654,10 +2686,12 @@ ublk_user_copy(struct kiocb *iocb, struct iov_iter
> > *iter, int dir)
> > {
> > struct ublk_device *ub = iocb->ki_filp->private_data;
> > struct ublk_queue *ubq;
> > struct request *req;
> > struct ublk_io *io;
> > + unsigned data_len;
> > + bool is_integrity;
> > size_t buf_off;
> > u16 tag, q_id;
> > ssize_t ret;
> >
> > if (!user_backed_iter(iter))
> > @@ -2667,10 +2701,11 @@ ublk_user_copy(struct kiocb *iocb, struct iov_iter
> > *iter, int dir)
> > return -EACCES;
> >
> > tag = ublk_pos_to_tag(iocb->ki_pos);
> > q_id = ublk_pos_to_hwq(iocb->ki_pos);
> > buf_off = ublk_pos_to_buf_off(iocb->ki_pos);
> > + is_integrity = ublk_pos_is_integrity(iocb->ki_pos);
>
> UBLKSRV_IO_INTEGRITY_FLAG can be set for device without UBLK_F_INTEGRITY,
> so UBLK_F_INTEGRITY need to be checked in case of `is_integrity`.
If UBLK_F_INTEGRITY isn't set, then UBLK_PARAM_TYPE_INTEGRITY isn't
allowed, so the ublk device won't support integrity data. Therefore,
blk_integrity_rq() will return false and ublk_copy_user_integrity()
will just return 0. Do you think it's important to return some error
code value instead? I would rather avoid the additional checks in the
hot path.
>
> >
> > if (q_id >= ub->dev_info.nr_hw_queues)
> > return -EINVAL;
> >
> > ubq = ublk_get_queue(ub, q_id);
> > @@ -2683,21 +2718,31 @@ ublk_user_copy(struct kiocb *iocb, struct iov_iter
> > *iter, int dir)
> > io = &ubq->ios[tag];
> > req = __ublk_check_and_get_req(ub, q_id, tag, io);
> > if (!req)
> > return -EINVAL;
> >
> > - if (buf_off > blk_rq_bytes(req)) {
> > + if (is_integrity) {
> > + struct blk_integrity *bi = &req->q->limits.integrity;
> > +
> > + data_len = bio_integrity_bytes(bi, blk_rq_sectors(req));
> > + } else {
> > + data_len = blk_rq_bytes(req);
> > + }
> > + if (buf_off > data_len) {
> > ret = -EINVAL;
> > goto out;
> > }
> >
> > if (!ublk_check_ubuf_dir(req, dir)) {
> > ret = -EACCES;
> > goto out;
> > }
> >
> > - ret = ublk_copy_user_pages(req, buf_off, iter, dir);
> > + if (is_integrity)
> > + ret = ublk_copy_user_integrity(req, buf_off, iter, dir);
> > + else
> > + ret = ublk_copy_user_pages(req, buf_off, iter, dir);
> >
> > out:
> > ublk_put_req_ref(io, req);
> > return ret;
> > }
> > @@ -3931,11 +3976,12 @@ static struct miscdevice ublk_misc = {
> > static int __init ublk_init(void)
> > {
> > int ret;
> >
> > BUILD_BUG_ON((u64)UBLKSRV_IO_BUF_OFFSET +
> > - UBLKSRV_IO_BUF_TOTAL_SIZE < UBLKSRV_IO_BUF_OFFSET);
> > + UBLKSRV_IO_BUF_TOTAL_SIZE +
> > + UBLKSRV_IO_INTEGRITY_FLAG < UBLKSRV_IO_BUF_OFFSET);
>
> Maybe it can be simplified as:
>
> BUILD_BUG_ON(UBLK_INTEGRITY_FLAG_OFF >= 63); /* Must fit in loff_t */
Okay, I think that works. Even if the addition of
UBLKSRV_IO_BUF_OFFSET causes an overflow to the next bit, it should
still fit within a 64-bit integer.
Thanks,
Caleb
>
> > BUILD_BUG_ON(sizeof(struct ublk_auto_buf_reg) != 8);
> >
> > init_waitqueue_head(&ublk_idr_wq);
> >
> > ret = misc_register(&ublk_misc);
> > diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> > index c1103ad5925b..3af7e3684834 100644
> > --- a/include/uapi/linux/ublk_cmd.h
> > +++ b/include/uapi/linux/ublk_cmd.h
> > @@ -132,10 +132,14 @@
> > #define UBLK_MAX_NR_QUEUES (1U << UBLK_QID_BITS)
> >
> > #define UBLKSRV_IO_BUF_TOTAL_BITS (UBLK_QID_OFF + UBLK_QID_BITS)
> > #define UBLKSRV_IO_BUF_TOTAL_SIZE (1ULL << UBLKSRV_IO_BUF_TOTAL_BITS)
> >
> > +/* Copy to/from request integrity buffer instead of data buffer */
> > +#define UBLK_INTEGRITY_FLAG_OFF UBLKSRV_IO_BUF_TOTAL_BITS
> > +#define UBLKSRV_IO_INTEGRITY_FLAG (1ULL << UBLK_INTEGRITY_FLAG_OFF)
> > +
> > /*
> > * 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
> > * for io_uring operations via the fixed buffer index.
> > * Note that the ublk server can never directly access the request data
> > memory.
> > --
> > 2.45.2
> >
>
> Thanks,
> Ming
>
