FreeBSD: convert teardown inactive lock to a read-mostly sleepable lock

The lock is taken all the time and as a regular read-write lock
avoidably serves as a mount point-wide contention point.

This forward ports FreeBSD revision r357322.

To quote aforementioned commit:

Sample result doing an incremental -j 40 build:
before: 173.30s user 458.97s system 2595% cpu 24.358 total
after:  168.58s user 254.92s system 2211% cpu 19.147 total

Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Ryan Moeller <[email protected]>
Signed-off-by: Mateusz Guzik <[email protected]>
Closes #10896 

1 files changed, 64 insertions, 1 deletions

diff --git a/include/os/freebsd/zfs/sys/zfs_vfsops_os.h b/include/os/freebsd/zfs/sys/zfs_vfsops_os.h
index 1b80ee7cb..e816e3933 100644
--- a/include/os/freebsd/zfs/sys/zfs_vfsops_os.h
+++ b/include/os/freebsd/zfs/sys/zfs_vfsops_os.h
@@ -27,18 +27,31 @@
 #ifndef	_SYS_FS_ZFS_VFSOPS_H
 #define	_SYS_FS_ZFS_VFSOPS_H
 
+#if __FreeBSD_version >= 1300109
+#define	TEARDOWN_INACTIVE_RMS
+#endif
+
 #include <sys/dataset_kstats.h>
 #include <sys/list.h>
 #include <sys/vfs.h>
 #include <sys/zil.h>
 #include <sys/sa.h>
 #include <sys/rrwlock.h>
+#ifdef TEARDOWN_INACTIVE_RMS
+#include <sys/rmlock.h>
+#endif
 #include <sys/zfs_ioctl.h>
 
 #ifdef	__cplusplus
 extern "C" {
 #endif
 
+#ifdef TEARDOWN_INACTIVE_RMS
+typedef struct rmslock zfs_teardown_lock_t;
+#else
+#define	zfs_teardown_lock_t krwlock_t
+#endif
+
 typedef struct zfsvfs zfsvfs_t;
 struct znode;
 
@@ -67,7 +80,7 @@ struct zfsvfs {
 	boolean_t	z_atime;	/* enable atimes mount option */
 	boolean_t	z_unmounted;	/* unmounted */
 	rrmlock_t	z_teardown_lock;
-	krwlock_t	z_teardown_inactive_lock;
+	zfs_teardown_lock_t z_teardown_inactive_lock;
 	list_t		z_all_znodes;	/* all vnodes in the fs */
 	uint64_t	z_nr_znodes;	/* number of znodes in the fs */
 	kmutex_t	z_znodes_lock;	/* lock for z_all_znodes */
@@ -98,6 +111,56 @@ struct zfsvfs {
 	struct task	z_unlinked_drain_task;
 };
 
+#ifdef TEARDOWN_INACTIVE_RMS
+#define	ZFS_INIT_TEARDOWN_INACTIVE(zfsvfs)	\
+	rms_init(&(zfsvfs)->z_teardown_inactive_lock, "zfs teardown inactive")
+
+#define	ZFS_DESTROY_TEARDOWN_INACTIVE(zfsvfs)	\
+	rms_destroy(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_TRYRLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rms_try_rlock(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_RLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rms_rlock(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_RUNLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rms_runlock(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_WLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rms_wlock(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_WUNLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rms_wunlock(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_TEARDOWN_INACTIVE_WLOCKED(zfsvfs)	\
+	rms_wowned(&(zfsvfs)->z_teardown_inactive_lock)
+#else
+#define	ZFS_INIT_TEARDOWN_INACTIVE(zfsvfs)	\
+	rw_init(&(zfsvfs)->z_teardown_inactive_lock, NULL, RW_DEFAULT, NULL)
+
+#define	ZFS_DESTROY_TEARDOWN_INACTIVE(zfsvfs)	\
+	rw_destroy(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_TRYRLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rw_tryenter(&(zfsvfs)->z_teardown_inactive_lock, RW_READER)
+
+#define	ZFS_RLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rw_enter(&(zfsvfs)->z_teardown_inactive_lock, RW_READER)
+
+#define	ZFS_RUNLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rw_exit(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_WLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rw_enter(&(zfsvfs)->z_teardown_inactive_lock, RW_WRITER)
+
+#define	ZFS_WUNLOCK_TEARDOWN_INACTIVE(zfsvfs)	\
+	rw_exit(&(zfsvfs)->z_teardown_inactive_lock)
+
+#define	ZFS_TEARDOWN_INACTIVE_WLOCKED(zfsvfs)	\
+	RW_WRITE_HELD(&(zfsvfs)->z_teardown_inactive_lock)
+#endif
+
 #define	ZSB_XATTR	0x0001		/* Enable user xattrs */
 /*
  * Normal filesystems (those not under .zfs/snapshot) have a total