netdev - [PATCH iproute2-next v2 2/2] rdma: Add copy-on-fork to get sys command

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Message-ID: <20210429064803.58458-3-galpress@amazon.com>
Date:   Thu, 29 Apr 2021 09:48:03 +0300
From:   Gal Pressman <galpress@...zon.com>
To:     David Ahern <dsahern@...il.com>
CC:     <linux-rdma@...r.kernel.org>, <netdev@...r.kernel.org>,
        Yossi Leybovich <sleybo@...zon.com>,
        Alexander Matushevsky <matua@...zon.com>,
        Leon Romanovsky <leonro@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Gal Pressman <galpress@...zon.com>
Subject: [PATCH iproute2-next v2 2/2] rdma: Add copy-on-fork to get sys command

The new attribute indicates that the kernel copies DMA pages on fork,
hence fork support through madvise and MADV_DONTFORK is not needed.

If the attribute is not reported (expected on older kernels),
copy-on-fork is disabled.

Example:
$ rdma sys
netns shared copy-on-fork on

Signed-off-by: Gal Pressman <galpress@...zon.com>
---
 rdma/sys.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/rdma/sys.c b/rdma/sys.c
index 8fb565d70598..fd785b253e20 100644
--- a/rdma/sys.c
+++ b/rdma/sys.c
@@ -20,6 +20,7 @@ static const char *netns_modes_str[] = {
 static int sys_show_parse_cb(const struct nlmsghdr *nlh, void *data)
 {
 	struct nlattr *tb[RDMA_NLDEV_ATTR_MAX] = {};
+	bool cof = false;
 
 	mnl_attr_parse(nlh, 0, rd_attr_cb, tb);
 
@@ -35,9 +36,17 @@ static int sys_show_parse_cb(const struct nlmsghdr *nlh, void *data)
 		else
 			mode_str = "unknown";
 
-		print_color_string(PRINT_ANY, COLOR_NONE, "netns", "netns %s\n",
+		print_color_string(PRINT_ANY, COLOR_NONE, "netns", "netns %s ",
 				   mode_str);
 	}
+
+	if (tb[RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK])
+		cof = mnl_attr_get_u8(tb[RDMA_NLDEV_SYS_ATTR_COPY_ON_FORK]);
+
+	print_color_on_off(PRINT_ANY, COLOR_NONE, "copy-on-fork",
+			   "copy-on-fork %s\n",
+			   cof);
+
 	return MNL_CB_OK;
 }
 
-- 
2.31.1