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Part 1 of making shared lookups more resilient with respect to forced

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unmounts.  When we upgrade a vnode lock from shared to exclusive during
a name cache lookup, fail the lookup with EBADF if the vnode is invalidated
while we are waiting for the exclusive lock.

Also, for correctness (though I'm not sure it can occur in practice),
downgrade an exclusively locked vnode if it should be share locked.

Tested by:	pho
This commit is contained in:
John Baldwin 2008-09-24 18:51:33 +00:00
parent c1fa2e4200
commit d2722d704c
2 changed files with 22 additions and 9 deletions
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26
sys/kern/vfs_cache.c
View file

@ -304,7 +304,9 @@ cache_zap(ncp)
* succeeds, the vnode is returned in *vpp, and a status of -1 is
* 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.
* fails, a status of zero is returned. If the directory vnode is
* recycled out from under us due to a forced unmount, a status of
* EBADF 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
@ -428,10 +430,18 @@ success:
* differently...
*/
ltype = cnp->cn_lkflags & LK_TYPE_MASK;
if (ltype == VOP_ISLOCKED(*vpp))
return (-1);
else if (ltype == LK_EXCLUSIVE)
vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
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 (EBADF);
}
} else
vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
}
return (-1);
}
ltype = 0; /* silence gcc warning */
@ -671,9 +681,9 @@ vfs_cache_lookup(ap)
error = cache_lookup(dvp, vpp, cnp);
if (error == 0)
return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
if (error == ENOENT)
return (error);
return (0);
if (error == -1)
return (0);
return (error);
}

5
sys/nfsclient/nfs_vnops.c
View file

@ -888,7 +888,10 @@ nfs_lookup(struct vop_lookup_args *ap)
*vpp = NULLVP;
return (error);
}
if ((error = cache_lookup(dvp, vpp, cnp)) && error != ENOENT) {
error = cache_lookup(dvp, vpp, cnp);
if (error > 0 && error != ENOENT)
return (error);
if (error == -1) {
struct vattr vattr;
newvp = *vpp;