/*- * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * Copyright (c) 1994 John S. Dyson * All rights reserved. * Copyright (c) 1994 David Greenman * All rights reserved. * * * This code is derived from software contributed to Berkeley by * The Mach Operating System project at Carnegie-Mellon University. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 * * * Copyright (c) 1987, 1990 Carnegie-Mellon University. * All rights reserved. * * Authors: Avadis Tevanian, Jr., Michael Wayne Young * * Permission to use, copy, modify and distribute this software and * its documentation is hereby granted, provided that both the copyright * notice and this permission notice appear in all copies of the * software, derivative works or modified versions, and any portions * thereof, and that both notices appear in supporting documentation. * * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. * * Carnegie Mellon requests users of this software to return to * * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU * School of Computer Science * Carnegie Mellon University * Pittsburgh PA 15213-3890 * * any improvements or extensions that they make and grant Carnegie the * rights to redistribute these changes. */ /* * Page fault handling module. */ #include __FBSDID("$FreeBSD$"); #include "opt_ktrace.h" #include "opt_vm.h" #include #include #include #include #include #include #include #include #include #include #include #ifdef KTRACE #include #endif #include #include #include #include #include #include #include #include #include #include #include #define PFBAK 4 #define PFFOR 4 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); #define VM_FAULT_READ_BEHIND 8 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) #define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND) #define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2) #define VM_FAULT_DONTNEED_MIN 1048576 struct faultstate { vm_page_t m; vm_object_t object; vm_pindex_t pindex; vm_page_t first_m; vm_object_t first_object; vm_pindex_t first_pindex; vm_map_t map; vm_map_entry_t entry; int lookup_still_valid; struct vnode *vp; }; static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead); static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, int faultcount, int reqpage); static inline void release_page(struct faultstate *fs) { vm_page_xunbusy(fs->m); vm_page_lock(fs->m); vm_page_deactivate(fs->m); vm_page_unlock(fs->m); fs->m = NULL; } static inline void unlock_map(struct faultstate *fs) { if (fs->lookup_still_valid) { vm_map_lookup_done(fs->map, fs->entry); fs->lookup_still_valid = FALSE; } } static void unlock_and_deallocate(struct faultstate *fs) { vm_object_pip_wakeup(fs->object); VM_OBJECT_WUNLOCK(fs->object); if (fs->object != fs->first_object) { VM_OBJECT_WLOCK(fs->first_object); vm_page_lock(fs->first_m); vm_page_free(fs->first_m); vm_page_unlock(fs->first_m); vm_object_pip_wakeup(fs->first_object); VM_OBJECT_WUNLOCK(fs->first_object); fs->first_m = NULL; } vm_object_deallocate(fs->first_object); unlock_map(fs); if (fs->vp != NULL) { vput(fs->vp); fs->vp = NULL; } } static void vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, vm_prot_t fault_type, int fault_flags, boolean_t set_wd) { boolean_t need_dirty; if (((prot & VM_PROT_WRITE) == 0 && (fault_flags & VM_FAULT_DIRTY) == 0) || (m->oflags & VPO_UNMANAGED) != 0) return; VM_OBJECT_ASSERT_LOCKED(m->object); need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) || (fault_flags & VM_FAULT_DIRTY) != 0; if (set_wd) vm_object_set_writeable_dirty(m->object); else /* * If two callers of vm_fault_dirty() with set_wd == * FALSE, one for the map entry with MAP_ENTRY_NOSYNC * flag set, other with flag clear, race, it is * possible for the no-NOSYNC thread to see m->dirty * != 0 and not clear VPO_NOSYNC. Take vm_page lock * around manipulation of VPO_NOSYNC and * vm_page_dirty() call, to avoid the race and keep * m->oflags consistent. */ vm_page_lock(m); /* * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC * if the page is already dirty to prevent data written with * the expectation of being synced from not being synced. * Likewise if this entry does not request NOSYNC then make * sure the page isn't marked NOSYNC. Applications sharing * data should use the same flags to avoid ping ponging. */ if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { if (m->dirty == 0) { m->oflags |= VPO_NOSYNC; } } else { m->oflags &= ~VPO_NOSYNC; } /* * If the fault is a write, we know that this page is being * written NOW so dirty it explicitly to save on * pmap_is_modified() calls later. * * Also tell the backing pager, if any, that it should remove * any swap backing since the page is now dirty. */ if (need_dirty) vm_page_dirty(m); if (!set_wd) vm_page_unlock(m); if (need_dirty) vm_pager_page_unswapped(m); } /* * TRYPAGER - used by vm_fault to calculate whether the pager for the * current object *might* contain the page. * * default objects are zero-fill, there is no real pager. */ #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired)) /* * vm_fault: * * Handle a page fault occurring at the given address, * requiring the given permissions, in the map specified. * If successful, the page is inserted into the * associated physical map. * * NOTE: the given address should be truncated to the * proper page address. * * KERN_SUCCESS is returned if the page fault is handled; otherwise, * a standard error specifying why the fault is fatal is returned. * * The map in question must be referenced, and remains so. * Caller may hold no locks. */ int vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags) { struct thread *td; int result; td = curthread; if ((td->td_pflags & TDP_NOFAULTING) != 0) return (KERN_PROTECTION_FAILURE); #ifdef KTRACE if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) ktrfault(vaddr, fault_type); #endif result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, NULL); #ifdef KTRACE if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) ktrfaultend(result); #endif return (result); } int vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags, vm_page_t *m_hold) { vm_prot_t prot; int alloc_req, era, faultcount, nera, reqpage, result; boolean_t growstack, is_first_object_locked, wired; int map_generation; vm_object_t next_object; vm_page_t marray[VM_FAULT_READ_MAX]; int hardfault; struct faultstate fs; struct vnode *vp; vm_page_t m; int ahead, behind, cluster_offset, error, locked; hardfault = 0; growstack = TRUE; PCPU_INC(cnt.v_vm_faults); fs.vp = NULL; faultcount = reqpage = 0; RetryFault:; /* * Find the backing store object and offset into it to begin the * search. */ fs.map = map; result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); if (result != KERN_SUCCESS) { if (growstack && result == KERN_INVALID_ADDRESS && map != kernel_map) { result = vm_map_growstack(curproc, vaddr); if (result != KERN_SUCCESS) return (KERN_FAILURE); growstack = FALSE; goto RetryFault; } return (result); } map_generation = fs.map->timestamp; if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { panic("vm_fault: fault on nofault entry, addr: %lx", (u_long)vaddr); } if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && fs.entry->wiring_thread != curthread) { vm_map_unlock_read(fs.map); vm_map_lock(fs.map); if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { if (fs.vp != NULL) { vput(fs.vp); fs.vp = NULL; } fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; vm_map_unlock_and_wait(fs.map, 0); } else vm_map_unlock(fs.map); goto RetryFault; } if (wired) fault_type = prot | (fault_type & VM_PROT_COPY); if (fs.vp == NULL /* avoid locked vnode leak */ && (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 && /* avoid calling vm_object_set_writeable_dirty() */ ((prot & VM_PROT_WRITE) == 0 || (fs.first_object->type != OBJT_VNODE && (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { VM_OBJECT_RLOCK(fs.first_object); if ((prot & VM_PROT_WRITE) != 0 && (fs.first_object->type == OBJT_VNODE || (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) goto fast_failed; m = vm_page_lookup(fs.first_object, fs.first_pindex); /* A busy page can be mapped for read|execute access. */ if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) goto fast_failed; result = pmap_enter(fs.map->pmap, vaddr, m, prot, fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), 0); if (result != KERN_SUCCESS) goto fast_failed; if (m_hold != NULL) { *m_hold = m; vm_page_lock(m); vm_page_hold(m); vm_page_unlock(m); } vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, FALSE); VM_OBJECT_RUNLOCK(fs.first_object); if (!wired) vm_fault_prefault(&fs, vaddr, 0, 0); vm_map_lookup_done(fs.map, fs.entry); curthread->td_ru.ru_minflt++; return (KERN_SUCCESS); fast_failed: if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { VM_OBJECT_RUNLOCK(fs.first_object); VM_OBJECT_WLOCK(fs.first_object); } } else { VM_OBJECT_WLOCK(fs.first_object); } /* * Make a reference to this object to prevent its disposal while we * are messing with it. Once we have the reference, the map is free * to be diddled. Since objects reference their shadows (and copies), * they will stay around as well. * * Bump the paging-in-progress count to prevent size changes (e.g. * truncation operations) during I/O. This must be done after * obtaining the vnode lock in order to avoid possible deadlocks. */ vm_object_reference_locked(fs.first_object); vm_object_pip_add(fs.first_object, 1); fs.lookup_still_valid = TRUE; fs.first_m = NULL; /* * Search for the page at object/offset. */ fs.object = fs.first_object; fs.pindex = fs.first_pindex; while (TRUE) { /* * If the object is dead, we stop here */ if (fs.object->flags & OBJ_DEAD) { unlock_and_deallocate(&fs); return (KERN_PROTECTION_FAILURE); } /* * See if page is resident */ fs.m = vm_page_lookup(fs.object, fs.pindex); if (fs.m != NULL) { /* * Wait/Retry if the page is busy. We have to do this * if the page is either exclusive or shared busy * because the vm_pager may be using read busy for * pageouts (and even pageins if it is the vnode * pager), and we could end up trying to pagein and * pageout the same page simultaneously. * * We can theoretically allow the busy case on a read * fault if the page is marked valid, but since such * pages are typically already pmap'd, putting that * special case in might be more effort then it is * worth. We cannot under any circumstances mess * around with a shared busied page except, perhaps, * to pmap it. */ if (vm_page_busied(fs.m)) { /* * Reference the page before unlocking and * sleeping so that the page daemon is less * likely to reclaim it. */ vm_page_aflag_set(fs.m, PGA_REFERENCED); if (fs.object != fs.first_object) { if (!VM_OBJECT_TRYWLOCK( fs.first_object)) { VM_OBJECT_WUNLOCK(fs.object); VM_OBJECT_WLOCK(fs.first_object); VM_OBJECT_WLOCK(fs.object); } vm_page_lock(fs.first_m); vm_page_free(fs.first_m); vm_page_unlock(fs.first_m); vm_object_pip_wakeup(fs.first_object); VM_OBJECT_WUNLOCK(fs.first_object); fs.first_m = NULL; } unlock_map(&fs); if (fs.m == vm_page_lookup(fs.object, fs.pindex)) { vm_page_sleep_if_busy(fs.m, "vmpfw"); } vm_object_pip_wakeup(fs.object); VM_OBJECT_WUNLOCK(fs.object); PCPU_INC(cnt.v_intrans); vm_object_deallocate(fs.first_object); goto RetryFault; } vm_page_lock(fs.m); vm_page_remque(fs.m); vm_page_unlock(fs.m); /* * Mark page busy for other processes, and the * pagedaemon. If it still isn't completely valid * (readable), jump to readrest, else break-out ( we * found the page ). */ vm_page_xbusy(fs.m); if (fs.m->valid != VM_PAGE_BITS_ALL) goto readrest; break; } /* * Page is not resident, If this is the search termination * or the pager might contain the page, allocate a new page. */ if (TRYPAGER || fs.object == fs.first_object) { if (fs.pindex >= fs.object->size) { unlock_and_deallocate(&fs); return (KERN_PROTECTION_FAILURE); } /* * Allocate a new page for this object/offset pair. * * Unlocked read of the p_flag is harmless. At * worst, the P_KILLED might be not observed * there, and allocation can fail, causing * restart and new reading of the p_flag. */ fs.m = NULL; if (!vm_page_count_severe() || P_KILLED(curproc)) { #if VM_NRESERVLEVEL > 0 vm_object_color(fs.object, atop(vaddr) - fs.pindex); #endif alloc_req = P_KILLED(curproc) ? VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; if (fs.object->type != OBJT_VNODE && fs.object->backing_object == NULL) alloc_req |= VM_ALLOC_ZERO; fs.m = vm_page_alloc(fs.object, fs.pindex, alloc_req); } if (fs.m == NULL) { unlock_and_deallocate(&fs); VM_WAITPFAULT; goto RetryFault; } else if (fs.m->valid == VM_PAGE_BITS_ALL) break; } readrest: /* * We have found a valid page or we have allocated a new page. * The page thus may not be valid or may not be entirely * valid. * * Attempt to fault-in the page if there is a chance that the * pager has it, and potentially fault in additional pages * at the same time. */ if (TRYPAGER) { int rv; u_char behavior = vm_map_entry_behavior(fs.entry); era = fs.entry->read_ahead; if (behavior == MAP_ENTRY_BEHAV_RANDOM || P_KILLED(curproc)) { behind = 0; nera = 0; ahead = 0; } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { behind = 0; nera = VM_FAULT_READ_AHEAD_MAX; ahead = nera; if (fs.pindex == fs.entry->next_read) vm_fault_dontneed(&fs, vaddr, ahead); } else if (fs.pindex == fs.entry->next_read) { /* * This is a sequential fault. Arithmetically * increase the requested number of pages in * the read-ahead window. The requested * number of pages is "# of sequential faults * x (read ahead min + 1) + read ahead min" */ behind = 0; nera = VM_FAULT_READ_AHEAD_MIN; if (era > 0) { nera += era + 1; if (nera > VM_FAULT_READ_AHEAD_MAX) nera = VM_FAULT_READ_AHEAD_MAX; } ahead = nera; if (era == VM_FAULT_READ_AHEAD_MAX) vm_fault_dontneed(&fs, vaddr, ahead); } else { /* * This is a non-sequential fault. Request a * cluster of pages that is aligned to a * VM_FAULT_READ_DEFAULT page offset boundary * within the object. Alignment to a page * offset boundary is more likely to coincide * with the underlying file system block than * alignment to a virtual address boundary. */ cluster_offset = fs.pindex % VM_FAULT_READ_DEFAULT; behind = ulmin(cluster_offset, atop(vaddr - fs.entry->start)); nera = 0; ahead = VM_FAULT_READ_DEFAULT - 1 - cluster_offset; } ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1); if (era != nera) fs.entry->read_ahead = nera; /* * Call the pager to retrieve the data, if any, after * releasing the lock on the map. We hold a ref on * fs.object and the pages are exclusive busied. */ unlock_map(&fs); if (fs.object->type == OBJT_VNODE) { vp = fs.object->handle; if (vp == fs.vp) goto vnode_locked; else if (fs.vp != NULL) { vput(fs.vp); fs.vp = NULL; } locked = VOP_ISLOCKED(vp); if (locked != LK_EXCLUSIVE) locked = LK_SHARED; /* Do not sleep for vnode lock while fs.m is busy */ error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT, curthread); if (error != 0) { vhold(vp); release_page(&fs); unlock_and_deallocate(&fs); error = vget(vp, locked | LK_RETRY | LK_CANRECURSE, curthread); vdrop(vp); fs.vp = vp; KASSERT(error == 0, ("vm_fault: vget failed")); goto RetryFault; } fs.vp = vp; } vnode_locked: KASSERT(fs.vp == NULL || !fs.map->system_map, ("vm_fault: vnode-backed object mapped by system map")); /* * now we find out if any other pages should be paged * in at this time this routine checks to see if the * pages surrounding this fault reside in the same * object as the page for this fault. If they do, * then they are faulted in also into the object. The * array "marray" returned contains an array of * vm_page_t structs where one of them is the * vm_page_t passed to the routine. The reqpage * return value is the index into the marray for the * vm_page_t passed to the routine. * * fs.m plus the additional pages are exclusive busied. */ faultcount = vm_fault_additional_pages( fs.m, behind, ahead, marray, &reqpage); rv = faultcount ? vm_pager_get_pages(fs.object, marray, faultcount, reqpage) : VM_PAGER_FAIL; if (rv == VM_PAGER_OK) { /* * Found the page. Leave it busy while we play * with it. */ /* * Relookup in case pager changed page. Pager * is responsible for disposition of old page * if moved. */ fs.m = vm_page_lookup(fs.object, fs.pindex); if (!fs.m) { unlock_and_deallocate(&fs); goto RetryFault; } hardfault++; break; /* break to PAGE HAS BEEN FOUND */ } /* * Remove the bogus page (which does not exist at this * object/offset); before doing so, we must get back * our object lock to preserve our invariant. * * Also wake up any other process that may want to bring * in this page. * * If this is the top-level object, we must leave the * busy page to prevent another process from rushing * past us, and inserting the page in that object at * the same time that we are. */ if (rv == VM_PAGER_ERROR) printf("vm_fault: pager read error, pid %d (%s)\n", curproc->p_pid, curproc->p_comm); /* * Data outside the range of the pager or an I/O error */ /* * XXX - the check for kernel_map is a kludge to work * around having the machine panic on a kernel space * fault w/ I/O error. */ if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || (rv == VM_PAGER_BAD)) { vm_page_lock(fs.m); vm_page_free(fs.m); vm_page_unlock(fs.m); fs.m = NULL; unlock_and_deallocate(&fs); return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); } if (fs.object != fs.first_object) { vm_page_lock(fs.m); vm_page_free(fs.m); vm_page_unlock(fs.m); fs.m = NULL; /* * XXX - we cannot just fall out at this * point, m has been freed and is invalid! */ } } /* * We get here if the object has default pager (or unwiring) * or the pager doesn't have the page. */ if (fs.object == fs.first_object) fs.first_m = fs.m; /* * Move on to the next object. Lock the next object before * unlocking the current one. */ fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); next_object = fs.object->backing_object; if (next_object == NULL) { /* * If there's no object left, fill the page in the top * object with zeros. */ if (fs.object != fs.first_object) { vm_object_pip_wakeup(fs.object); VM_OBJECT_WUNLOCK(fs.object); fs.object = fs.first_object; fs.pindex = fs.first_pindex; fs.m = fs.first_m; VM_OBJECT_WLOCK(fs.object); } fs.first_m = NULL; /* * Zero the page if necessary and mark it valid. */ if ((fs.m->flags & PG_ZERO) == 0) { pmap_zero_page(fs.m); } else { PCPU_INC(cnt.v_ozfod); } PCPU_INC(cnt.v_zfod); fs.m->valid = VM_PAGE_BITS_ALL; /* Don't try to prefault neighboring pages. */ faultcount = 1; break; /* break to PAGE HAS BEEN FOUND */ } else { KASSERT(fs.object != next_object, ("object loop %p", next_object)); VM_OBJECT_WLOCK(next_object); vm_object_pip_add(next_object, 1); if (fs.object != fs.first_object) vm_object_pip_wakeup(fs.object); VM_OBJECT_WUNLOCK(fs.object); fs.object = next_object; } } vm_page_assert_xbusied(fs.m); /* * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock * is held.] */ /* * If the page is being written, but isn't already owned by the * top-level object, we have to copy it into a new page owned by the * top-level object. */ if (fs.object != fs.first_object) { /* * We only really need to copy if we want to write it. */ if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { /* * This allows pages to be virtually copied from a * backing_object into the first_object, where the * backing object has no other refs to it, and cannot * gain any more refs. Instead of a bcopy, we just * move the page from the backing object to the * first object. Note that we must mark the page * dirty in the first object so that it will go out * to swap when needed. */ is_first_object_locked = FALSE; if ( /* * Only one shadow object */ (fs.object->shadow_count == 1) && /* * No COW refs, except us */ (fs.object->ref_count == 1) && /* * No one else can look this object up */ (fs.object->handle == NULL) && /* * No other ways to look the object up */ ((fs.object->type == OBJT_DEFAULT) || (fs.object->type == OBJT_SWAP)) && (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && /* * We don't chase down the shadow chain */ fs.object == fs.first_object->backing_object) { /* * get rid of the unnecessary page */ vm_page_lock(fs.first_m); vm_page_free(fs.first_m); vm_page_unlock(fs.first_m); /* * grab the page and put it into the * process'es object. The page is * automatically made dirty. */ if (vm_page_rename(fs.m, fs.first_object, fs.first_pindex)) { unlock_and_deallocate(&fs); goto RetryFault; } #if VM_NRESERVLEVEL > 0 /* * Rename the reservation. */ vm_reserv_rename(fs.m, fs.first_object, fs.object, OFF_TO_IDX( fs.first_object->backing_object_offset)); #endif vm_page_xbusy(fs.m); fs.first_m = fs.m; fs.m = NULL; PCPU_INC(cnt.v_cow_optim); } else { /* * Oh, well, lets copy it. */ pmap_copy_page(fs.m, fs.first_m); fs.first_m->valid = VM_PAGE_BITS_ALL; if (wired && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) { vm_page_lock(fs.first_m); vm_page_wire(fs.first_m); vm_page_unlock(fs.first_m); vm_page_lock(fs.m); vm_page_unwire(fs.m, PQ_INACTIVE); vm_page_unlock(fs.m); } /* * We no longer need the old page or object. */ release_page(&fs); } /* * fs.object != fs.first_object due to above * conditional */ vm_object_pip_wakeup(fs.object); VM_OBJECT_WUNLOCK(fs.object); /* * Only use the new page below... */ fs.object = fs.first_object; fs.pindex = fs.first_pindex; fs.m = fs.first_m; if (!is_first_object_locked) VM_OBJECT_WLOCK(fs.object); PCPU_INC(cnt.v_cow_faults); curthread->td_cow++; } else { prot &= ~VM_PROT_WRITE; } } /* * We must verify that the maps have not changed since our last * lookup. */ if (!fs.lookup_still_valid) { vm_object_t retry_object; vm_pindex_t retry_pindex; vm_prot_t retry_prot; if (!vm_map_trylock_read(fs.map)) { release_page(&fs); unlock_and_deallocate(&fs); goto RetryFault; } fs.lookup_still_valid = TRUE; if (fs.map->timestamp != map_generation) { result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); /* * If we don't need the page any longer, put it on the inactive * list (the easiest thing to do here). If no one needs it, * pageout will grab it eventually. */ if (result != KERN_SUCCESS) { release_page(&fs); unlock_and_deallocate(&fs); /* * If retry of map lookup would have blocked then * retry fault from start. */ if (result == KERN_FAILURE) goto RetryFault; return (result); } if ((retry_object != fs.first_object) || (retry_pindex != fs.first_pindex)) { release_page(&fs); unlock_and_deallocate(&fs); goto RetryFault; } /* * Check whether the protection has changed or the object has * been copied while we left the map unlocked. Changing from * read to write permission is OK - we leave the page * write-protected, and catch the write fault. Changing from * write to read permission means that we can't mark the page * write-enabled after all. */ prot &= retry_prot; } } /* * If the page was filled by a pager, update the map entry's * last read offset. Since the pager does not return the * actual set of pages that it read, this update is based on * the requested set. Typically, the requested and actual * sets are the same. * * XXX The following assignment modifies the map * without holding a write lock on it. */ if (hardfault) fs.entry->next_read = fs.pindex + faultcount - reqpage; vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); vm_page_assert_xbusied(fs.m); /* * Page must be completely valid or it is not fit to * map into user space. vm_pager_get_pages() ensures this. */ KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, ("vm_fault: page %p partially invalid", fs.m)); VM_OBJECT_WUNLOCK(fs.object); /* * Put this page into the physical map. We had to do the unlock above * because pmap_enter() may sleep. We don't put the page * back on the active queue until later so that the pageout daemon * won't find it (yet). */ pmap_enter(fs.map->pmap, vaddr, fs.m, prot, fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && wired == 0) vm_fault_prefault(&fs, vaddr, faultcount, reqpage); VM_OBJECT_WLOCK(fs.object); vm_page_lock(fs.m); /* * If the page is not wired down, then put it where the pageout daemon * can find it. */ if (fault_flags & VM_FAULT_CHANGE_WIRING) { if (wired) vm_page_wire(fs.m); else vm_page_unwire(fs.m, PQ_ACTIVE); } else vm_page_activate(fs.m); if (m_hold != NULL) { *m_hold = fs.m; vm_page_hold(fs.m); } vm_page_unlock(fs.m); vm_page_xunbusy(fs.m); /* * Unlock everything, and return */ unlock_and_deallocate(&fs); if (hardfault) { PCPU_INC(cnt.v_io_faults); curthread->td_ru.ru_majflt++; } else curthread->td_ru.ru_minflt++; return (KERN_SUCCESS); } /* * Speed up the reclamation of pages that precede the faulting pindex within * the first object of the shadow chain. Essentially, perform the equivalent * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes * the faulting pindex by the cluster size when the pages read by vm_fault() * cross a cluster-size boundary. The cluster size is the greater of the * smallest superpage size and VM_FAULT_DONTNEED_MIN. * * When "fs->first_object" is a shadow object, the pages in the backing object * that precede the faulting pindex are deactivated by vm_fault(). So, this * function must only be concerned with pages in the first object. */ static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) { vm_map_entry_t entry; vm_object_t first_object, object; vm_offset_t end, start; vm_page_t m, m_next; vm_pindex_t pend, pstart; vm_size_t size; object = fs->object; VM_OBJECT_ASSERT_WLOCKED(object); first_object = fs->first_object; if (first_object != object) { if (!VM_OBJECT_TRYWLOCK(first_object)) { VM_OBJECT_WUNLOCK(object); VM_OBJECT_WLOCK(first_object); VM_OBJECT_WLOCK(object); } } /* Neither fictitious nor unmanaged pages can be reclaimed. */ if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { size = VM_FAULT_DONTNEED_MIN; if (MAXPAGESIZES > 1 && size < pagesizes[1]) size = pagesizes[1]; end = rounddown2(vaddr, size); if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && (entry = fs->entry)->start < end) { if (end - entry->start < size) start = entry->start; else start = end - size; pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); pstart = OFF_TO_IDX(entry->offset) + atop(start - entry->start); m_next = vm_page_find_least(first_object, pstart); pend = OFF_TO_IDX(entry->offset) + atop(end - entry->start); while ((m = m_next) != NULL && m->pindex < pend) { m_next = TAILQ_NEXT(m, listq); if (m->valid != VM_PAGE_BITS_ALL || vm_page_busied(m)) continue; vm_page_lock(m); if (m->hold_count == 0 && m->wire_count == 0) vm_page_advise(m, MADV_DONTNEED); vm_page_unlock(m); } } } if (first_object != object) VM_OBJECT_WUNLOCK(first_object); } /* * vm_fault_prefault provides a quick way of clustering * pagefaults into a processes address space. It is a "cousin" * of vm_map_pmap_enter, except it runs at page fault time instead * of mmap time. */ static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, int faultcount, int reqpage) { pmap_t pmap; vm_map_entry_t entry; vm_object_t backing_object, lobject; vm_offset_t addr, starta; vm_pindex_t pindex; vm_page_t m; int backward, forward, i; pmap = fs->map->pmap; if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) return; if (faultcount > 0) { backward = reqpage; forward = faultcount - reqpage - 1; } else { backward = PFBAK; forward = PFFOR; } entry = fs->entry; starta = addra - backward * PAGE_SIZE; if (starta < entry->start) { starta = entry->start; } else if (starta > addra) { starta = 0; } /* * Generate the sequence of virtual addresses that are candidates for * prefaulting in an outward spiral from the faulting virtual address, * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... * If the candidate address doesn't have a backing physical page, then * the loop immediately terminates. */ for (i = 0; i < 2 * imax(backward, forward); i++) { addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : PAGE_SIZE); if (addr > addra + forward * PAGE_SIZE) addr = 0; if (addr < starta || addr >= entry->end) continue; if (!pmap_is_prefaultable(pmap, addr)) continue; pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; lobject = entry->object.vm_object; VM_OBJECT_RLOCK(lobject); while ((m = vm_page_lookup(lobject, pindex)) == NULL && lobject->type == OBJT_DEFAULT && (backing_object = lobject->backing_object) != NULL) { KASSERT((lobject->backing_object_offset & PAGE_MASK) == 0, ("vm_fault_prefault: unaligned object offset")); pindex += lobject->backing_object_offset >> PAGE_SHIFT; VM_OBJECT_RLOCK(backing_object); VM_OBJECT_RUNLOCK(lobject); lobject = backing_object; } if (m == NULL) { VM_OBJECT_RUNLOCK(lobject); break; } if (m->valid == VM_PAGE_BITS_ALL && (m->flags & PG_FICTITIOUS) == 0) pmap_enter_quick(pmap, addr, m, entry->protection); VM_OBJECT_RUNLOCK(lobject); } } /* * Hold each of the physical pages that are mapped by the specified range of * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid * and allow the specified types of access, "prot". If all of the implied * pages are successfully held, then the number of held pages is returned * together with pointers to those pages in the array "ma". However, if any * of the pages cannot be held, -1 is returned. */ int vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, vm_prot_t prot, vm_page_t *ma, int max_count) { vm_offset_t end, va; vm_page_t *mp; int count; boolean_t pmap_failed; if (len == 0) return (0); end = round_page(addr + len); addr = trunc_page(addr); /* * Check for illegal addresses. */ if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) return (-1); if (atop(end - addr) > max_count) panic("vm_fault_quick_hold_pages: count > max_count"); count = atop(end - addr); /* * Most likely, the physical pages are resident in the pmap, so it is * faster to try pmap_extract_and_hold() first. */ pmap_failed = FALSE; for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { *mp = pmap_extract_and_hold(map->pmap, va, prot); if (*mp == NULL) pmap_failed = TRUE; else if ((prot & VM_PROT_WRITE) != 0 && (*mp)->dirty != VM_PAGE_BITS_ALL) { /* * Explicitly dirty the physical page. Otherwise, the * caller's changes may go unnoticed because they are * performed through an unmanaged mapping or by a DMA * operation. * * The object lock is not held here. * See vm_page_clear_dirty_mask(). */ vm_page_dirty(*mp); } } if (pmap_failed) { /* * One or more pages could not be held by the pmap. Either no * page was mapped at the specified virtual address or that * mapping had insufficient permissions. Attempt to fault in * and hold these pages. */ for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) if (*mp == NULL && vm_fault_hold(map, va, prot, VM_FAULT_NORMAL, mp) != KERN_SUCCESS) goto error; } return (count); error: for (mp = ma; mp < ma + count; mp++) if (*mp != NULL) { vm_page_lock(*mp); vm_page_unhold(*mp); vm_page_unlock(*mp); } return (-1); } /* * Routine: * vm_fault_copy_entry * Function: * Create new shadow object backing dst_entry with private copy of * all underlying pages. When src_entry is equal to dst_entry, * function implements COW for wired-down map entry. Otherwise, * it forks wired entry into dst_map. * * In/out conditions: * The source and destination maps must be locked for write. * The source map entry must be wired down (or be a sharing map * entry corresponding to a main map entry that is wired down). */ void vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, vm_map_entry_t dst_entry, vm_map_entry_t src_entry, vm_ooffset_t *fork_charge) { vm_object_t backing_object, dst_object, object, src_object; vm_pindex_t dst_pindex, pindex, src_pindex; vm_prot_t access, prot; vm_offset_t vaddr; vm_page_t dst_m; vm_page_t src_m; boolean_t upgrade; #ifdef lint src_map++; #endif /* lint */ upgrade = src_entry == dst_entry; access = prot = dst_entry->protection; src_object = src_entry->object.vm_object; src_pindex = OFF_TO_IDX(src_entry->offset); if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { dst_object = src_object; vm_object_reference(dst_object); } else { /* * Create the top-level object for the destination entry. (Doesn't * actually shadow anything - we copy the pages directly.) */ dst_object = vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(dst_entry->end - dst_entry->start)); #if VM_NRESERVLEVEL > 0 dst_object->flags |= OBJ_COLORED; dst_object->pg_color = atop(dst_entry->start); #endif } VM_OBJECT_WLOCK(dst_object); KASSERT(upgrade || dst_entry->object.vm_object == NULL, ("vm_fault_copy_entry: vm_object not NULL")); if (src_object != dst_object) { dst_entry->object.vm_object = dst_object; dst_entry->offset = 0; dst_object->charge = dst_entry->end - dst_entry->start; } if (fork_charge != NULL) { KASSERT(dst_entry->cred == NULL, ("vm_fault_copy_entry: leaked swp charge")); dst_object->cred = curthread->td_ucred; crhold(dst_object->cred); *fork_charge += dst_object->charge; } else if (dst_object->cred == NULL) { KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", dst_entry)); dst_object->cred = dst_entry->cred; dst_entry->cred = NULL; } /* * If not an upgrade, then enter the mappings in the pmap as * read and/or execute accesses. Otherwise, enter them as * write accesses. * * A writeable large page mapping is only created if all of * the constituent small page mappings are modified. Marking * PTEs as modified on inception allows promotion to happen * without taking potentially large number of soft faults. */ if (!upgrade) access &= ~VM_PROT_WRITE; /* * Loop through all of the virtual pages within the entry's * range, copying each page from the source object to the * destination object. Since the source is wired, those pages * must exist. In contrast, the destination is pageable. * Since the destination object does share any backing storage * with the source object, all of its pages must be dirtied, * regardless of whether they can be written. */ for (vaddr = dst_entry->start, dst_pindex = 0; vaddr < dst_entry->end; vaddr += PAGE_SIZE, dst_pindex++) { again: /* * Find the page in the source object, and copy it in. * Because the source is wired down, the page will be * in memory. */ if (src_object != dst_object) VM_OBJECT_RLOCK(src_object); object = src_object; pindex = src_pindex + dst_pindex; while ((src_m = vm_page_lookup(object, pindex)) == NULL && (backing_object = object->backing_object) != NULL) { /* * Unless the source mapping is read-only or * it is presently being upgraded from * read-only, the first object in the shadow * chain should provide all of the pages. In * other words, this loop body should never be * executed when the source mapping is already * read/write. */ KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || upgrade, ("vm_fault_copy_entry: main object missing page")); VM_OBJECT_RLOCK(backing_object); pindex += OFF_TO_IDX(object->backing_object_offset); if (object != dst_object) VM_OBJECT_RUNLOCK(object); object = backing_object; } KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); if (object != dst_object) { /* * Allocate a page in the destination object. */ dst_m = vm_page_alloc(dst_object, (src_object == dst_object ? src_pindex : 0) + dst_pindex, VM_ALLOC_NORMAL); if (dst_m == NULL) { VM_OBJECT_WUNLOCK(dst_object); VM_OBJECT_RUNLOCK(object); VM_WAIT; VM_OBJECT_WLOCK(dst_object); goto again; } pmap_copy_page(src_m, dst_m); VM_OBJECT_RUNLOCK(object); dst_m->valid = VM_PAGE_BITS_ALL; dst_m->dirty = VM_PAGE_BITS_ALL; } else { dst_m = src_m; if (vm_page_sleep_if_busy(dst_m, "fltupg")) goto again; vm_page_xbusy(dst_m); KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, ("invalid dst page %p", dst_m)); } VM_OBJECT_WUNLOCK(dst_object); /* * Enter it in the pmap. If a wired, copy-on-write * mapping is being replaced by a write-enabled * mapping, then wire that new mapping. */ pmap_enter(dst_map->pmap, vaddr, dst_m, prot, access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); /* * Mark it no longer busy, and put it on the active list. */ VM_OBJECT_WLOCK(dst_object); if (upgrade) { if (src_m != dst_m) { vm_page_lock(src_m); vm_page_unwire(src_m, PQ_INACTIVE); vm_page_unlock(src_m); vm_page_lock(dst_m); vm_page_wire(dst_m); vm_page_unlock(dst_m); } else { KASSERT(dst_m->wire_count > 0, ("dst_m %p is not wired", dst_m)); } } else { vm_page_lock(dst_m); vm_page_activate(dst_m); vm_page_unlock(dst_m); } vm_page_xunbusy(dst_m); } VM_OBJECT_WUNLOCK(dst_object); if (upgrade) { dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); vm_object_deallocate(src_object); } } /* * This routine checks around the requested page for other pages that * might be able to be faulted in. This routine brackets the viable * pages for the pages to be paged in. * * Inputs: * m, rbehind, rahead * * Outputs: * marray (array of vm_page_t), reqpage (index of requested page) * * Return value: * number of pages in marray */ static int vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) vm_page_t m; int rbehind; int rahead; vm_page_t *marray; int *reqpage; { int i,j; vm_object_t object; vm_pindex_t pindex, startpindex, endpindex, tpindex; vm_page_t rtm; int cbehind, cahead; VM_OBJECT_ASSERT_WLOCKED(m->object); object = m->object; pindex = m->pindex; cbehind = cahead = 0; /* * if the requested page is not available, then give up now */ if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { return 0; } if ((cbehind == 0) && (cahead == 0)) { *reqpage = 0; marray[0] = m; return 1; } if (rahead > cahead) { rahead = cahead; } if (rbehind > cbehind) { rbehind = cbehind; } /* * scan backward for the read behind pages -- in memory */ if (pindex > 0) { if (rbehind > pindex) { rbehind = pindex; startpindex = 0; } else { startpindex = pindex - rbehind; } if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && rtm->pindex >= startpindex) startpindex = rtm->pindex + 1; /* tpindex is unsigned; beware of numeric underflow. */ for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && tpindex < pindex; i++, tpindex--) { rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | VM_ALLOC_IFNOTCACHED); if (rtm == NULL) { /* * Shift the allocated pages to the * beginning of the array. */ for (j = 0; j < i; j++) { marray[j] = marray[j + tpindex + 1 - startpindex]; } break; } marray[tpindex - startpindex] = rtm; } } else { startpindex = 0; i = 0; } marray[i] = m; /* page offset of the required page */ *reqpage = i; tpindex = pindex + 1; i++; /* * scan forward for the read ahead pages */ endpindex = tpindex + rahead; if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) endpindex = rtm->pindex; if (endpindex > object->size) endpindex = object->size; for (; tpindex < endpindex; i++, tpindex++) { rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | VM_ALLOC_IFNOTCACHED); if (rtm == NULL) { break; } marray[i] = rtm; } /* return number of pages */ return i; } /* * Block entry into the machine-independent layer's page fault handler by * the calling thread. Subsequent calls to vm_fault() by that thread will * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of * spurious page faults. */ int vm_fault_disable_pagefaults(void) { return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); } void vm_fault_enable_pagefaults(int save) { curthread_pflags_restore(save); }