On 14-Mar-19 17:49, Jason Gunthorpe wrote:> Every file offset 'key/cookie' has zero in the lower PAGE_SHIFT > bits, as mmap only works on page aligned offsets. > > The xarray key should be the page number to access - converted from > the offset by stripping the lower PAGE_SHIFT bits (done by vm_pgoff > already) and masking the upper flag bit> > So with the 64 bit offset argument you only have 52 bits to to work > with. > - 12 are zero for PAGE_SHIFT > - 32 are the page number for the xarray key > - N are padding > - N are the flags at a fixed location in the 64 bit offset> > Userspace rdma-core can always use a 64 bit file offset for mmap. > Makes sense. >> I'll take a look into changing this into an xarray. >> What did you mean by a cyclic allocating xarray? We can't reuse the keys as the >> entries should be valid until application exit. > > Use xa_alloc_cyclic Thanks.
