Merge tag 'nfsd-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux

Pull nfsd updates from Chuck Lever:
 "New features:

   - Support for server-side disconnect injection via debugfs

   - Protocol definitions for new RPC_AUTH_TLS authentication flavor

  Performance improvements:

   - Reduce page allocator traffic in the NFSD splice read actor

   - Reduce CPU utilization in svcrdma's Send completion handler

  Notable bug fixes:

   - Stabilize lockd operation when re-exporting NFS mounts

   - Fix the use of %.*s in NFSD tracepoints

   - Fix /proc/sys/fs/nfs/nsm_use_hostnames"

* tag 'nfsd-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux: (31 commits)
  nfsd: fix crash on LOCKT on reexported NFSv3
  nfs: don't allow reexport reclaims
  lockd: don't attempt blocking locks on nfs reexports
  nfs: don't atempt blocking locks on nfs reexports
  Keep read and write fds with each nlm_file
  lockd: update nlm_lookup_file reexport comment
  nlm: minor refactoring
  nlm: minor nlm_lookup_file argument change
  lockd: lockd server-side shouldn't set fl_ops
  SUNRPC: Add documentation for the fail_sunrpc/ directory
  SUNRPC: Server-side disconnect injection
  SUNRPC: Move client-side disconnect injection
  SUNRPC: Add a /sys/kernel/debug/fail_sunrpc/ directory
  svcrdma: xpt_bc_xprt is already clear in __svc_rdma_free()
  nfsd4: Fix forced-expiry locking
  rpc: fix gss_svc_init cleanup on failure
  SUNRPC: Add RPC_AUTH_TLS protocol numbers
  lockd: change the proc_handler for nsm_use_hostnames
  sysctl: introduce new proc handler proc_dobool
  SUNRPC: Fix a NULL pointer deref in trace_svc_stats_latency()
  ...

Documentation/fault-injection/fault-injection.rst

@@ -24,6 +24,10 @@ Available fault injection capabilities
 
   injects futex deadlock and uaddr fault errors.
 
+- fail_sunrpc
+
+  injects kernel RPC client and server failures.
+
 - fail_make_request
 
   injects disk IO errors on devices permitted by setting
@@ -151,6 +155,20 @@ configuration of fault-injection capabilities.
 	default is 'N', setting it to 'Y' will disable failure injections
 	when dealing with private (address space) futexes.
 
+- /sys/kernel/debug/fail_sunrpc/ignore-client-disconnect:
+
+	Format: { 'Y' | 'N' }
+
+	default is 'N', setting it to 'Y' will disable disconnect
+	injection on the RPC client.
+
+- /sys/kernel/debug/fail_sunrpc/ignore-server-disconnect:
+
+	Format: { 'Y' | 'N' }
+
+	default is 'N', setting it to 'Y' will disable disconnect
+	injection on the RPC server.
+
 - /sys/kernel/debug/fail_function/inject:
 
 	Format: { 'function-name' | '!function-name' | '' }

fs/lockd/svc.c

@@ -584,7 +584,7 @@ static struct ctl_table nlm_sysctls[] = {
 		.data		= &nsm_use_hostnames,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dobool,
 	},
 	{
 		.procname	= "nsm_local_state",

fs/lockd/svc4proc.c

@@ -40,12 +40,15 @@ nlm4svc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
 
 	/* Obtain file pointer. Not used by FREE_ALL call. */
 	if (filp != NULL) {
-		if ((error = nlm_lookup_file(rqstp, &file, &lock->fh)) != 0)
+		int mode = lock_to_openmode(&lock->fl);
+
+		error = nlm_lookup_file(rqstp, &file, lock);
+		if (error)
 			goto no_locks;
 		*filp = file;
 
 		/* Set up the missing parts of the file_lock structure */
-		lock->fl.fl_file  = file->f_file;
+		lock->fl.fl_file  = file->f_file[mode];
 		lock->fl.fl_pid = current->tgid;
 		lock->fl.fl_lmops = &nlmsvc_lock_operations;
 		nlmsvc_locks_init_private(&lock->fl, host, (pid_t)lock->svid);

fs/lockd/svclock.c

@@ -31,6 +31,7 @@
 #include <linux/lockd/nlm.h>
 #include <linux/lockd/lockd.h>
 #include <linux/kthread.h>
+#include <linux/exportfs.h>
 
 #define NLMDBG_FACILITY		NLMDBG_SVCLOCK
 
@@ -395,28 +396,10 @@ nlmsvc_release_lockowner(struct nlm_lock *lock)
 		nlmsvc_put_lockowner(lock->fl.fl_owner);
 }
 
-static void nlmsvc_locks_copy_lock(struct file_lock *new, struct file_lock *fl)
-{
-	struct nlm_lockowner *nlm_lo = (struct nlm_lockowner *)fl->fl_owner;
-	new->fl_owner = nlmsvc_get_lockowner(nlm_lo);
-}
-
-static void nlmsvc_locks_release_private(struct file_lock *fl)
-{
-	nlmsvc_put_lockowner((struct nlm_lockowner *)fl->fl_owner);
-}
-
-static const struct file_lock_operations nlmsvc_lock_ops = {
-	.fl_copy_lock = nlmsvc_locks_copy_lock,
-	.fl_release_private = nlmsvc_locks_release_private,
-};
-
 void nlmsvc_locks_init_private(struct file_lock *fl, struct nlm_host *host,
 						pid_t pid)
 {
 	fl->fl_owner = nlmsvc_find_lockowner(host, pid);
-	if (fl->fl_owner != NULL)
-		fl->fl_ops = &nlmsvc_lock_ops;
 }
 
 /*
@@ -488,17 +471,24 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 	    struct nlm_cookie *cookie, int reclaim)
 {
 	struct nlm_block	*block = NULL;
+	struct inode		*inode = nlmsvc_file_inode(file);
 	int			error;
+	int			mode;
+	int			async_block = 0;
 	__be32			ret;
 
 	dprintk("lockd: nlmsvc_lock(%s/%ld, ty=%d, pi=%d, %Ld-%Ld, bl=%d)\n",
-				locks_inode(file->f_file)->i_sb->s_id,
-				locks_inode(file->f_file)->i_ino,
+				inode->i_sb->s_id, inode->i_ino,
 				lock->fl.fl_type, lock->fl.fl_pid,
 				(long long)lock->fl.fl_start,
 				(long long)lock->fl.fl_end,
 				wait);
 
+	if (inode->i_sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS) {
+		async_block = wait;
+		wait = 0;
+	}
+
 	/* Lock file against concurrent access */
 	mutex_lock(&file->f_mutex);
 	/* Get existing block (in case client is busy-waiting)
@@ -542,7 +532,8 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 
 	if (!wait)
 		lock->fl.fl_flags &= ~FL_SLEEP;
-	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
+	mode = lock_to_openmode(&lock->fl);
+	error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
 	lock->fl.fl_flags &= ~FL_SLEEP;
 
 	dprintk("lockd: vfs_lock_file returned %d\n", error);
@@ -558,7 +549,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 			 */
 			if (wait)
 				break;
-			ret = nlm_lck_denied;
+			ret = async_block ? nlm_lck_blocked : nlm_lck_denied;
 			goto out;
 		case FILE_LOCK_DEFERRED:
 			if (wait)
@@ -595,12 +586,13 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 		struct nlm_lock *conflock, struct nlm_cookie *cookie)
 {
 	int			error;
+	int			mode;
 	__be32			ret;
 	struct nlm_lockowner	*test_owner;
 
 	dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
-				locks_inode(file->f_file)->i_sb->s_id,
-				locks_inode(file->f_file)->i_ino,
+				nlmsvc_file_inode(file)->i_sb->s_id,
+				nlmsvc_file_inode(file)->i_ino,
 				lock->fl.fl_type,
 				(long long)lock->fl.fl_start,
 				(long long)lock->fl.fl_end);
@@ -613,7 +605,8 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 	/* If there's a conflicting lock, remember to clean up the test lock */
 	test_owner = (struct nlm_lockowner *)lock->fl.fl_owner;
 
-	error = vfs_test_lock(file->f_file, &lock->fl);
+	mode = lock_to_openmode(&lock->fl);
+	error = vfs_test_lock(file->f_file[mode], &lock->fl);
 	if (error) {
 		/* We can't currently deal with deferred test requests */
 		if (error == FILE_LOCK_DEFERRED)
@@ -634,7 +627,7 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 	conflock->caller = "somehost";	/* FIXME */
 	conflock->len = strlen(conflock->caller);
 	conflock->oh.len = 0;		/* don't return OH info */
-	conflock->svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
+	conflock->svid = lock->fl.fl_pid;
 	conflock->fl.fl_type = lock->fl.fl_type;
 	conflock->fl.fl_start = lock->fl.fl_start;
 	conflock->fl.fl_end = lock->fl.fl_end;
@@ -659,11 +652,11 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 __be32
 nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 {
-	int	error;
+	int	error = 0;
 
 	dprintk("lockd: nlmsvc_unlock(%s/%ld, pi=%d, %Ld-%Ld)\n",
-				locks_inode(file->f_file)->i_sb->s_id,
-				locks_inode(file->f_file)->i_ino,
+				nlmsvc_file_inode(file)->i_sb->s_id,
+				nlmsvc_file_inode(file)->i_ino,
 				lock->fl.fl_pid,
 				(long long)lock->fl.fl_start,
 				(long long)lock->fl.fl_end);
@@ -672,7 +665,12 @@ nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
 	nlmsvc_cancel_blocked(net, file, lock);
 
 	lock->fl.fl_type = F_UNLCK;
-	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
+	if (file->f_file[O_RDONLY])
+		error = vfs_lock_file(file->f_file[O_RDONLY], F_SETLK,
+					&lock->fl, NULL);
+	if (file->f_file[O_WRONLY])
+		error = vfs_lock_file(file->f_file[O_WRONLY], F_SETLK,
+					&lock->fl, NULL);
 
 	return (error < 0)? nlm_lck_denied_nolocks : nlm_granted;
 }
@@ -689,10 +687,11 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
 {
 	struct nlm_block	*block;
 	int status = 0;
+	int mode;
 
 	dprintk("lockd: nlmsvc_cancel(%s/%ld, pi=%d, %Ld-%Ld)\n",
-				locks_inode(file->f_file)->i_sb->s_id,
-				locks_inode(file->f_file)->i_ino,
+				nlmsvc_file_inode(file)->i_sb->s_id,
+				nlmsvc_file_inode(file)->i_ino,
 				lock->fl.fl_pid,
 				(long long)lock->fl.fl_start,
 				(long long)lock->fl.fl_end);
@@ -704,7 +703,8 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
 	block = nlmsvc_lookup_block(file, lock);
 	mutex_unlock(&file->f_mutex);
 	if (block != NULL) {
-		vfs_cancel_lock(block->b_file->f_file,
+		mode = lock_to_openmode(&lock->fl);
+		vfs_cancel_lock(block->b_file->f_file[mode],
 				&block->b_call->a_args.lock.fl);
 		status = nlmsvc_unlink_block(block);
 		nlmsvc_release_block(block);
@@ -788,9 +788,21 @@ nlmsvc_notify_blocked(struct file_lock *fl)
 	printk(KERN_WARNING "lockd: notification for unknown block!\n");
 }
 
+static fl_owner_t nlmsvc_get_owner(fl_owner_t owner)
+{
+	return nlmsvc_get_lockowner(owner);
+}
+
+static void nlmsvc_put_owner(fl_owner_t owner)
+{
+	nlmsvc_put_lockowner(owner);
+}
+
 const struct lock_manager_operations nlmsvc_lock_operations = {
 	.lm_notify = nlmsvc_notify_blocked,
 	.lm_grant = nlmsvc_grant_deferred,
+	.lm_get_owner = nlmsvc_get_owner,
+	.lm_put_owner = nlmsvc_put_owner,
 };
 
 /*
@@ -809,6 +821,7 @@ nlmsvc_grant_blocked(struct nlm_block *block)
 {
 	struct nlm_file		*file = block->b_file;
 	struct nlm_lock		*lock = &block->b_call->a_args.lock;
+	int			mode;
 	int			error;
 	loff_t			fl_start, fl_end;
 
@@ -834,7 +847,8 @@ nlmsvc_grant_blocked(struct nlm_block *block)
 	lock->fl.fl_flags |= FL_SLEEP;
 	fl_start = lock->fl.fl_start;
 	fl_end = lock->fl.fl_end;
-	error = vfs_lock_file(file->f_file, F_SETLK, &lock->fl, NULL);
+	mode = lock_to_openmode(&lock->fl);
+	error = vfs_lock_file(file->f_file[mode], F_SETLK, &lock->fl, NULL);
 	lock->fl.fl_flags &= ~FL_SLEEP;
 	lock->fl.fl_start = fl_start;
 	lock->fl.fl_end = fl_end;

fs/lockd/svcproc.c

@@ -55,6 +55,7 @@ nlmsvc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
 	struct nlm_host		*host = NULL;
 	struct nlm_file		*file = NULL;
 	struct nlm_lock		*lock = &argp->lock;
+	int			mode;
 	__be32			error = 0;
 
 	/* nfsd callbacks must have been installed for this procedure */
@@ -69,13 +70,14 @@ nlmsvc_retrieve_args(struct svc_rqst *rqstp, struct nlm_args *argp,
 
 	/* Obtain file pointer. Not used by FREE_ALL call. */
 	if (filp != NULL) {
-		error = cast_status(nlm_lookup_file(rqstp, &file, &lock->fh));
+		error = cast_status(nlm_lookup_file(rqstp, &file, lock));
 		if (error != 0)
 			goto no_locks;
 		*filp = file;
 
 		/* Set up the missing parts of the file_lock structure */
-		lock->fl.fl_file  = file->f_file;
+		mode = lock_to_openmode(&lock->fl);
+		lock->fl.fl_file  = file->f_file[mode];
 		lock->fl.fl_pid = current->tgid;
 		lock->fl.fl_lmops = &nlmsvc_lock_operations;
 		nlmsvc_locks_init_private(&lock->fl, host, (pid_t)lock->svid);

fs/lockd/svcsubs.c

@@ -45,7 +45,7 @@ static inline void nlm_debug_print_fh(char *msg, struct nfs_fh *f)
 
 static inline void nlm_debug_print_file(char *msg, struct nlm_file *file)
 {
-	struct inode *inode = locks_inode(file->f_file);
+	struct inode *inode = nlmsvc_file_inode(file);
 
 	dprintk("lockd: %s %s/%ld\n",
 		msg, inode->i_sb->s_id, inode->i_ino);
@@ -71,56 +71,75 @@ static inline unsigned int file_hash(struct nfs_fh *f)
 	return tmp & (FILE_NRHASH - 1);
 }
 
+int lock_to_openmode(struct file_lock *lock)
+{
+	return (lock->fl_type == F_WRLCK) ? O_WRONLY : O_RDONLY;
+}
+
+/*
+ * Open the file. Note that if we're reexporting, for example,
+ * this could block the lockd thread for a while.
+ *
+ * We have to make sure we have the right credential to open
+ * the file.
+ */
+static __be32 nlm_do_fopen(struct svc_rqst *rqstp,
+			   struct nlm_file *file, int mode)
+{
+	struct file **fp = &file->f_file[mode];
+	__be32	nfserr;
+
+	if (*fp)
+		return 0;
+	nfserr = nlmsvc_ops->fopen(rqstp, &file->f_handle, fp, mode);
+	if (nfserr)
+		dprintk("lockd: open failed (error %d)\n", nfserr);
+	return nfserr;
+}
+
 /*
  * Lookup file info. If it doesn't exist, create a file info struct
  * and open a (VFS) file for the given inode.
- *
- * FIXME:
- * Note that we open the file O_RDONLY even when creating write locks.
- * This is not quite right, but for now, we assume the client performs
- * the proper R/W checking.
  */
 __be32
 nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
-					struct nfs_fh *f)
+					struct nlm_lock *lock)
 {
 	struct nlm_file	*file;
 	unsigned int	hash;
 	__be32		nfserr;
+	int		mode;
 
-	nlm_debug_print_fh("nlm_lookup_file", f);
+	nlm_debug_print_fh("nlm_lookup_file", &lock->fh);
 
-	hash = file_hash(f);
+	hash = file_hash(&lock->fh);
+	mode = lock_to_openmode(&lock->fl);
 
 	/* Lock file table */
 	mutex_lock(&nlm_file_mutex);
 
 	hlist_for_each_entry(file, &nlm_files[hash], f_list)
-		if (!nfs_compare_fh(&file->f_handle, f))
+		if (!nfs_compare_fh(&file->f_handle, &lock->fh)) {
+			mutex_lock(&file->f_mutex);
+			nfserr = nlm_do_fopen(rqstp, file, mode);
+			mutex_unlock(&file->f_mutex);
 			goto found;
-
-	nlm_debug_print_fh("creating file for", f);
+		}
+	nlm_debug_print_fh("creating file for", &lock->fh);
 
 	nfserr = nlm_lck_denied_nolocks;
 	file = kzalloc(sizeof(*file), GFP_KERNEL);
 	if (!file)
-		goto out_unlock;
+		goto out_free;
 
-	memcpy(&file->f_handle, f, sizeof(struct nfs_fh));
+	memcpy(&file->f_handle, &lock->fh, sizeof(struct nfs_fh));
 	mutex_init(&file->f_mutex);
 	INIT_HLIST_NODE(&file->f_list);
 	INIT_LIST_HEAD(&file->f_blocks);
 
-	/* Open the file. Note that this must not sleep for too long, else
-	 * we would lock up lockd:-) So no NFS re-exports, folks.
-	 *
-	 * We have to make sure we have the right credential to open
-	 * the file.
-	 */
-	if ((nfserr = nlmsvc_ops->fopen(rqstp, f, &file->f_file)) != 0) {
-		dprintk("lockd: open failed (error %d)\n", nfserr);
-		goto out_free;
-	}
+	nfserr = nlm_do_fopen(rqstp, file, mode);
+	if (nfserr)
+		goto out_unlock;
 
 	hlist_add_head(&file->f_list, &nlm_files[hash]);
 
@@ -128,7 +147,6 @@ nlm_lookup_file(struct svc_rqst *rqstp, struct nlm_file **result,
 	dprintk("lockd: found file %p (count %d)\n", file, file->f_count);
 	*result = file;
 	file->f_count++;
-	nfserr = 0;
 
 out_unlock:
 	mutex_unlock(&nlm_file_mutex);
@@ -148,13 +166,34 @@ nlm_delete_file(struct nlm_file *file)
 	nlm_debug_print_file("closing file", file);
 	if (!hlist_unhashed(&file->f_list)) {
 		hlist_del(&file->f_list);
-		nlmsvc_ops->fclose(file->f_file);
+		if (file->f_file[O_RDONLY])
+			nlmsvc_ops->fclose(file->f_file[O_RDONLY]);
+		if (file->f_file[O_WRONLY])
+			nlmsvc_ops->fclose(file->f_file[O_WRONLY]);
 		kfree(file);
 	} else {
 		printk(KERN_WARNING "lockd: attempt to release unknown file!\n");
 	}
 }
 
+static int nlm_unlock_files(struct nlm_file *file)
+{
+	struct file_lock lock;
+	struct file *f;
+
+	lock.fl_type  = F_UNLCK;
+	lock.fl_start = 0;
+	lock.fl_end   = OFFSET_MAX;
+	for (f = file->f_file[0]; f <= file->f_file[1]; f++) {
+		if (f && vfs_lock_file(f, F_SETLK, &lock, NULL) < 0) {
+			pr_warn("lockd: unlock failure in %s:%d\n",
+				__FILE__, __LINE__);
+			return 1;
+		}
+	}
+	return 0;
+}
+
 /*
  * Loop over all locks on the given file and perform the specified
  * action.
@@ -182,17 +221,10 @@ nlm_traverse_locks(struct nlm_host *host, struct nlm_file *file,
 
 		lockhost = ((struct nlm_lockowner *)fl->fl_owner)->host;
 		if (match(lockhost, host)) {
-			struct file_lock lock = *fl;
 
 			spin_unlock(&flctx->flc_lock);
-			lock.fl_type  = F_UNLCK;
-			lock.fl_start = 0;
-			lock.fl_end   = OFFSET_MAX;
-			if (vfs_lock_file(file->f_file, F_SETLK, &lock, NULL) < 0) {
-				printk("lockd: unlock failure in %s:%d\n",
-						__FILE__, __LINE__);
+			if (nlm_unlock_files(file))
 				return 1;
-			}
 			goto again;
 		}
 	}
@@ -246,6 +278,15 @@ nlm_file_inuse(struct nlm_file *file)
 	return 0;
 }
 
+static void nlm_close_files(struct nlm_file *file)
+{
+	struct file *f;
+
+	for (f = file->f_file[0]; f <= file->f_file[1]; f++)
+		if (f)
+			nlmsvc_ops->fclose(f);
+}
+
 /*
  * Loop over all files in the file table.
  */
@@ -276,7 +317,7 @@ nlm_traverse_files(void *data, nlm_host_match_fn_t match,
 			if (list_empty(&file->f_blocks) && !file->f_locks
 			 && !file->f_shares && !file->f_count) {
 				hlist_del(&file->f_list);
-				nlmsvc_ops->fclose(file->f_file);
+				nlm_close_files(file);
 				kfree(file);
 			}
 		}
@@ -410,12 +451,13 @@ nlmsvc_invalidate_all(void)
 	nlm_traverse_files(NULL, nlmsvc_is_client, NULL);
 }
 
+
 static int
 nlmsvc_match_sb(void *datap, struct nlm_file *file)
 {
 	struct super_block *sb = datap;
 
-	return sb == locks_inode(file->f_file)->i_sb;
+	return sb == nlmsvc_file_inode(file)->i_sb;
 }
 
 /**

fs/nfs/export.c

@@ -180,5 +180,5 @@ const struct export_operations nfs_export_ops = {
 	.fetch_iversion = nfs_fetch_iversion,
 	.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|
 		EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS|
-		EXPORT_OP_NOATOMIC_ATTR,
+		EXPORT_OP_NOATOMIC_ATTR|EXPORT_OP_SYNC_LOCKS,
 };

fs/nfs/file.c

@@ -806,6 +806,9 @@ int nfs_lock(struct file *filp, int cmd, struct file_lock *fl)
 
 	nfs_inc_stats(inode, NFSIOS_VFSLOCK);
 
+	if (fl->fl_flags & FL_RECLAIM)
+		return -ENOGRACE;
+
 	if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FCNTL)
 		is_local = 1;
 

fs/nfsd/lockd.c

@@ -25,9 +25,11 @@
  * Note: we hold the dentry use count while the file is open.
  */
 static __be32
-nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp)
+nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp,
+		int mode)
 {
 	__be32		nfserr;
+	int		access;
 	struct svc_fh	fh;
 
 	/* must initialize before using! but maxsize doesn't matter */
@@ -36,7 +38,9 @@ nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f, struct file **filp)
 	memcpy((char*)&fh.fh_handle.fh_base, f->data, f->size);
 	fh.fh_export = NULL;
 
-	nfserr = nfsd_open(rqstp, &fh, S_IFREG, NFSD_MAY_LOCK, filp);
+	access = (mode == O_WRONLY) ? NFSD_MAY_WRITE : NFSD_MAY_READ;
+	access |= NFSD_MAY_LOCK;
+	nfserr = nfsd_open(rqstp, &fh, S_IFREG, access, filp);
 	fh_put(&fh);
  	/* We return nlm error codes as nlm doesn't know
 	 * about nfsd, but nfsd does know about nlm..

fs/nfsd/nfs4state.c

@@ -2687,9 +2687,9 @@ static void force_expire_client(struct nfs4_client *clp)
 
 	trace_nfsd_clid_admin_expired(&clp->cl_clientid);
 
-	spin_lock(&clp->cl_lock);
+	spin_lock(&nn->client_lock);
 	clp->cl_time = 0;
-	spin_unlock(&clp->cl_lock);
+	spin_unlock(&nn->client_lock);
 
 	wait_event(expiry_wq, atomic_read(&clp->cl_rpc_users) == 0);
 	spin_lock(&nn->client_lock);
@@ -6821,6 +6821,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	struct nfsd4_blocked_lock *nbl = NULL;
 	struct file_lock *file_lock = NULL;
 	struct file_lock *conflock = NULL;
+	struct super_block *sb;
 	__be32 status = 0;
 	int lkflg;
 	int err;
@@ -6842,6 +6843,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		dprintk("NFSD: nfsd4_lock: permission denied!\n");
 		return status;
 	}
+	sb = cstate->current_fh.fh_dentry->d_sb;
 
 	if (lock->lk_is_new) {
 		if (nfsd4_has_session(cstate))
@@ -6887,10 +6889,14 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	if (!locks_in_grace(net) && lock->lk_reclaim)
 		goto out;
 
+	if (lock->lk_reclaim)
+		fl_flags |= FL_RECLAIM;
+
 	fp = lock_stp->st_stid.sc_file;
 	switch (lock->lk_type) {
 		case NFS4_READW_LT:
-			if (nfsd4_has_session(cstate))
+			if (nfsd4_has_session(cstate) &&
+			    !(sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS))
 				fl_flags |= FL_SLEEP;
 			fallthrough;
 		case NFS4_READ_LT:
@@ -6902,7 +6908,8 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 			fl_type = F_RDLCK;
 			break;
 		case NFS4_WRITEW_LT:
-			if (nfsd4_has_session(cstate))
+			if (nfsd4_has_session(cstate) &&
+			    !(sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS))
 				fl_flags |= FL_SLEEP;
 			fallthrough;
 		case NFS4_WRITE_LT:
@@ -7022,8 +7029,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 /*
  * The NFSv4 spec allows a client to do a LOCKT without holding an OPEN,
  * so we do a temporary open here just to get an open file to pass to
- * vfs_test_lock.  (Arguably perhaps test_lock should be done with an
- * inode operation.)
+ * vfs_test_lock.
  */
 static __be32 nfsd_test_lock(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file_lock *lock)
 {
@@ -7038,7 +7044,9 @@ static __be32 nfsd_test_lock(struct svc_rqst *rqstp, struct svc_fh *fhp, struct
 							NFSD_MAY_READ));
 	if (err)
 		goto out;
+	lock->fl_file = nf->nf_file;
 	err = nfserrno(vfs_test_lock(nf->nf_file, lock));
+	lock->fl_file = NULL;
 out:
 	fh_unlock(fhp);
 	nfsd_file_put(nf);

fs/nfsd/nfsproc.c

@@ -881,6 +881,7 @@ nfserrno (int errno)
 		{ nfserr_serverfault, -ENFILE },
 		{ nfserr_io, -EUCLEAN },
 		{ nfserr_perm, -ENOKEY },
+		{ nfserr_no_grace, -ENOGRACE},
 	};
 	int	i;
 

fs/nfsd/trace.h

@@ -400,18 +400,16 @@ TRACE_EVENT(nfsd_dirent,
 	TP_STRUCT__entry(
 		__field(u32, fh_hash)
 		__field(u64, ino)
-		__field(int, len)
-		__dynamic_array(unsigned char, name, namlen)
+		__string_len(name, name, namlen)
 	),
 	TP_fast_assign(
 		__entry->fh_hash = fhp ? knfsd_fh_hash(&fhp->fh_handle) : 0;
 		__entry->ino = ino;
-		__entry->len = namlen;
-		memcpy(__get_str(name), name, namlen);
+		__assign_str_len(name, name, namlen)
 	),
-	TP_printk("fh_hash=0x%08x ino=%llu name=%.*s",
-		__entry->fh_hash, __entry->ino,
-		__entry->len, __get_str(name))
+	TP_printk("fh_hash=0x%08x ino=%llu name=%s",
+		__entry->fh_hash, __entry->ino, __get_str(name)
+	)
 )
 
 #include "state.h"
@@ -608,7 +606,7 @@ DECLARE_EVENT_CLASS(nfsd_clid_class,
 		__array(unsigned char, addr, sizeof(struct sockaddr_in6))
 		__field(unsigned long, flavor)
 		__array(unsigned char, verifier, NFS4_VERIFIER_SIZE)
-		__dynamic_array(char, name, clp->cl_name.len + 1)
+		__string_len(name, name, clp->cl_name.len)
 	),
 	TP_fast_assign(
 		__entry->cl_boot = clp->cl_clientid.cl_boot;
@@ -618,8 +616,7 @@ DECLARE_EVENT_CLASS(nfsd_clid_class,
 		__entry->flavor = clp->cl_cred.cr_flavor;
 		memcpy(__entry->verifier, (void *)&clp->cl_verifier,
 		       NFS4_VERIFIER_SIZE);
-		memcpy(__get_str(name), clp->cl_name.data, clp->cl_name.len);
-		__get_str(name)[clp->cl_name.len] = '\0';
+		__assign_str_len(name, clp->cl_name.data, clp->cl_name.len);
 	),
 	TP_printk("addr=%pISpc name='%s' verifier=0x%s flavor=%s client=%08x:%08x",
 		__entry->addr, __get_str(name),

fs/nfsd/vfs.c

@@ -244,7 +244,6 @@ nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
  * returned. Otherwise the covered directory is returned.
  * NOTE: this mountpoint crossing is not supported properly by all
  *   clients and is explicitly disallowed for NFSv3
- *      NeilBrown <neilb@cse.unsw.edu.au>
  */
 __be32
 nfsd_lookup(struct svc_rqst *rqstp, struct svc_fh *fhp, const char *name,
@@ -826,26 +825,16 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 	struct svc_rqst *rqstp = sd->u.data;
 	struct page **pp = rqstp->rq_next_page;
 	struct page *page = buf->page;
-	size_t size;
-
-	size = sd->len;
 
 	if (rqstp->rq_res.page_len == 0) {
-		get_page(page);
-		put_page(*rqstp->rq_next_page);
-		*(rqstp->rq_next_page++) = page;
+		svc_rqst_replace_page(rqstp, page);
 		rqstp->rq_res.page_base = buf->offset;
-		rqstp->rq_res.page_len = size;
 	} else if (page != pp[-1]) {
-		get_page(page);
-		if (*rqstp->rq_next_page)
-			put_page(*rqstp->rq_next_page);
-		*(rqstp->rq_next_page++) = page;
-		rqstp->rq_res.page_len += size;
-	} else
-		rqstp->rq_res.page_len += size;
+		svc_rqst_replace_page(rqstp, page);
+	}
+	rqstp->rq_res.page_len += sd->len;
 
-	return size;
+	return sd->len;
 }
 
 static int nfsd_direct_splice_actor(struct pipe_inode_info *pipe,

include/linux/errno.h

@@ -31,5 +31,6 @@
 #define EJUKEBOX	528	/* Request initiated, but will not complete before timeout */
 #define EIOCBQUEUED	529	/* iocb queued, will get completion event */
 #define ERECALLCONFLICT	530	/* conflict with recalled state */
+#define ENOGRACE	531	/* NFS file lock reclaim refused */
 
 #endif

include/linux/exportfs.h

@@ -221,6 +221,8 @@ struct export_operations {
 #define EXPORT_OP_NOATOMIC_ATTR		(0x10) /* Filesystem cannot supply
 						  atomic attribute updates
 						*/
+#define EXPORT_OP_SYNC_LOCKS		(0x20) /* Filesystem can't do
+						  asychronous blocking locks */
 	unsigned long	flags;
 };
 

include/linux/fs.h

@@ -1037,6 +1037,7 @@ static inline struct file *get_file(struct file *f)
 #define FL_UNLOCK_PENDING	512 /* Lease is being broken */
 #define FL_OFDLCK	1024	/* lock is "owned" by struct file */
 #define FL_LAYOUT	2048	/* outstanding pNFS layout */
+#define FL_RECLAIM	4096	/* reclaiming from a reboot server */
 
 #define FL_CLOSE_POSIX (FL_POSIX | FL_CLOSE)
 

include/linux/lockd/bind.h

@@ -27,7 +27,8 @@ struct rpc_task;
 struct nlmsvc_binding {
 	__be32			(*fopen)(struct svc_rqst *,
 						struct nfs_fh *,
-						struct file **);
+						struct file **,
+						int mode);
 	void			(*fclose)(struct file *);
 };
 

include/linux/lockd/lockd.h

@@ -10,6 +10,8 @@
 #ifndef LINUX_LOCKD_LOCKD_H
 #define LINUX_LOCKD_LOCKD_H
 
+/* XXX: a lot of this should really be under fs/lockd. */
+
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <net/ipv6.h>
@@ -154,7 +156,8 @@ struct nlm_rqst {
 struct nlm_file {
 	struct hlist_node	f_list;		/* linked list */
 	struct nfs_fh		f_handle;	/* NFS file handle */
-	struct file *		f_file;		/* VFS file pointer */
+	struct file *		f_file[2];	/* VFS file pointers,
+						   indexed by O_ flags */
 	struct nlm_share *	f_shares;	/* DOS shares */
 	struct list_head	f_blocks;	/* blocked locks */
 	unsigned int		f_locks;	/* guesstimate # of locks */
@@ -267,6 +270,7 @@ typedef int	  (*nlm_host_match_fn_t)(void *cur, struct nlm_host *ref);
 /*
  * Server-side lock handling
  */
+int		  lock_to_openmode(struct file_lock *);
 __be32		  nlmsvc_lock(struct svc_rqst *, struct nlm_file *,
 			      struct nlm_host *, struct nlm_lock *, int,
 			      struct nlm_cookie *, int);
@@ -286,7 +290,7 @@ void		  nlmsvc_locks_init_private(struct file_lock *, struct nlm_host *, pid_t);
  * File handling for the server personality
  */
 __be32		  nlm_lookup_file(struct svc_rqst *, struct nlm_file **,
-					struct nfs_fh *);
+					struct nlm_lock *);
 void		  nlm_release_file(struct nlm_file *);
 void		  nlmsvc_release_lockowner(struct nlm_lock *);
 void		  nlmsvc_mark_resources(struct net *);
@@ -301,7 +305,8 @@ int           nlmsvc_unlock_all_by_ip(struct sockaddr *server_addr);
 
 static inline struct inode *nlmsvc_file_inode(struct nlm_file *file)
 {
-	return locks_inode(file->f_file);
+	return locks_inode(file->f_file[O_RDONLY] ?
+			   file->f_file[O_RDONLY] : file->f_file[O_WRONLY]);
 }
 
 static inline int __nlm_privileged_request4(const struct sockaddr *sap)

include/linux/sunrpc/msg_prot.h

@@ -20,6 +20,7 @@ enum rpc_auth_flavors {
 	RPC_AUTH_DES   = 3,
 	RPC_AUTH_KRB   = 4,
 	RPC_AUTH_GSS   = 6,
+	RPC_AUTH_TLS   = 7,
 	RPC_AUTH_MAXFLAVOR = 8,
 	/* pseudoflavors: */
 	RPC_AUTH_GSS_KRB5  = 390003,

include/linux/sunrpc/svc.h

@@ -19,6 +19,7 @@
 #include <linux/sunrpc/svcauth.h>
 #include <linux/wait.h>
 #include <linux/mm.h>
+#include <linux/pagevec.h>
 
 /* statistics for svc_pool structures */
 struct svc_pool_stats {
@@ -256,6 +257,7 @@ struct svc_rqst {
 	struct page *		*rq_next_page; /* next reply page to use */
 	struct page *		*rq_page_end;  /* one past the last page */
 
+	struct pagevec		rq_pvec;
 	struct kvec		rq_vec[RPCSVC_MAXPAGES]; /* generally useful.. */
 	struct bio_vec		rq_bvec[RPCSVC_MAXPAGES];
 
@@ -502,6 +504,8 @@ struct svc_rqst *svc_rqst_alloc(struct svc_serv *serv,
 					struct svc_pool *pool, int node);
 struct svc_rqst *svc_prepare_thread(struct svc_serv *serv,
 					struct svc_pool *pool, int node);
+void		   svc_rqst_replace_page(struct svc_rqst *rqstp,
+					 struct page *page);
 void		   svc_rqst_free(struct svc_rqst *);
 void		   svc_exit_thread(struct svc_rqst *);
 unsigned int	   svc_pool_map_get(void);
@@ -523,6 +527,7 @@ void		   svc_wake_up(struct svc_serv *);
 void		   svc_reserve(struct svc_rqst *rqstp, int space);
 struct svc_pool *  svc_pool_for_cpu(struct svc_serv *serv, int cpu);
 char *		   svc_print_addr(struct svc_rqst *, char *, size_t);
+const char *	   svc_proc_name(const struct svc_rqst *rqstp);
 int		   svc_encode_result_payload(struct svc_rqst *rqstp,
 					     unsigned int offset,
 					     unsigned int length);

include/linux/sunrpc/svc_rdma.h

@@ -90,9 +90,9 @@ struct svcxprt_rdma {
 	struct ib_pd         *sc_pd;
 
 	spinlock_t	     sc_send_lock;
-	struct list_head     sc_send_ctxts;
+	struct llist_head    sc_send_ctxts;
 	spinlock_t	     sc_rw_ctxt_lock;
-	struct list_head     sc_rw_ctxts;
+	struct llist_head    sc_rw_ctxts;
 
 	u32		     sc_pending_recvs;
 	u32		     sc_recv_batch;
@@ -150,7 +150,7 @@ struct svc_rdma_recv_ctxt {
 };
 
 struct svc_rdma_send_ctxt {
-	struct list_head	sc_list;
+	struct llist_node	sc_node;
 	struct rpc_rdma_cid	sc_cid;
 
 	struct ib_send_wr	sc_send_wr;
@@ -207,6 +207,7 @@ extern void svc_rdma_send_error_msg(struct svcxprt_rdma *rdma,
 				    struct svc_rdma_send_ctxt *sctxt,
 				    struct svc_rdma_recv_ctxt *rctxt,
 				    int status);
+extern void svc_rdma_wake_send_waiters(struct svcxprt_rdma *rdma, int avail);
 extern int svc_rdma_sendto(struct svc_rqst *);
 extern int svc_rdma_result_payload(struct svc_rqst *rqstp, unsigned int offset,
 				   unsigned int length);

include/linux/sunrpc/xdr.h

@@ -95,6 +95,7 @@ xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
 #define	rpc_auth_unix	cpu_to_be32(RPC_AUTH_UNIX)
 #define	rpc_auth_short	cpu_to_be32(RPC_AUTH_SHORT)
 #define	rpc_auth_gss	cpu_to_be32(RPC_AUTH_GSS)
+#define	rpc_auth_tls	cpu_to_be32(RPC_AUTH_TLS)
 
 #define	rpc_call	cpu_to_be32(RPC_CALL)
 #define	rpc_reply	cpu_to_be32(RPC_REPLY)

include/linux/sunrpc/xprt.h

@@ -288,7 +288,6 @@ struct rpc_xprt {
 	const char		*address_strings[RPC_DISPLAY_MAX];
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 	struct dentry		*debugfs;		/* debugfs directory */
-	atomic_t		inject_disconnect;
 #endif
 	struct rcu_head		rcu;
 	const struct xprt_class	*xprt_class;
@@ -502,21 +501,4 @@ static inline int xprt_test_and_set_binding(struct rpc_xprt *xprt)
 	return test_and_set_bit(XPRT_BINDING, &xprt->state);
 }
 
-#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
-extern unsigned int rpc_inject_disconnect;
-static inline void xprt_inject_disconnect(struct rpc_xprt *xprt)
-{
-	if (!rpc_inject_disconnect)
-		return;
-	if (atomic_dec_return(&xprt->inject_disconnect))
-		return;
-	atomic_set(&xprt->inject_disconnect, rpc_inject_disconnect);
-	xprt->ops->inject_disconnect(xprt);
-}
-#else
-static inline void xprt_inject_disconnect(struct rpc_xprt *xprt)
-{
-}
-#endif
-
 #endif /* _LINUX_SUNRPC_XPRT_H */

include/linux/sysctl.h

@@ -48,6 +48,8 @@ typedef int proc_handler(struct ctl_table *ctl, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
 
 int proc_dostring(struct ctl_table *, int, void *, size_t *, loff_t *);
+int proc_dobool(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos);
 int proc_dointvec(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);

include/trace/events/sunrpc.h

@@ -1642,7 +1642,7 @@ TRACE_EVENT(svc_process,
 		__field(u32, vers)
 		__field(u32, proc)
 		__string(service, name)
-		__string(procedure, rqst->rq_procinfo->pc_name)
+		__string(procedure, svc_proc_name(rqst))
 		__string(addr, rqst->rq_xprt ?
 			 rqst->rq_xprt->xpt_remotebuf : "(null)")
 	),
@@ -1652,7 +1652,7 @@ TRACE_EVENT(svc_process,
 		__entry->vers = rqst->rq_vers;
 		__entry->proc = rqst->rq_proc;
 		__assign_str(service, name);
-		__assign_str(procedure, rqst->rq_procinfo->pc_name);
+		__assign_str(procedure, svc_proc_name(rqst));
 		__assign_str(addr, rqst->rq_xprt ?
 			     rqst->rq_xprt->xpt_remotebuf : "(null)");
 	),
@@ -1918,7 +1918,7 @@ TRACE_EVENT(svc_stats_latency,
 	TP_STRUCT__entry(
 		__field(u32, xid)
 		__field(unsigned long, execute)
-		__string(procedure, rqst->rq_procinfo->pc_name)
+		__string(procedure, svc_proc_name(rqst))
 		__string(addr, rqst->rq_xprt->xpt_remotebuf)
 	),
 
@@ -1926,7 +1926,7 @@ TRACE_EVENT(svc_stats_latency,
 		__entry->xid = be32_to_cpu(rqst->rq_xid);
 		__entry->execute = ktime_to_us(ktime_sub(ktime_get(),
 							 rqst->rq_stime));
-		__assign_str(procedure, rqst->rq_procinfo->pc_name);
+		__assign_str(procedure, svc_proc_name(rqst));
 		__assign_str(addr, rqst->rq_xprt->xpt_remotebuf);
 	),
 

include/trace/trace_events.h

@@ -102,6 +102,9 @@ TRACE_MAKE_SYSTEM_STR();
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(char, item, -1)
 
@@ -197,6 +200,9 @@ TRACE_MAKE_SYSTEM_STR();
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)
 
@@ -459,6 +465,9 @@ static struct trace_event_functions trace_event_type_funcs_##call = {	\
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)
 
@@ -507,6 +516,9 @@ static struct trace_event_fields trace_event_fields_##call[] = {	\
 #define __string(item, src) __dynamic_array(char, item,			\
 		    strlen((src) ? (const char *)(src) : "(null)") + 1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, (len) + 1)
+
 /*
  * __bitmask_size_in_bytes_raw is the number of bytes needed to hold
  * num_possible_cpus().
@@ -670,10 +682,20 @@ static inline notrace int trace_event_get_offsets_##call(		\
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
 
+#undef __string_len
+#define __string_len(item, src, len) __dynamic_array(char, item, -1)
+
 #undef __assign_str
 #define __assign_str(dst, src)						\
 	strcpy(__get_str(dst), (src) ? (const char *)(src) : "(null)");
 
+#undef __assign_str_len
+#define __assign_str_len(dst, src, len)					\
+	do {								\
+		memcpy(__get_str(dst), (src), (len));			\
+		__get_str(dst)[len] = '\0';				\
+	} while(0)
+
 #undef __bitmask
 #define __bitmask(item, nr_bits) __dynamic_array(unsigned long, item, -1)
 

include/uapi/linux/nfsd/nfsfh.h

@@ -33,7 +33,6 @@ struct nfs_fhbase_old {
 
 /*
  * This is the new flexible, extensible style NFSv2/v3/v4 file handle.
- * by Neil Brown <neilb@cse.unsw.edu.au> - March 2000
  *
  * The file handle starts with a sequence of four-byte words.
  * The first word contains a version number (1) and three descriptor bytes

kernel/sysctl.c

@@ -536,6 +536,21 @@ static void proc_put_char(void **buf, size_t *size, char c)
 	}
 }
 
+static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp,
+				int *valp,
+				int write, void *data)
+{
+	if (write) {
+		*(bool *)valp = *lvalp;
+	} else {
+		int val = *(bool *)valp;
+
+		*lvalp = (unsigned long)val;
+		*negp = false;
+	}
+	return 0;
+}
+
 static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
 				 int *valp,
 				 int write, void *data)
@@ -798,6 +813,26 @@ static int do_proc_douintvec(struct ctl_table *table, int write,
 				   buffer, lenp, ppos, conv, data);
 }
 
+/**
+ * proc_dobool - read/write a bool
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
+ * values from/to the user buffer, treated as an ASCII string.
+ *
+ * Returns 0 on success.
+ */
+int proc_dobool(struct ctl_table *table, int write, void *buffer,
+		size_t *lenp, loff_t *ppos)
+{
+	return do_proc_dointvec(table, write, buffer, lenp, ppos,
+				do_proc_dobool_conv, NULL);
+}
+
 /**
  * proc_dointvec - read a vector of integers
  * @table: the sysctl table
@@ -1630,6 +1665,12 @@ int proc_dostring(struct ctl_table *table, int write,
 	return -ENOSYS;
 }
 
+int proc_dobool(struct ctl_table *table, int write,
+		void *buffer, size_t *lenp, loff_t *ppos)
+{
+	return -ENOSYS;
+}
+
 int proc_dointvec(struct ctl_table *table, int write,
 		  void *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -3425,6 +3466,7 @@ int __init sysctl_init(void)
  * No sense putting this after each symbol definition, twice,
  * exception granted :-)
  */
+EXPORT_SYMBOL(proc_dobool);
 EXPORT_SYMBOL(proc_dointvec);
 EXPORT_SYMBOL(proc_douintvec);
 EXPORT_SYMBOL(proc_dointvec_jiffies);

lib/Kconfig.debug

@@ -1945,6 +1945,13 @@ config FAIL_MMC_REQUEST
 	  and to test how the mmc host driver handles retries from
 	  the block device.
 
+config FAIL_SUNRPC
+	bool "Fault-injection capability for SunRPC"
+	depends on FAULT_INJECTION_DEBUG_FS && SUNRPC_DEBUG
+	help
+	  Provide fault-injection capability for SunRPC and
+	  its consumers.
+
 config FAULT_INJECTION_STACKTRACE_FILTER
 	bool "stacktrace filter for fault-injection capabilities"
 	depends on FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT

net/sunrpc/auth_gss/svcauth_gss.c

@@ -1980,7 +1980,7 @@ gss_svc_init_net(struct net *net)
 		goto out2;
 	return 0;
 out2:
-	destroy_use_gss_proxy_proc_entry(net);
+	rsi_cache_destroy_net(net);
 out1:
 	rsc_cache_destroy_net(net);
 	return rv;

net/sunrpc/debugfs.c

@@ -8,14 +8,14 @@
 #include <linux/debugfs.h>
 #include <linux/sunrpc/sched.h>
 #include <linux/sunrpc/clnt.h>
+
 #include "netns.h"
+#include "fail.h"
 
 static struct dentry *topdir;
 static struct dentry *rpc_clnt_dir;
 static struct dentry *rpc_xprt_dir;
 
-unsigned int rpc_inject_disconnect;
-
 static int
 tasks_show(struct seq_file *f, void *v)
 {
@@ -235,8 +235,6 @@ rpc_xprt_debugfs_register(struct rpc_xprt *xprt)
 	/* make tasks file */
 	debugfs_create_file("info", S_IFREG | 0400, xprt->debugfs, xprt,
 			    &xprt_info_fops);
-
-	atomic_set(&xprt->inject_disconnect, rpc_inject_disconnect);
 }
 
 void
@@ -246,56 +244,30 @@ rpc_xprt_debugfs_unregister(struct rpc_xprt *xprt)
 	xprt->debugfs = NULL;
 }
 
-static int
-fault_open(struct inode *inode, struct file *filp)
-{
-	filp->private_data = kmalloc(128, GFP_KERNEL);
-	if (!filp->private_data)
-		return -ENOMEM;
-	return 0;
-}
+#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
+struct fail_sunrpc_attr fail_sunrpc = {
+	.attr			= FAULT_ATTR_INITIALIZER,
+};
+EXPORT_SYMBOL_GPL(fail_sunrpc);
 
-static int
-fault_release(struct inode *inode, struct file *filp)
+static void fail_sunrpc_init(void)
 {
-	kfree(filp->private_data);
-	return 0;
-}
+	struct dentry *dir;
 
-static ssize_t
-fault_disconnect_read(struct file *filp, char __user *user_buf,
-		      size_t len, loff_t *offset)
-{
-	char *buffer = (char *)filp->private_data;
-	size_t size;
+	dir = fault_create_debugfs_attr("fail_sunrpc", NULL,
+					&fail_sunrpc.attr);
 
-	size = sprintf(buffer, "%u\n", rpc_inject_disconnect);
-	return simple_read_from_buffer(user_buf, len, offset, buffer, size);
-}
+	debugfs_create_bool("ignore-client-disconnect", S_IFREG | 0600, dir,
+			    &fail_sunrpc.ignore_client_disconnect);
 
-static ssize_t
-fault_disconnect_write(struct file *filp, const char __user *user_buf,
-		       size_t len, loff_t *offset)
+	debugfs_create_bool("ignore-server-disconnect", S_IFREG | 0600, dir,
+			    &fail_sunrpc.ignore_server_disconnect);
+}
+#else
+static void fail_sunrpc_init(void)
 {
-	char buffer[16];
-
-	if (len >= sizeof(buffer))
-		len = sizeof(buffer) - 1;
-	if (copy_from_user(buffer, user_buf, len))
-		return -EFAULT;
-	buffer[len] = '\0';
-	if (kstrtouint(buffer, 10, &rpc_inject_disconnect))
-		return -EINVAL;
-	return len;
 }
-
-static const struct file_operations fault_disconnect_fops = {
-	.owner		= THIS_MODULE,
-	.open		= fault_open,
-	.read		= fault_disconnect_read,
-	.write		= fault_disconnect_write,
-	.release	= fault_release,
-};
+#endif
 
 void __exit
 sunrpc_debugfs_exit(void)
@@ -309,16 +281,11 @@ sunrpc_debugfs_exit(void)
 void __init
 sunrpc_debugfs_init(void)
 {
-	struct dentry *rpc_fault_dir;
-
 	topdir = debugfs_create_dir("sunrpc", NULL);
 
 	rpc_clnt_dir = debugfs_create_dir("rpc_clnt", topdir);
 
 	rpc_xprt_dir = debugfs_create_dir("rpc_xprt", topdir);
 
-	rpc_fault_dir = debugfs_create_dir("inject_fault", topdir);
-
-	debugfs_create_file("disconnect", S_IFREG | 0400, rpc_fault_dir, NULL,
-			    &fault_disconnect_fops);
+	fail_sunrpc_init();
 }

net/sunrpc/fail.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2021, Oracle. All rights reserved.
+ */
+
+#ifndef _NET_SUNRPC_FAIL_H_
+#define _NET_SUNRPC_FAIL_H_
+
+#include <linux/fault-inject.h>
+
+#if IS_ENABLED(CONFIG_FAULT_INJECTION)
+
+struct fail_sunrpc_attr {
+	struct fault_attr	attr;
+
+	bool			ignore_client_disconnect;
+
+	bool			ignore_server_disconnect;
+};
+
+extern struct fail_sunrpc_attr fail_sunrpc;
+
+#endif /* CONFIG_FAULT_INJECTION */
+
+#endif /* _NET_SUNRPC_FAIL_H_ */

net/sunrpc/svc.c

@@ -31,6 +31,8 @@
 
 #include <trace/events/sunrpc.h>
 
+#include "fail.h"
+
 #define RPCDBG_FACILITY	RPCDBG_SVCDSP
 
 static void svc_unregister(const struct svc_serv *serv, struct net *net);
@@ -838,6 +840,27 @@ svc_set_num_threads_sync(struct svc_serv *serv, struct svc_pool *pool, int nrser
 }
 EXPORT_SYMBOL_GPL(svc_set_num_threads_sync);
 
+/**
+ * svc_rqst_replace_page - Replace one page in rq_pages[]
+ * @rqstp: svc_rqst with pages to replace
+ * @page: replacement page
+ *
+ * When replacing a page in rq_pages, batch the release of the
+ * replaced pages to avoid hammering the page allocator.
+ */
+void svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page)
+{
+	if (*rqstp->rq_next_page) {
+		if (!pagevec_space(&rqstp->rq_pvec))
+			__pagevec_release(&rqstp->rq_pvec);
+		pagevec_add(&rqstp->rq_pvec, *rqstp->rq_next_page);
+	}
+
+	get_page(page);
+	*(rqstp->rq_next_page++) = page;
+}
+EXPORT_SYMBOL_GPL(svc_rqst_replace_page);
+
 /*
  * Called from a server thread as it's exiting. Caller must hold the "service
  * mutex" for the service.
@@ -1503,6 +1526,12 @@ svc_process(struct svc_rqst *rqstp)
 	struct svc_serv		*serv = rqstp->rq_server;
 	u32			dir;
 
+#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
+	if (!fail_sunrpc.ignore_server_disconnect &&
+	    should_fail(&fail_sunrpc.attr, 1))
+		svc_xprt_deferred_close(rqstp->rq_xprt);
+#endif
+
 	/*
 	 * Setup response xdr_buf.
 	 * Initially it has just one page
@@ -1629,6 +1658,21 @@ u32 svc_max_payload(const struct svc_rqst *rqstp)
 }
 EXPORT_SYMBOL_GPL(svc_max_payload);
 
+/**
+ * svc_proc_name - Return RPC procedure name in string form
+ * @rqstp: svc_rqst to operate on
+ *
+ * Return value:
+ *   Pointer to a NUL-terminated string
+ */
+const char *svc_proc_name(const struct svc_rqst *rqstp)
+{
+	if (rqstp && rqstp->rq_procinfo)
+		return rqstp->rq_procinfo->pc_name;
+	return "unknown";
+}
+
+
 /**
  * svc_encode_result_payload - mark a range of bytes as a result payload
  * @rqstp: svc_rqst to operate on

net/sunrpc/svc_xprt.c

@@ -539,6 +539,7 @@ static void svc_xprt_release(struct svc_rqst *rqstp)
 	kfree(rqstp->rq_deferred);
 	rqstp->rq_deferred = NULL;
 
+	pagevec_release(&rqstp->rq_pvec);
 	svc_free_res_pages(rqstp);
 	rqstp->rq_res.page_len = 0;
 	rqstp->rq_res.page_base = 0;
@@ -664,6 +665,8 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
 	struct xdr_buf *arg = &rqstp->rq_arg;
 	unsigned long pages, filled;
 
+	pagevec_init(&rqstp->rq_pvec);
+
 	pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT;
 	if (pages > RPCSVC_MAXPAGES) {
 		pr_warn_once("svc: warning: pages=%lu > RPCSVC_MAXPAGES=%lu\n",

net/sunrpc/xprt.c

@@ -56,6 +56,7 @@
 
 #include "sunrpc.h"
 #include "sysfs.h"
+#include "fail.h"
 
 /*
  * Local variables
@@ -855,6 +856,19 @@ xprt_init_autodisconnect(struct timer_list *t)
 	queue_work(xprtiod_workqueue, &xprt->task_cleanup);
 }
 
+#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
+static void xprt_inject_disconnect(struct rpc_xprt *xprt)
+{
+	if (!fail_sunrpc.ignore_client_disconnect &&
+	    should_fail(&fail_sunrpc.attr, 1))
+		xprt->ops->inject_disconnect(xprt);
+}
+#else
+static inline void xprt_inject_disconnect(struct rpc_xprt *xprt)
+{
+}
+#endif
+
 bool xprt_lock_connect(struct rpc_xprt *xprt,
 		struct rpc_task *task,
 		void *cookie)

net/sunrpc/xprtrdma/svc_rdma_rw.c

@@ -35,6 +35,7 @@ static void svc_rdma_wc_read_done(struct ib_cq *cq, struct ib_wc *wc);
  * controlling svcxprt_rdma is destroyed.
  */
 struct svc_rdma_rw_ctxt {
+	struct llist_node	rw_node;
 	struct list_head	rw_list;
 	struct rdma_rw_ctx	rw_ctx;
 	unsigned int		rw_nents;
@@ -53,19 +54,19 @@ static struct svc_rdma_rw_ctxt *
 svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
 {
 	struct svc_rdma_rw_ctxt *ctxt;
+	struct llist_node *node;
 
 	spin_lock(&rdma->sc_rw_ctxt_lock);
-
-	ctxt = svc_rdma_next_ctxt(&rdma->sc_rw_ctxts);
-	if (ctxt) {
-		list_del(&ctxt->rw_list);
+	node = llist_del_first(&rdma->sc_rw_ctxts);
 	spin_unlock(&rdma->sc_rw_ctxt_lock);
+	if (node) {
+		ctxt = llist_entry(node, struct svc_rdma_rw_ctxt, rw_node);
 	} else {
-		spin_unlock(&rdma->sc_rw_ctxt_lock);
 		ctxt = kmalloc(struct_size(ctxt, rw_first_sgl, SG_CHUNK_SIZE),
 			       GFP_KERNEL);
 		if (!ctxt)
 			goto out_noctx;
+
 		INIT_LIST_HEAD(&ctxt->rw_list);
 	}
 
@@ -83,14 +84,18 @@ svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
 	return NULL;
 }
 
-static void svc_rdma_put_rw_ctxt(struct svcxprt_rdma *rdma,
-				 struct svc_rdma_rw_ctxt *ctxt)
+static void __svc_rdma_put_rw_ctxt(struct svcxprt_rdma *rdma,
+				   struct svc_rdma_rw_ctxt *ctxt,
+				   struct llist_head *list)
 {
 	sg_free_table_chained(&ctxt->rw_sg_table, SG_CHUNK_SIZE);
+	llist_add(&ctxt->rw_node, list);
+}
 
-	spin_lock(&rdma->sc_rw_ctxt_lock);
-	list_add(&ctxt->rw_list, &rdma->sc_rw_ctxts);
-	spin_unlock(&rdma->sc_rw_ctxt_lock);
+static void svc_rdma_put_rw_ctxt(struct svcxprt_rdma *rdma,
+				 struct svc_rdma_rw_ctxt *ctxt)
+{
+	__svc_rdma_put_rw_ctxt(rdma, ctxt, &rdma->sc_rw_ctxts);
 }
 
 /**
@@ -101,9 +106,10 @@ static void svc_rdma_put_rw_ctxt(struct svcxprt_rdma *rdma,
 void svc_rdma_destroy_rw_ctxts(struct svcxprt_rdma *rdma)
 {
 	struct svc_rdma_rw_ctxt *ctxt;
+	struct llist_node *node;
 
-	while ((ctxt = svc_rdma_next_ctxt(&rdma->sc_rw_ctxts)) != NULL) {
-		list_del(&ctxt->rw_list);
+	while ((node = llist_del_first(&rdma->sc_rw_ctxts)) != NULL) {
+		ctxt = llist_entry(node, struct svc_rdma_rw_ctxt, rw_node);
 		kfree(ctxt);
 	}
 }
@@ -171,20 +177,35 @@ static void svc_rdma_cc_init(struct svcxprt_rdma *rdma,
 	cc->cc_sqecount = 0;
 }
 
+/*
+ * The consumed rw_ctx's are cleaned and placed on a local llist so
+ * that only one atomic llist operation is needed to put them all
+ * back on the free list.
+ */
 static void svc_rdma_cc_release(struct svc_rdma_chunk_ctxt *cc,
 				enum dma_data_direction dir)
 {
 	struct svcxprt_rdma *rdma = cc->cc_rdma;
+	struct llist_node *first, *last;
 	struct svc_rdma_rw_ctxt *ctxt;
+	LLIST_HEAD(free);
 
+	first = last = NULL;
 	while ((ctxt = svc_rdma_next_ctxt(&cc->cc_rwctxts)) != NULL) {
 		list_del(&ctxt->rw_list);
 
 		rdma_rw_ctx_destroy(&ctxt->rw_ctx, rdma->sc_qp,
 				    rdma->sc_port_num, ctxt->rw_sg_table.sgl,
 				    ctxt->rw_nents, dir);
-		svc_rdma_put_rw_ctxt(rdma, ctxt);
+		__svc_rdma_put_rw_ctxt(rdma, ctxt, &free);
+
+		ctxt->rw_node.next = first;
+		first = &ctxt->rw_node;
+		if (!last)
+			last = first;
 	}
+	if (first)
+		llist_add_batch(first, last, &rdma->sc_rw_ctxts);
 }
 
 /* State for sending a Write or Reply chunk.
@@ -248,8 +269,7 @@ static void svc_rdma_write_done(struct ib_cq *cq, struct ib_wc *wc)
 
 	trace_svcrdma_wc_write(wc, &cc->cc_cid);
 
-	atomic_add(cc->cc_sqecount, &rdma->sc_sq_avail);
-	wake_up(&rdma->sc_send_wait);
+	svc_rdma_wake_send_waiters(rdma, cc->cc_sqecount);
 
 	if (unlikely(wc->status != IB_WC_SUCCESS))
 		svc_xprt_deferred_close(&rdma->sc_xprt);
@@ -304,9 +324,7 @@ static void svc_rdma_wc_read_done(struct ib_cq *cq, struct ib_wc *wc)
 
 	trace_svcrdma_wc_read(wc, &cc->cc_cid);
 
-	atomic_add(cc->cc_sqecount, &rdma->sc_sq_avail);
-	wake_up(&rdma->sc_send_wait);
-
+	svc_rdma_wake_send_waiters(rdma, cc->cc_sqecount);
 	cc->cc_status = wc->status;
 	complete(&cc->cc_done);
 	return;

net/sunrpc/xprtrdma/svc_rdma_sendto.c

@@ -113,13 +113,6 @@
 
 static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc);
 
-static inline struct svc_rdma_send_ctxt *
-svc_rdma_next_send_ctxt(struct list_head *list)
-{
-	return list_first_entry_or_null(list, struct svc_rdma_send_ctxt,
-					sc_list);
-}
-
 static void svc_rdma_send_cid_init(struct svcxprt_rdma *rdma,
 				   struct rpc_rdma_cid *cid)
 {
@@ -182,9 +175,10 @@ svc_rdma_send_ctxt_alloc(struct svcxprt_rdma *rdma)
 void svc_rdma_send_ctxts_destroy(struct svcxprt_rdma *rdma)
 {
 	struct svc_rdma_send_ctxt *ctxt;
+	struct llist_node *node;
 
-	while ((ctxt = svc_rdma_next_send_ctxt(&rdma->sc_send_ctxts))) {
-		list_del(&ctxt->sc_list);
+	while ((node = llist_del_first(&rdma->sc_send_ctxts)) != NULL) {
+		ctxt = llist_entry(node, struct svc_rdma_send_ctxt, sc_node);
 		ib_dma_unmap_single(rdma->sc_pd->device,
 				    ctxt->sc_sges[0].addr,
 				    rdma->sc_max_req_size,
@@ -204,12 +198,13 @@ void svc_rdma_send_ctxts_destroy(struct svcxprt_rdma *rdma)
 struct svc_rdma_send_ctxt *svc_rdma_send_ctxt_get(struct svcxprt_rdma *rdma)
 {
 	struct svc_rdma_send_ctxt *ctxt;
+	struct llist_node *node;
 
 	spin_lock(&rdma->sc_send_lock);
-	ctxt = svc_rdma_next_send_ctxt(&rdma->sc_send_ctxts);
-	if (!ctxt)
+	node = llist_del_first(&rdma->sc_send_ctxts);
+	if (!node)
 		goto out_empty;
-	list_del(&ctxt->sc_list);
+	ctxt = llist_entry(node, struct svc_rdma_send_ctxt, sc_node);
 	spin_unlock(&rdma->sc_send_lock);
 
 out:
@@ -253,9 +248,21 @@ void svc_rdma_send_ctxt_put(struct svcxprt_rdma *rdma,
 					     ctxt->sc_sges[i].length);
 	}
 
-	spin_lock(&rdma->sc_send_lock);
-	list_add(&ctxt->sc_list, &rdma->sc_send_ctxts);
-	spin_unlock(&rdma->sc_send_lock);
+	llist_add(&ctxt->sc_node, &rdma->sc_send_ctxts);
+}
+
+/**
+ * svc_rdma_wake_send_waiters - manage Send Queue accounting
+ * @rdma: controlling transport
+ * @avail: Number of additional SQEs that are now available
+ *
+ */
+void svc_rdma_wake_send_waiters(struct svcxprt_rdma *rdma, int avail)
+{
+	atomic_add(avail, &rdma->sc_sq_avail);
+	smp_mb__after_atomic();
+	if (unlikely(waitqueue_active(&rdma->sc_send_wait)))
+		wake_up(&rdma->sc_send_wait);
 }
 
 /**
@@ -275,11 +282,9 @@ static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc)
 
 	trace_svcrdma_wc_send(wc, &ctxt->sc_cid);
 
+	svc_rdma_wake_send_waiters(rdma, 1);
 	complete(&ctxt->sc_done);
 
-	atomic_inc(&rdma->sc_sq_avail);
-	wake_up(&rdma->sc_send_wait);
-
 	if (unlikely(wc->status != IB_WC_SUCCESS))
 		svc_xprt_deferred_close(&rdma->sc_xprt);
 }

net/sunrpc/xprtrdma/svc_rdma_transport.c

@@ -136,9 +136,9 @@ static struct svcxprt_rdma *svc_rdma_create_xprt(struct svc_serv *serv,
 	svc_xprt_init(net, &svc_rdma_class, &cma_xprt->sc_xprt, serv);
 	INIT_LIST_HEAD(&cma_xprt->sc_accept_q);
 	INIT_LIST_HEAD(&cma_xprt->sc_rq_dto_q);
-	INIT_LIST_HEAD(&cma_xprt->sc_send_ctxts);
+	init_llist_head(&cma_xprt->sc_send_ctxts);
 	init_llist_head(&cma_xprt->sc_recv_ctxts);
-	INIT_LIST_HEAD(&cma_xprt->sc_rw_ctxts);
+	init_llist_head(&cma_xprt->sc_rw_ctxts);
 	init_waitqueue_head(&cma_xprt->sc_send_wait);
 
 	spin_lock_init(&cma_xprt->sc_lock);
@@ -545,7 +545,6 @@ static void __svc_rdma_free(struct work_struct *work)
 {
 	struct svcxprt_rdma *rdma =
 		container_of(work, struct svcxprt_rdma, sc_work);
-	struct svc_xprt *xprt = &rdma->sc_xprt;
 
 	/* This blocks until the Completion Queues are empty */
 	if (rdma->sc_qp && !IS_ERR(rdma->sc_qp))
@@ -553,12 +552,6 @@ static void __svc_rdma_free(struct work_struct *work)
 
 	svc_rdma_flush_recv_queues(rdma);
 
-	/* Final put of backchannel client transport */
-	if (xprt->xpt_bc_xprt) {
-		xprt_put(xprt->xpt_bc_xprt);
-		xprt->xpt_bc_xprt = NULL;
-	}
-
 	svc_rdma_destroy_rw_ctxts(rdma);
 	svc_rdma_send_ctxts_destroy(rdma);
 	svc_rdma_recv_ctxts_destroy(rdma);

samples/trace_events/trace-events-sample.h

@@ -141,6 +141,33 @@
  *         In most cases, the __assign_str() macro will take the same
  *         parameters as the __string() macro had to declare the string.
  *
+ *   __string_len: This is a helper to a __dynamic_array, but it understands
+ *	   that the array has characters in it, and with the combined
+ *         use of __assign_str_len(), it will allocate 'len' + 1 bytes
+ *         in the ring buffer and add a '\0' to the string. This is
+ *         useful if the string being saved has no terminating '\0' byte.
+ *         It requires that the length of the string is known as it acts
+ *         like a memcpy().
+ *
+ *         Declared with:
+ *
+ *         __string_len(foo, bar, len)
+ *
+ *         To assign this string, use the helper macro __assign_str_len().
+ *
+ *         __assign_str(foo, bar, len);
+ *
+ *         Then len + 1 is allocated to the ring buffer, and a nul terminating
+ *         byte is added. This is similar to:
+ *
+ *         memcpy(__get_str(foo), bar, len);
+ *         __get_str(foo)[len] = 0;
+ *
+ *        The advantage of using this over __dynamic_array, is that it
+ *        takes care of allocating the extra byte on the ring buffer
+ *        for the '\0' terminating byte, and __get_str(foo) can be used
+ *        in the TP_printk().
+ *
  *   __bitmask: This is another kind of __dynamic_array, but it expects
  *         an array of longs, and the number of bits to parse. It takes
  *         two parameters (name, nr_bits), where name is the name of the