Convert the global mutex protecting the directory lookup name cache from a
mutex to a reader/writer lock. Lookup operations first grab a read lock and perform the lookup. If the operation results in a need to modify the cache, then it tries to do an upgrade. If that fails, it drops the read lock, obtains a write lock, and redoes the lookup.
This commit is contained in:
John Baldwin
parent
c222ece0cc
commit
9078981ab1
@ -42,9 +42,9 @@ __FBSDID("$FreeBSD$");
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mount.h>
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#include <sys/mutex.h>
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#include <sys/namei.h>
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#include <sys/proc.h>
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#include <sys/rwlock.h>
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#include <sys/syscallsubr.h>
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#include <sys/sysctl.h>
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#include <sys/sysproto.h>
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@ -109,11 +109,14 @@ SYSCTL_ULONG(_debug, OID_AUTO, numcachepl, CTLFLAG_RD, &numcachepl, 0, "");
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#endif
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struct nchstats nchstats; /* cache effectiveness statistics */
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static struct mtx cache_lock;
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MTX_SYSINIT(vfscache, &cache_lock, "Name Cache", MTX_DEF);
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static struct rwlock cache_lock;
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RW_SYSINIT(vfscache, &cache_lock, "Name Cache");
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#define CACHE_LOCK() mtx_lock(&cache_lock)
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#define CACHE_UNLOCK() mtx_unlock(&cache_lock)
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#define CACHE_UPGRADE_LOCK() rw_try_upgrade(&cache_lock)
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#define CACHE_RLOCK() rw_rlock(&cache_lock)
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#define CACHE_RUNLOCK() rw_runlock(&cache_lock)
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#define CACHE_WLOCK() rw_wlock(&cache_lock)
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#define CACHE_WUNLOCK() rw_wunlock(&cache_lock)
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/*
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* UMA zones for the VFS cache.
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@ -162,6 +165,7 @@ static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps);
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static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits);
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static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps);
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static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits);
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static u_long numupgrades; STATNODE(CTLFLAG_RD, numupgrades, &numupgrades);
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SYSCTL_OPAQUE(_vfs_cache, OID_AUTO, nchstats, CTLFLAG_RD | CTLFLAG_MPSAFE,
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&nchstats, sizeof(nchstats), "LU", "VFS cache effectiveness statistics");
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@ -200,12 +204,12 @@ sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
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/* Scan hash tables for applicable entries */
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for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
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CACHE_LOCK();
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CACHE_RLOCK();
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count = 0;
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LIST_FOREACH(ncp, ncpp, nc_hash) {
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count++;
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}
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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error = SYSCTL_OUT(req, &count, sizeof(count));
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if (error)
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return (error);
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@ -235,11 +239,11 @@ sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
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/* Scan hash tables for applicable entries */
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for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
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count = 0;
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CACHE_LOCK();
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CACHE_RLOCK();
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LIST_FOREACH(ncp, ncpp, nc_hash) {
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count++;
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}
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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if (count)
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used++;
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if (maxlength < count)
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@ -277,7 +281,7 @@ cache_zap(ncp)
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{
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struct vnode *vp;
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mtx_assert(&cache_lock, MA_OWNED);
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rw_assert(&cache_lock, RA_WLOCKED);
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CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp, ncp->nc_vp);
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vp = NULL;
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LIST_REMOVE(ncp, nc_hash);
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@ -324,16 +328,19 @@ cache_lookup(dvp, vpp, cnp)
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{
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struct namecache *ncp;
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u_int32_t hash;
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int error, ltype;
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int error, ltype, wlocked;
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if (!doingcache) {
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cnp->cn_flags &= ~MAKEENTRY;
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return (0);
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}
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retry:
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CACHE_LOCK();
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CACHE_RLOCK();
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wlocked = 0;
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numcalls++;
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error = 0;
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retry_wlocked:
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if (cnp->cn_nameptr[0] == '.') {
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if (cnp->cn_namelen == 1) {
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*vpp = dvp;
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@ -346,8 +353,7 @@ retry:
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dotdothits++;
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if (dvp->v_dd == NULL ||
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(cnp->cn_flags & MAKEENTRY) == 0) {
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CACHE_UNLOCK();
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return (0);
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goto unlock;
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}
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*vpp = dvp->v_dd;
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CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
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@ -366,23 +372,24 @@ retry:
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}
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/* We failed to find an entry */
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if (ncp == 0) {
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if (ncp == NULL) {
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if ((cnp->cn_flags & MAKEENTRY) == 0) {
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nummisszap++;
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} else {
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nummiss++;
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}
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nchstats.ncs_miss++;
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CACHE_UNLOCK();
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return (0);
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goto unlock;
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}
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/* We don't want to have an entry, so dump it */
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if ((cnp->cn_flags & MAKEENTRY) == 0) {
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numposzaps++;
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nchstats.ncs_badhits++;
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if (!wlocked && !CACHE_UPGRADE_LOCK())
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goto wlock;
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cache_zap(ncp);
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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return (0);
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}
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@ -400,11 +407,15 @@ retry:
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if (cnp->cn_nameiop == CREATE) {
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numnegzaps++;
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nchstats.ncs_badhits++;
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if (!wlocked && !CACHE_UPGRADE_LOCK())
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goto wlock;
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cache_zap(ncp);
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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return (0);
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}
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if (!wlocked && !CACHE_UPGRADE_LOCK())
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goto wlock;
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numneghits++;
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/*
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* We found a "negative" match, so we shift it to the end of
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@ -417,9 +428,20 @@ retry:
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nchstats.ncs_neghits++;
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if (ncp->nc_flag & NCF_WHITE)
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cnp->cn_flags |= ISWHITEOUT;
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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return (ENOENT);
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wlock:
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/*
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* We need to update the cache after our lookup, so upgrade to
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* a write lock and retry the operation.
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*/
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CACHE_RUNLOCK();
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CACHE_WLOCK();
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numupgrades++;
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wlocked = 1;
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goto retry_wlocked;
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success:
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/*
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* On success we return a locked and ref'd vnode as per the lookup
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@ -427,7 +449,10 @@ success:
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*/
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if (dvp == *vpp) { /* lookup on "." */
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VREF(*vpp);
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CACHE_UNLOCK();
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if (wlocked)
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CACHE_WUNLOCK();
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else
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CACHE_RUNLOCK();
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/*
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* When we lookup "." we still can be asked to lock it
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* differently...
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@ -453,7 +478,10 @@ success:
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VOP_UNLOCK(dvp, 0);
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}
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VI_LOCK(*vpp);
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CACHE_UNLOCK();
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if (wlocked)
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CACHE_WUNLOCK();
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else
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CACHE_RUNLOCK();
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error = vget(*vpp, cnp->cn_lkflags | LK_INTERLOCK, cnp->cn_thread);
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if (cnp->cn_flags & ISDOTDOT)
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vn_lock(dvp, ltype | LK_RETRY);
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@ -466,6 +494,13 @@ success:
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ASSERT_VOP_ELOCKED(*vpp, "cache_lookup");
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}
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return (-1);
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unlock:
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if (wlocked)
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CACHE_WUNLOCK();
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else
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CACHE_RUNLOCK();
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return (0);
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}
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/*
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@ -509,10 +544,10 @@ cache_enter(dvp, vp, cnp)
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* cache_purge() time.
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*/
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if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
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CACHE_LOCK();
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CACHE_WLOCK();
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if (!TAILQ_EMPTY(&dvp->v_cache_dst))
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dvp->v_dd = vp;
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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return;
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}
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}
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@ -531,7 +566,7 @@ cache_enter(dvp, vp, cnp)
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hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT);
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bcopy(cnp->cn_nameptr, ncp->nc_name, len);
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hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
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CACHE_LOCK();
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CACHE_WLOCK();
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/*
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* See if this vnode or negative entry is already in the cache
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@ -543,7 +578,7 @@ cache_enter(dvp, vp, cnp)
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if (n2->nc_dvp == dvp &&
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n2->nc_nlen == cnp->cn_namelen &&
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!bcmp(n2->nc_name, cnp->cn_nameptr, n2->nc_nlen)) {
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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cache_free(ncp);
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return;
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}
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@ -587,7 +622,7 @@ cache_enter(dvp, vp, cnp)
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vhold(dvp);
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if (zap)
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cache_zap(ncp);
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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}
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/*
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@ -618,13 +653,13 @@ cache_purge(vp)
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{
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CTR1(KTR_VFS, "cache_purge(%p)", vp);
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CACHE_LOCK();
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CACHE_WLOCK();
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while (!LIST_EMPTY(&vp->v_cache_src))
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cache_zap(LIST_FIRST(&vp->v_cache_src));
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while (!TAILQ_EMPTY(&vp->v_cache_dst))
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cache_zap(TAILQ_FIRST(&vp->v_cache_dst));
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vp->v_dd = NULL;
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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}
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/*
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@ -638,14 +673,14 @@ cache_purgevfs(mp)
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struct namecache *ncp, *nnp;
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/* Scan hash tables for applicable entries */
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CACHE_LOCK();
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CACHE_WLOCK();
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for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) {
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LIST_FOREACH_SAFE(ncp, ncpp, nc_hash, nnp) {
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if (ncp->nc_dvp->v_mount == mp)
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cache_zap(ncp);
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}
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}
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CACHE_UNLOCK();
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CACHE_WUNLOCK();
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}
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/*
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@ -845,7 +880,7 @@ vn_vptocnp(struct vnode **vp, char **bp, char *buf, u_int *buflen)
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int error, vfslocked;
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vhold(*vp);
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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vfslocked = VFS_LOCK_GIANT((*vp)->v_mount);
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vn_lock(*vp, LK_SHARED | LK_RETRY);
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error = VOP_VPTOCNP(*vp, &dvp, buf, buflen);
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@ -858,10 +893,10 @@ vn_vptocnp(struct vnode **vp, char **bp, char *buf, u_int *buflen)
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}
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*bp = buf + *buflen;
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*vp = dvp;
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CACHE_LOCK();
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CACHE_RLOCK();
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if ((*vp)->v_iflag & VI_DOOMED) {
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/* forced unmount */
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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vdrop(*vp);
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return (ENOENT);
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}
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@ -887,7 +922,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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error = 0;
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slash_prefixed = 0;
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CACHE_LOCK();
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CACHE_RLOCK();
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numfullpathcalls++;
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if (vp->v_type != VDIR) {
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ncp = TAILQ_FIRST(&vp->v_cache_dst);
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@ -896,7 +931,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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*--bp = ncp->nc_name[i];
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if (bp == buf) {
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numfullpathfail4++;
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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return (ENOMEM);
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}
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vp = ncp->nc_dvp;
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@ -910,7 +945,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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buflen--;
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if (buflen < 0) {
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numfullpathfail4++;
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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return (ENOMEM);
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}
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slash_prefixed = 1;
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@ -918,7 +953,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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while (vp != rdir && vp != rootvnode) {
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if (vp->v_vflag & VV_ROOT) {
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if (vp->v_iflag & VI_DOOMED) { /* forced unmount */
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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error = EBADF;
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break;
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}
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@ -927,7 +962,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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}
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if (vp->v_type != VDIR) {
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numfullpathfail1++;
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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error = ENOTDIR;
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break;
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}
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@ -939,7 +974,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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*--bp = ncp->nc_name[i];
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if (bp == buf) {
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numfullpathfail4++;
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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error = ENOMEM;
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break;
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}
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@ -954,7 +989,7 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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buflen--;
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if (buflen < 0) {
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numfullpathfail4++;
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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error = ENOMEM;
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break;
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}
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@ -965,14 +1000,14 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
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if (!slash_prefixed) {
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if (bp == buf) {
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numfullpathfail4++;
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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return (ENOMEM);
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} else {
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*--bp = '/';
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}
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}
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numfullpathfound++;
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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*retbuf = bp;
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return (0);
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@ -984,15 +1019,15 @@ vn_commname(struct vnode *vp, char *buf, u_int buflen)
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struct namecache *ncp;
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int l;
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CACHE_LOCK();
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CACHE_RLOCK();
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ncp = TAILQ_FIRST(&vp->v_cache_dst);
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if (!ncp) {
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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return (ENOENT);
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}
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l = min(ncp->nc_nlen, buflen - 1);
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memcpy(buf, ncp->nc_name, l);
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CACHE_UNLOCK();
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CACHE_RUNLOCK();
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buf[l] = '\0';
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return (0);
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}
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Loading…
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Reference in New Issue
Block a user