From 6cc9e215eb277513719c32b9ba40e5012b02db57 Mon Sep 17 00:00:00 2001 From: Gal Pressman Date: Sun, 18 Apr 2021 15:10:25 +0300 Subject: RDMA/nldev: Add copy-on-fork attribute to get sys command The new attribute indicates that the kernel copies DMA pages on fork, hence libibverbs' fork support through madvise and MADV_DONTFORK is not needed. The introduced attribute is always reported as supported since the kernel has the patch that added the copy-on-fork behavior. This allows the userspace library to identify older vs newer kernel versions. Extra care should be taken when backporting this patch as it relies on the fact that the copy-on-fork patch is merged, hence no check for support is added. Don't backport this patch unless you also have the following series: commit 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes") and commit 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm"). Fixes: 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes") Fixes: 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm") Link: https://lore.kernel.org/r/20210418121025.66849-1-galpress@amazon.com Signed-off-by: Gal Pressman Reviewed-by: Leon Romanovsky Signed-off-by: Jason Gunthorpe --- include/uapi/rdma/rdma_netlink.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/uapi/rdma') diff --git a/include/uapi/rdma/rdma_netlink.h b/include/uapi/rdma/rdma_netlink.h index 2c8d405ec924..75a1ae2311d8 100644 --- a/include/uapi/rdma/rdma_netlink.h +++ b/include/uapi/rdma/rdma_netlink.h @@ -546,6 +546,9 @@ enum rdma_nldev_attr { RDMA_NLDEV_ATTR_MIN_RANGE, /* u32 */ RDMA_NLDEV_ATTR_MAX_RANGE, /* u32 */ + + RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK, /* u8 */ + /* * Always the end */ -- cgit v1.2.3