svn commit: r324378 - head/sys/kern
Mateusz Guzik
mjg at FreeBSD.org
Fri Oct 6 23:05:57 UTC 2017
Author: mjg
Date: Fri Oct 6 23:05:55 2017
New Revision: 324378
URL: https://svnweb.freebsd.org/changeset/base/324378
Log:
namecache: factor out ~MAKEENTRY lookups from the common path
Lookups of the sort are rare compared to regular ones and succesfull ones
result in removing entries from the cache.
In the current code buckets are rlocked and a trylock dance is performed,
which can fail and cause a restart. Fixing it will require a little bit
of surgery and in order to keep the code maintaineable the 2 cases have
to split.
MFC after: 1 week
Modified:
head/sys/kern/vfs_cache.c
Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c Fri Oct 6 21:52:28 2017 (r324377)
+++ head/sys/kern/vfs_cache.c Fri Oct 6 23:05:55 2017 (r324378)
@@ -1058,7 +1058,6 @@ cache_lookup_unlock(struct rwlock *blp, struct mtx *vl
if (blp != NULL) {
rw_runlock(blp);
- mtx_assert(vlp, MA_NOTOWNED);
} else {
mtx_unlock(vlp);
}
@@ -1117,6 +1116,82 @@ cache_lookup_dot(struct vnode *dvp, struct vnode **vpp
* not recursively acquired.
*/
+static __noinline int
+cache_lookup_nomakeentry(struct vnode *dvp, struct vnode **vpp,
+ struct componentname *cnp, struct timespec *tsp, int *ticksp)
+{
+ struct namecache *ncp;
+ struct rwlock *blp;
+ struct mtx *dvlp, *dvlp2;
+ uint32_t hash;
+ int error;
+
+ if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
+ counter_u64_add(dotdothits, 1);
+ dvlp = VP2VNODELOCK(dvp);
+ dvlp2 = NULL;
+ mtx_lock(dvlp);
+retry_dotdot:
+ ncp = dvp->v_cache_dd;
+ if (ncp == NULL) {
+ SDT_PROBE3(vfs, namecache, lookup, miss, dvp,
+ "..", NULL);
+ mtx_unlock(dvlp);
+ return (0);
+ }
+ if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
+ if (ncp->nc_dvp != dvp)
+ panic("dvp %p v_cache_dd %p\n", dvp, ncp);
+ if (!cache_zap_locked_vnode_kl2(ncp,
+ dvp, &dvlp2))
+ goto retry_dotdot;
+ MPASS(dvp->v_cache_dd == NULL);
+ mtx_unlock(dvlp);
+ if (dvlp2 != NULL)
+ mtx_unlock(dvlp2);
+ cache_free(ncp);
+ } else {
+ dvp->v_cache_dd = NULL;
+ mtx_unlock(dvlp);
+ if (dvlp2 != NULL)
+ mtx_unlock(dvlp2);
+ }
+ return (0);
+ }
+
+ hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
+ blp = HASH2BUCKETLOCK(hash);
+retry:
+ rw_rlock(blp);
+
+ LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
+ counter_u64_add(numchecks, 1);
+ if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
+ !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen))
+ break;
+ }
+
+ /* We failed to find an entry */
+ if (ncp == NULL) {
+ rw_runlock(blp);
+ SDT_PROBE3(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
+ NULL);
+ counter_u64_add(nummisszap, 1);
+ return (0);
+ }
+
+ counter_u64_add(numposzaps, 1);
+
+ error = cache_zap_rlocked_bucket(ncp, blp);
+ if (error != 0) {
+ zap_and_exit_bucket_fail++;
+ cache_maybe_yield();
+ goto retry;
+ }
+ cache_free(ncp);
+ return (0);
+}
+
int
cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
struct timespec *tsp, int *ticksp)
@@ -1132,69 +1207,51 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, st
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
+
+ counter_u64_add(numcalls, 1);
+
+ if (__predict_false(cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.'))
+ return (cache_lookup_dot(dvp, vpp, cnp, tsp, ticksp));
+
+ if ((cnp->cn_flags & MAKEENTRY) == 0)
+ return (cache_lookup_nomakeentry(dvp, vpp, cnp, tsp, ticksp));
+
retry:
blp = NULL;
- dvlp = VP2VNODELOCK(dvp);
error = 0;
- counter_u64_add(numcalls, 1);
-
- if (cnp->cn_nameptr[0] == '.') {
- if (cnp->cn_namelen == 1)
- return (cache_lookup_dot(dvp, vpp, cnp, tsp, ticksp));
- if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
- counter_u64_add(dotdothits, 1);
- dvlp2 = NULL;
- mtx_lock(dvlp);
-retry_dotdot:
- ncp = dvp->v_cache_dd;
- if (ncp == NULL) {
- SDT_PROBE3(vfs, namecache, lookup, miss, dvp,
- "..", NULL);
- mtx_unlock(dvlp);
- return (0);
- }
- if ((cnp->cn_flags & MAKEENTRY) == 0) {
- if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
- if (ncp->nc_dvp != dvp)
- panic("dvp %p v_cache_dd %p\n", dvp, ncp);
- if (!cache_zap_locked_vnode_kl2(ncp,
- dvp, &dvlp2))
- goto retry_dotdot;
- MPASS(dvp->v_cache_dd == NULL);
- mtx_unlock(dvlp);
- if (dvlp2 != NULL)
- mtx_unlock(dvlp2);
- cache_free(ncp);
- } else {
- dvp->v_cache_dd = NULL;
- mtx_unlock(dvlp);
- if (dvlp2 != NULL)
- mtx_unlock(dvlp2);
- }
- return (0);
- }
- if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
- if (ncp->nc_flag & NCF_NEGATIVE)
- *vpp = NULL;
- else
- *vpp = ncp->nc_vp;
- } else
- *vpp = ncp->nc_dvp;
- /* Return failure if negative entry was found. */
- if (*vpp == NULL)
- goto negative_success;
- CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
- dvp, cnp->cn_nameptr, *vpp);
- SDT_PROBE3(vfs, namecache, lookup, hit, dvp, "..",
- *vpp);
- cache_out_ts(ncp, tsp, ticksp);
- if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
- NCF_DTS && tsp != NULL) {
- ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
- *tsp = ncp_ts->nc_dotdottime;
- }
- goto success;
+ if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
+ counter_u64_add(dotdothits, 1);
+ dvlp = VP2VNODELOCK(dvp);
+ dvlp2 = NULL;
+ mtx_lock(dvlp);
+ ncp = dvp->v_cache_dd;
+ if (ncp == NULL) {
+ SDT_PROBE3(vfs, namecache, lookup, miss, dvp,
+ "..", NULL);
+ mtx_unlock(dvlp);
+ return (0);
}
+ if ((ncp->nc_flag & NCF_ISDOTDOT) != 0) {
+ if (ncp->nc_flag & NCF_NEGATIVE)
+ *vpp = NULL;
+ else
+ *vpp = ncp->nc_vp;
+ } else
+ *vpp = ncp->nc_dvp;
+ /* Return failure if negative entry was found. */
+ if (*vpp == NULL)
+ goto negative_success;
+ CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
+ dvp, cnp->cn_nameptr, *vpp);
+ SDT_PROBE3(vfs, namecache, lookup, hit, dvp, "..",
+ *vpp);
+ cache_out_ts(ncp, tsp, ticksp);
+ if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
+ NCF_DTS && tsp != NULL) {
+ ncp_ts = __containerof(ncp, struct namecache_ts, nc_nc);
+ *tsp = ncp_ts->nc_dotdottime;
+ }
+ goto success;
}
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
@@ -1210,21 +1267,11 @@ retry_dotdot:
/* We failed to find an entry */
if (ncp == NULL) {
+ rw_runlock(blp);
SDT_PROBE3(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
NULL);
- if ((cnp->cn_flags & MAKEENTRY) == 0) {
- counter_u64_add(nummisszap, 1);
- } else {
- counter_u64_add(nummiss, 1);
- }
- cache_lookup_unlock(blp, dvlp);
+ counter_u64_add(nummiss, 1);
return (0);
- }
-
- /* We don't want to have an entry, so dump it */
- if ((cnp->cn_flags & MAKEENTRY) == 0) {
- counter_u64_add(numposzaps, 1);
- goto zap_and_exit;
}
/* We found a "positive" match, return the vnode */
More information about the svn-src-all
mailing list