On Mon, Apr 05, 2021 at 03:15:18PM +0300, Gal Pressman wrote: > On 05/04/2021 14:57, Leon Romanovsky wrote: > > 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 > > Should I put the original commit here? There were quite a lot of bug fixes and > followups that are required. IMHO, the last commit SHA will be enough, the one that has working functionality from your POV. 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? > > Should be fine. > > Thanks
