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Date:      Mon, 19 Aug 2019 23:09:38 +0000 (UTC)
From:      Jeff Roberson <jeff@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r351241 - in head/sys: cddl/contrib/opensolaris/uts/common/fs/zfs kern vm
Message-ID:  <201908192309.x7JN9cgL095450@repo.freebsd.org>

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Author: jeff
Date: Mon Aug 19 23:09:38 2019
New Revision: 351241
URL: https://svnweb.freebsd.org/changeset/base/351241

Log:
  Use an atomic reference count for paging in progress so that callers do not
  require the object lock.
  
  Reviewed by:	markj
  Tested by:	pho (as part of a larger branch)
  Sponsored by:	Netflix
  Differential Revision:	https://reviews.freebsd.org/D21311

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
  head/sys/kern/vfs_cluster.c
  head/sys/kern/vfs_subr.c
  head/sys/vm/swap_pager.c
  head/sys/vm/vm_object.c
  head/sys/vm/vm_object.h

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	Mon Aug 19 23:01:59 2019	(r351240)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	Mon Aug 19 23:09:38 2019	(r351241)
@@ -451,7 +451,7 @@ page_unbusy(vm_page_t pp)
 {
 
 	vm_page_sunbusy(pp);
-	vm_object_pip_subtract(pp->object, 1);
+	vm_object_pip_wakeup(pp->object);
 }
 
 static vm_page_t
@@ -523,6 +523,7 @@ update_pages(vnode_t *vp, int64_t start, int len, objs
 
 	off = start & PAGEOFFSET;
 	zfs_vmobject_wlock(obj);
+	vm_object_pip_add(obj, 1);
 	for (start &= PAGEMASK; len > 0; start += PAGESIZE) {
 		vm_page_t pp;
 		int nbytes = imin(PAGESIZE - off, len);
@@ -541,7 +542,7 @@ update_pages(vnode_t *vp, int64_t start, int len, objs
 		len -= nbytes;
 		off = 0;
 	}
-	vm_object_pip_wakeupn(obj, 0);
+	vm_object_pip_wakeup(obj);
 	zfs_vmobject_wunlock(obj);
 }
 

Modified: head/sys/kern/vfs_cluster.c
==============================================================================
--- head/sys/kern/vfs_cluster.c	Mon Aug 19 23:01:59 2019	(r351240)
+++ head/sys/kern/vfs_cluster.c	Mon Aug 19 23:09:38 2019	(r351241)
@@ -479,7 +479,8 @@ cluster_rbuild(struct vnode *vp, u_quad_t filesize, da
 			}
 			if (tsize > 0) {
 clean_sbusy:
-				vm_object_pip_add(tbp->b_bufobj->bo_object, -j);
+				vm_object_pip_wakeupn(tbp->b_bufobj->bo_object,
+				    j);
 				for (k = 0; k < j; k++)
 					vm_page_sunbusy(tbp->b_pages[k]);
 				VM_OBJECT_WUNLOCK(tbp->b_bufobj->bo_object);

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Mon Aug 19 23:01:59 2019	(r351240)
+++ head/sys/kern/vfs_subr.c	Mon Aug 19 23:09:38 2019	(r351241)
@@ -1786,13 +1786,9 @@ bufobj_invalbuf(struct bufobj *bo, int flags, int slpf
 	 */
 	do {
 		bufobj_wwait(bo, 0, 0);
-		if ((flags & V_VMIO) == 0) {
+		if ((flags & V_VMIO) == 0 && bo->bo_object != NULL) {
 			BO_UNLOCK(bo);
-			if (bo->bo_object != NULL) {
-				VM_OBJECT_WLOCK(bo->bo_object);
-				vm_object_pip_wait(bo->bo_object, "bovlbx");
-				VM_OBJECT_WUNLOCK(bo->bo_object);
-			}
+			vm_object_pip_wait_unlocked(bo->bo_object, "bovlbx");
 			BO_LOCK(bo);
 		}
 	} while (bo->bo_numoutput > 0);

Modified: head/sys/vm/swap_pager.c
==============================================================================
--- head/sys/vm/swap_pager.c	Mon Aug 19 23:01:59 2019	(r351240)
+++ head/sys/vm/swap_pager.c	Mon Aug 19 23:09:38 2019	(r351241)
@@ -1256,7 +1256,7 @@ swap_pager_getpages(vm_object_t object, vm_page_t *ma,
 	while ((ma[0]->oflags & VPO_SWAPINPROG) != 0) {
 		ma[0]->oflags |= VPO_SWAPSLEEP;
 		VM_CNT_INC(v_intrans);
-		if (VM_OBJECT_SLEEP(object, &object->paging_in_progress, PSWP,
+		if (VM_OBJECT_SLEEP(object, &object->handle, PSWP,
 		    "swread", hz * 20)) {
 			printf(
 "swap_pager: indefinite wait buffer: bufobj: %p, blkno: %jd, size: %ld\n",
@@ -1531,7 +1531,7 @@ swp_pager_async_iodone(struct buf *bp)
 		m->oflags &= ~VPO_SWAPINPROG;
 		if (m->oflags & VPO_SWAPSLEEP) {
 			m->oflags &= ~VPO_SWAPSLEEP;
-			wakeup(&object->paging_in_progress);
+			wakeup(&object->handle);
 		}
 
 		if (bp->b_ioflags & BIO_ERROR) {

Modified: head/sys/vm/vm_object.c
==============================================================================
--- head/sys/vm/vm_object.c	Mon Aug 19 23:01:59 2019	(r351240)
+++ head/sys/vm/vm_object.c	Mon Aug 19 23:09:38 2019	(r351241)
@@ -80,6 +80,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 #include <sys/mutex.h>
 #include <sys/proc.h>		/* for curproc, pageproc */
+#include <sys/refcount.h>
 #include <sys/socket.h>
 #include <sys/resourcevar.h>
 #include <sys/rwlock.h>
@@ -221,7 +222,7 @@ vm_object_zinit(void *mem, int size, int flags)
 	object->type = OBJT_DEAD;
 	object->ref_count = 0;
 	vm_radix_init(&object->rtree);
-	object->paging_in_progress = 0;
+	refcount_init(&object->paging_in_progress, 0);
 	object->resident_page_count = 0;
 	object->shadow_count = 0;
 	object->flags = OBJ_DEAD;
@@ -371,52 +372,44 @@ void
 vm_object_pip_add(vm_object_t object, short i)
 {
 
-	VM_OBJECT_ASSERT_WLOCKED(object);
-	object->paging_in_progress += i;
+	refcount_acquiren(&object->paging_in_progress, i);
 }
 
 void
-vm_object_pip_subtract(vm_object_t object, short i)
+vm_object_pip_wakeup(vm_object_t object)
 {
 
-	VM_OBJECT_ASSERT_WLOCKED(object);
-	object->paging_in_progress -= i;
+	refcount_release(&object->paging_in_progress);
 }
 
 void
-vm_object_pip_wakeup(vm_object_t object)
+vm_object_pip_wakeupn(vm_object_t object, short i)
 {
 
-	VM_OBJECT_ASSERT_WLOCKED(object);
-	object->paging_in_progress--;
-	if ((object->flags & OBJ_PIPWNT) && object->paging_in_progress == 0) {
-		vm_object_clear_flag(object, OBJ_PIPWNT);
-		wakeup(object);
-	}
+	refcount_releasen(&object->paging_in_progress, i);
 }
 
 void
-vm_object_pip_wakeupn(vm_object_t object, short i)
+vm_object_pip_wait(vm_object_t object, char *waitid)
 {
 
 	VM_OBJECT_ASSERT_WLOCKED(object);
-	if (i)
-		object->paging_in_progress -= i;
-	if ((object->flags & OBJ_PIPWNT) && object->paging_in_progress == 0) {
-		vm_object_clear_flag(object, OBJ_PIPWNT);
-		wakeup(object);
+
+	while (object->paging_in_progress) {
+		VM_OBJECT_WUNLOCK(object);
+		refcount_wait(&object->paging_in_progress, waitid, PVM);
+		VM_OBJECT_WLOCK(object);
 	}
 }
 
 void
-vm_object_pip_wait(vm_object_t object, char *waitid)
+vm_object_pip_wait_unlocked(vm_object_t object, char *waitid)
 {
 
-	VM_OBJECT_ASSERT_WLOCKED(object);
-	while (object->paging_in_progress) {
-		object->flags |= OBJ_PIPWNT;
-		VM_OBJECT_SLEEP(object, object, PVM, waitid, 0);
-	}
+	VM_OBJECT_ASSERT_UNLOCKED(object);
+
+	while (object->paging_in_progress)
+		refcount_wait(&object->paging_in_progress, waitid, PVM);
 }
 
 /*
@@ -615,9 +608,10 @@ retry:
 						}
 					} else if (object->paging_in_progress) {
 						VM_OBJECT_WUNLOCK(robject);
-						object->flags |= OBJ_PIPWNT;
-						VM_OBJECT_SLEEP(object, object,
-						    PDROP | PVM, "objde2", 0);
+						VM_OBJECT_WUNLOCK(object);
+						refcount_wait(
+						    &object->paging_in_progress,
+						    "objde2", PVM);
 						VM_OBJECT_WLOCK(robject);
 						temp = robject->backing_object;
 						if (object == temp) {
@@ -761,14 +755,6 @@ vm_object_terminate(vm_object_t object)
 	vm_object_set_flag(object, OBJ_DEAD);
 
 	/*
-	 * wait for the pageout daemon to be done with the object
-	 */
-	vm_object_pip_wait(object, "objtrm");
-
-	KASSERT(!object->paging_in_progress,
-		("vm_object_terminate: pageout in progress"));
-
-	/*
 	 * Clean and free the pages, as appropriate. All references to the
 	 * object are gone, so we don't need to lock it.
 	 */
@@ -789,6 +775,14 @@ vm_object_terminate(vm_object_t object)
 
 		VM_OBJECT_WLOCK(object);
 	}
+
+	/*
+	 * wait for the pageout daemon to be done with the object
+	 */
+	vm_object_pip_wait(object, "objtrm");
+
+	KASSERT(!object->paging_in_progress,
+		("vm_object_terminate: pageout in progress"));
 
 	KASSERT(object->ref_count == 0, 
 		("vm_object_terminate: object with references, ref_count=%d",

Modified: head/sys/vm/vm_object.h
==============================================================================
--- head/sys/vm/vm_object.h	Mon Aug 19 23:01:59 2019	(r351240)
+++ head/sys/vm/vm_object.h	Mon Aug 19 23:09:38 2019	(r351241)
@@ -111,7 +111,7 @@ struct vm_object {
 	objtype_t type;			/* type of pager */
 	u_short flags;			/* see below */
 	u_short pg_color;		/* (c) color of first page in obj */
-	u_int paging_in_progress;	/* Paging (in or out) so don't collapse or destroy */
+	volatile u_int paging_in_progress; /* Paging (in or out) so don't collapse or destroy */
 	int resident_page_count;	/* number of resident pages */
 	struct vm_object *backing_object; /* object that I'm a shadow of */
 	vm_ooffset_t backing_object_offset;/* Offset in backing object */
@@ -183,7 +183,6 @@ struct vm_object {
 #define	OBJ_DEAD	0x0008		/* dead objects (during rundown) */
 #define	OBJ_NOSPLIT	0x0010		/* dont split this object */
 #define	OBJ_UMTXDEAD	0x0020		/* umtx pshared was terminated */
-#define	OBJ_PIPWNT	0x0040		/* paging in progress wanted */
 #define	OBJ_PG_DTOR	0x0080		/* dont reset object, leave that for dtor */
 #define	OBJ_MIGHTBEDIRTY 0x0100		/* object might be dirty, only for vnode */
 #define	OBJ_TMPFS_NODE	0x0200		/* object belongs to tmpfs VREG node */
@@ -309,10 +308,10 @@ vm_object_reserv(vm_object_t object)
 
 void vm_object_clear_flag(vm_object_t object, u_short bits);
 void vm_object_pip_add(vm_object_t object, short i);
-void vm_object_pip_subtract(vm_object_t object, short i);
 void vm_object_pip_wakeup(vm_object_t object);
 void vm_object_pip_wakeupn(vm_object_t object, short i);
 void vm_object_pip_wait(vm_object_t object, char *waitid);
+void vm_object_pip_wait_unlocked(vm_object_t object, char *waitid);
 
 void umtx_shm_object_init(vm_object_t object);
 void umtx_shm_object_terminated(vm_object_t object);



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