nfsd: untangle code in nfsd4_deleg_getattr_conflict()

The code in nfsd4_deleg_getattr_conflict() is convoluted and buggy.

With this patch we:
 - properly handle non-nfsd leases.  We must not assume flc_owner is a
    delegation unless fl_lmops == &nfsd_lease_mng_ops
 - move the main code out of the for loop
 - have a single exit which calls nfs4_put_stid()
   (and other exits which don't need to call that)

[ jlayton: refactored on top of Neil's other patch: nfsd: fix
	   nfsd4_deleg_getattr_conflict in presence of third party lease ]

Fixes: c5967721 ("NFSD: handle GETATTR conflict with write delegation")
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4state.c

@@ -8834,6 +8834,7 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
 	__be32 status;
 	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
 	struct file_lock_context *ctx;
+	struct nfs4_delegation *dp = NULL;
 	struct file_lease *fl;
 	struct iattr attrs;
 	struct nfs4_cb_fattr *ncf;
@@ -8843,53 +8844,48 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
 	ctx = locks_inode_context(inode);
 	if (!ctx)
 		return 0;
+
+#define NON_NFSD_LEASE ((void *)1)
+
 	spin_lock(&ctx->flc_lock);
 	for_each_file_lock(fl, &ctx->flc_lease) {
-		unsigned char type = fl->c.flc_type;
-
 		if (fl->c.flc_flags == FL_LAYOUT)
 			continue;
-		if (fl->fl_lmops != &nfsd_lease_mng_ops) {
-			/*
-			 * non-nfs lease, if it's a lease with F_RDLCK then
-			 * we are done; there isn't any write delegation
-			 * on this inode
-			 */
-			if (type == F_RDLCK)
+		if (fl->c.flc_type == F_WRLCK) {
+			if (fl->fl_lmops == &nfsd_lease_mng_ops)
+				dp = fl->c.flc_owner;
+			else
+				dp = NON_NFSD_LEASE;
+		}
 		break;
-
-			nfsd_stats_wdeleg_getattr_inc(nn);
+	}
+	if (dp == NULL || dp == NON_NFSD_LEASE ||
+	    dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker)) {
 		spin_unlock(&ctx->flc_lock);
-
-			status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
+		if (dp == NON_NFSD_LEASE) {
+			status = nfserrno(nfsd_open_break_lease(inode,
+								NFSD_MAY_READ));
 			if (status != nfserr_jukebox ||
 			    !nfsd_wait_for_delegreturn(rqstp, inode))
 				return status;
-			return 0;
 		}
-		if (type == F_WRLCK) {
-			struct nfs4_delegation *dp = fl->c.flc_owner;
-
-			if (dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker)) {
-				spin_unlock(&ctx->flc_lock);
 		return 0;
 	}
+
 	nfsd_stats_wdeleg_getattr_inc(nn);
-			dp = fl->c.flc_owner;
 	refcount_inc(&dp->dl_stid.sc_count);
 	ncf = &dp->dl_cb_fattr;
 	nfs4_cb_getattr(&dp->dl_cb_fattr);
 	spin_unlock(&ctx->flc_lock);
+
 	wait_on_bit_timeout(&ncf->ncf_cb_flags, CB_GETATTR_BUSY,
 			    TASK_INTERRUPTIBLE, NFSD_CB_GETATTR_TIMEOUT);
 	if (ncf->ncf_cb_status) {
 		/* Recall delegation only if client didn't respond */
 		status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
 		if (status != nfserr_jukebox ||
-						!nfsd_wait_for_delegreturn(rqstp, inode)) {
-					nfs4_put_stid(&dp->dl_stid);
-					return status;
-				}
+		    !nfsd_wait_for_delegreturn(rqstp, inode))
+			goto out_status;
 	}
 	if (!ncf->ncf_file_modified &&
 	    (ncf->ncf_initial_cinfo != ncf->ncf_cb_change ||
@@ -8909,18 +8905,15 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
 		err = notify_change(&nop_mnt_idmap, dentry, &attrs, NULL);
 		inode_unlock(inode);
 		if (err) {
-					nfs4_put_stid(&dp->dl_stid);
-					return nfserrno(err);
+			status = nfserrno(err);
+			goto out_status;
 		}
 		ncf->ncf_cur_fsize = ncf->ncf_cb_fsize;
 		*size = ncf->ncf_cur_fsize;
 		*modified = true;
 	}
+	status = 0;
+out_status:
 	nfs4_put_stid(&dp->dl_stid);
-			return 0;
-		}
-		break;
-	}
-	spin_unlock(&ctx->flc_lock);
-	return 0;
+	return status;
 }