nfsd: fix handling of readdir in v4root vs. mount upcall timeout

If v4 READDIR operation hits a mountpoint and gets back an error,
then it will include that entry in the reply and set RDATTR_ERROR for it
to the error.

That's fine for "normal" exported filesystems, but on the v4root, we
need to be more careful to only expose the existence of dentries that
lead to exports.

If the mountd upcall times out while checking to see whether a
mountpoint on the v4root is exported, then we have no recourse other
than to fail the whole operation.

Cc: Steve Dickson <steved@redhat.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216777
Reported-by: JianHong Yin <yin-jianhong@163.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: <stable@vger.kernel.org>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 2b4ae858c89bea21798cbb8e2b5125523354c01d..ebb4d02a42ce68110c564b09245202228f6f2864 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3629,6 +3629,17 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen,
        case nfserr_noent:
                xdr_truncate_encode(xdr, start_offset);
                goto skip_entry;
+       case nfserr_jukebox:
+               /*
+                * The pseudoroot should only display dentries that lead to
+                * exports. If we get EJUKEBOX here, then we can't tell whether
+                * this entry should be included. Just fail the whole READDIR
+                * with NFS4ERR_DELAY in that case, and hope that the situation
+                * will resolve itself by the client's next attempt.
+                */
+               if (cd->rd_fhp->fh_export->ex_flags & NFSEXP_V4ROOT)
+                       goto fail;
+               fallthrough;
        default:
                /*
                 * If the client requested the RDATTR_ERROR attribute,