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cache: perform . lockup without the namecache lock

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Reviewed by:	kib
This commit is contained in:
mjg 2016-01-21 01:07:05 +00:00
parent a7359714be
commit fc47375f70
1 changed files with 24 additions and 28 deletions
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52
sys/kern/vfs_cache.c
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@ -508,7 +508,6 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
return (0);
}
retry:
CACHE_RLOCK();
wlocked = 0;
counter_u64_add(numcalls, 1);
error = 0;
@ -525,8 +524,28 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
timespecclear(tsp);
if (ticksp != NULL)
*ticksp = ticks;
goto success;
VREF(*vpp);
/*
* When we lookup "." we still can be asked to lock it
* differently...
*/
ltype = cnp->cn_lkflags & LK_TYPE_MASK;
if (ltype != VOP_ISLOCKED(*vpp)) {
if (ltype == LK_EXCLUSIVE) {
vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
if ((*vpp)->v_iflag & VI_DOOMED) {
/* forced unmount */
vrele(*vpp);
*vpp = NULL;
return (ENOENT);
}
} else
vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
}
return (-1);
}
if (!wlocked)
CACHE_RLOCK();
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
counter_u64_add(dotdothits, 1);
if (dvp->v_cache_dd == NULL) {
@ -562,7 +581,8 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
nc_dotdottime;
goto success;
}
}
} else if (!wlocked)
CACHE_RLOCK();
hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp);
LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
@ -652,31 +672,7 @@ cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp,
* On success we return a locked and ref'd vnode as per the lookup
* protocol.
*/
if (dvp == *vpp) { /* lookup on "." */
VREF(*vpp);
if (wlocked)
CACHE_WUNLOCK();
else
CACHE_RUNLOCK();
/*
* When we lookup "." we still can be asked to lock it
* differently...
*/
ltype = cnp->cn_lkflags & LK_TYPE_MASK;
if (ltype != VOP_ISLOCKED(*vpp)) {
if (ltype == LK_EXCLUSIVE) {
vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
if ((*vpp)->v_iflag & VI_DOOMED) {
/* forced unmount */
vrele(*vpp);
*vpp = NULL;
return (ENOENT);
}
} else
vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
}
return (-1);
}
MPASS(dvp != *vpp);
ltype = 0; /* silence gcc warning */
if (cnp->cn_flags & ISDOTDOT) {
ltype = VOP_ISLOCKED(dvp);