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Code Issues Releases Activity

- Move the logic that locks and refs the new vnode from vfs_cache_lookup()

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to cache_lookup().  This allows us to acquire the vnode interlock before
   dropping the cache lock.  This protects the vnodes identity until we
   have locked it.

Sponsored by:	Isilon Systems, Inc.
This commit is contained in:
Jeff Roberson 2005-03-29 12:59:06 +00:00
parent b6a9d20adc
commit 5280e61f2f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=144296
1 changed files with 33 additions and 35 deletions
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68
sys/kern/vfs_cache.c
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@ -328,6 +328,10 @@ cache_leaf_test(struct vnode *vp)
* returned. If the lookup determines that the name does not exist
* (negative cacheing), a status of ENOENT is returned. If the lookup
* fails, a status of zero is returned.
*
* vpp is locked and ref'd on return. If we're looking up DOTDOT, dvp is
* unlocked. If we're looking up . an extra ref is taken, but the lock is
* not recursively acquired.
*/
int
@ -343,7 +347,7 @@ cache_lookup(dvp, vpp, cnp)
cnp->cn_flags &= ~MAKEENTRY;
return (0);
}
retry:
CACHE_LOCK();
numcalls++;
@ -351,8 +355,7 @@ cache_lookup(dvp, vpp, cnp)
if (cnp->cn_namelen == 1) {
*vpp = dvp;
dothits++;
CACHE_UNLOCK();
return (-1);
goto success;
}
if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
dotdothits++;
@ -363,8 +366,7 @@ cache_lookup(dvp, vpp, cnp)
return (0);
}
*vpp = dvp->v_dd;
CACHE_UNLOCK();
return (-1);
goto success;
}
}
@ -403,8 +405,7 @@ cache_lookup(dvp, vpp, cnp)
numposhits++;
nchstats.ncs_goodhits++;
*vpp = ncp->nc_vp;
CACHE_UNLOCK();
return (-1);
goto success;
}
/* We found a negative match, and want to create it, so purge */
@ -430,6 +431,28 @@ cache_lookup(dvp, vpp, cnp)
cnp->cn_flags |= ISWHITEOUT;
CACHE_UNLOCK();
return (ENOENT);
success:
/*
* On success we return a locked and ref'd vnode as per the lookup
* protocol.
*/
if (dvp == *vpp) { /* lookup on "." */
VREF(*vpp);
CACHE_UNLOCK();
return (-1);
}
if (cnp->cn_flags & ISDOTDOT)
VOP_UNLOCK(dvp, 0, cnp->cn_thread);
VI_LOCK(*vpp);
CACHE_UNLOCK();
if (vget(*vpp, cnp->cn_lkflags | LK_INTERLOCK, cnp->cn_thread)) {
if (cnp->cn_flags & ISDOTDOT)
vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, cnp->cn_thread);
*vpp = NULL;
goto retry;
}
return (-1);
}
/*
@ -632,14 +655,13 @@ vfs_cache_lookup(ap)
struct componentname *a_cnp;
} */ *ap;
{
struct vnode *dvp, *vp;
struct vnode *dvp;
int error;
struct vnode **vpp = ap->a_vpp;
struct componentname *cnp = ap->a_cnp;
struct ucred *cred = cnp->cn_cred;
int flags = cnp->cn_flags;
struct thread *td = cnp->cn_thread;
u_long vpid; /* capability number of vnode */
*vpp = NULL;
dvp = ap->a_dvp;
@ -652,39 +674,15 @@ vfs_cache_lookup(ap)
return (EROFS);
error = VOP_ACCESS(dvp, VEXEC, cred, td);
if (error)
return (error);
error = cache_lookup(dvp, vpp, cnp);
if (!error)
if (error == 0)
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
if (error == ENOENT)
return (error);
vp = *vpp;
vpid = vp->v_id;
if (dvp == vp) { /* lookup on "." */
VREF(vp);
error = 0;
} else if (flags & ISDOTDOT) {
VOP_UNLOCK(dvp, 0, td);
error = vget(vp, cnp->cn_lkflags, td);
if (error)
vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, td);
} else
error = vget(vp, cnp->cn_lkflags, td);
/*
* Check that the capability number did not change
* while we were waiting for the lock.
*/
if (!error) {
if (vpid == vp->v_id)
return (0);
vput(vp);
if (flags & ISDOTDOT)
vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY, td);
}
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
return (0);
}