nfsd: fix initial getattr on write delegation

At this point in compound processing, currentfh refers to the parent of
the file, not the file itself. Get the correct dentry from the delegation
stateid instead.

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

fs/nfsd/nfs4state.c

@@ -5914,6 +5914,28 @@ static void nfsd4_open_deleg_none_ext(struct nfsd4_open *open, int status)
 	}
 }
 
+static bool
+nfs4_delegation_stat(struct nfs4_delegation *dp, struct svc_fh *currentfh,
+		     struct kstat *stat)
+{
+	struct nfsd_file *nf = find_rw_file(dp->dl_stid.sc_file);
+	struct path path;
+	int rc;
+
+	if (!nf)
+		return false;
+
+	path.mnt = currentfh->fh_export->ex_path.mnt;
+	path.dentry = file_dentry(nf->nf_file);
+
+	rc = vfs_getattr(&path, stat,
+			 (STATX_SIZE | STATX_CTIME | STATX_CHANGE_COOKIE),
+			 AT_STATX_SYNC_AS_STAT);
+
+	nfsd_file_put(nf);
+	return rc == 0;
+}
+
 /*
  * The Linux NFS server does not offer write delegations to NFSv4.0
  * clients in order to avoid conflicts between write delegations and
@@ -5949,7 +5971,6 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
 	int cb_up;
 	int status = 0;
 	struct kstat stat;
-	struct path path;
 
 	cb_up = nfsd4_cb_channel_good(oo->oo_owner.so_client);
 	open->op_recall = false;
@@ -5985,20 +6006,16 @@ nfs4_open_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp,
 	memcpy(&open->op_delegate_stateid, &dp->dl_stid.sc_stateid, sizeof(dp->dl_stid.sc_stateid));
 
 	if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) {
-		open->op_delegate_type = NFS4_OPEN_DELEGATE_WRITE;
-		trace_nfsd_deleg_write(&dp->dl_stid.sc_stateid);
-		path.mnt = currentfh->fh_export->ex_path.mnt;
-		path.dentry = currentfh->fh_dentry;
-		if (vfs_getattr(&path, &stat,
-				(STATX_SIZE | STATX_CTIME | STATX_CHANGE_COOKIE),
-				AT_STATX_SYNC_AS_STAT)) {
+		if (!nfs4_delegation_stat(dp, currentfh, &stat)) {
 			nfs4_put_stid(&dp->dl_stid);
 			destroy_delegation(dp);
 			goto out_no_deleg;
 		}
+		open->op_delegate_type = NFS4_OPEN_DELEGATE_WRITE;
 		dp->dl_cb_fattr.ncf_cur_fsize = stat.size;
 		dp->dl_cb_fattr.ncf_initial_cinfo =
 			nfsd4_change_attribute(&stat, d_inode(currentfh->fh_dentry));
+		trace_nfsd_deleg_write(&dp->dl_stid.sc_stateid);
 	} else {
 		open->op_delegate_type = NFS4_OPEN_DELEGATE_READ;
 		trace_nfsd_deleg_read(&dp->dl_stid.sc_stateid);