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nfscl: Add support for read delegations and atomic upgrade

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For NFSv4.1/4.2, an atomic upgrade of a delegation from a
read delegation to a write delegation is allowed and can
result in significantly improved performance.
This patch adds this upgrade to the NFSv4.1/4.2 client and
enables use of read delegations.

For a test case of building a FreeBSD kernel (sources and
output objects) over a NFSv4.2 mount, these changes reduced
the elapsed time by 30% and included a reduction of 80% for
RPC counts when delegations were enabled.  As such, with this
patch there are at least certain cases where enabling
delegations seems to be worth the increased complexity they
bring.

This patch should only affect the NFSv4.1/4.2 behaviour
when delegations are enabled, which is not the default.

MFC after:	1 month
This commit is contained in:
Rick Macklem 2024-06-12 16:41:12 -07:00
parent 4308d6e0fc
commit bb53f071e8
3 changed files with 26 additions and 20 deletions
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38
sys/fs/nfsclient/nfs_clstate.c
View File

@ -439,18 +439,6 @@ nfscl_deleg(mount_t mp, struct nfsclclient *clp, u_int8_t *nfhp,
KASSERT(mp != NULL, ("nfscl_deleg: mp NULL"));
nmp = VFSTONFS(mp);
/*
* First, if we have received a Read delegation for a file on a
* read/write file system, just return it, because they aren't
* useful, imho.
*/
if (dp != NULL && !NFSMNT_RDONLY(mp) &&
(dp->nfsdl_flags & NFSCLDL_READ)) {
nfscl_trydelegreturn(dp, cred, nmp, p);
free(dp, M_NFSCLDELEG);
*dpp = NULL;
return (0);
}
/*
* Since a delegation might be added to the mount,
@ -478,17 +466,35 @@ nfscl_deleg(mount_t mp, struct nfsclclient *clp, u_int8_t *nfhp,
nfscl_delegcnt++;
} else {
/*
* Delegation already exists, what do we do if a new one??
* A delegation already exists. If the new one is a Write
* delegation and the old one a Read delegation, return the
* Read delegation. Otherwise, return the new delegation.
*/
if (dp != NULL) {
printf("Deleg already exists!\n");
free(dp, M_NFSCLDELEG);
*dpp = NULL;
if ((dp->nfsdl_flags & NFSCLDL_WRITE) != 0 &&
(tdp->nfsdl_flags & NFSCLDL_READ) != 0) {
TAILQ_REMOVE(&clp->nfsc_deleg, tdp, nfsdl_list);
LIST_REMOVE(tdp, nfsdl_hash);
*dpp = NULL;
TAILQ_INSERT_HEAD(&clp->nfsc_deleg, dp,
nfsdl_list);
LIST_INSERT_HEAD(NFSCLDELEGHASH(clp, nfhp,
fhlen), dp, nfsdl_hash);
dp->nfsdl_timestamp = NFSD_MONOSEC + 120;
} else {
*dpp = NULL;
tdp = dp; /* Return this one. */
}
} else {
*dpp = tdp;
tdp = NULL;
}
}
NFSUNLOCKCLSTATE();
if (tdp != NULL) {
nfscl_trydelegreturn(tdp, cred, nmp, p);
free(tdp, M_NFSCLDELEG);
}
return (0);
}

6
sys/fs/nfsclient/nfs_clsubs.c
View File

@ -188,7 +188,7 @@ ncl_getattrcache(struct vnode *vp, struct vattr *vaper)
np = VTONFS(vp);
vap = &np->n_vattr.na_vattr;
nmp = VFSTONFS(vp->v_mount);
mustflush = nfscl_mustflush(vp); /* must be before mtx_lock() */
mustflush = nfscl_nodeleg(vp, 0); /* must be before mtx_lock() */
NFSLOCKNODE(np);
/* XXX n_mtime doesn't seem to be updated on a miss-and-reload */
timeo = (time_second - np->n_mtime.tv_sec) / 10;
@ -221,8 +221,8 @@ ncl_getattrcache(struct vnode *vp, struct vattr *vaper)
(time_second - np->n_attrstamp), timeo);
#endif
if ((time_second - np->n_attrstamp) >= timeo &&
(mustflush != 0 || np->n_attrstamp == 0)) {
if (mustflush != 0 && (np->n_attrstamp == 0 ||
time_second - np->n_attrstamp >= timeo)) {
nfsstatsv1.attrcache_misses++;
NFSUNLOCKNODE(np);
KDTRACE_NFS_ATTRCACHE_GET_MISS(vp);

2
sys/fs/nfsclient/nfs_clvnops.c
View File

@ -940,7 +940,7 @@ nfs_close(struct vop_close_args *ap)
/*
* Get attributes so "change" is up to date.
*/
if (error == 0 && nfscl_mustflush(vp) != 0 &&
if (error == 0 && nfscl_nodeleg(vp, 0) != 0 &&
vp->v_type == VREG &&
(VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NOCTO) == 0) {
ret = nfsrpc_getattr(vp, cred, ap->a_td, &nfsva);