In vm_object_page_clean(), do not clean OBJ_MIGHTBEDIRTY object flag

if the filesystem performed short write and we are skipping the page
due to this.

Propogate write error from the pager back to the callers of
vm_pageout_flush().  Report the failure to write a page from the
requested range as the FALSE return value from vm_object_page_clean(),
and propagate it back to msync(2) to return EIO to usermode.

While there, convert the clearobjflags variable in the
vm_object_page_clean() and arguments of the helper functions to
boolean.

PR:	kern/165927
Reviewed by:	alc
MFC after:	2 weeks

sys/vm/vm_contig.c

@@ -137,7 +137,8 @@ vm_contig_launder_page(vm_page_t m, vm_page_t *next)
 			   object->type == OBJT_DEFAULT) {
 			vm_page_unlock_queues();
 			m_tmp = m;
-			vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC, 0, NULL);
+			vm_pageout_flush(&m_tmp, 1, VM_PAGER_PUT_SYNC, 0,
+			    NULL, NULL);
 			VM_OBJECT_UNLOCK(object);
 			vm_page_lock_queues();
 			return (0);

sys/vm/vm_map.c

@@ -2591,6 +2591,7 @@ vm_map_sync(
 	vm_object_t object;
 	vm_ooffset_t offset;
 	unsigned int last_timestamp;
+	boolean_t failed;
 
 	vm_map_lock_read(map);
 	VM_MAP_RANGE_CHECK(map, start, end);
@@ -2620,6 +2621,7 @@ vm_map_sync(
 
 	if (invalidate)
 		pmap_remove(map->pmap, start, end);
+	failed = FALSE;
 
 	/*
 	 * Make a second pass, cleaning/uncaching pages from the indicated
@@ -2648,7 +2650,8 @@ vm_map_sync(
 		vm_object_reference(object);
 		last_timestamp = map->timestamp;
 		vm_map_unlock_read(map);
-		vm_object_sync(object, offset, size, syncio, invalidate);
+		if (!vm_object_sync(object, offset, size, syncio, invalidate))
+			failed = TRUE;
 		start += size;
 		vm_object_deallocate(object);
 		vm_map_lock_read(map);
@@ -2658,7 +2661,7 @@ vm_map_sync(
 	}
 
 	vm_map_unlock_read(map);
-	return (KERN_SUCCESS);
+	return (failed ? KERN_FAILURE : KERN_SUCCESS);
 }
 
 /*

sys/vm/vm_mmap.c

@@ -508,6 +508,8 @@ sys_msync(td, uap)
 		return (EINVAL);	/* Sun returns ENOMEM? */
 	case KERN_INVALID_ARGUMENT:
 		return (EBUSY);
+	case KERN_FAILURE:
+		return (EIO);
 	default:
 		return (EINVAL);
 	}

sys/vm/vm_object.c

@@ -101,9 +101,10 @@ SYSCTL_INT(_vm, OID_AUTO, old_msync, CTLFLAG_RW, &old_msync, 0,
     "Use old (insecure) msync behavior");
 
 static int	vm_object_page_collect_flush(vm_object_t object, vm_page_t p,
-		    int pagerflags, int flags, int *clearobjflags);
+		    int pagerflags, int flags, boolean_t *clearobjflags,
+		    boolean_t *eio);
 static boolean_t vm_object_page_remove_write(vm_page_t p, int flags,
-		    int *clearobjflags);
+		    boolean_t *clearobjflags);
 static void	vm_object_qcollapse(vm_object_t object);
 static void	vm_object_vndeallocate(vm_object_t object);
 
@@ -775,7 +776,7 @@ vm_object_terminate(vm_object_t object)
  * page should be flushed, and FALSE otherwise.
  */
 static boolean_t
-vm_object_page_remove_write(vm_page_t p, int flags, int *clearobjflags)
+vm_object_page_remove_write(vm_page_t p, int flags, boolean_t *clearobjflags)
 {
 
 	/*
@@ -784,7 +785,7 @@ vm_object_page_remove_write(vm_page_t p, int flags, int *clearobjflags)
 	 * cleared in this case so we do not have to set them.
 	 */
 	if ((flags & OBJPC_NOSYNC) != 0 && (p->oflags & VPO_NOSYNC) != 0) {
-		*clearobjflags = 0;
+		*clearobjflags = FALSE;
 		return (FALSE);
 	} else {
 		pmap_remove_write(p);
@@ -806,21 +807,25 @@ vm_object_page_remove_write(vm_page_t p, int flags, int *clearobjflags)
  *	Odd semantics: if start == end, we clean everything.
  *
  *	The object must be locked.
+ *
+ *	Returns FALSE if some page from the range was not written, as
+ *	reported by the pager, and TRUE otherwise.
  */
-void
+boolean_t
 vm_object_page_clean(vm_object_t object, vm_ooffset_t start, vm_ooffset_t end,
     int flags)
 {
 	vm_page_t np, p;
 	vm_pindex_t pi, tend, tstart;
-	int clearobjflags, curgeneration, n, pagerflags;
+	int curgeneration, n, pagerflags;
+	boolean_t clearobjflags, eio, res;
 
 	mtx_assert(&vm_page_queue_mtx, MA_NOTOWNED);
 	VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
 	KASSERT(object->type == OBJT_VNODE, ("Not a vnode object"));
 	if ((object->flags & OBJ_MIGHTBEDIRTY) == 0 ||
 	    object->resident_page_count == 0)
-		return;
+		return (TRUE);
 
 	pagerflags = (flags & (OBJPC_SYNC | OBJPC_INVAL)) != 0 ?
 	    VM_PAGER_PUT_SYNC : VM_PAGER_CLUSTER_OK;
@@ -829,6 +834,7 @@ vm_object_page_clean(vm_object_t object, vm_ooffset_t start, vm_ooffset_t end,
 	tstart = OFF_TO_IDX(start);
 	tend = (end == 0) ? object->size : OFF_TO_IDX(end + PAGE_MASK);
 	clearobjflags = tstart == 0 && tend >= object->size;
+	res = TRUE;
 
 rescan:
 	curgeneration = object->generation;
@@ -845,7 +851,7 @@ vm_object_page_clean(vm_object_t object, vm_ooffset_t start, vm_ooffset_t end,
 				if ((flags & OBJPC_SYNC) != 0)
 					goto rescan;
 				else
-					clearobjflags = 0;
+					clearobjflags = FALSE;
 			}
 			np = vm_page_find_least(object, pi);
 			continue;
@@ -854,12 +860,16 @@ vm_object_page_clean(vm_object_t object, vm_ooffset_t start, vm_ooffset_t end,
 			continue;
 
 		n = vm_object_page_collect_flush(object, p, pagerflags,
-		    flags, &clearobjflags);
+		    flags, &clearobjflags, &eio);
+		if (eio) {
+			res = FALSE;
+			clearobjflags = FALSE;
+		}
 		if (object->generation != curgeneration) {
 			if ((flags & OBJPC_SYNC) != 0)
 				goto rescan;
 			else
-				clearobjflags = 0;
+				clearobjflags = FALSE;
 		}
 
 		/*
@@ -874,8 +884,10 @@ vm_object_page_clean(vm_object_t object, vm_ooffset_t start, vm_ooffset_t end,
 		 * behind, but there is not much we can do there if
 		 * filesystem refuses to write it.
 		 */
-		if (n == 0)
+		if (n == 0) {
 			n = 1;
+			clearobjflags = FALSE;
+		}
 		np = vm_page_find_least(object, pi + n);
 	}
 #if 0
@@ -884,11 +896,12 @@ vm_object_page_clean(vm_object_t object, vm_ooffset_t start, vm_ooffset_t end,
 
 	if (clearobjflags)
 		vm_object_clear_flag(object, OBJ_MIGHTBEDIRTY);
+	return (res);
 }
 
 static int
 vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags,
-    int flags, int *clearobjflags)
+    int flags, boolean_t *clearobjflags, boolean_t *eio)
 {
 	vm_page_t ma[vm_pageout_page_count], p_first, tp;
 	int count, i, mreq, runlen;
@@ -921,7 +934,7 @@ vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags,
 	for (tp = p_first, i = 0; i < count; tp = TAILQ_NEXT(tp, listq), i++)
 		ma[i] = tp;
 
-	vm_pageout_flush(ma, count, pagerflags, mreq, &runlen);
+	vm_pageout_flush(ma, count, pagerflags, mreq, &runlen, eio);
 	return (runlen);
 }
 
@@ -939,17 +952,20 @@ vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags,
  * Note: certain anonymous maps, such as MAP_NOSYNC maps,
  * may start out with a NULL object.
  */
-void
+boolean_t
 vm_object_sync(vm_object_t object, vm_ooffset_t offset, vm_size_t size,
     boolean_t syncio, boolean_t invalidate)
 {
 	vm_object_t backing_object;
 	struct vnode *vp;
 	struct mount *mp;
-	int flags, fsync_after;
+	int error, flags, fsync_after;
+	boolean_t res;
 
 	if (object == NULL)
-		return;
+		return (TRUE);
+	res = TRUE;
+	error = 0;
 	VM_OBJECT_LOCK(object);
 	while ((backing_object = object->backing_object) != NULL) {
 		VM_OBJECT_LOCK(backing_object);
@@ -995,13 +1011,16 @@ vm_object_sync(vm_object_t object, vm_ooffset_t offset, vm_size_t size,
 			fsync_after = FALSE;
 		}
 		VM_OBJECT_LOCK(object);
-		vm_object_page_clean(object, offset, offset + size, flags);
+		res = vm_object_page_clean(object, offset, offset + size,
+		    flags);
 		VM_OBJECT_UNLOCK(object);
 		if (fsync_after)
-			(void) VOP_FSYNC(vp, MNT_WAIT, curthread);
+			error = VOP_FSYNC(vp, MNT_WAIT, curthread);
 		VOP_UNLOCK(vp, 0);
 		VFS_UNLOCK_GIANT(vfslocked);
 		vn_finished_write(mp);
+		if (error != 0)
+			res = FALSE;
 		VM_OBJECT_LOCK(object);
 	}
 	if ((object->type == OBJT_VNODE ||
@@ -1021,6 +1040,7 @@ vm_object_sync(vm_object_t object, vm_ooffset_t offset, vm_size_t size,
 		    OFF_TO_IDX(offset + size + PAGE_MASK), flags);
 	}
 	VM_OBJECT_UNLOCK(object);
+	return (res);
 }
 
 /*

sys/vm/vm_object.h

@@ -227,7 +227,7 @@ void vm_object_set_writeable_dirty (vm_object_t);
 void vm_object_init (void);
 void vm_object_page_cache(vm_object_t object, vm_pindex_t start,
     vm_pindex_t end);
-void vm_object_page_clean(vm_object_t object, vm_ooffset_t start,
+boolean_t vm_object_page_clean(vm_object_t object, vm_ooffset_t start,
     vm_ooffset_t end, int flags);
 void vm_object_page_remove(vm_object_t object, vm_pindex_t start,
     vm_pindex_t end, int options);
@@ -238,7 +238,7 @@ void vm_object_reference_locked(vm_object_t);
 int  vm_object_set_memattr(vm_object_t object, vm_memattr_t memattr);
 void vm_object_shadow (vm_object_t *, vm_ooffset_t *, vm_size_t);
 void vm_object_split(vm_map_entry_t);
-void vm_object_sync(vm_object_t, vm_ooffset_t, vm_size_t, boolean_t,
+boolean_t vm_object_sync(vm_object_t, vm_ooffset_t, vm_size_t, boolean_t,
     boolean_t);
 void vm_object_madvise (vm_object_t, vm_pindex_t, int, int);
 #endif				/* _KERNEL */

sys/vm/vm_pageout.c

@@ -445,7 +445,8 @@ vm_pageout_clean(vm_page_t m)
 	/*
 	 * we allow reads during pageouts...
 	 */
-	return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL));
+	return (vm_pageout_flush(&mc[page_base], pageout_count, 0, 0, NULL,
+	    NULL));
 }
 
 /*
@@ -459,9 +460,12 @@ vm_pageout_clean(vm_page_t m)
  *
  *	Returned runlen is the count of pages between mreq and first
  *	page after mreq with status VM_PAGER_AGAIN.
+ *	*eio is set to TRUE if pager returned VM_PAGER_ERROR or VM_PAGER_FAIL
+ *	for any page in runlen set.
  */
 int
-vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen)
+vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen,
+    boolean_t *eio)
 {
 	vm_object_t object = mc[0]->object;
 	int pageout_status[count];
@@ -493,6 +497,8 @@ vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen)
 	vm_pager_put_pages(object, mc, count, flags, pageout_status);
 
 	runlen = count - mreq;
+	if (eio != NULL)
+		*eio = FALSE;
 	for (i = 0; i < count; i++) {
 		vm_page_t mt = mc[i];
 
@@ -522,6 +528,8 @@ vm_pageout_flush(vm_page_t *mc, int count, int flags, int mreq, int *prunlen)
 			vm_page_lock(mt);
 			vm_page_activate(mt);
 			vm_page_unlock(mt);
+			if (eio != NULL && i >= mreq && i - mreq < runlen)
+				*eio = TRUE;
 			break;
 		case VM_PAGER_AGAIN:
 			if (i >= mreq && i - mreq < runlen)

sys/vm/vm_pageout.h

@@ -102,7 +102,7 @@ extern void vm_waitpfault(void);
 
 #ifdef _KERNEL
 boolean_t vm_pageout_fallback_object_lock(vm_page_t, vm_page_t *);
-int vm_pageout_flush(vm_page_t *, int, int, int, int *);
+int vm_pageout_flush(vm_page_t *, int, int, int, int *, boolean_t *);
 void vm_pageout_oom(int shortage);
 boolean_t vm_pageout_page_lock(vm_page_t, vm_page_t *);
 void vm_contig_grow_cache(int, vm_paddr_t, vm_paddr_t);