vm_fault.c (df794f5cafcae1a8e94a54731a89b28e987c2156) vm_fault.c (be9d4fd6b4c5b38ae1c1b2357dd877a364e3c792)
1/*-
2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
3 *
4 * Copyright (c) 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * Copyright (c) 1994 John S. Dyson
7 * All rights reserved.
8 * Copyright (c) 1994 David Greenman

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1354 }
1355
1356 /*
1357 * Default objects have no pager so no exclusive busy exists
1358 * to protect this page in the chain. Skip to the next
1359 * object without dropping the lock to preserve atomicity of
1360 * shadow faults.
1361 */
1/*-
2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
3 *
4 * Copyright (c) 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * Copyright (c) 1994 John S. Dyson
7 * All rights reserved.
8 * Copyright (c) 1994 David Greenman

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1354 }
1355
1356 /*
1357 * Default objects have no pager so no exclusive busy exists
1358 * to protect this page in the chain. Skip to the next
1359 * object without dropping the lock to preserve atomicity of
1360 * shadow faults.
1361 */
1362 if (fs.object->type == OBJT_DEFAULT) {
1363 if (vm_fault_next(&fs))
1364 continue;
1365 /* Don't try to prefault neighboring pages. */
1366 faultcount = 1;
1367 break;
1368 }
1362 if (fs.object->type != OBJT_DEFAULT) {
1363 /*
1364 * At this point, we have either allocated a new page
1365 * or found an existing page that is only partially
1366 * valid.
1367 *
1368 * We hold a reference on the current object and the
1369 * page is exclusive busied. The exclusive busy
1370 * prevents simultaneous faults and collapses while
1371 * the object lock is dropped.
1372 */
1373 VM_OBJECT_WUNLOCK(fs.object);
1369
1374
1370 /*
1371 * At this point, we have either allocated a new page or found
1372 * an existing page that is only partially valid.
1373 *
1374 * We hold a reference on the current object and the page is
1375 * exclusive busied. The exclusive busy prevents simultaneous
1376 * faults and collapses while the object lock is dropped.
1377 */
1378 VM_OBJECT_WUNLOCK(fs.object);
1375 /*
1376 * If the pager for the current object might have
1377 * the page, then determine the number of additional
1378 * pages to read and potentially reprioritize
1379 * previously read pages for earlier reclamation.
1380 * These operations should only be performed once per
1381 * page fault. Even if the current pager doesn't
1382 * have the page, the number of additional pages to
1383 * read will apply to subsequent objects in the
1384 * shadow chain.
1385 */
1386 if (nera == -1 && !P_KILLED(curproc))
1387 nera = vm_fault_readahead(&fs);
1379
1388
1380 /*
1381 * If the pager for the current object might have the page,
1382 * then determine the number of additional pages to read and
1383 * potentially reprioritize previously read pages for earlier
1384 * reclamation. These operations should only be performed
1385 * once per page fault. Even if the current pager doesn't
1386 * have the page, the number of additional pages to read will
1387 * apply to subsequent objects in the shadow chain.
1388 */
1389 if (nera == -1 && !P_KILLED(curproc))
1390 nera = vm_fault_readahead(&fs);
1391
1392 rv = vm_fault_getpages(&fs, nera, &behind, &ahead);
1393 if (rv == KERN_SUCCESS) {
1394 faultcount = behind + 1 + ahead;
1395 hardfault = true;
1396 break; /* break to PAGE HAS BEEN FOUND. */
1389 rv = vm_fault_getpages(&fs, nera, &behind, &ahead);
1390 if (rv == KERN_SUCCESS) {
1391 faultcount = behind + 1 + ahead;
1392 hardfault = true;
1393 break; /* break to PAGE HAS BEEN FOUND. */
1394 }
1395 if (rv == KERN_RESOURCE_SHORTAGE)
1396 goto RetryFault;
1397 VM_OBJECT_WLOCK(fs.object);
1398 if (rv == KERN_OUT_OF_BOUNDS) {
1399 fault_page_free(&fs.m);
1400 unlock_and_deallocate(&fs);
1401 return (rv);
1402 }
1397 }
1403 }
1398 if (rv == KERN_RESOURCE_SHORTAGE)
1399 goto RetryFault;
1400 VM_OBJECT_WLOCK(fs.object);
1401 if (rv == KERN_OUT_OF_BOUNDS) {
1402 fault_page_free(&fs.m);
1403 unlock_and_deallocate(&fs);
1404 return (rv);
1405 }
1406
1407 /*
1408 * The page was not found in the current object. Try to
1409 * traverse into a backing object or zero fill if none is
1410 * found.
1411 */
1412 if (!vm_fault_next(&fs)) {
1413 /* Don't try to prefault neighboring pages. */

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1405 /*
1406 * The page was not found in the current object. Try to
1407 * traverse into a backing object or zero fill if none is
1408 * found.
1409 */
1410 if (!vm_fault_next(&fs)) {
1411 /* Don't try to prefault neighboring pages. */

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