On Mon, Apr 05, 2021 at 02:47:21PM +0300, Gal Pressman wrote: > 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. Please be more specific, add SHA-1 of that patch and wrote the same comment near "err = nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK, 1);" line. Thanks > > Copy-on-fork attribute is read-only, trying to change it through the set > sys command will result in an error. > > Signed-off-by: Gal Pressman <galpress@xxxxxxxxxx> > --- > PR was sent: > https://github.com/linux-rdma/rdma-core/pull/975 > --- > drivers/infiniband/core/nldev.c | 19 ++++++++++++++----- > include/uapi/rdma/rdma_netlink.h | 2 ++ > 2 files changed, 16 insertions(+), 5 deletions(-) > > diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c > index b8dc002a2478..87c68301c25b 100644 > --- a/drivers/infiniband/core/nldev.c > +++ b/drivers/infiniband/core/nldev.c > @@ -146,6 +146,7 @@ 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, > @@ -1693,12 +1694,19 @@ static int nldev_sys_get_doit(struct sk_buff *skb, struct nlmsghdr *nlh, > > err = nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_NETNS_MODE, > (u8)ib_devices_shared_netns); > - if (err) { > - nlmsg_free(msg); > - return err; > - } > + if (err) > + goto err_nlmsg_free; > + > + err = nla_put_u8(msg, RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK, 1); > + if (err) > + goto err_nlmsg_free; Is it important to have an ability to fail here? Can we simply ignore failure? > + > nlmsg_end(msg, nlh); > return rdma_nl_unicast(sock_net(skb->sk), msg, NETLINK_CB(skb).portid); > + > +err_nlmsg_free: > + nlmsg_free(msg); > + return err; > } > > static int nldev_set_sys_set_doit(struct sk_buff *skb, struct nlmsghdr *nlh, > @@ -1710,7 +1718,8 @@ static int nldev_set_sys_set_doit(struct sk_buff *skb, struct nlmsghdr *nlh, > > err = nlmsg_parse(nlh, 0, tb, RDMA_NLDEV_ATTR_MAX - 1, > nldev_policy, extack); > - if (err || !tb[RDMA_NLDEV_SYS_ATTR_NETNS_MODE]) > + if (err || !tb[RDMA_NLDEV_SYS_ATTR_NETNS_MODE] || > + tb[RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK]) > return -EINVAL; > > enable = nla_get_u8(tb[RDMA_NLDEV_SYS_ATTR_NETNS_MODE]); > diff --git a/include/uapi/rdma/rdma_netlink.h b/include/uapi/rdma/rdma_netlink.h > index d2f5b8396243..342c9db5b3c1 100644 > --- a/include/uapi/rdma/rdma_netlink.h > +++ b/include/uapi/rdma/rdma_netlink.h > @@ -533,6 +533,8 @@ enum rdma_nldev_attr { > > RDMA_NLDEV_ATTR_RES_RAW, /* binary */ > > + RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK, /* u8 */ > + > /* > * Always the end > */ > > base-commit: adb76a520d068a54ee5ca82e756cf8e5a47363a4 > -- > 2.31.1 >
