[Linaro-mm-sig] Re: [PATCH rc] RDMA: Handle the return code from dma_resv_wait_timeout() properly

On Tue, Aug 16, 2022 at 5:03 PM Jason Gunthorpe jgg@nvidia.com wrote:

ib_umem_dmabuf_map_pages() returns 0 on success and -ERRNO on failure.

dma_resv_wait_timeout() uses a different scheme:

• Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
• greater than zero on success.

This results in ib_umem_dmabuf_map_pages() being non-functional as a positive return will be understood to be an error by drivers.

Fixes: f30bceab16d1 ("RDMA: use dma_resv_wait() instead of extracting the fence") Cc: stable@kernel.org Tested-by: Maor Gottlieb maorg@nvidia.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com

---

drivers/infiniband/core/umem_dmabuf.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)

Oded, I assume the Habana driver will hit this as well - does this mean you are not testing upstream kernels?

Thanks Jason for letting me know.

You are correct, we don't use upstream kernels. We use a back-ported EFA driver for 5.15 which in that version, ib_umem_dmabuf_map_pages() calls dma_resv_excl_fence(). So I guess that's why we didn't encounter this issue.

Thanks, oded

diff --git a/drivers/infiniband/core/umem_dmabuf.c b/drivers/infiniband/core/umem_dmabuf.c index fce80a4a5147cd..04c04e6d24c358 100644 --- a/drivers/infiniband/core/umem_dmabuf.c +++ b/drivers/infiniband/core/umem_dmabuf.c @@ -18,6 +18,7 @@ int ib_umem_dmabuf_map_pages(struct ib_umem_dmabuf *umem_dmabuf) struct scatterlist *sg; unsigned long start, end, cur = 0; unsigned int nmap = 0;

•   long ret;
    int i;
  
    dma_resv_assert_held(umem_dmabuf->attach->dmabuf->resv);
  

@@ -67,9 +68,14 @@ int ib_umem_dmabuf_map_pages(struct ib_umem_dmabuf *umem_dmabuf) * may be not up-to-date. Wait for the exporter to finish * the migration. */

•   return dma_resv_wait_timeout(umem_dmabuf->attach->dmabuf->resv,
  

•   ret = dma_resv_wait_timeout(umem_dmabuf->attach->dmabuf->resv,
                                 DMA_RESV_USAGE_KERNEL,
                                 false, MAX_SCHEDULE_TIMEOUT);
  

•   if (ret < 0)
  

•           return ret;
  

•   if (ret == 0)
  

•           return -ETIMEDOUT;
  

•   return 0;
  

} EXPORT_SYMBOL(ib_umem_dmabuf_map_pages);

base-commit: 568035b01cfb107af8d2e4bd2fb9aea22cf5b868

2.37.2