linux-kernel - Re: [PATCH 06/17] staging: lustre: get entropy from nid when nid set.

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Date:   Thu, 8 Mar 2018 00:19:04 +0000
From:   "Dilger, Andreas" <andreas.dilger@...el.com>
To:     NeilBrown <neilb@...e.com>
CC:     "Drokin, Oleg" <oleg.drokin@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        James Simmons <jsimmons@...radead.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        Lustre Development List <lustre-devel@...ts.lustre.org>
Subject: Re: [PATCH 06/17] staging: lustre: get entropy from nid when nid
 set.

On Mar 1, 2018, at 16:31, NeilBrown <neilb@...e.com> wrote:
> 
> When the 'lustre' module is loaded, it gets a list of
> net devices and uses the node ids to  add entropy
> to the prng.  This means that the network interfaces need
> to be configured before the module is loaded, which prevents
> the module from being compiled into a monolithic kernel.
> 
> So move this entropy addition to the moment when
> the interface is imported to LNet and the node id is first known.

It took me a while to convince myself this is correct, but this is
moving the entropy addition earlier in the startup sequence, and
that is a good thing.  The important factor is to ensure that the
client UUID (generated at mount time) is unique across all clients,
and adding the node address to the entropy ensures this, even if many
thousands of identical diskless nodes boot and mount simultaneously.

Reviewed-by: Andreas Dilger <andreas.dilger@...el.com>

> Signed-off-by: NeilBrown <neilb@...e.com>
> ---
> drivers/staging/lustre/lnet/lnet/api-ni.c     |    7 +++++++
> drivers/staging/lustre/lustre/llite/super25.c |   17 +----------------
> 2 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lnet/lnet/api-ni.c b/drivers/staging/lustre/lnet/lnet/api-ni.c
> index 48d25ccadbb3..90266be0132d 100644
> --- a/drivers/staging/lustre/lnet/lnet/api-ni.c
> +++ b/drivers/staging/lustre/lnet/lnet/api-ni.c
> @@ -1214,6 +1214,7 @@ lnet_startup_lndni(struct lnet_ni *ni, struct lnet_ioctl_config_data *conf)
> 	struct lnet_lnd *lnd;
> 	struct lnet_tx_queue *tq;
> 	int i;
> +	u32 seed;
> 
> 	lnd_type = LNET_NETTYP(LNET_NIDNET(ni->ni_nid));
> 
> @@ -1352,6 +1353,12 @@ lnet_startup_lndni(struct lnet_ni *ni, struct lnet_ioctl_config_data *conf)
> 		tq->tq_credits = lnet_ni_tq_credits(ni);
> 	}
> 
> +	/* Nodes with small feet have little entropy. The NID for this
> +	 * node gives the most entropy in the low bits.
> +	 */
> +	seed = LNET_NIDADDR(ni->ni_nid);
> +	add_device_randomness(&seed, sizeof(seed));
> +
> 	CDEBUG(D_LNI, "Added LNI %s [%d/%d/%d/%d]\n",
> 	       libcfs_nid2str(ni->ni_nid), ni->ni_peertxcredits,
> 	       lnet_ni_tq_credits(ni) * LNET_CPT_NUMBER,
> diff --git a/drivers/staging/lustre/lustre/llite/super25.c b/drivers/staging/lustre/lustre/llite/super25.c
> index 9b0bb3541a84..861e7a60f408 100644
> --- a/drivers/staging/lustre/lustre/llite/super25.c
> +++ b/drivers/staging/lustre/lustre/llite/super25.c
> @@ -85,8 +85,7 @@ MODULE_ALIAS_FS("lustre");
> 
> static int __init lustre_init(void)
> {
> -	struct lnet_process_id lnet_id;
> -	int i, rc;
> +	int rc;
> 
> 	BUILD_BUG_ON(sizeof(LUSTRE_VOLATILE_HDR) !=
> 		     LUSTRE_VOLATILE_HDR_LEN + 1);
> @@ -125,20 +124,6 @@ static int __init lustre_init(void)
> 		goto out_debugfs;
> 	}
> 
> -	/* Nodes with small feet have little entropy. The NID for this
> -	 * node gives the most entropy in the low bits
> -	 */
> -	for (i = 0;; i++) {
> -		u32 seed;
> -
> -		if (LNetGetId(i, &lnet_id) == -ENOENT)
> -			break;
> -		if (LNET_NETTYP(LNET_NIDNET(lnet_id.nid)) != LOLND) {
> -			 seed = LNET_NIDADDR(lnet_id.nid);
> -			 add_device_randomness(&seed, sizeof(seed));
> -		}
> -	}
> -
> 	rc = vvp_global_init();
> 	if (rc != 0)
> 		goto out_sysfs;
> 
> 

Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation