diff options
| -rw-r--r-- | sys/nfsclient/nfs_vnops.c | 38 |
1 files changed, 32 insertions, 6 deletions
diff --git a/sys/nfsclient/nfs_vnops.c b/sys/nfsclient/nfs_vnops.c index 7dfd298da6d2..dc619275aeac 100644 --- a/sys/nfsclient/nfs_vnops.c +++ b/sys/nfsclient/nfs_vnops.c @@ -924,6 +924,7 @@ nfs_lookup(struct vop_lookup_args *ap) struct vnode **vpp = ap->a_vpp; struct mount *mp = dvp->v_mount; struct vattr vattr; + time_t dmtime; int flags = cnp->cn_flags; struct vnode *newvp; struct nfsmount *nmp; @@ -935,7 +936,7 @@ nfs_lookup(struct vop_lookup_args *ap) int error = 0, attrflag, fhsize, ltype; int v3 = NFS_ISV3(dvp); struct thread *td = cnp->cn_thread; - + *vpp = NULLVP; if ((flags & ISLASTCN) && (mp->mnt_flag & MNT_RDONLY) && (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) @@ -992,6 +993,19 @@ nfs_lookup(struct vop_lookup_args *ap) np->n_dmtime = 0; mtx_unlock(&np->n_mtx); } + + /* + * Cache the modification time of the parent directory in case + * the lookup fails and results in adding the first negative + * name cache entry for the directory. Since this is reading + * a single time_t, don't bother with locking. The + * modification time may be a bit stale, but it must be read + * before performing the lookup RPC to prevent a race where + * another lookup updates the timestamp on the directory after + * the lookup RPC has been performed on the server but before + * n_dmtime is set at the end of this function. + */ + dmtime = np->n_vattr.va_mtime.tv_sec; error = 0; newvp = NULLVP; nfsstats.lookupcache_misses++; @@ -1130,13 +1144,25 @@ nfsmout: * Maintain n_dmtime as the modification time * of the parent directory when the oldest -ve * name cache entry for this directory was - * added. + * added. If a -ve cache entry has already + * been added with a newer modification time + * by a concurrent lookup, then don't bother + * adding a cache entry. The modification + * time of the directory might have changed + * due to the file this lookup failed to find + * being created. In that case a subsequent + * lookup would incorrectly use the entry + * added here instead of doing an extra + * lookup. */ mtx_lock(&np->n_mtx); - if (np->n_dmtime == 0) - np->n_dmtime = np->n_vattr.va_mtime.tv_sec; - mtx_unlock(&np->n_mtx); - cache_enter(dvp, NULL, cnp); + if (np->n_dmtime <= dmtime) { + if (np->n_dmtime == 0) + np->n_dmtime = dmtime; + mtx_unlock(&np->n_mtx); + cache_enter(dvp, NULL, cnp); + } else + mtx_unlock(&np->n_mtx); } return (ENOENT); } |