Home | History | Annotate | Line # | Download | only in uvm
uvm_page_status.c revision 1.1.2.1 
      1 /*	$NetBSD: uvm_page_status.c,v 1.1.2.1 2011/11/02 21:55:39 yamt Exp $	*/
      2 
      3 /*-
      4  * Copyright (c)2011 YAMAMOTO Takashi,
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: uvm_page_status.c,v 1.1.2.1 2011/11/02 21:55:39 yamt Exp $");
     31 
     32 #include <sys/param.h>
     33 #include <sys/systm.h>
     34 
     35 #include <uvm/uvm.h>
     36 
     37 /*
     38  * page dirtiness status tracking
     39  *
     40  * separated from uvm_page.c mainly for rump
     41  */
     42 
     43 /*
     44  * uvm_pagegetdirty: return the dirtiness status (one of UVM_PAGE_STATUS_
     45  * values) of the page.
     46  */
     47 
     48 unsigned int
     49 uvm_pagegetdirty(struct vm_page *pg)
     50 {
     51 	struct uvm_object * const uobj __unused = pg->uobject;
     52 	const uint64_t idx __unused = pg->offset >> PAGE_SHIFT;
     53 
     54 	KASSERT((~pg->flags & (PG_CLEAN|PG_DIRTY)) != 0);
     55 	KASSERT(uvm_page_locked_p(pg));
     56 	KASSERT(uobj == NULL || ((pg->flags & PG_CLEAN) == 0) ==
     57 	    radix_tree_get_tag(&uobj->uo_pages, idx, UVM_PAGE_DIRTY_TAG));
     58 	return pg->flags & (PG_CLEAN|PG_DIRTY);
     59 }
     60 
     61 /*
     62  * uvm_pagemarkdirty: set the dirtiness status (one of UVM_PAGE_STATUS_ values)
     63  * of the page.
     64  */
     65 
     66 void
     67 uvm_pagemarkdirty(struct vm_page *pg, unsigned int status)
     68 {
     69 	struct uvm_object * const uobj = pg->uobject;
     70 	const uint64_t idx = pg->offset >> PAGE_SHIFT;
     71 
     72 	KASSERT((~status & (PG_CLEAN|PG_DIRTY)) != 0);
     73 	KASSERT((status & ~(PG_CLEAN|PG_DIRTY)) == 0);
     74 	KASSERT(uvm_page_locked_p(pg));
     75 	KASSERT(uobj == NULL || ((pg->flags & PG_CLEAN) == 0) ==
     76 	    radix_tree_get_tag(&uobj->uo_pages, idx, UVM_PAGE_DIRTY_TAG));
     77 
     78 	if (uvm_pagegetdirty(pg) == status) {
     79 		return;
     80 	}
     81 	/*
     82 	 * set UVM_PAGE_DIRTY_TAG tag unless known CLEAN so that putpages can
     83 	 * find possibly-dirty pages quickly.
     84 	 */
     85 	if (uobj != NULL) {
     86 		if (status == UVM_PAGE_STATUS_CLEAN) {
     87 			radix_tree_clear_tag(&uobj->uo_pages, idx,
     88 			    UVM_PAGE_DIRTY_TAG);
     89 		} else {
     90 			radix_tree_set_tag(&uobj->uo_pages, idx,
     91 			    UVM_PAGE_DIRTY_TAG);
     92 		}
     93 	}
     94 	if (status == UVM_PAGE_STATUS_UNKNOWN) {
     95 		/*
     96 		 * start relying on pmap-level dirtiness tracking.
     97 		 */
     98 		pmap_clear_modify(pg);
     99 	}
    100 	pg->flags &= ~(PG_CLEAN|PG_DIRTY);
    101 	pg->flags |= status;
    102 	KASSERT(uobj == NULL || ((pg->flags & PG_CLEAN) == 0) ==
    103 	    radix_tree_get_tag(&uobj->uo_pages, idx, UVM_PAGE_DIRTY_TAG));
    104 }
    105 
    106 /*
    107  * uvm_pagecheckdirty: check if page is dirty, and remove its dirty-marks.
    108  *
    109  * called with the owner locked.
    110  */
    111 
    112 bool
    113 uvm_pagecheckdirty(struct vm_page *pg, bool protected)
    114 {
    115 	const unsigned int oldstatus = uvm_pagegetdirty(pg);
    116 	bool modified;
    117 
    118 	KASSERT(uvm_page_locked_p(pg));
    119 
    120 	/*
    121 	 * if protected is true, mark the page CLEAN.
    122 	 * otherwise mark the page UNKNOWN unless it's CLEAN.
    123 	 *
    124 	 * possible transitions:
    125 	 *
    126 	 *	CLEAN   -> CLEAN  , modified = false
    127 	 *	UNKNOWN -> UNKNOWN, modified = true
    128 	 *	UNKNOWN -> UNKNOWN, modified = false
    129 	 *	UNKNOWN -> CLEAN  , modified = true
    130 	 *	UNKNOWN -> CLEAN  , modified = false
    131 	 *	DIRTY   -> UNKNOWN, modified = true
    132 	 *	DIRTY   -> CLEAN  , modified = true
    133 	 *
    134 	 * pmap_clear_modify is necessary if either of
    135 	 * oldstatus or newstatus is UVM_PAGE_STATUS_UNKNOWN.
    136 	 */
    137 
    138 	if (oldstatus == UVM_PAGE_STATUS_CLEAN) {
    139 		modified = false;
    140 	} else {
    141 		const unsigned int newstatus =
    142 		    protected ? UVM_PAGE_STATUS_CLEAN : UVM_PAGE_STATUS_UNKNOWN;
    143 
    144 		if (oldstatus == UVM_PAGE_STATUS_DIRTY) {
    145 			modified = true;
    146 			if (newstatus == UVM_PAGE_STATUS_UNKNOWN) {
    147 				pmap_clear_modify(pg);
    148 			}
    149 		} else {
    150 			modified = pmap_clear_modify(pg);
    151 		}
    152 		uvm_pagemarkdirty(pg, newstatus);
    153 	}
    154 	return modified;
    155 }
    156