Merge tag 'nfs-for-5.19-1' of git://git.linux-nfs.org/projects/anna/linux-nfs

Pull NFS client updates from Anna Schumaker:
 "New Features:
   - Add support for 'dacl' and 'sacl' attributes

  Bugfixes and Cleanups:
   - Fixes for reporting mapping errors
   - Fixes for memory allocation errors
   - Improve warning message when locks are lost
   - Update documentation for the nfs4_unique_id parameter
   - Add an explanation of NFSv4 client identifiers
   - Ensure the i_size attribute is written to the fscache storage
   - Fix freeing uninitialized nfs4_labels
   - Better handling when xprtrdma bc_serv is NULL
   - Mark qualified async operations as MOVEABLE tasks"

* tag 'nfs-for-5.19-1' of git://git.linux-nfs.org/projects/anna/linux-nfs:
  NFSv4.1 mark qualified async operations as MOVEABLE tasks
  xprtrdma: treat all calls not a bcall when bc_serv is NULL
  NFSv4: Fix free of uninitialized nfs4_label on referral lookup.
  NFS: Pass i_size to fscache_unuse_cookie() when a file is released
  Documentation: Add an explanation of NFSv4 client identifiers
  NFS: update documentation for the nfs4_unique_id parameter
  NFS: Improve warning message when locks are lost.
  NFSv4.1: Enable access to the NFSv4.1 'dacl' and 'sacl' attributes
  NFSv4: Add encoders/decoders for the NFSv4.1 dacl and sacl attributes
  NFSv4: Specify the type of ACL to cache
  NFSv4: Don't hold the layoutget locks across multiple RPC calls
  pNFS/files: Fall back to I/O through the MDS on non-fatal layout errors
  NFS: Further fixes to the writeback error handling
  NFSv4/pNFS: Do not fail I/O when we fail to allocate the pNFS layout
  NFS: Memory allocation failures are not server fatal errors
  NFS: Don't report errors from nfs_pageio_complete() more than once
  NFS: Do not report flush errors in nfs_write_end()
  NFS: Don't report ENOSPC write errors twice
  NFS: fsync() should report filesystem errors over EINTR/ERESTARTSYS
  NFS: Do not report EINTR/ERESTARTSYS as mapping errors

Author: torvalds

Documentation/admin-guide/nfs/nfs-client.rst

@@ -36,10 +36,9 @@ administrative requirements that require particular behavior that does not
 work well as part of an nfs_client_id4 string.
 
 The nfs.nfs4_unique_id boot parameter specifies a unique string that can be
-used instead of a system's node name when an NFS client identifies itself to
-a server.  Thus, if the system's node name is not unique, or it changes, its
-nfs.nfs4_unique_id stays the same, preventing collision with other clients
-or loss of state during NFS reboot recovery or transparent state migration.
+used together with  a system's node name when an NFS client identifies itself to
+a server.  Thus, if the system's node name is not unique, its
+nfs.nfs4_unique_id can help prevent collisions with other clients.
 
 The nfs.nfs4_unique_id string is typically a UUID, though it can contain
 anything that is believed to be unique across all NFS clients.  An
@@ -53,8 +52,12 @@ outstanding NFSv4 state has expired, to prevent loss of NFSv4 state.
 
 This string can be stored in an NFS client's grub.conf, or it can be provided
 via a net boot facility such as PXE.  It may also be specified as an nfs.ko
-module parameter.  Specifying a uniquifier string is not support for NFS
-clients running in containers.
+module parameter.
+
+This uniquifier string will be the same for all NFS clients running in
+containers unless it is overridden by a value written to
+/sys/fs/nfs/net/nfs_client/identifier which will be local to the network
+namespace of the process which writes.
 
 
 The DNS resolver

Documentation/filesystems/nfs/client-identifier.rst

@@ -0,0 +1,216 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================
+NFSv4 client identifier
+=======================
+
+This document explains how the NFSv4 protocol identifies client
+instances in order to maintain file open and lock state during
+system restarts. A special identifier and principal are maintained
+on each client. These can be set by administrators, scripts
+provided by site administrators, or tools provided by Linux
+distributors.
+
+There are risks if a client's NFSv4 identifier and its principal
+are not chosen carefully.
+
+
+Introduction
+------------
+
+The NFSv4 protocol uses "lease-based file locking". Leases help
+NFSv4 servers provide file lock guarantees and manage their
+resources.
+
+Simply put, an NFSv4 server creates a lease for each NFSv4 client.
+The server collects each client's file open and lock state under
+the lease for that client.
+
+The client is responsible for periodically renewing its leases.
+While a lease remains valid, the server holding that lease
+guarantees the file locks the client has created remain in place.
+
+If a client stops renewing its lease (for example, if it crashes),
+the NFSv4 protocol allows the server to remove the client's open
+and lock state after a certain period of time. When a client
+restarts, it indicates to servers that open and lock state
+associated with its previous leases is no longer valid and can be
+destroyed immediately.
+
+In addition, each NFSv4 server manages a persistent list of client
+leases. When the server restarts and clients attempt to recover
+their state, the server uses this list to distinguish amongst
+clients that held state before the server restarted and clients
+sending fresh OPEN and LOCK requests. This enables file locks to
+persist safely across server restarts.
+
+NFSv4 client identifiers
+------------------------
+
+Each NFSv4 client presents an identifier to NFSv4 servers so that
+they can associate the client with its lease. Each client's
+identifier consists of two elements:
+
+  - co_ownerid: An arbitrary but fixed string.
+
+  - boot verifier: A 64-bit incarnation verifier that enables a
+    server to distinguish successive boot epochs of the same client.
+
+The NFSv4.0 specification refers to these two items as an
+"nfs_client_id4". The NFSv4.1 specification refers to these two
+items as a "client_owner4".
+
+NFSv4 servers tie this identifier to the principal and security
+flavor that the client used when presenting it. Servers use this
+principal to authorize subsequent lease modification operations
+sent by the client. Effectively this principal is a third element of
+the identifier.
+
+As part of the identity presented to servers, a good
+"co_ownerid" string has several important properties:
+
+  - The "co_ownerid" string identifies the client during reboot
+    recovery, therefore the string is persistent across client
+    reboots.
+  - The "co_ownerid" string helps servers distinguish the client
+    from others, therefore the string is globally unique. Note
+    that there is no central authority that assigns "co_ownerid"
+    strings.
+  - Because it often appears on the network in the clear, the
+    "co_ownerid" string does not reveal private information about
+    the client itself.
+  - The content of the "co_ownerid" string is set and unchanging
+    before the client attempts NFSv4 mounts after a restart.
+  - The NFSv4 protocol places a 1024-byte limit on the size of the
+    "co_ownerid" string.
+
+Protecting NFSv4 lease state
+----------------------------
+
+NFSv4 servers utilize the "client_owner4" as described above to
+assign a unique lease to each client. Under this scheme, there are
+circumstances where clients can interfere with each other. This is
+referred to as "lease stealing".
+
+If distinct clients present the same "co_ownerid" string and use
+the same principal (for example, AUTH_SYS and UID 0), a server is
+unable to tell that the clients are not the same. Each distinct
+client presents a different boot verifier, so it appears to the
+server as if there is one client that is rebooting frequently.
+Neither client can maintain open or lock state in this scenario.
+
+If distinct clients present the same "co_ownerid" string and use
+distinct principals, the server is likely to allow the first client
+to operate normally but reject subsequent clients with the same
+"co_ownerid" string.
+
+If a client's "co_ownerid" string or principal are not stable,
+state recovery after a server or client reboot is not guaranteed.
+If a client unexpectedly restarts but presents a different
+"co_ownerid" string or principal to the server, the server orphans
+the client's previous open and lock state. This blocks access to
+locked files until the server removes the orphaned state.
+
+If the server restarts and a client presents a changed "co_ownerid"
+string or principal to the server, the server will not allow the
+client to reclaim its open and lock state, and may give those locks
+to other clients in the meantime. This is referred to as "lock
+stealing".
+
+Lease stealing and lock stealing increase the potential for denial
+of service and in rare cases even data corruption.
+
+Selecting an appropriate client identifier
+------------------------------------------
+
+By default, the Linux NFSv4 client implementation constructs its
+"co_ownerid" string starting with the words "Linux NFS" followed by
+the client's UTS node name (the same node name, incidentally, that
+is used as the "machine name" in an AUTH_SYS credential). In small
+deployments, this construction is usually adequate. Often, however,
+the node name by itself is not adequately unique, and can change
+unexpectedly. Problematic situations include:
+
+  - NFS-root (diskless) clients, where the local DCHP server (or
+    equivalent) does not provide a unique host name.
+
+  - "Containers" within a single Linux host.  If each container has
+    a separate network namespace, but does not use the UTS namespace
+    to provide a unique host name, then there can be multiple NFS
+    client instances with the same host name.
+
+  - Clients across multiple administrative domains that access a
+    common NFS server. If hostnames are not assigned centrally
+    then uniqueness cannot be guaranteed unless a domain name is
+    included in the hostname.
+
+Linux provides two mechanisms to add uniqueness to its "co_ownerid"
+string:
+
+    nfs.nfs4_unique_id
+      This module parameter can set an arbitrary uniquifier string
+      via the kernel command line, or when the "nfs" module is
+      loaded.
+
+    /sys/fs/nfs/client/net/identifier
+      This virtual file, available since Linux 5.3, is local to the
+      network namespace in which it is accessed and so can provide
+      distinction between network namespaces (containers) when the
+      hostname remains uniform.
+
+Note that this file is empty on name-space creation. If the
+container system has access to some sort of per-container identity
+then that uniquifier can be used. For example, a uniquifier might
+be formed at boot using the container's internal identifier:
+
+    sha256sum /etc/machine-id | awk '{print $1}' \\
+        > /sys/fs/nfs/client/net/identifier
+
+Security considerations
+-----------------------
+
+The use of cryptographic security for lease management operations
+is strongly encouraged.
+
+If NFS with Kerberos is not configured, a Linux NFSv4 client uses
+AUTH_SYS and UID 0 as the principal part of its client identity.
+This configuration is not only insecure, it increases the risk of
+lease and lock stealing. However, it might be the only choice for
+client configurations that have no local persistent storage.
+"co_ownerid" string uniqueness and persistence is critical in this
+case.
+
+When a Kerberos keytab is present on a Linux NFS client, the client
+attempts to use one of the principals in that keytab when
+identifying itself to servers. The "sec=" mount option does not
+control this behavior. Alternately, a single-user client with a
+Kerberos principal can use that principal in place of the client's
+host principal.
+
+Using Kerberos for this purpose enables the client and server to
+use the same lease for operations covered by all "sec=" settings.
+Additionally, the Linux NFS client uses the RPCSEC_GSS security
+flavor with Kerberos and the integrity QOS to prevent in-transit
+modification of lease modification requests.
+
+Additional notes
+----------------
+The Linux NFSv4 client establishes a single lease on each NFSv4
+server it accesses. NFSv4 mounts from a Linux NFSv4 client of a
+particular server then share that lease.
+
+Once a client establishes open and lock state, the NFSv4 protocol
+enables lease state to transition to other servers, following data
+that has been migrated. This hides data migration completely from
+running applications. The Linux NFSv4 client facilitates state
+migration by presenting the same "client_owner4" to all servers it
+encounters.
+
+========
+See Also
+========
+
+  - nfs(5)
+  - kerberos(7)
+  - RFC 7530 for the NFSv4.0 specification
+  - RFC 8881 for the NFSv4.1 specification.

Documentation/filesystems/nfs/index.rst

@@ -6,6 +6,8 @@ NFS
 .. toctree::
    :maxdepth: 1
 
+   client-identifier
+   exporting
    pnfs
    rpc-cache
    rpc-server-gss

fs/nfs/file.c

@@ -206,15 +206,16 @@ static int
 nfs_file_fsync_commit(struct file *file, int datasync)
 {
 	struct inode *inode = file_inode(file);
-	int ret;
+	int ret, ret2;
 
 	dprintk("NFS: fsync file(%pD2) datasync %d\n", file, datasync);
 
 	nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
 	ret = nfs_commit_inode(inode, FLUSH_SYNC);
-	if (ret < 0)
-		return ret;
-	return file_check_and_advance_wb_err(file);
+	ret2 = file_check_and_advance_wb_err(file);
+	if (ret2 < 0)
+		return ret2;
+	return ret;
 }
 
 int
@@ -387,11 +388,8 @@ static int nfs_write_end(struct file *file, struct address_space *mapping,
 		return status;
 	NFS_I(mapping->host)->write_io += copied;
 
-	if (nfs_ctx_key_to_expire(ctx, mapping->host)) {
-		status = nfs_wb_all(mapping->host);
-		if (status < 0)
-			return status;
-	}
+	if (nfs_ctx_key_to_expire(ctx, mapping->host))
+		nfs_wb_all(mapping->host);
 
 	return copied;
 }
@@ -606,18 +604,6 @@ static const struct vm_operations_struct nfs_file_vm_ops = {
 	.page_mkwrite = nfs_vm_page_mkwrite,
 };
 
-static int nfs_need_check_write(struct file *filp, struct inode *inode,
-				int error)
-{
-	struct nfs_open_context *ctx;
-
-	ctx = nfs_file_open_context(filp);
-	if (nfs_error_is_fatal_on_server(error) ||
-	    nfs_ctx_key_to_expire(ctx, inode))
-		return 1;
-	return 0;
-}
-
 ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
 {
 	struct file *file = iocb->ki_filp;
@@ -645,7 +631,7 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
 	if (iocb->ki_flags & IOCB_APPEND || iocb->ki_pos > i_size_read(inode)) {
 		result = nfs_revalidate_file_size(inode, file);
 		if (result)
-			goto out;
+			return result;
 	}
 
 	nfs_clear_invalid_mapping(file->f_mapping);
@@ -664,6 +650,7 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
 
 	written = result;
 	iocb->ki_pos += written;
+	nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
 
 	if (mntflags & NFS_MOUNT_WRITE_EAGER) {
 		result = filemap_fdatawrite_range(file->f_mapping,
@@ -681,17 +668,22 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
 	}
 	result = generic_write_sync(iocb, written);
 	if (result < 0)
-		goto out;
+		return result;
 
+out:
 	/* Return error values */
 	error = filemap_check_wb_err(file->f_mapping, since);
-	if (nfs_need_check_write(file, inode, error)) {
-		int err = nfs_wb_all(inode);
-		if (err < 0)
-			result = err;
+	switch (error) {
+	default:
+		break;
+	case -EDQUOT:
+	case -EFBIG:
+	case -ENOSPC:
+		nfs_wb_all(inode);
+		error = file_check_and_advance_wb_err(file);
+		if (error < 0)
+			result = error;
 	}
-	nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, written);
-out:
 	return result;
 
 out_swapfile:

fs/nfs/filelayout/filelayout.c

@@ -839,7 +839,12 @@ fl_pnfs_update_layout(struct inode *ino,
 
 	lseg = pnfs_update_layout(ino, ctx, pos, count, iomode, strict_iomode,
 				  gfp_flags);
-	if (IS_ERR_OR_NULL(lseg))
+	if (IS_ERR(lseg)) {
+		/* Fall back to MDS on recoverable errors */
+		if (!nfs_error_is_fatal_on_server(PTR_ERR(lseg)))
+			lseg = NULL;
+		goto out;
+	} else if (!lseg)
 		goto out;
 
 	lo = NFS_I(ino)->layout;

fs/nfs/fscache.c

@@ -231,11 +231,10 @@ void nfs_fscache_release_file(struct inode *inode, struct file *filp)
 {
 	struct nfs_fscache_inode_auxdata auxdata;
 	struct fscache_cookie *cookie = nfs_i_fscache(inode);
+	loff_t i_size = i_size_read(inode);
 
-	if (fscache_cookie_valid(cookie)) {
-		nfs_fscache_update_auxdata(&auxdata, inode);
-		fscache_unuse_cookie(cookie, &auxdata, NULL);
-	}
+	nfs_fscache_update_auxdata(&auxdata, inode);
+	fscache_unuse_cookie(cookie, &auxdata, &i_size);
 }
 
 /*

fs/nfs/internal.h

@@ -841,6 +841,7 @@ static inline bool nfs_error_is_fatal_on_server(int err)
 	case 0:
 	case -ERESTARTSYS:
 	case -EINTR:
+	case -ENOMEM:
 		return false;
 	}
 	return nfs_error_is_fatal(err);