> Subject: [PATCH 02/14] RDMA/umem: Prevent small pages from being returned by
> ib_umem_find_best_pgsz()
>
> rdma_for_each_block() makes assumptions about how the SGL is constructed that
> don't work if the block size is below the page size used to to build the SGL.
>
> The rules for umem SGL construction require that the SG's all be PAGE_SIZE
> aligned and we don't encode the actual byte offset of the VA range inside the SGL
> using offset and length. So rdma_for_each_block() has no idea where the actual
> starting/ending point is to compute the first/last block boundary if the starting
> address should be within a SGL.
Not sure if we were exposed today. i.e. rdma drivers working with block sizes smaller than system page size?
Nevertheless it's a good find and looks right thing to do for now.
>
> Fixing the SGL construction turns out to be really hard, and will be the subject of
> other patches. For now block smaller pages.
>
> Fixes: 4a35339958f1 ("RDMA/umem: Add API to find best driver supported page
> size in an MR")
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
Reviewed-by: Shiraz Saleem <shiraz.saleem@xxxxxxxxx>
