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
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parent
1e4bf1e35f
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=208603
@ -932,7 +932,7 @@ nfs_lookup(struct vop_lookup_args *ap)
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struct mbuf *mreq, *mrep, *md, *mb;
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long len;
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nfsfh_t *fhp;
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struct nfsnode *np;
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struct nfsnode *np, *newnp;
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int error = 0, attrflag, fhsize, ltype;
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int v3 = NFS_ISV3(dvp);
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struct thread *td = cnp->cn_thread;
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@ -958,10 +958,27 @@ nfs_lookup(struct vop_lookup_args *ap)
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* change time of the file matches our cached copy.
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* Otherwise, we discard the cache entry and fallback
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* to doing a lookup RPC.
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*
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* To better handle stale file handles and attributes,
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* clear the attribute cache of this node if it is a
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* leaf component, part of an open() call, and not
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* locally modified before fetching the attributes.
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* This should allow stale file handles to be detected
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* here where we can fall back to a LOOKUP RPC to
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* recover rather than having nfs_open() detect the
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* stale file handle and failing open(2) with ESTALE.
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*/
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newvp = *vpp;
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if (!VOP_GETATTR(newvp, &vattr, cnp->cn_cred)
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&& vattr.va_ctime.tv_sec == VTONFS(newvp)->n_ctime) {
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newnp = VTONFS(newvp);
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if ((cnp->cn_flags & (ISLASTCN | ISOPEN)) ==
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(ISLASTCN | ISOPEN) && !(newnp->n_flag & NMODIFIED)) {
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mtx_lock(&newnp->n_mtx);
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newnp->n_attrstamp = 0;
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KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp);
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mtx_unlock(&newnp->n_mtx);
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}
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if (VOP_GETATTR(newvp, &vattr, cnp->cn_cred) == 0 &&
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vattr.va_ctime.tv_sec == newnp->n_ctime) {
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nfsstats.lookupcache_hits++;
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if (cnp->cn_nameiop != LOOKUP &&
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(flags & ISLASTCN))
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