Linux does not HAVE_DNLC

Since Linux does not have the Directory Name Lookup Cache, we don't need
the code to manage it.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tim Chase <tim@chase2k.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
Closes openzfs#8031

Makefile.am

@@ -117,7 +117,7 @@ cppcheck:
 		cppcheck --quiet --force --error-exitcode=2 --inline-suppr \
 			--suppressions-list=.github/suppressions.txt \
 			-UHAVE_SSE2 -UHAVE_AVX512F -UHAVE_UIO_ZEROCOPY \
-			-UHAVE_DNLC ${top_srcdir}; \
+			${top_srcdir}; \
 	else \
 		echo "skipping cppcheck because cppcheck is not installed"; \
 	fi

module/zfs/zfs_dir.c

@@ -99,11 +99,6 @@ zfs_match_find(zfsvfs_t *zfsvfs, znode_t *dzp, char *name, matchtype_t mt,
 
 	*zoid = ZFS_DIRENT_OBJ(*zoid);
 
-#ifdef HAVE_DNLC
-	if (error == ENOENT && update)
-		dnlc_update(ZTOI(dzp), name, DNLC_NO_VNODE);
-#endif /* HAVE_DNLC */
-
 	return (error);
 }
 
@@ -151,9 +146,6 @@ zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
 	boolean_t	update;
 	matchtype_t	mt = 0;
 	uint64_t	zoid;
-#ifdef HAVE_DNLC
-	vnode_t		*vp = NULL;
-#endif /* HAVE_DNLC */
 	int		error = 0;
 	int		cmpflags;
 
@@ -320,29 +312,8 @@ zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
 		if (error == 0)
 			error = (zoid == 0 ? SET_ERROR(ENOENT) : 0);
 	} else {
-#ifdef HAVE_DNLC
-		if (update)
-			vp = dnlc_lookup(ZTOI(dzp), name);
-		if (vp == DNLC_NO_VNODE) {
-			iput(vp);
-			error = SET_ERROR(ENOENT);
-		} else if (vp) {
-			if (flag & ZNEW) {
-				zfs_dirent_unlock(dl);
-				iput(vp);
-				return (SET_ERROR(EEXIST));
-			}
-			*dlpp = dl;
-			*zpp = VTOZ(vp);
-			return (0);
-		} else {
-			error = zfs_match_find(zfsvfs, dzp, name, mt,
-			    update, direntflags, realpnp, &zoid);
-		}
-#else
 		error = zfs_match_find(zfsvfs, dzp, name, mt,
 		    update, direntflags, realpnp, &zoid);
-#endif /* HAVE_DNLC */
 	}
 	if (error) {
 		if (error != ENOENT || (flag & ZEXISTS)) {
@@ -359,10 +330,6 @@ zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
 			zfs_dirent_unlock(dl);
 			return (error);
 		}
-#ifdef HAVE_DNLC
-		if (!(flag & ZXATTR) && update)
-			dnlc_update(ZTOI(dzp), name, ZTOI(*zpp));
-#endif /* HAVE_DNLC */
 	}
 
 	*dlpp = dl;
@@ -901,10 +868,6 @@ zfs_link_destroy(zfs_dirlock_t *dl, znode_t *zp, dmu_tx_t *tx, int flag,
 	int count = 0;
 	int error;
 
-#ifdef HAVE_DNLC
-	dnlc_remove(ZTOI(dzp), dl->dl_name);
-#endif /* HAVE_DNLC */
-
 	if (!(flag & ZRENAMING)) {
 		mutex_enter(&zp->z_lock);
 

module/zfs/zfs_vnops.c

@@ -1208,27 +1208,6 @@ zfs_lookup(struct inode *dip, char *nm, struct inode **ipp, int flags,
 				return (0);
 			}
 			return (error);
-#ifdef HAVE_DNLC
-		} else if (!zdp->z_zfsvfs->z_norm &&
-		    (zdp->z_zfsvfs->z_case == ZFS_CASE_SENSITIVE)) {
-
-			vnode_t *tvp = dnlc_lookup(dvp, nm);
-
-			if (tvp) {
-				error = zfs_fastaccesschk_execute(zdp, cr);
-				if (error) {
-					iput(tvp);
-					return (error);
-				}
-				if (tvp == DNLC_NO_VNODE) {
-					iput(tvp);
-					return (SET_ERROR(ENOENT));
-				} else {
-					*vpp = tvp;
-					return (specvp_check(vpp, cr));
-				}
-			}
-#endif /* HAVE_DNLC */
 		}
 	}
 
@@ -1765,13 +1744,6 @@ zfs_remove(struct inode *dip, char *name, cred_t *cr, int flags)
 		goto out;
 	}
 
-#ifdef HAVE_DNLC
-	if (realnmp)
-		dnlc_remove(dvp, realnmp->pn_buf);
-	else
-		dnlc_remove(dvp, name);
-#endif /* HAVE_DNLC */
-
 	mutex_enter(&zp->z_lock);
 	may_delete_now = atomic_read(&ip->i_count) == 1 && !(zp->z_is_mapped);
 	mutex_exit(&zp->z_lock);