From b367632ec210dfa1299497abf89c8a24634409a7 Mon Sep 17 00:00:00 2001 From: John Baldwin Date: Thu, 27 May 2010 18:07:20 +0000 Subject: [PATCH] More gracefully handle stale file handles and attributes when opening a file via NFS. Specifically, to satisfy close-to-open-consistency, the NFS client always performs at least one RPC on a file during an open(2) to see if the file has changed. Normally this RPC is an ACCESS or GETATTR RPC that is forced by flushing a file's attribute cache during nfs_open() and then requesting new attributes. However, if the file is noticed to be stale during nfs_open(), the only recourse is to fail the open(2) call with ESTALE. On the other hand, if the ACCESS or GETATTR RPC is sent during nfs_lookup(), then the NFS client can fall back to a LOOKUP RPC to obtain the new file handle in the case that a file has been replaced. This change causes the NFS client to flush the attribute cache during nfs_lookup() when validating a name cache hit if the attributes fetched during nfs_lookup() can be reused in nfs_open(). This allows the client to open a replaced file via the new file handle the first time that it notices a replaced file rather than failing with ESTALE in some cases. Reviewed by: rmacklem, bde Reviewed by: mohans (older version) MFC after: 1 week --- sys/nfsclient/nfs_vnops.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/sys/nfsclient/nfs_vnops.c b/sys/nfsclient/nfs_vnops.c index 64953fe19cd..589711139b9 100644 --- a/sys/nfsclient/nfs_vnops.c +++ b/sys/nfsclient/nfs_vnops.c @@ -932,7 +932,7 @@ nfs_lookup(struct vop_lookup_args *ap) struct mbuf *mreq, *mrep, *md, *mb; long len; nfsfh_t *fhp; - struct nfsnode *np; + struct nfsnode *np, *newnp; int error = 0, attrflag, fhsize, ltype; int v3 = NFS_ISV3(dvp); struct thread *td = cnp->cn_thread; @@ -958,10 +958,27 @@ nfs_lookup(struct vop_lookup_args *ap) * change time of the file matches our cached copy. * Otherwise, we discard the cache entry and fallback * to doing a lookup RPC. + * + * To better handle stale file handles and attributes, + * clear the attribute cache of this node if it is a + * leaf component, part of an open() call, and not + * locally modified before fetching the attributes. + * This should allow stale file handles to be detected + * here where we can fall back to a LOOKUP RPC to + * recover rather than having nfs_open() detect the + * stale file handle and failing open(2) with ESTALE. */ newvp = *vpp; - if (!VOP_GETATTR(newvp, &vattr, cnp->cn_cred) - && vattr.va_ctime.tv_sec == VTONFS(newvp)->n_ctime) { + newnp = VTONFS(newvp); + if ((cnp->cn_flags & (ISLASTCN | ISOPEN)) == + (ISLASTCN | ISOPEN) && !(newnp->n_flag & NMODIFIED)) { + mtx_lock(&newnp->n_mtx); + newnp->n_attrstamp = 0; + KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp); + mtx_unlock(&newnp->n_mtx); + } + if (VOP_GETATTR(newvp, &vattr, cnp->cn_cred) == 0 && + vattr.va_ctime.tv_sec == newnp->n_ctime) { nfsstats.lookupcache_hits++; if (cnp->cn_nameiop != LOOKUP && (flags & ISLASTCN))