Commit 91d2e9b5 authored by Chuck Lever's avatar Chuck Lever
Browse files

NFSD: Clean up the nfsd_net::nfssvc_boot field 



There are two boot-time fields in struct nfsd_net: one called
boot_time and one called nfssvc_boot. The latter is used only to
form write verifiers, but its documenting comment declares:

        /* Time of server startup */

Since commit 27c438f5 ("nfsd: Support the server resetting the
boot verifier"), this field can be reset at any time; it's no
longer tied to server restart. So that comment is stale.

Also, according to pahole, struct timespec64 is 16 bytes long on
x86_64. The nfssvc_boot field is used only to form a write verifier,
which is 8 bytes long.

Let's clarify this situation by manufacturing an 8-byte verifier
in nfs_reset_boot_verifier() and storing only that in struct
nfsd_net.

We're grabbing 128 bits of time, so compress all of those into a
64-bit verifier instead of throwing out the high-order bits.
In the future, the siphash_key can be re-used for other hashed
objects per-nfsd_net.

Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent cdc55660

fs/nfsd/netns.h

+5 −3
Original line number Original line Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <net/net_namespace.h>

#include <net/net_namespace.h>

#include <net/netns/generic.h>

#include <net/netns/generic.h>

#include <linux/percpu_counter.h>

#include <linux/percpu_counter.h>

#include <linux/siphash.h>





/* Hash tables for nfs4_clientid state */

/* Hash tables for nfs4_clientid state */

#define CLIENT_HASH_BITS                 4

#define CLIENT_HASH_BITS                 4
@@ -108,9 +109,8 @@ struct nfsd_net { 
	bool nfsd_net_up;

	bool nfsd_net_up;

	bool lockd_up;

	bool lockd_up;





	/* Time of server startup */

	seqlock_t writeverf_lock;

	struct timespec64 nfssvc_boot;

	unsigned char writeverf[8];

	seqlock_t boot_lock;





	/*

	/*

	 * Max number of connections this nfsd container will allow. Defaults

	 * Max number of connections this nfsd container will allow. Defaults
@@ -187,6 +187,8 @@ struct nfsd_net { 
	char			nfsd_name[UNX_MAXNODENAME+1];

	char			nfsd_name[UNX_MAXNODENAME+1];





	struct nfsd_fcache_disposal *fcache_disposal;

	struct nfsd_fcache_disposal *fcache_disposal;



	siphash_key_t		siphash_key;

};

};





/* Simple check to find out if a given net was properly initialized */

/* Simple check to find out if a given net was properly initialized */

fs/nfsd/nfsctl.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -1483,7 +1483,8 @@ static __net_init int nfsd_init_net(struct net *net) 
	nn->clientid_counter = nn->clientid_base + 1;

	nn->clientid_counter = nn->clientid_base + 1;

	nn->s2s_cp_cl_id = nn->clientid_counter++;

	nn->s2s_cp_cl_id = nn->clientid_counter++;





	seqlock_init(&nn->boot_lock);

	get_random_bytes(&nn->siphash_key, sizeof(nn->siphash_key));

	seqlock_init(&nn->writeverf_lock);





	return 0;

	return 0;

fs/nfsd/nfssvc.c

+38 −13
Original line number Original line Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/module.h>

#include <linux/module.h>

#include <linux/fs_struct.h>

#include <linux/fs_struct.h>

#include <linux/swap.h>

#include <linux/swap.h>

#include <linux/siphash.h>





#include <linux/sunrpc/stats.h>

#include <linux/sunrpc/stats.h>

#include <linux/sunrpc/svcsock.h>

#include <linux/sunrpc/svcsock.h>
@@ -344,33 +345,57 @@ static bool nfsd_needs_lockd(struct nfsd_net *nn) 
	return nfsd_vers(nn, 2, NFSD_TEST) || nfsd_vers(nn, 3, NFSD_TEST);

	return nfsd_vers(nn, 2, NFSD_TEST) || nfsd_vers(nn, 3, NFSD_TEST);

}

}





/**

 * nfsd_copy_boot_verifier - Atomically copy a write verifier

 * @verf: buffer in which to receive the verifier cookie

 * @nn: NFS net namespace

 *

 * This function provides a wait-free mechanism for copying the

 * namespace's boot verifier without tearing it.

 */

void nfsd_copy_boot_verifier(__be32 verf[2], struct nfsd_net *nn)

void nfsd_copy_boot_verifier(__be32 verf[2], struct nfsd_net *nn)

{

{

	int seq = 0;

	int seq = 0;





	do {

	do {

		read_seqbegin_or_lock(&nn->boot_lock, &seq);

		read_seqbegin_or_lock(&nn->writeverf_lock, &seq);

		/*

		memcpy(verf, nn->writeverf, sizeof(*verf));

		 * This is opaque to client, so no need to byte-swap. Use

	} while (need_seqretry(&nn->writeverf_lock, seq));

		 * __force to keep sparse happy. y2038 time_t overflow is

	done_seqretry(&nn->writeverf_lock, seq);

		 * irrelevant in this usage

		 */

		verf[0] = (__force __be32)nn->nfssvc_boot.tv_sec;

		verf[1] = (__force __be32)nn->nfssvc_boot.tv_nsec;

	} while (need_seqretry(&nn->boot_lock, seq));

	done_seqretry(&nn->boot_lock, seq);

}

}





static void nfsd_reset_boot_verifier_locked(struct nfsd_net *nn)

static void nfsd_reset_boot_verifier_locked(struct nfsd_net *nn)

{

{

	ktime_get_raw_ts64(&nn->nfssvc_boot);

	struct timespec64 now;

	u64 verf;



	/*

	 * Because the time value is hashed, y2038 time_t overflow

	 * is irrelevant in this usage.

	 */

	ktime_get_raw_ts64(&now);

	verf = siphash_2u64(now.tv_sec, now.tv_nsec, &nn->siphash_key);

	memcpy(nn->writeverf, &verf, sizeof(nn->writeverf));

}

}





/**

 * nfsd_reset_boot_verifier - Generate a new boot verifier

 * @nn: NFS net namespace

 *

 * This function updates the ->writeverf field of @nn. This field

 * contains an opaque cookie that, according to Section 18.32.3 of

 * RFC 8881, "the client can use to determine whether a server has

 * changed instance state (e.g., server restart) between a call to

 * WRITE and a subsequent call to either WRITE or COMMIT.  This

 * cookie MUST be unchanged during a single instance of the NFSv4.1

 * server and MUST be unique between instances of the NFSv4.1

 * server."

 */

void nfsd_reset_boot_verifier(struct nfsd_net *nn)

void nfsd_reset_boot_verifier(struct nfsd_net *nn)

{

{

	write_seqlock(&nn->boot_lock);

	write_seqlock(&nn->writeverf_lock);

	nfsd_reset_boot_verifier_locked(nn);

	nfsd_reset_boot_verifier_locked(nn);

	write_sequnlock(&nn->boot_lock);

	write_sequnlock(&nn->writeverf_lock);

}

}





static int nfsd_startup_net(struct net *net, const struct cred *cred)

static int nfsd_startup_net(struct net *net, const struct cred *cred)