fs/nfsd: fix update of inode attrs in CB_GETATTR

Currently, we copy the mtime and ctime to the in-core inode and then
mark the inode dirty. This is fine for certain types of filesystems, but
not all. Some require a real setattr to properly change these values
(e.g. ceph or reexported NFS).

Fix this code to call notify_change() instead, which is the proper way
to effect a setattr. There is one problem though:

In this case, the client is holding a write delegation and has sent us
attributes to update our cache. We don't want to break the delegation
for this since that would defeat the purpose. Add a new ATTR_DELEG flag
that makes notify_change bypass the try_break_deleg call.

Fixes: c5967721e106 ("NFSD: handle GETATTR conflict with write delegation")
Reviewed-by: Christian Brauner <[e-mail]>
Signed-off-by: Jeff Layton <[e-mail]>
Signed-off-by: Chuck Lever <[e-mail]>

fs/attr.c

···
 	error = security_inode_setattr(idmap, dentry, attr);
 	if (error)
 		return error;
-	error = try_break_deleg(inode, delegated_inode);
-	if (error)
-		return error;
+
+	/*
+	 * If ATTR_DELEG is set, then these attributes are being set on
+	 * behalf of the holder of a write delegation. We want to avoid
+	 * breaking the delegation in this case.
+	 */
+	if (!(ia_valid & ATTR_DELEG)) {
+		error = try_break_deleg(inode, delegated_inode);
+		if (error)
+			return error;
+	}
 
 	if (inode->i_op->setattr)
 		error = inode->i_op->setattr(idmap, dentry, attr);

fs/nfsd/nfs4state.c

···
 /**
  * nfsd4_deleg_getattr_conflict - Recall if GETATTR causes conflict
  * @rqstp: RPC transaction context
- * @inode: file to be checked for a conflict
+ * @dentry: dentry of inode to be checked for a conflict
  * @modified: return true if file was modified
  * @size: new size of file if modified is true
  *
···
  * code is returned.
  */
 __be32
-nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct inode *inode,
+nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
 				bool *modified, u64 *size)
 {
 	__be32 status;
···
 	struct file_lease *fl;
 	struct iattr attrs;
 	struct nfs4_cb_fattr *ncf;
+	struct inode *inode = d_inode(dentry);
 
 	*modified = false;
 	ctx = locks_inode_context(inode);
···
 					ncf->ncf_cur_fsize != ncf->ncf_cb_fsize))
 				ncf->ncf_file_modified = true;
 			if (ncf->ncf_file_modified) {
+				int err;
+
 				/*
 				 * Per section 10.4.3 of RFC 8881, the server would
 				 * not update the file's metadata with the client's
 				 * modified size
 				 */
 				attrs.ia_mtime = attrs.ia_ctime = current_time(inode);
-				attrs.ia_valid = ATTR_MTIME | ATTR_CTIME;
-				setattr_copy(&nop_mnt_idmap, inode, &attrs);
-				mark_inode_dirty(inode);
+				attrs.ia_valid = ATTR_MTIME | ATTR_CTIME | ATTR_DELEG;
+				inode_lock(inode);
+				err = notify_change(&nop_mnt_idmap, dentry, &attrs, NULL);
+				inode_unlock(inode);
+				if (err) {
+					nfs4_put_stid(&dp->dl_stid);
+					return nfserrno(err);
+				}
 				ncf->ncf_cur_fsize = ncf->ncf_cb_fsize;
 				*size = ncf->ncf_cur_fsize;
 				*modified = true;

fs/nfsd/nfs4xdr.c

···
 	}
 	args.size = 0;
 	if (attrmask[0] & (FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE)) {
-		status = nfsd4_deleg_getattr_conflict(rqstp, d_inode(dentry),
+		status = nfsd4_deleg_getattr_conflict(rqstp, dentry,
 					&file_modified, &size);
 		if (status)
 			goto out;

fs/nfsd/state.h

···
 }
 
 extern __be32 nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp,
-		struct inode *inode, bool *file_modified, u64 *size);
+		struct dentry *dentry, bool *file_modified, u64 *size);
 #endif   /* NFSD4_STATE_H */

include/linux/fs.h

···
 #define ATTR_OPEN	(1 << 15) /* Truncating from open(O_TRUNC) */
 #define ATTR_TIMES_SET	(1 << 16)
 #define ATTR_TOUCH	(1 << 17)
+#define ATTR_DELEG	(1 << 18) /* Delegated attrs. Don't break write delegations */
 
 /*
  * Whiteout is represented by a char device.  The following constants define the