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. >> >> 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
