On 2024/11/6 20:08, Leon Romanovsky wrote: > On Tue, Nov 05, 2024 at 08:08:39PM +0800, Junxian Huang wrote: >> ib_map_mr_sg() and ib_map_mr_sg_pi() allow ULPs to specify NULL as >> the sg_offset/data_sg_offset/meta_sg_offset arguments. Drivers who >> need to derefernce these arguments have to add NULL pointer checks >> to avoid crashing the kernel. >> >> This can be optimized by adding dummy sg_offset pointer to these >> two APIs. When the sg_offset arguments are NULL, pass the pointer >> of dummy to drivers. Drivers can always get a valid pointer, so no >> need to add NULL pointer checks. >> >> Junxian Huang (2): >> RDMA/core: Add dummy sg_offset pointer for ib_map_mr_sg() and >> ib_map_mr_sg_pi() >> RDMA: Delete NULL pointer checks for sg_offset in .map_mr_sg ops >> >> drivers/infiniband/core/verbs.c | 12 +++++++++--- >> drivers/infiniband/hw/mlx5/mr.c | 18 ++++++------------ >> drivers/infiniband/sw/rdmavt/trace_mr.h | 2 +- >> 3 files changed, 16 insertions(+), 16 deletions(-) > > So what does this change give us? > We have same functionality, same number of lines, same everything ... > Actually this is inspired by an hns bug. When ib_map_mr_sg() passes a NULL sg_offset pointer to hns_roce_map_mr_sg(), we dereference this pointer without a NULL check. Of course we can fix it by adding NULL check in hns, but I think this patch may be a better solution since the sg_offset is guaranteed to be a valid pointer. This could benefit future drivers who also want to dereference sg_offset, they won't need to care about NULL checks. Junxian > Thanks > >> >> -- >> 2.33.0 >> >>
