Nul-terminate strings in the VFS name cache, which negligibly change

the size and cost of name cache entries, but make adding debugging and tracing easier. Add SDT DTrace probes for various namecache events: vfs:namecache:enter:done - new entry in the name cache, passed parent directory vnode pointer, name added to the cache, and child vnode pointer. vfs:namecache:enter_negative:done - new negative entry in the name cache, passed parent vnode pointer, name added to the cache. vfs:namecache:fullpath:enter - call to vn_fullpath1() is made, passed the vnode to resolve to a name. vfs:namecache:fullpath:hit - vn_fullpath1() successfully resolved a search for the parent of an object using the namecache, passed the discovered parent directory vnode pointer, name, and child vnode pointer. vfs:namecache:fullpath:miss - vn_fullpath1() failed to resolve a search for the parent of an object using the namecache, passed the child vnode pointer. vfs:namecache:fullpath:return - vn_fullpath1() has completed, passed the error number, and if that is zero, the vnode to resolve, and the returned path. vfs:namecache:lookup:hit - postive name cache entry hit, passed the parent directory vnode pointer, name, and child vnode pointer. vfs:namecache:lookup:hit_negative - negative name cache entry hit, passed the parent directory vnode pointer and name. vfs:namecache:lookup:miss - name cache miss, passed the parent directory pointer and the full remaining component name (not terminated after the cache miss component). vfs:namecache:purge:done - name cache purge for a vnode, passed the vnode pointer to purge. vfs:namecache:purge_negative:done - name cache purge of negative entries for children of a vnode, passed the vnode pointer to purge. vfs:namecache:purgevfs - name cache purge for a mountpoint, passed the mount pointer. Separate probes will also be invoked for each cache entry zapped. vfs:namecache:zap:done - name cache entry zapped, passed the parent directory vnode pointer, name, and child vnode pointer. vfs:namecache:zap_negative:done - negative name cache entry zapped, passed the parent directory vnode pointer and name. For any probes involving an extant name cache entry (enter, hit, zapp), we use the nul-terminated string for the name component. For misses, the remainder of the path, including later components, is provided as an argument instead since there is no handy nul-terminated version of the string around. This is arguably a bug. MFC after: 1 month Sponsored by: Google, Inc. Reviewed by: jhb, kan, kib (earlier version)
svn path=/head/; revision=190829
2024-12-25 11:37:56 +00:00 · 2009-04-07 20:58:56 +00:00 · 2009-04-07 20:58:56 +00:00 · 5d5c174869 · 2020-12-20 02:59:44 +00:00
commit 5d5c174869
parent ec85f7fa39
1 changed files with 96 additions and 10 deletions
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@ -35,6 +35,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");

+#include "opt_kdtrace.h"
 #include "opt_ktrace.h"

 #include <sys/param.h>
@ -47,6 +48,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/namei.h>
 #include <sys/proc.h>
 #include <sys/rwlock.h>
+#include <sys/sdt.h>
 #include <sys/syscallsubr.h>
 #include <sys/sysctl.h>
 #include <sys/sysproto.h>
@ -58,6 +60,31 @@ __FBSDID("$FreeBSD$");

 #include <vm/uma.h>

+SDT_PROVIDER_DECLARE(vfs);
+SDT_PROBE_DEFINE3(vfs, namecache, enter, done, "struct vnode *", "char *",
+    "struct vnode *");
+SDT_PROBE_DEFINE2(vfs, namecache, enter_negative, done, "struct vnode *",
+    "char *");
+SDT_PROBE_DEFINE1(vfs, namecache, fullpath, entry, "struct vnode *");
+SDT_PROBE_DEFINE3(vfs, namecache, fullpath, hit, "struct vnode *",
+    "struct char *", "struct vnode *");
+SDT_PROBE_DEFINE1(vfs, namecache, fullpath, miss, "struct vnode *");
+SDT_PROBE_DEFINE3(vfs, namecache, fullpath, return, "int", "struct vnode *",
+    "struct char *");
+SDT_PROBE_DEFINE3(vfs, namecache, lookup, hit, "struct vnode *", "char *",
+    "struct vnode *");
+SDT_PROBE_DEFINE2(vfs, namecache, lookup, hit_negative, "struct vnode *",
+    "char *");
+SDT_PROBE_DEFINE2(vfs, namecache, lookup, miss, "struct vnode *",
+    "char *");
+SDT_PROBE_DEFINE1(vfs, namecache, purge, done, "struct vnode *");
+SDT_PROBE_DEFINE1(vfs, namecache, purge_negative, done, "struct vnode *");
+SDT_PROBE_DEFINE1(vfs, namecache, purgevfs, done, "struct mount *");
+SDT_PROBE_DEFINE3(vfs, namecache, zap, done, "struct vnode *", "char *",
+    "struct vnode *");
+SDT_PROBE_DEFINE2(vfs, namecache, zap_negative, done, "struct vnode *",
+    "char *");
+
 /*
 * This structure describes the elements in the cache of recent
 * names looked up by namei.
@ -71,7 +98,7 @@ struct	namecache {
 	struct	vnode *nc_vp;		/* vnode the name refers to */
 	u_char	nc_flag;		/* flag bits */
 	u_char	nc_nlen;		/* length of name */
-	char	nc_name[0];		/* segment name */
+	char	nc_name[0];		/* segment name + nul */
 };

 /*
@ -133,9 +160,10 @@ RW_SYSINIT(vfscache, &cache_lock, "Name Cache");
 static uma_zone_t cache_zone_small;
 static uma_zone_t cache_zone_large;

-#define	CACHE_PATH_CUTOFF	32
-#define	CACHE_ZONE_SMALL	(sizeof(struct namecache) + CACHE_PATH_CUTOFF)
-#define	CACHE_ZONE_LARGE	(sizeof(struct namecache) + NAME_MAX)
+#define	CACHE_PATH_CUTOFF	35
+#define	CACHE_ZONE_SMALL	(sizeof(struct namecache) + CACHE_PATH_CUTOFF \
+				    + 1)
+#define	CACHE_ZONE_LARGE	(sizeof(struct namecache) + NAME_MAX + 1)

 #define cache_alloc(len)	uma_zalloc(((len) <= CACHE_PATH_CUTOFF) ? \
 	cache_zone_small : cache_zone_large, M_WAITOK)
@ -291,6 +319,15 @@ cache_zap(ncp)

 	rw_assert(&cache_lock, RA_WLOCKED);
 	CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp, ncp->nc_vp);
+#ifdef KDTRACE_HOOKS
+	if (ncp->nc_vp != NULL) {
+		SDT_PROBE(vfs, namecache, zap, done, ncp->nc_dvp,
+		    ncp->nc_name, ncp->nc_vp, 0, 0);
+	} else {
+		SDT_PROBE(vfs, namecache, zap_negative, done, ncp->nc_dvp,
+		    ncp->nc_name, 0, 0, 0);
+	}
+#endif
 	vp = NULL;
 	LIST_REMOVE(ncp, nc_hash);
 	if (ncp->nc_flag & NCF_ISDOTDOT) {
@ -361,12 +398,17 @@ cache_lookup(dvp, vpp, cnp)
 			CTR2(KTR_VFS, "cache_lookup(%p, %s) found via .",
 			    dvp, cnp->cn_nameptr);
 			dothits++;
+			SDT_PROBE(vfs, namecache, lookup, hit, dvp, ".",
+			    *vpp, 0, 0);
 			goto success;
 		}
 		if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
 			dotdothits++;
-			if (dvp->v_cache_dd == NULL)
+			if (dvp->v_cache_dd == NULL) {
+				SDT_PROBE(vfs, namecache, lookup, miss, dvp,
+				    "..", NULL, 0, 0);
 				goto unlock;
+			}
 			if ((cnp->cn_flags & MAKEENTRY) == 0) {
 				if (dvp->v_cache_dd->nc_flag & NCF_ISDOTDOT)
 					cache_zap(dvp->v_cache_dd);
@ -379,6 +421,8 @@ cache_lookup(dvp, vpp, cnp)
 				*vpp = dvp->v_cache_dd->nc_dvp;
 			CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
 			    dvp, cnp->cn_nameptr, *vpp);
+			SDT_PROBE(vfs, namecache, lookup, hit, dvp, "..",
+			    *vpp, 0, 0);
 			goto success;
 		}
 	}
@ -394,6 +438,8 @@ cache_lookup(dvp, vpp, cnp)

 	/* We failed to find an entry */
 	if (ncp == NULL) {
+		SDT_PROBE(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
+		    NULL, 0, 0);
 		if ((cnp->cn_flags & MAKEENTRY) == 0) {
 			nummisszap++;
 		} else {
@ -421,6 +467,8 @@ cache_lookup(dvp, vpp, cnp)
 		*vpp = ncp->nc_vp;
 		CTR4(KTR_VFS, "cache_lookup(%p, %s) found %p via ncp %p",
 		    dvp, cnp->cn_nameptr, *vpp, ncp);
+		SDT_PROBE(vfs, namecache, lookup, hit, dvp, ncp->nc_name,
+		    *vpp, 0, 0);
 		goto success;
 	}

@ -449,6 +497,8 @@ cache_lookup(dvp, vpp, cnp)
 	nchstats.ncs_neghits++;
 	if (ncp->nc_flag & NCF_WHITE)
 		cnp->cn_flags |= ISWHITEOUT;
+	SDT_PROBE(vfs, namecache, lookup, hit_negative, dvp, ncp->nc_name,
+	    0, 0, 0);
 	CACHE_WUNLOCK();
 	return (ENOENT);

@ -579,6 +629,8 @@ cache_enter(dvp, vp, cnp)
 				}
 			}
 			dvp->v_cache_dd = NULL;
+			SDT_PROBE(vfs, namecache, enter, done, dvp, "..", vp,
+			    0, 0);
 			CACHE_WUNLOCK();
 			flag = NCF_ISDOTDOT;
 		}
@ -597,7 +649,7 @@ cache_enter(dvp, vp, cnp)
 	ncp->nc_flag = flag;
 	len = ncp->nc_nlen = cnp->cn_namelen;
 	hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT);
-	bcopy(cnp->cn_nameptr, ncp->nc_name, len);
+	strlcpy(ncp->nc_name, cnp->cn_nameptr, len + 1);
 	hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
 	CACHE_WLOCK();

@ -667,8 +719,12 @@ cache_enter(dvp, vp, cnp)
 	 */
 	if (vp) {
 		TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
+		SDT_PROBE(vfs, namecache, enter, done, dvp, ncp->nc_name, vp,
+		    0, 0);
 	} else {
 		TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
+		SDT_PROBE(vfs, namecache, enter_negative, done, dvp,
+		    ncp->nc_name, 0, 0, 0);
 	}
 	if (numneg * ncnegfactor > numcache) {
 		ncp = TAILQ_FIRST(&ncneg);
@ -709,6 +765,7 @@ cache_purge(vp)
 {

 	CTR1(KTR_VFS, "cache_purge(%p)", vp);
+	SDT_PROBE(vfs, namecache, purge, done, vp, 0, 0, 0, 0);
 	CACHE_WLOCK();
 	while (!LIST_EMPTY(&vp->v_cache_src))
 		cache_zap(LIST_FIRST(&vp->v_cache_src));
@ -733,6 +790,7 @@ cache_purge_negative(vp)
 	struct namecache *cp, *ncp;

 	CTR1(KTR_VFS, "cache_purge_negative(%p)", vp);
+	SDT_PROBE(vfs, namecache, purge_negative, done, vp, 0, 0, 0, 0);
 	CACHE_WLOCK();
 	LIST_FOREACH_SAFE(cp, &vp->v_cache_src, nc_src, ncp) {
 		if (cp->nc_vp == NULL)
@ -752,6 +810,7 @@ cache_purgevfs(mp)
 	struct namecache *ncp, *nnp;

 	/* Scan hash tables for applicable entries */
+	SDT_PROBE(vfs, namecache, purgevfs, done, mp, 0, 0, 0, 0);
 	CACHE_WLOCK();
 	for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) {
 		LIST_FOREACH_SAFE(ncp, ncpp, nc_hash, nnp) {
@ -998,6 +1057,9 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 	char *bp;
 	int error, i, slash_prefixed;
 	struct namecache *ncp;
+#ifdef KDTRACE_HOOKS
+	struct vnode *startvp = vp;
+#endif

 	buflen--;
 	bp = buf + buflen;
@ -1005,6 +1067,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 	error = 0;
 	slash_prefixed = 0;

+	SDT_PROBE(vfs, namecache, fullpath, entry, vp, 0, 0, 0, 0);
 	CACHE_RLOCK();
 	numfullpathcalls++;
 	if (vp->v_type != VDIR) {
@ -1016,18 +1079,31 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 			if (bp == buf) {
 				numfullpathfail4++;
 				CACHE_RUNLOCK();
-				return (ENOMEM);
+				error = ENOMEM;
+				SDT_PROBE(vfs, namecache, fullpath, return,
+				    error, startvp, NULL, 0, 0);
+				return (error);
 			}
+			SDT_PROBE(vfs, namecache, fullpath, hit, ncp->nc_dvp,
+			    ncp->nc_name, vp, 0, 0);
 			vp = ncp->nc_dvp;
 		} else {
+			SDT_PROBE(vfs, namecache, fullpath, miss, vp, 0, 0,
+			    0, 0);
 			error = vn_vptocnp(&vp, &bp, buf, &buflen);
-			if (error)
+			if (error) {
+				SDT_PROBE(vfs, namecache, fullpath, return,
+				    error, startvp, NULL, 0, 0);
 				return (error);
+			}
 		}
 		if (buflen <= 0) {
 			numfullpathfail4++;
 			CACHE_RUNLOCK();
-			return (ENOMEM);
+			error = ENOMEM;
+			SDT_PROBE(vfs, namecache, fullpath, return, error,
+			    startvp, NULL, 0, 0);
+			return (error);
 		}
 		*--bp = '/';
 		buflen--;
@ -1062,8 +1138,12 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 				error = ENOMEM;
 				break;
 			}
+			SDT_PROBE(vfs, namecache, fullpath, hit, ncp->nc_dvp,
+			    ncp->nc_name, vp, 0, 0);
 			vp = ncp->nc_dvp;
 		} else {
+			SDT_PROBE(vfs, namecache, fullpath, miss, vp, 0, 0,
+			    0, 0);
 			error = vn_vptocnp(&vp, &bp, buf, &buflen);
 			if (error)
 				break;
@ -1078,12 +1158,17 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 		buflen--;
 		slash_prefixed = 1;
 	}
-	if (error)
+	if (error) {
+		SDT_PROBE(vfs, namecache, fullpath, return, error, startvp,
+		    NULL, 0, 0);
 		return (error);
+	}
 	if (!slash_prefixed) {
 		if (bp == buf) {
 			numfullpathfail4++;
 			CACHE_RUNLOCK();
+			SDT_PROBE(vfs, namecache, fullpath, return, 0,
+			    startvp, bp, 0, 0);
 			return (ENOMEM);
 		} else
 			*--bp = '/';
@ -1091,6 +1176,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 	numfullpathfound++;
 	CACHE_RUNLOCK();

+	SDT_PROBE(vfs, namecache, fullpath, return, 0, startvp, bp, 0, 0);
 	*retbuf = bp;
 	return (0);
 }