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authorGal Pressman <galpress@amazon.com>2021-04-18 15:10:25 +0300
committerJason Gunthorpe <jgg@nvidia.com>2021-04-27 21:33:20 +0300
commit6cc9e215eb277513719c32b9ba40e5012b02db57 (patch)
treee6c1fe58ae43e5a4e4d95a299a8abb123593194e /drivers/infiniband
parent34b39efa5ae82fc0ad0acc27653c12a56328dbbe (diff)
downloadlinux-6cc9e215eb277513719c32b9ba40e5012b02db57.tar.xz
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 <galpress@amazon.com> Reviewed-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Diffstat (limited to 'drivers/infiniband')
-rw-r--r--drivers/infiniband/core/nldev.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
index bd7f675463f6..34d0cc1a4147 100644
--- a/drivers/infiniband/core/nldev.c
+++ b/drivers/infiniband/core/nldev.c
@@ -153,6 +153,7 @@ static const struct nla_policy nldev_policy[RDMA_NLDEV_ATTR_MAX] = {
[RDMA_NLDEV_ATTR_UVERBS_DRIVER_ID] = { .type = NLA_U32 },
[RDMA_NLDEV_NET_NS_FD] = { .type = NLA_U32 },
[RDMA_NLDEV_SYS_ATTR_NETNS_MODE] = { .type = NLA_U8 },
+ [RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK] = { .type = NLA_U8 },
};
static int put_driver_name_print_type(struct sk_buff *msg, const char *name,
@@ -1849,6 +1850,19 @@ static int nldev_sys_get_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
nlmsg_free(msg);
return err;
}
+
+ /*
+ * Copy-on-fork is supported.
+ * See commits:
+ * 70e806e4e645 ("mm: Do early cow for pinned pages during fork() for ptes")
+ * 4eae4efa2c29 ("hugetlb: do early cow when page pinned on src mm")
+ * for more details. Don't backport this without them.
+ *
+ * Return value ignored on purpose, assume copy-on-fork is not
+ * supported in case of failure.
+ */
+ nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK, 1);
+
nlmsg_end(msg, nlh);
return rdma_nl_unicast(sock_net(skb->sk), msg, NETLINK_CB(skb).portid);
}