git: bb53f071e85a - main - nfscl: Add support for read delegations and atomic upgrade

The branch main has been updated by rmacklem:

URL: https://cgit.FreeBSD.org/src/commit/?id=bb53f071e85a2ebb5b405e7fec4661a725b7caf5

commit bb53f071e85a2ebb5b405e7fec4661a725b7caf5
Author:     Rick Macklem <rmacklem@FreeBSD.org>
AuthorDate: 2024-06-12 23:41:12 +0000
Commit:     Rick Macklem <rmacklem@FreeBSD.org>
CommitDate: 2024-06-12 23:41:12 +0000

    nfscl: Add support for read delegations and atomic upgrade
    
    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
---
 sys/fs/nfsclient/nfs_clstate.c | 38 ++++++++++++++++++++++----------------
 sys/fs/nfsclient/nfs_clsubs.c  |  6 +++---
 sys/fs/nfsclient/nfs_clvnops.c |  2 +-
 3 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/sys/fs/nfsclient/nfs_clstate.c b/sys/fs/nfsclient/nfs_clstate.c
index aef5d71592af..0a1eb51e279f 100644
--- a/sys/fs/nfsclient/nfs_clstate.c
+++ b/sys/fs/nfsclient/nfs_clstate.c
@@ -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);
 }
 
diff --git a/sys/fs/nfsclient/nfs_clsubs.c b/sys/fs/nfsclient/nfs_clsubs.c
index 80ab979d22d7..8bb51e29e1d1 100644
--- a/sys/fs/nfsclient/nfs_clsubs.c
+++ b/sys/fs/nfsclient/nfs_clsubs.c
@@ -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);
diff --git a/sys/fs/nfsclient/nfs_clvnops.c b/sys/fs/nfsclient/nfs_clvnops.c
index 76a3cdf9281e..13341dfc26e0 100644
--- a/sys/fs/nfsclient/nfs_clvnops.c
+++ b/sys/fs/nfsclient/nfs_clvnops.c
@@ -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);