kern.maxlockf for byte range lock limit

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

Hello

I recently hit a bug where mariadb import failed befause of 
maxlocksperuid limit:a
http://mail-index.netbsd.org/netbsd-users/2021/07/09/msg027330.html

Attached is a patch that documents ENOMEM for fcntl() and flock()
and that adds a sysctl kern.maxlockf to make the limit configurable.

Opinions?

-- 
Emmanuel Dreyfus
manu%netbsd.org@localhost

Index: sys/sys/sysctl.h
===================================================================
RCS file: /cvsroot/src/sys/sys/sysctl.h,v
retrieving revision 1.233
diff -U4 -r1.233 sysctl.h
--- sys/sys/sysctl.h	13 Apr 2021 01:10:24 -0000	1.233
+++ sys/sys/sysctl.h	9 Jul 2021 14:29:32 -0000
@@ -274,8 +274,9 @@
 #define	KERN_SYSVIPC		82	/* node: SysV IPC parameters */
 #define	KERN_BOOTTIME		83	/* struct: time kernel was booted */
 #define	KERN_EVCNT		84	/* struct: evcnts */
 #define	KERN_SOFIXEDBUF		85	/* bool: fixed socket buffer sizes */
+#define	KERN_MAXLOCKF		86	/* int: max file locks per user */
 
 /*
  *  KERN_CLOCKRATE structure
  */
Index: sys/kern/init_sysctl.c
===================================================================
RCS file: /cvsroot/src/sys/kern/init_sysctl.c,v
retrieving revision 1.227
diff -U4 -r1.227 init_sysctl.c
--- sys/kern/init_sysctl.c	20 Sep 2020 12:51:57 -0000	1.227
+++ sys/kern/init_sysctl.c	9 Jul 2021 14:29:32 -0000
@@ -146,8 +146,10 @@
 {
 	extern int kern_logsigexit;	/* defined in kern/kern_sig.c */
 	extern fixpt_t ccpu;		/* defined in kern/kern_synch.c */
 	extern int dumponpanic;		/* defined in kern/subr_prf.c */
+	extern int maxlocksperuid;	/* defined in kern/vfs_lockf.c */
+
 	const struct sysctlnode *rnode;
 
 	sysctl_createv(clog, 0, NULL, NULL,
 		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
@@ -587,8 +589,14 @@
 			CTLTYPE_INT, "messages",
 			SYSCTL_DESCR("Kernel message verbosity"),
 			sysctl_kern_messages, 0, NULL, 0,
 			CTL_KERN, CTL_CREATE, CTL_EOL);
+	sysctl_createv(clog, 0, NULL, NULL,
+		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
+		       CTLTYPE_INT, "maxlockf",
+		       SYSCTL_DESCR("File byte range lock limit per uid"),
+		       NULL, 0, &maxlocksperuid, 0,
+		       CTL_KERN, KERN_MAXLOCKF, CTL_EOL);
 }
 
 SYSCTL_SETUP(sysctl_hw_misc_setup, "sysctl hw subtree misc setup")
 {
Index: lib/libc/sys/fcntl.2
===================================================================
RCS file: /cvsroot/src/lib/libc/sys/fcntl.2,v
retrieving revision 1.45
diff -U4 -r1.45 fcntl.2
--- lib/libc/sys/fcntl.2	27 Sep 2019 07:20:07 -0000	1.45
+++ lib/libc/sys/fcntl.2	9 Jul 2021 14:29:32 -0000
@@ -548,8 +548,19 @@
 .Fa cmd
 is
 .Dv F_GETPATH
 and insufficient memory is available.
+.Pp
+The argument
+.Fa cmd
+is
+.Dv F_GETLK ,
+.Dv F_SETLK ,
+or
+.Dv F_SETLKW ,
+and the file byte range lock limit for the current unprivilegied user 
+has been reached. It can be modifed using sysctl
+.Li kern.maxlockf .
 .It Bq Er ERANGE
 The argument
 .Fa cmd
 is
Index: lib/libc/sys/flock.2
===================================================================
RCS file: /cvsroot/src/lib/libc/sys/flock.2,v
retrieving revision 1.22
diff -U4 -r1.22 flock.2
--- lib/libc/sys/flock.2	15 Oct 2011 21:35:50 -0000	1.22
+++ lib/libc/sys/flock.2	9 Jul 2021 14:29:32 -0000
@@ -136,8 +136,12 @@
 .Dv LOCK_EX ,
 .Dv LOCK_SH ,
 or
 .Dv LOCK_UN .
+.It Bq Eq ENOMEM
+The file byte range lock limit for the current unprivilegied user 
+has been reached. It can be modifed using sysctl
+.Li kern.maxlockf .
 .It Bq Er EOPNOTSUPP
 The argument
 .Fa fd
 refers to an object other than a file.