[src/trunk]: src/sys Add vfs_trybusy() and mountlist_iterator_trynext() and u...

[hannken <hannken%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/e3bc4036316c
branches:  trunk
changeset: 353008:e3bc4036316c
user:      hannken <hannken%NetBSD.org@localhost>
date:      Mon Apr 17 08:34:27 2017 +0000

description:
Add vfs_trybusy() and mountlist_iterator_trynext() and use it for the syncer.

diffstat:

 sys/kern/vfs_mount.c |  53 ++++++++++++++++++++++++++++++++++++++++++++-------
 sys/kern/vfs_subr.c  |   6 ++--
 sys/sys/mount.h      |   4 ++-
 3 files changed, 51 insertions(+), 12 deletions(-)

diffs (161 lines):

diff -r c1aaae609bb4 -r e3bc4036316c sys/kern/vfs_mount.c
--- a/sys/kern/vfs_mount.c      Mon Apr 17 08:33:40 2017 +0000
+++ b/sys/kern/vfs_mount.c      Mon Apr 17 08:34:27 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_mount.c,v 1.57 2017/04/17 08:32:55 hannken Exp $   */
+/*     $NetBSD: vfs_mount.c,v 1.58 2017/04/17 08:34:27 hannken Exp $   */
 
 /*-
  * Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.57 2017/04/17 08:32:55 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.58 2017/04/17 08:34:27 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -311,13 +311,17 @@
  * => The caller must hold a pre-existing reference to the mount.
  * => Will fail if the file system is being unmounted, or is unmounted.
  */
-int
-vfs_busy(struct mount *mp)
+static inline int
+_vfs_busy(struct mount *mp, bool wait)
 {
 
        KASSERT(mp->mnt_refcnt > 0);
 
-       mutex_enter(&mp->mnt_unmounting);
+       if (wait) {
+               mutex_enter(&mp->mnt_unmounting);
+       } else if (!mutex_tryenter(&mp->mnt_unmounting)) {
+               return EBUSY;
+       }
        if (__predict_false((mp->mnt_iflag & IMNT_GONE) != 0)) {
                mutex_exit(&mp->mnt_unmounting);
                return ENOENT;
@@ -329,6 +333,20 @@
        return 0;
 }
 
+int
+vfs_busy(struct mount *mp)
+{
+
+       return _vfs_busy(mp, true);
+}
+
+int
+vfs_trybusy(struct mount *mp)
+{
+
+       return _vfs_busy(mp, false);
+}
+
 /*
  * Unbusy a busy filesystem.
  *
@@ -1524,11 +1542,12 @@
  * Return the next mount or NULL for this iterator.
  * Mark it busy on success.
  */
-struct mount *
-mountlist_iterator_next(mount_iterator_t *mi)
+static inline struct mount *
+_mountlist_iterator_next(mount_iterator_t *mi, bool wait)
 {
        struct mountlist_entry *me, *marker = &mi->mi_entry;
        struct mount *mp;
+       int error;
 
        if (marker->me_mount != NULL) {
                vfs_unbusy(marker->me_mount);
@@ -1559,7 +1578,11 @@
                mutex_exit(&mountlist_lock);
 
                /* Try to mark this mount busy and return on success. */
-               if (vfs_busy(mp) == 0) {
+               if (wait)
+                       error = vfs_busy(mp);
+               else
+                       error = vfs_trybusy(mp);
+               if (error == 0) {
                        vfs_rele(mp);
                        marker->me_mount = mp;
                        return mp;
@@ -1569,6 +1592,20 @@
        }
 }
 
+struct mount *
+mountlist_iterator_next(mount_iterator_t *mi)
+{
+
+       return _mountlist_iterator_next(mi, true);
+}
+
+struct mount *
+mountlist_iterator_trynext(mount_iterator_t *mi)
+{
+
+       return _mountlist_iterator_next(mi, false);
+}
+
 /*
  * Attach new mount to the end of the mount list.
  */
diff -r c1aaae609bb4 -r e3bc4036316c sys/kern/vfs_subr.c
--- a/sys/kern/vfs_subr.c       Mon Apr 17 08:33:40 2017 +0000
+++ b/sys/kern/vfs_subr.c       Mon Apr 17 08:34:27 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_subr.c,v 1.462 2017/04/12 10:26:33 hannken Exp $   */
+/*     $NetBSD: vfs_subr.c,v 1.463 2017/04/17 08:34:27 hannken Exp $   */
 
 /*-
  * Copyright (c) 1997, 1998, 2004, 2005, 2007, 2008 The NetBSD Foundation, Inc.
@@ -68,7 +68,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_subr.c,v 1.462 2017/04/12 10:26:33 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_subr.c,v 1.463 2017/04/17 08:34:27 hannken Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
@@ -775,7 +775,7 @@
                 * Sync mounts whose dirty time has expired.
                 */
                mountlist_iterator_init(&iter);
-               while ((mp = mountlist_iterator_next(iter)) != NULL) {
+               while ((mp = mountlist_iterator_trynext(iter)) != NULL) {
                        if ((mp->mnt_iflag & IMNT_ONWORKLIST) == 0 ||
                            mp->mnt_synclist_slot != syncer_delayno) {
                                continue;
diff -r c1aaae609bb4 -r e3bc4036316c sys/sys/mount.h
--- a/sys/sys/mount.h   Mon Apr 17 08:33:40 2017 +0000
+++ b/sys/sys/mount.h   Mon Apr 17 08:34:27 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mount.h,v 1.225 2017/04/17 08:32:01 hannken Exp $      */
+/*     $NetBSD: mount.h,v 1.226 2017/04/17 08:34:27 hannken Exp $      */
 
 /*
  * Copyright (c) 1989, 1991, 1993
@@ -417,6 +417,7 @@
 bool   vfs_unmountall1(struct lwp *, bool, bool);
 bool   vfs_unmount_forceone(struct lwp *);
 int    vfs_busy(struct mount *);
+int    vfs_trybusy(struct mount *);
 int    vfs_rootmountalloc(const char *, const char *, struct mount **);
 void   vfs_unbusy(struct mount *);
 int    vfs_attach(struct vfsops *);
@@ -496,6 +497,7 @@
 void   mountlist_iterator_init(mount_iterator_t **);
 void   mountlist_iterator_destroy(mount_iterator_t *);
 struct mount *mountlist_iterator_next(mount_iterator_t *);
+struct mount *mountlist_iterator_trynext(mount_iterator_t *);
 struct mount *_mountlist_next(struct mount *);
 void   mountlist_append(struct mount *);
 void   mountlist_remove(struct mount *);