/* $NetBSD: vfs_cache.c,v 1.120 2017/03/18 22:36:56 riastradh Exp $ */ /*- * Copyright (c) 2008 The NetBSD Foundation, Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ /* * Copyright (c) 1989, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)vfs_cache.c 8.3 (Berkeley) 8/22/94 */ #include __KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.120 2017/03/18 22:36:56 riastradh Exp $"); #ifdef _KERNEL_OPT #include "opt_ddb.h" #include "opt_dtrace.h" #include "opt_revcache.h" #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define NAMECACHE_ENTER_REVERSE /* * Name caching works as follows: * * Names found by directory scans are retained in a cache * for future reference. It is managed LRU, so frequently * used names will hang around. Cache is indexed by hash value * obtained from (dvp, name) where dvp refers to the directory * containing name. * * For simplicity (and economy of storage), names longer than * a maximum length of NCHNAMLEN are not cached; they occur * infrequently in any case, and are almost never of interest. * * Upon reaching the last segment of a path, if the reference * is for DELETE, or NOCACHE is set (rewrite), and the * name is located in the cache, it will be dropped. */ /* * Cache entry lifetime: * * nonexistent * ---create---> active * ---invalidate---> queued * ---reclaim---> nonexistent. * * States: * - Nonexistent. Cache entry does not exist. * * - Active. cache_lookup, cache_lookup_raw, cache_revlookup can look * up, acquire references, and hand off references to vnodes, * e.g. via v_interlock. Marked by nonnull ncp->nc_dvp. * * - Queued. Pending desstruction by cache_reclaim. Cannot be used by * cache_lookup, cache_lookup_raw, or cache_revlookup. May still be * on lists. Marked by null ncp->nc_dvp. * * Transitions: * * - Create: nonexistent--->active * * Done by cache_enter(dvp, vp, name, namelen, cnflags), called by * VOP_LOOKUP after the answer is found. Allocates a struct * namecache object, initializes it with the above fields, and * activates it by inserting it into the forward and reverse tables. * * - Invalidate: active--->queued * * Done by cache_invalidate. If not already invalidated, nullify * ncp->nc_dvp and ncp->nc_vp, and add to cache_gcqueue. Called, * among various other places, in cache_lookup(dvp, name, namelen, * nameiop, cnflags, &iswht, &vp) when MAKEENTRY is missing from * cnflags. * * - Reclaim: queued--->nonexistent * * Done by cache_reclaim. Disassociate ncp from any lists it is on * and free memory. */ /* * Locking. * * L namecache_lock Global lock for namecache table and queues. * C struct nchcpu::cpu_lock Per-CPU lock to reduce read contention. * N struct namecache::nc_lock Per-entry lock. * V struct vnode::v_interlock Vnode interlock. * * Lock order: L -> C -> N -> V * * Examples: * . L->C: cache_reclaim * . C->N->V: cache_lookup * . L->N->V: cache_purge1, cache_revlookup * * All use serialized by namecache_lock: * * nclruhead / struct namecache::nc_lru * ncvhashtbl / struct namecache::nc_vhash * struct vnode_impl::vi_dnclist / struct namecache::nc_dvlist * struct vnode_impl::vi_nclist / struct namecache::nc_vlist * nchstats * * - Insertion serialized by namecache_lock, * - read protected by per-CPU lock, * - insert/read ordering guaranteed by memory barriers, and * - deletion allowed only under namecache_lock and *all* per-CPU locks * in CPU_INFO_FOREACH order: * * nchashtbl / struct namecache::nc_hash * * The per-CPU locks exist only to reduce the probability of * contention between readers. We do not bind to a CPU, so * contention is still possible. * * All use serialized by struct namecache::nc_lock: * * struct namecache::nc_dvp * struct namecache::nc_vp * struct namecache::nc_gcqueue (*) * struct namecache::nc_hittime (**) * * (*) Once on the queue, only cache_thread uses this nc_gcqueue, unlocked. * (**) cache_prune reads nc_hittime unlocked, since approximate is OK. * * Unlocked because stable after initialization: * * struct namecache::nc_dvp * struct namecache::nc_vp * struct namecache::nc_flags * struct namecache::nc_nlen * struct namecache::nc_name * * Unlocked because approximation is OK: * * struct nchcpu::cpu_stats * struct nchcpu::cpu_stats_last * * Updates under namecache_lock or any per-CPU lock are marked with * COUNT, while updates outside those locks are marked with COUNT_UNL. * * - The theory seems to have been that you could replace COUNT_UNL by * atomic operations -- except that doesn't help unless you also * replace COUNT by atomic operations, because mixing atomics and * nonatomics is a recipe for failure. * - We use 32-bit per-CPU counters and 64-bit global counters under * the theory that 32-bit counters are less likely to be hosed by * nonatomic increment. */ /* * The comment below is preserved for posterity in case it is * important, but it is clear that everywhere the namecache_count_*() * functions are called, other cache_*() functions that take the same * locks are also called, so I can't imagine how this could be a * problem: * * N.B.: Attempting to protect COUNT_UNL() increments by taking * a per-cpu lock in the namecache_count_*() functions causes * a deadlock. Don't do that, use atomic increments instead if * the imperfections here bug you. */ /* * struct nchstats_percpu: * * Per-CPU counters. */ struct nchstats_percpu _NAMEI_CACHE_STATS(uint32_t); /* * struct nchcpu: * * Per-CPU namecache state: lock and per-CPU counters. */ struct nchcpu { kmutex_t cpu_lock; struct nchstats_percpu cpu_stats; /* XXX maybe __cacheline_aligned would improve this? */ struct nchstats_percpu cpu_stats_last; /* from last sample */ }; /* * The type for the hash code. While the hash function generates a * u32, the hash code has historically been passed around as a u_long, * and the value is modified by xor'ing a uintptr_t, so it's not * entirely clear what the best type is. For now I'll leave it * unchanged as u_long. */ typedef u_long nchash_t; /* * Structures associated with name cacheing. */ static kmutex_t *namecache_lock __read_mostly; static pool_cache_t namecache_cache __read_mostly; static TAILQ_HEAD(, namecache) nclruhead __cacheline_aligned; static LIST_HEAD(nchashhead, namecache) *nchashtbl __read_mostly; static u_long nchash __read_mostly; #define NCHASH2(hash, dvp) \ (((hash) ^ ((uintptr_t)(dvp) >> 3)) & nchash) static LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl __read_mostly; static u_long ncvhash __read_mostly; #define NCVHASH(vp) (((uintptr_t)(vp) >> 3) & ncvhash) /* Number of cache entries allocated. */ static long numcache __cacheline_aligned; /* Garbage collection queue and number of entries pending in it. */ static void *cache_gcqueue; static u_int cache_gcpend; /* Cache effectiveness statistics. This holds total from per-cpu stats */ struct nchstats nchstats __cacheline_aligned; /* * Macros to count an event, update the central stats with per-cpu * values and add current per-cpu increments to the subsystem total * last collected by cache_reclaim(). */ #define CACHE_STATS_CURRENT /* nothing */ #define COUNT(cpup, f) ((cpup)->cpu_stats.f++) #define UPDATE(cpup, f) do { \ struct nchcpu *Xcpup = (cpup); \ uint32_t Xcnt = (volatile uint32_t) Xcpup->cpu_stats.f; \ nchstats.f += Xcnt - Xcpup->cpu_stats_last.f; \ Xcpup->cpu_stats_last.f = Xcnt; \ } while (/* CONSTCOND */ 0) #define ADD(stats, cpup, f) do { \ struct nchcpu *Xcpup = (cpup); \ stats.f += Xcpup->cpu_stats.f - Xcpup->cpu_stats_last.f; \ } while (/* CONSTCOND */ 0) /* Do unlocked stats the same way. Use a different name to allow mind changes */ #define COUNT_UNL(cpup, f) COUNT((cpup), f) static const int cache_lowat = 95; static const int cache_hiwat = 98; static const int cache_hottime = 5; /* number of seconds */ static int doingcache = 1; /* 1 => enable the cache */ static struct evcnt cache_ev_scan; static struct evcnt cache_ev_gc; static struct evcnt cache_ev_over; static struct evcnt cache_ev_under; static struct evcnt cache_ev_forced; static struct namecache *cache_lookup_entry( const struct vnode *, const char *, size_t); static void cache_thread(void *); static void cache_invalidate(struct namecache *); static void cache_disassociate(struct namecache *); static void cache_reclaim(void); static int cache_ctor(void *, void *, int); static void cache_dtor(void *, void *); static struct sysctllog *sysctllog; static void sysctl_cache_stat_setup(void); SDT_PROVIDER_DEFINE(vfs); SDT_PROBE_DEFINE1(vfs, namecache, invalidate, done, "struct vnode *"); SDT_PROBE_DEFINE1(vfs, namecache, purge, parents, "struct vnode *"); SDT_PROBE_DEFINE1(vfs, namecache, purge, children, "struct vnode *"); SDT_PROBE_DEFINE2(vfs, namecache, purge, name, "char *", "size_t"); SDT_PROBE_DEFINE1(vfs, namecache, purge, vfs, "struct mount *"); SDT_PROBE_DEFINE3(vfs, namecache, lookup, hit, "struct vnode *", "char *", "size_t"); SDT_PROBE_DEFINE3(vfs, namecache, lookup, miss, "struct vnode *", "char *", "size_t"); SDT_PROBE_DEFINE3(vfs, namecache, lookup, toolong, "struct vnode *", "char *", "size_t"); SDT_PROBE_DEFINE2(vfs, namecache, revlookup, success, "struct vnode *", "struct vnode *"); SDT_PROBE_DEFINE2(vfs, namecache, revlookup, fail, "struct vnode *", "int"); SDT_PROBE_DEFINE2(vfs, namecache, prune, done, "int", "int"); SDT_PROBE_DEFINE3(vfs, namecache, enter, toolong, "struct vnode *", "char *", "size_t"); SDT_PROBE_DEFINE3(vfs, namecache, enter, done, "struct vnode *", "char *", "size_t"); /* * Compute the hash for an entry. * * (This is for now a wrapper around namei_hash, whose interface is * for the time being slightly inconvenient.) */ static nchash_t cache_hash(const char *name, size_t namelen) { const char *endptr; endptr = name + namelen; return namei_hash(name, &endptr); } /* * Invalidate a cache entry and enqueue it for garbage collection. * The caller needs to hold namecache_lock or a per-cpu lock to hold * off cache_reclaim(). */ static void cache_invalidate(struct namecache *ncp) { void *head; KASSERT(mutex_owned(&ncp->nc_lock)); if (ncp->nc_dvp != NULL) { SDT_PROBE(vfs, namecache, invalidate, done, ncp->nc_dvp, 0, 0, 0, 0); ncp->nc_vp = NULL; ncp->nc_dvp = NULL; do { head = cache_gcqueue; ncp->nc_gcqueue = head; } while (atomic_cas_ptr(&cache_gcqueue, head, ncp) != head); atomic_inc_uint(&cache_gcpend); } } /* * Disassociate a namecache entry from any vnodes it is attached to, * and remove from the global LRU list. */ static void cache_disassociate(struct namecache *ncp) { KASSERT(mutex_owned(namecache_lock)); KASSERT(ncp->nc_dvp == NULL); if (ncp->nc_lru.tqe_prev != NULL) { TAILQ_REMOVE(&nclruhead, ncp, nc_lru); ncp->nc_lru.tqe_prev = NULL; } if (ncp->nc_vhash.le_prev != NULL) { LIST_REMOVE(ncp, nc_vhash); ncp->nc_vhash.le_prev = NULL; } if (ncp->nc_vlist.le_prev != NULL) { LIST_REMOVE(ncp, nc_vlist); ncp->nc_vlist.le_prev = NULL; } if (ncp->nc_dvlist.le_prev != NULL) { LIST_REMOVE(ncp, nc_dvlist); ncp->nc_dvlist.le_prev = NULL; } } /* * Lock all CPUs to prevent any cache lookup activity. Conceptually, * this locks out all "readers". */ static void cache_lock_cpus(void) { CPU_INFO_ITERATOR cii; struct cpu_info *ci; struct nchcpu *cpup; /* * Lock out all CPUs first, then harvest per-cpu stats. This * is probably not quite as cache-efficient as doing the lock * and harvest at the same time, but allows cache_stat_sysctl() * to make do with a per-cpu lock. */ for (CPU_INFO_FOREACH(cii, ci)) { cpup = ci->ci_data.cpu_nch; mutex_enter(&cpup->cpu_lock); } for (CPU_INFO_FOREACH(cii, ci)) { cpup = ci->ci_data.cpu_nch; UPDATE(cpup, ncs_goodhits); UPDATE(cpup, ncs_neghits); UPDATE(cpup, ncs_badhits); UPDATE(cpup, ncs_falsehits); UPDATE(cpup, ncs_miss); UPDATE(cpup, ncs_long); UPDATE(cpup, ncs_pass2); UPDATE(cpup, ncs_2passes); UPDATE(cpup, ncs_revhits); UPDATE(cpup, ncs_revmiss); } } /* * Release all CPU locks. */ static void cache_unlock_cpus(void) { CPU_INFO_ITERATOR cii; struct cpu_info *ci; struct nchcpu *cpup; for (CPU_INFO_FOREACH(cii, ci)) { cpup = ci->ci_data.cpu_nch; mutex_exit(&cpup->cpu_lock); } } /* * Find a single cache entry and return it locked. * The caller needs to hold namecache_lock or a per-cpu lock to hold * off cache_reclaim(). */ static struct namecache * cache_lookup_entry(const struct vnode *dvp, const char *name, size_t namelen) { struct nchashhead *ncpp; struct namecache *ncp; nchash_t hash; KASSERT(dvp != NULL); hash = cache_hash(name, namelen); ncpp = &nchashtbl[NCHASH2(hash, dvp)]; LIST_FOREACH(ncp, ncpp, nc_hash) { membar_datadep_consumer(); /* for Alpha... */ if (ncp->nc_dvp != dvp || ncp->nc_nlen != namelen || memcmp(ncp->nc_name, name, (u_int)ncp->nc_nlen)) continue; mutex_enter(&ncp->nc_lock); if (__predict_true(ncp->nc_dvp == dvp)) { ncp->nc_hittime = hardclock_ticks; SDT_PROBE(vfs, namecache, lookup, hit, dvp, name, namelen, 0, 0); return ncp; } /* Raced: entry has been nullified. */ mutex_exit(&ncp->nc_lock); } SDT_PROBE(vfs, namecache, lookup, miss, dvp, name, namelen, 0, 0); return NULL; } /* * Look for a the name in the cache. We don't do this * if the segment name is long, simply so the cache can avoid * holding long names (which would either waste space, or * add greatly to the complexity). * * Lookup is called with DVP pointing to the directory to search, * and CNP providing the name of the entry being sought: cn_nameptr * is the name, cn_namelen is its length, and cn_flags is the flags * word from the namei operation. * * DVP must be locked. * * There are three possible non-error return states: * 1. Nothing was found in the cache. Nothing is known about * the requested name. * 2. A negative entry was found in the cache, meaning that the * requested name definitely does not exist. * 3. A positive entry was found in the cache, meaning that the * requested name does exist and that we are providing the * vnode. * In these cases the results are: * 1. 0 returned; VN is set to NULL. * 2. 1 returned; VN is set to NULL. * 3. 1 returned; VN is set to the vnode found. * * The additional result argument ISWHT is set to zero, unless a * negative entry is found that was entered as a whiteout, in which * case ISWHT is set to one. * * The ISWHT_RET argument pointer may be null. In this case an * assertion is made that the whiteout flag is not set. File systems * that do not support whiteouts can/should do this. * * Filesystems that do support whiteouts should add ISWHITEOUT to * cnp->cn_flags if ISWHT comes back nonzero. * * When a vnode is returned, it is locked, as per the vnode lookup * locking protocol. * * There is no way for this function to fail, in the sense of * generating an error that requires aborting the namei operation. * * (Prior to October 2012, this function returned an integer status, * and a vnode, and mucked with the flags word in CNP for whiteouts. * The integer status was -1 for "nothing found", ENOENT for "a * negative entry found", 0 for "a positive entry found", and possibly * other errors, and the value of VN might or might not have been set * depending on what error occurred.) */ bool cache_lookup(struct vnode *dvp, const char *name, size_t namelen, uint32_t nameiop, uint32_t cnflags, int *iswht_ret, struct vnode **vn_ret) { struct namecache *ncp; struct vnode *vp; struct nchcpu *cpup; int error; bool hit; /* Establish default result values */ if (iswht_ret != NULL) { *iswht_ret = 0; } *vn_ret = NULL; if (__predict_false(!doingcache)) { return false; } cpup = curcpu()->ci_data.cpu_nch; mutex_enter(&cpup->cpu_lock); if (__predict_false(namelen > NCHNAMLEN)) { SDT_PROBE(vfs, namecache, lookup, toolong, dvp, name, namelen, 0, 0); COUNT(cpup, ncs_long); mutex_exit(&cpup->cpu_lock); /* found nothing */ return false; } ncp = cache_lookup_entry(dvp, name, namelen); if (__predict_false(ncp == NULL)) { COUNT(cpup, ncs_miss); mutex_exit(&cpup->cpu_lock); /* found nothing */ return false; } if ((cnflags & MAKEENTRY) == 0) { COUNT(cpup, ncs_badhits); /* * Last component and we are renaming or deleting, * the cache entry is invalid, or otherwise don't * want cache entry to exist. */ cache_invalidate(ncp); mutex_exit(&ncp->nc_lock); mutex_exit(&cpup->cpu_lock); /* found nothing */ return false; } if (ncp->nc_vp == NULL) { if (iswht_ret != NULL) { /* * Restore the ISWHITEOUT flag saved earlier. */ KASSERT((ncp->nc_flags & ~ISWHITEOUT) == 0); *iswht_ret = (ncp->nc_flags & ISWHITEOUT) != 0; } else { KASSERT(ncp->nc_flags == 0); } if (__predict_true(nameiop != CREATE || (cnflags & ISLASTCN) == 0)) { COUNT(cpup, ncs_neghits); /* found neg entry; vn is already null from above */ hit = true; } else { COUNT(cpup, ncs_badhits); /* * Last component and we are preparing to create * the named object, so flush the negative cache * entry. */ cache_invalidate(ncp); /* found nothing */ hit = false; } mutex_exit(&ncp->nc_lock); mutex_exit(&cpup->cpu_lock); return hit; } vp = ncp->nc_vp; mutex_enter(vp->v_interlock); mutex_exit(&ncp->nc_lock); mutex_exit(&cpup->cpu_lock); /* * Unlocked except for the vnode interlock. Call vcache_tryvget(). */ error = vcache_tryvget(vp); if (error) { KASSERT(error == EBUSY); /* * This vnode is being cleaned out. * XXX badhits? */ COUNT_UNL(cpup, ncs_falsehits); /* found nothing */ return false; } COUNT_UNL(cpup, ncs_goodhits); /* found it */ *vn_ret = vp; return true; } /* * Cut-'n-pasted version of the above without the nameiop argument. */ bool cache_lookup_raw(struct vnode *dvp, const char *name, size_t namelen, uint32_t cnflags, int *iswht_ret, struct vnode **vn_ret) { struct namecache *ncp; struct vnode *vp; struct nchcpu *cpup; int error; /* Establish default results. */ if (iswht_ret != NULL) { *iswht_ret = 0; } *vn_ret = NULL; if (__predict_false(!doingcache)) { /* found nothing */ return false; } cpup = curcpu()->ci_data.cpu_nch; mutex_enter(&cpup->cpu_lock); if (__predict_false(namelen > NCHNAMLEN)) { COUNT(cpup, ncs_long); mutex_exit(&cpup->cpu_lock); /* found nothing */ return false; } ncp = cache_lookup_entry(dvp, name, namelen); if (__predict_false(ncp == NULL)) { COUNT(cpup, ncs_miss); mutex_exit(&cpup->cpu_lock); /* found nothing */ return false; } vp = ncp->nc_vp; if (vp == NULL) { /* * Restore the ISWHITEOUT flag saved earlier. */ if (iswht_ret != NULL) { KASSERT((ncp->nc_flags & ~ISWHITEOUT) == 0); /*cnp->cn_flags |= ncp->nc_flags;*/ *iswht_ret = (ncp->nc_flags & ISWHITEOUT) != 0; } COUNT(cpup, ncs_neghits); mutex_exit(&ncp->nc_lock); mutex_exit(&cpup->cpu_lock); /* found negative entry; vn is already null from above */ return true; } mutex_enter(vp->v_interlock); mutex_exit(&ncp->nc_lock); mutex_exit(&cpup->cpu_lock); /* * Unlocked except for the vnode interlock. Call vcache_tryvget(). */ error = vcache_tryvget(vp); if (error) { KASSERT(error == EBUSY); /* * This vnode is being cleaned out. * XXX badhits? */ COUNT_UNL(cpup, ncs_falsehits); /* found nothing */ return false; } COUNT_UNL(cpup, ncs_goodhits); /* XXX can be "badhits" */ /* found it */ *vn_ret = vp; return true; } /* * Scan cache looking for name of directory entry pointing at vp. * * If the lookup succeeds the vnode is referenced and stored in dvpp. * * If bufp is non-NULL, also place the name in the buffer which starts * at bufp, immediately before *bpp, and move bpp backwards to point * at the start of it. (Yes, this is a little baroque, but it's done * this way to cater to the whims of getcwd). * * Returns 0 on success, -1 on cache miss, positive errno on failure. */ int cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp) { struct namecache *ncp; struct vnode *dvp; struct ncvhashhead *nvcpp; struct nchcpu *cpup; char *bp; int error, nlen; if (!doingcache) goto out; nvcpp = &ncvhashtbl[NCVHASH(vp)]; /* * We increment counters in the local CPU's per-cpu stats. * We don't take the per-cpu lock, however, since this function * is the only place these counters are incremented so no one * will be racing with us to increment them. */ cpup = curcpu()->ci_data.cpu_nch; mutex_enter(namecache_lock); LIST_FOREACH(ncp, nvcpp, nc_vhash) { mutex_enter(&ncp->nc_lock); if (ncp->nc_vp == vp && (dvp = ncp->nc_dvp) != NULL && dvp != vp) { /* avoid pesky . entries.. */ #ifdef DIAGNOSTIC if (ncp->nc_nlen == 1 && ncp->nc_name[0] == '.') panic("cache_revlookup: found entry for ."); if (ncp->nc_nlen == 2 && ncp->nc_name[0] == '.' && ncp->nc_name[1] == '.') panic("cache_revlookup: found entry for .."); #endif COUNT(cpup, ncs_revhits); nlen = ncp->nc_nlen; if (bufp) { bp = *bpp; bp -= nlen; if (bp <= bufp) { *dvpp = NULL; mutex_exit(&ncp->nc_lock); mutex_exit(namecache_lock); SDT_PROBE(vfs, namecache, revlookup, fail, vp, ERANGE, 0, 0, 0); return (ERANGE); } memcpy(bp, ncp->nc_name, nlen); *bpp = bp; } mutex_enter(dvp->v_interlock); mutex_exit(&ncp->nc_lock); mutex_exit(namecache_lock); error = vcache_tryvget(dvp); if (error) { KASSERT(error == EBUSY); if (bufp) (*bpp) += nlen; *dvpp = NULL; SDT_PROBE(vfs, namecache, revlookup, fail, vp, error, 0, 0, 0); return -1; } *dvpp = dvp; SDT_PROBE(vfs, namecache, revlookup, success, vp, dvp, 0, 0, 0); return (0); } mutex_exit(&ncp->nc_lock); } COUNT(cpup, ncs_revmiss); mutex_exit(namecache_lock); out: *dvpp = NULL; return (-1); } /* * Add an entry to the cache */ void cache_enter(struct vnode *dvp, struct vnode *vp, const char *name, size_t namelen, uint32_t cnflags) { struct namecache *ncp; struct namecache *oncp; struct nchashhead *ncpp; struct ncvhashhead *nvcpp; nchash_t hash; /* First, check whether we can/should add a cache entry. */ if ((cnflags & MAKEENTRY) == 0 || __predict_false(namelen > NCHNAMLEN || !doingcache)) { SDT_PROBE(vfs, namecache, enter, toolong, vp, name, namelen, 0, 0); return; } SDT_PROBE(vfs, namecache, enter, done, vp, name, namelen, 0, 0); if (numcache > desiredvnodes) { mutex_enter(namecache_lock); cache_ev_forced.ev_count++; cache_reclaim(); mutex_exit(namecache_lock); } ncp = pool_cache_get(namecache_cache, PR_WAITOK); mutex_enter(namecache_lock); numcache++; /* * Concurrent lookups in the same directory may race for a * cache entry. if there's a duplicated entry, free it. */ oncp = cache_lookup_entry(dvp, name, namelen); if (oncp) { cache_invalidate(oncp); mutex_exit(&oncp->nc_lock); } /* Grab the vnode we just found. */ mutex_enter(&ncp->nc_lock); ncp->nc_vp = vp; ncp->nc_flags = 0; ncp->nc_hittime = 0; ncp->nc_gcqueue = NULL; if (vp == NULL) { /* * For negative hits, save the ISWHITEOUT flag so we can * restore it later when the cache entry is used again. */ ncp->nc_flags = cnflags & ISWHITEOUT; } /* Fill in cache info. */ ncp->nc_dvp = dvp; LIST_INSERT_HEAD(&VNODE_TO_VIMPL(dvp)->vi_dnclist, ncp, nc_dvlist); if (vp) LIST_INSERT_HEAD(&VNODE_TO_VIMPL(vp)->vi_nclist, ncp, nc_vlist); else { ncp->nc_vlist.le_prev = NULL; ncp->nc_vlist.le_next = NULL; } KASSERT(namelen <= NCHNAMLEN); ncp->nc_nlen = namelen; memcpy(ncp->nc_name, name, (unsigned)ncp->nc_nlen); TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); hash = cache_hash(name, namelen); ncpp = &nchashtbl[NCHASH2(hash, dvp)]; /* * Flush updates before making visible in table. No need for a * memory barrier on the other side: to see modifications the * list must be followed, meaning a dependent pointer load. * The below is LIST_INSERT_HEAD() inlined, with the memory * barrier included in the correct place. */ if ((ncp->nc_hash.le_next = ncpp->lh_first) != NULL) ncpp->lh_first->nc_hash.le_prev = &ncp->nc_hash.le_next; ncp->nc_hash.le_prev = &ncpp->lh_first; membar_producer(); ncpp->lh_first = ncp; ncp->nc_vhash.le_prev = NULL; ncp->nc_vhash.le_next = NULL; /* * Create reverse-cache entries (used in getcwd) for directories. * (and in linux procfs exe node) */ if (vp != NULL && vp != dvp && #ifndef NAMECACHE_ENTER_REVERSE vp->v_type == VDIR && #endif (ncp->nc_nlen > 2 || (ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') || (/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) { nvcpp = &ncvhashtbl[NCVHASH(vp)]; LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); } mutex_exit(&ncp->nc_lock); mutex_exit(namecache_lock); } /* * Name cache initialization, from vfs_init() when we are booting */ void nchinit(void) { int error; TAILQ_INIT(&nclruhead); namecache_cache = pool_cache_init(sizeof(struct namecache), coherency_unit, 0, 0, "ncache", NULL, IPL_NONE, cache_ctor, cache_dtor, NULL); KASSERT(namecache_cache != NULL); namecache_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); nchashtbl = hashinit(desiredvnodes, HASH_LIST, true, &nchash); ncvhashtbl = #ifdef NAMECACHE_ENTER_REVERSE hashinit(desiredvnodes, HASH_LIST, true, &ncvhash); #else hashinit(desiredvnodes/8, HASH_LIST, true, &ncvhash); #endif error = kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, cache_thread, NULL, NULL, "cachegc"); if (error != 0) panic("nchinit %d", error); evcnt_attach_dynamic(&cache_ev_scan, EVCNT_TYPE_MISC, NULL, "namecache", "entries scanned"); evcnt_attach_dynamic(&cache_ev_gc, EVCNT_TYPE_MISC, NULL, "namecache", "entries collected"); evcnt_attach_dynamic(&cache_ev_over, EVCNT_TYPE_MISC, NULL, "namecache", "over scan target"); evcnt_attach_dynamic(&cache_ev_under, EVCNT_TYPE_MISC, NULL, "namecache", "under scan target"); evcnt_attach_dynamic(&cache_ev_forced, EVCNT_TYPE_MISC, NULL, "namecache", "forced reclaims"); sysctl_cache_stat_setup(); } static int cache_ctor(void *arg, void *obj, int flag) { struct namecache *ncp; ncp = obj; mutex_init(&ncp->nc_lock, MUTEX_DEFAULT, IPL_NONE); return 0; } static void cache_dtor(void *arg, void *obj) { struct namecache *ncp; ncp = obj; mutex_destroy(&ncp->nc_lock); } /* * Called once for each CPU in the system as attached. */ void cache_cpu_init(struct cpu_info *ci) { struct nchcpu *cpup; size_t sz; sz = roundup2(sizeof(*cpup), coherency_unit) + coherency_unit; cpup = kmem_zalloc(sz, KM_SLEEP); cpup = (void *)roundup2((uintptr_t)cpup, coherency_unit); mutex_init(&cpup->cpu_lock, MUTEX_DEFAULT, IPL_NONE); ci->ci_data.cpu_nch = cpup; } /* * Name cache reinitialization, for when the maximum number of vnodes increases. */ void nchreinit(void) { struct namecache *ncp; struct nchashhead *oldhash1, *hash1; struct ncvhashhead *oldhash2, *hash2; u_long i, oldmask1, oldmask2, mask1, mask2; hash1 = hashinit(desiredvnodes, HASH_LIST, true, &mask1); hash2 = #ifdef NAMECACHE_ENTER_REVERSE hashinit(desiredvnodes, HASH_LIST, true, &mask2); #else hashinit(desiredvnodes/8, HASH_LIST, true, &mask2); #endif mutex_enter(namecache_lock); cache_lock_cpus(); oldhash1 = nchashtbl; oldmask1 = nchash; nchashtbl = hash1; nchash = mask1; oldhash2 = ncvhashtbl; oldmask2 = ncvhash; ncvhashtbl = hash2; ncvhash = mask2; for (i = 0; i <= oldmask1; i++) { while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) { LIST_REMOVE(ncp, nc_hash); ncp->nc_hash.le_prev = NULL; } } for (i = 0; i <= oldmask2; i++) { while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) { LIST_REMOVE(ncp, nc_vhash); ncp->nc_vhash.le_prev = NULL; } } cache_unlock_cpus(); mutex_exit(namecache_lock); hashdone(oldhash1, HASH_LIST, oldmask1); hashdone(oldhash2, HASH_LIST, oldmask2); } /* * Cache flush, a particular vnode; called when a vnode is renamed to * hide entries that would now be invalid */ void cache_purge1(struct vnode *vp, const char *name, size_t namelen, int flags) { struct namecache *ncp, *ncnext; mutex_enter(namecache_lock); if (flags & PURGE_PARENTS) { SDT_PROBE(vfs, namecache, purge, parents, vp, 0, 0, 0, 0); for (ncp = LIST_FIRST(&VNODE_TO_VIMPL(vp)->vi_nclist); ncp != NULL; ncp = ncnext) { ncnext = LIST_NEXT(ncp, nc_vlist); mutex_enter(&ncp->nc_lock); cache_invalidate(ncp); mutex_exit(&ncp->nc_lock); cache_disassociate(ncp); } } if (flags & PURGE_CHILDREN) { SDT_PROBE(vfs, namecache, purge, children, vp, 0, 0, 0, 0); for (ncp = LIST_FIRST(&VNODE_TO_VIMPL(vp)->vi_dnclist); ncp != NULL; ncp = ncnext) { ncnext = LIST_NEXT(ncp, nc_dvlist); mutex_enter(&ncp->nc_lock); cache_invalidate(ncp); mutex_exit(&ncp->nc_lock); cache_disassociate(ncp); } } if (name != NULL) { SDT_PROBE(vfs, namecache, purge, name, name, namelen, 0, 0, 0); ncp = cache_lookup_entry(vp, name, namelen); if (ncp) { cache_invalidate(ncp); mutex_exit(&ncp->nc_lock); cache_disassociate(ncp); } } mutex_exit(namecache_lock); } /* * Cache flush, a whole filesystem; called when filesys is umounted to * remove entries that would now be invalid. */ void cache_purgevfs(struct mount *mp) { struct namecache *ncp, *nxtcp; SDT_PROBE(vfs, namecache, purge, vfs, mp, 0, 0, 0, 0); mutex_enter(namecache_lock); for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { nxtcp = TAILQ_NEXT(ncp, nc_lru); mutex_enter(&ncp->nc_lock); if (ncp->nc_dvp != NULL && ncp->nc_dvp->v_mount == mp) { /* Free the resources we had. */ cache_invalidate(ncp); cache_disassociate(ncp); } mutex_exit(&ncp->nc_lock); } cache_reclaim(); mutex_exit(namecache_lock); } /* * Scan global list invalidating entries until we meet a preset target. * Prefer to invalidate entries that have not scored a hit within * cache_hottime seconds. We sort the LRU list only for this routine's * benefit. */ static void cache_prune(int incache, int target) { struct namecache *ncp, *nxtcp, *sentinel; int items, recent, tryharder; KASSERT(mutex_owned(namecache_lock)); SDT_PROBE(vfs, namecache, prune, done, incache, target, 0, 0, 0); items = 0; tryharder = 0; recent = hardclock_ticks - hz * cache_hottime; sentinel = NULL; for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { if (incache <= target) break; items++; nxtcp = TAILQ_NEXT(ncp, nc_lru); if (ncp == sentinel) { /* * If we looped back on ourself, then ignore * recent entries and purge whatever we find. */ tryharder = 1; } if (ncp->nc_dvp == NULL) continue; if (!tryharder && (ncp->nc_hittime - recent) > 0) { if (sentinel == NULL) sentinel = ncp; TAILQ_REMOVE(&nclruhead, ncp, nc_lru); TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); continue; } mutex_enter(&ncp->nc_lock); if (ncp->nc_dvp != NULL) { cache_invalidate(ncp); cache_disassociate(ncp); incache--; } mutex_exit(&ncp->nc_lock); } cache_ev_scan.ev_count += items; } /* * Collect dead cache entries from all CPUs and garbage collect. */ static void cache_reclaim(void) { struct namecache *ncp, *next; int items; KASSERT(mutex_owned(namecache_lock)); /* * If the number of extant entries not awaiting garbage collection * exceeds the high water mark, then reclaim stale entries until we * reach our low water mark. */ items = numcache - cache_gcpend; if (items > (uint64_t)desiredvnodes * cache_hiwat / 100) { cache_prune(items, (int)((uint64_t)desiredvnodes * cache_lowat / 100)); cache_ev_over.ev_count++; } else cache_ev_under.ev_count++; /* * Stop forward lookup activity on all CPUs and garbage collect dead * entries. */ cache_lock_cpus(); ncp = cache_gcqueue; cache_gcqueue = NULL; items = cache_gcpend; cache_gcpend = 0; while (ncp != NULL) { next = ncp->nc_gcqueue; cache_disassociate(ncp); KASSERT(ncp->nc_dvp == NULL); if (ncp->nc_hash.le_prev != NULL) { LIST_REMOVE(ncp, nc_hash); ncp->nc_hash.le_prev = NULL; } pool_cache_put(namecache_cache, ncp); ncp = next; } cache_unlock_cpus(); numcache -= items; cache_ev_gc.ev_count += items; } /* * Cache maintainence thread, awakening once per second to: * * => keep number of entries below the high water mark * => sort pseudo-LRU list * => garbage collect dead entries */ static void cache_thread(void *arg) { mutex_enter(namecache_lock); for (;;) { cache_reclaim(); kpause("cachegc", false, hz, namecache_lock); } } #ifdef DDB void namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) { struct vnode *dvp = NULL; struct namecache *ncp; TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { if (ncp->nc_vp == vp && ncp->nc_dvp != NULL) { (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); dvp = ncp->nc_dvp; } } if (dvp == NULL) { (*pr)("name not found\n"); return; } vp = dvp; TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { if (ncp->nc_vp == vp) { (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); } } } #endif void namecache_count_pass2(void) { struct nchcpu *cpup = curcpu()->ci_data.cpu_nch; COUNT_UNL(cpup, ncs_pass2); } void namecache_count_2passes(void) { struct nchcpu *cpup = curcpu()->ci_data.cpu_nch; COUNT_UNL(cpup, ncs_2passes); } /* * Fetch the current values of the stats. We return the most * recent values harvested into nchstats by cache_reclaim(), which * will be less than a second old. */ static int cache_stat_sysctl(SYSCTLFN_ARGS) { struct nchstats stats; struct nchcpu *my_cpup; #ifdef CACHE_STATS_CURRENT CPU_INFO_ITERATOR cii; struct cpu_info *ci; #endif /* CACHE_STATS_CURRENT */ if (oldp == NULL) { *oldlenp = sizeof(stats); return 0; } if (*oldlenp < sizeof(stats)) { *oldlenp = 0; return 0; } /* * Take this CPU's per-cpu lock to hold off cache_reclaim() * from doing a stats update while doing minimal damage to * concurrent operations. */ sysctl_unlock(); my_cpup = curcpu()->ci_data.cpu_nch; mutex_enter(&my_cpup->cpu_lock); stats = nchstats; #ifdef CACHE_STATS_CURRENT for (CPU_INFO_FOREACH(cii, ci)) { struct nchcpu *cpup = ci->ci_data.cpu_nch; ADD(stats, cpup, ncs_goodhits); ADD(stats, cpup, ncs_neghits); ADD(stats, cpup, ncs_badhits); ADD(stats, cpup, ncs_falsehits); ADD(stats, cpup, ncs_miss); ADD(stats, cpup, ncs_long); ADD(stats, cpup, ncs_pass2); ADD(stats, cpup, ncs_2passes); ADD(stats, cpup, ncs_revhits); ADD(stats, cpup, ncs_revmiss); } #endif /* CACHE_STATS_CURRENT */ mutex_exit(&my_cpup->cpu_lock); sysctl_relock(); *oldlenp = sizeof(stats); return sysctl_copyout(l, &stats, oldp, sizeof(stats)); } static void sysctl_cache_stat_setup(void) { KASSERT(sysctllog == NULL); sysctl_createv(&sysctllog, 0, NULL, NULL, CTLFLAG_PERMANENT, CTLTYPE_STRUCT, "namecache_stats", SYSCTL_DESCR("namecache statistics"), cache_stat_sysctl, 0, NULL, 0, CTL_VFS, CTL_CREATE, CTL_EOL); }