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freebsd-nq/sys/vm/vm_fault.c
Alan Cox f4ecdf056e Complete the page queues locking needed for the page-based copy- 
on-write (COW) mechanism.  (This mechanism is used by the zero-copy
TCP/IP implementation.)
 - Extend the scope of the page queues lock in vm_fault()
   to cover vm_page_cowfault().
 - Modify vm_page_cowfault() to release the page queues lock
   if it sleeps.
2002-10-19 18:34:39 +00:00

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/*
* 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.
*
* $FreeBSD$
*/
/*
* Page fault handling module.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_kern.h>
#include <vm/vm_pager.h>
#include <vm/vnode_pager.h>
#include <vm/vm_extern.h>
static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
#define VM_FAULT_READ_AHEAD 8
#define VM_FAULT_READ_BEHIND 7
#define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
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 __inline void
release_page(struct faultstate *fs)
{
vm_page_lock_queues();
vm_page_wakeup(fs->m);
vm_page_deactivate(fs->m);
vm_page_unlock_queues();
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_things(struct faultstate *fs, int dealloc)
{
GIANT_REQUIRED;
vm_object_pip_wakeup(fs->object);
if (fs->object != fs->first_object) {
vm_page_lock_queues();
vm_page_free(fs->first_m);
vm_page_unlock_queues();
vm_object_pip_wakeup(fs->first_object);
fs->first_m = NULL;
}
if (dealloc) {
vm_object_deallocate(fs->first_object);
}
unlock_map(fs);
if (fs->vp != NULL) {
vput(fs->vp);
fs->vp = NULL;
}
}
#define unlock_things(fs) _unlock_things(fs, 0)
#define unlock_and_deallocate(fs) _unlock_things(fs, 1)
/*
* 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_WIRE_MASK) == 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)
{
vm_prot_t prot;
int result;
boolean_t growstack, wired;
int map_generation;
vm_object_t next_object;
vm_page_t marray[VM_FAULT_READ];
int hardfault;
int faultcount;
struct faultstate fs;
hardfault = 0;
growstack = TRUE;
atomic_add_int(&cnt.v_vm_faults, 1);
mtx_lock(&Giant);
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 (result != KERN_PROTECTION_FAILURE ||
(fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) {
if (growstack && result == KERN_INVALID_ADDRESS &&
map != kernel_map && curproc != NULL) {
result = vm_map_growstack(curproc, vaddr);
if (result != KERN_SUCCESS) {
mtx_unlock(&Giant);
return (KERN_FAILURE);
}
growstack = FALSE;
goto RetryFault;
}
mtx_unlock(&Giant);
return (result);
}
/*
* If we are user-wiring a r/w segment, and it is COW, then
* we need to do the COW operation. Note that we don't COW
* currently RO sections now, because it is NOT desirable
* to COW .text. We simply keep .text from ever being COW'ed
* and take the heat that one cannot debug wired .text sections.
*/
result = vm_map_lookup(&fs.map, vaddr,
VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE,
&fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired);
if (result != KERN_SUCCESS) {
mtx_unlock(&Giant);
return (result);
}
/*
* If we don't COW now, on a user wire, the user will never
* be able to write to the mapping. If we don't make this
* restriction, the bookkeeping would be nearly impossible.
*
* XXX The following assignment modifies the map without
* holding a write lock on it.
*/
if ((fs.entry->protection & VM_PROT_WRITE) == 0)
fs.entry->max_protection &= ~VM_PROT_WRITE;
}
map_generation = fs.map->timestamp;
if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
panic("vm_fault: fault on nofault entry, addr: %lx",
(u_long)vaddr);
}
/*
* 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.
*
* XXX vnode_pager_lock() can block without releasing the map lock.
*/
vm_object_reference(fs.first_object);
fs.vp = vnode_pager_lock(fs.first_object);
vm_object_pip_add(fs.first_object, 1);
#ifdef ENABLE_VFS_IOOPT
if ((fault_type & VM_PROT_WRITE) &&
(fs.first_object->type == OBJT_VNODE)) {
vm_freeze_copyopts(fs.first_object,
fs.first_pindex, fs.first_pindex + 1);
}
#endif
fs.lookup_still_valid = TRUE;
if (wired)
fault_type = prot;
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);
mtx_unlock(&Giant);
return (KERN_PROTECTION_FAILURE);
}
/*
* See if page is resident
*/
fs.m = vm_page_lookup(fs.object, fs.pindex);
if (fs.m != NULL) {
int queue, s;
/*
* check for page-based copy on write
*/
vm_page_lock_queues();
if ((fs.m->cow) &&
(fault_type & VM_PROT_WRITE)) {
s = splvm();
vm_page_cowfault(fs.m);
splx(s);
vm_page_unlock_queues();
unlock_things(&fs);
goto RetryFault;
}
/*
* Wait/Retry if the page is busy. We have to do this
* if the page is busy via either PG_BUSY or
* vm_page_t->busy because the vm_pager may be using
* vm_page_t->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 vm_page_t->busy page except, perhaps,
* to pmap it.
*/
if ((fs.m->flags & PG_BUSY) || fs.m->busy) {
vm_page_unlock_queues();
unlock_things(&fs);
(void)vm_page_sleep_busy(fs.m, TRUE, "vmpfw");
cnt.v_intrans++;
vm_object_deallocate(fs.first_object);
goto RetryFault;
}
queue = fs.m->queue;
s = splvm();
vm_pageq_remove_nowakeup(fs.m);
splx(s);
if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) {
vm_page_activate(fs.m);
vm_page_unlock_queues();
unlock_and_deallocate(&fs);
VM_WAITPFAULT;
goto RetryFault;
}
/*
* 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_busy(fs.m);
vm_page_unlock_queues();
if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
fs.m->object != kernel_object && fs.m->object != kmem_object) {
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);
mtx_unlock(&Giant);
return (KERN_PROTECTION_FAILURE);
}
/*
* Allocate a new page for this object/offset pair.
*/
fs.m = NULL;
if (!vm_page_count_severe()) {
fs.m = vm_page_alloc(fs.object, fs.pindex,
(fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO);
}
if (fs.m == NULL) {
unlock_and_deallocate(&fs);
VM_WAITPFAULT;
goto RetryFault;
}
}
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;
int reqpage;
int ahead, behind;
u_char behavior = vm_map_entry_behavior(fs.entry);
if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
ahead = 0;
behind = 0;
} else {
behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
if (behind > VM_FAULT_READ_BEHIND)
behind = VM_FAULT_READ_BEHIND;
ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
if (ahead > VM_FAULT_READ_AHEAD)
ahead = VM_FAULT_READ_AHEAD;
}
if ((fs.first_object->type != OBJT_DEVICE) &&
(behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
(behavior != MAP_ENTRY_BEHAV_RANDOM &&
fs.pindex >= fs.entry->lastr &&
fs.pindex < fs.entry->lastr + VM_FAULT_READ))
) {
vm_pindex_t firstpindex, tmppindex;
if (fs.first_pindex < 2 * VM_FAULT_READ)
firstpindex = 0;
else
firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
vm_page_lock_queues();
/*
* note: partially valid pages cannot be
* included in the lookahead - NFS piecemeal
* writes will barf on it badly.
*/
for (tmppindex = fs.first_pindex - 1;
tmppindex >= firstpindex;
--tmppindex) {
vm_page_t mt;
mt = vm_page_lookup(fs.first_object, tmppindex);
if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL))
break;
if (mt->busy ||
(mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
mt->hold_count ||
mt->wire_count)
continue;
if (mt->dirty == 0)
vm_page_test_dirty(mt);
if (mt->dirty) {
vm_page_protect(mt, VM_PROT_NONE);
vm_page_deactivate(mt);
} else {
vm_page_cache(mt);
}
}
vm_page_unlock_queues();
ahead += behind;
behind = 0;
}
/*
* 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 PG_BUSY'd.
*
* XXX vm_fault_additional_pages() can block
* without releasing the map lock.
*/
faultcount = vm_fault_additional_pages(
fs.m, behind, ahead, marray, &reqpage);
/*
* update lastr imperfectly (we do not know how much
* getpages will actually read), but good enough.
*
* XXX The following assignment modifies the map
* without holding a write lock on it.
*/
fs.entry->lastr = fs.pindex + faultcount - behind;
/*
* 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 PG_BUSY'd.
*/
unlock_map(&fs);
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_queues();
vm_page_free(fs.m);
vm_page_unlock_queues();
fs.m = NULL;
unlock_and_deallocate(&fs);
mtx_unlock(&Giant);
return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
}
if (fs.object != fs.first_object) {
vm_page_lock_queues();
vm_page_free(fs.m);
vm_page_unlock_queues();
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);
fs.object = fs.first_object;
fs.pindex = fs.first_pindex;
fs.m = fs.first_m;
}
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 {
cnt.v_ozfod++;
}
cnt.v_zfod++;
fs.m->valid = VM_PAGE_BITS_ALL;
break; /* break to PAGE HAS BEEN FOUND */
} else {
if (fs.object != fs.first_object) {
vm_object_pip_wakeup(fs.object);
}
KASSERT(fs.object != next_object, ("object loop %p", next_object));
fs.object = next_object;
vm_object_pip_add(fs.object, 1);
}
}
KASSERT((fs.m->flags & PG_BUSY) != 0,
("vm_fault: not busy after main loop"));
/*
* 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_WRITE) {
/*
* 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.
*/
if (map_generation == fs.map->timestamp &&
/*
* 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)) &&
/*
* We don't chase down the shadow chain
*/
(fs.object == fs.first_object->backing_object) &&
/*
* grab the lock if we need to
*/
(fs.lookup_still_valid || vm_map_trylock(fs.map))) {
fs.lookup_still_valid = 1;
/*
* get rid of the unnecessary page
*/
vm_page_lock_queues();
vm_page_protect(fs.first_m, VM_PROT_NONE);
vm_page_free(fs.first_m);
vm_page_unlock_queues();
fs.first_m = NULL;
/*
* grab the page and put it into the
* process'es object. The page is
* automatically made dirty.
*/
vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
fs.first_m = fs.m;
vm_page_busy(fs.first_m);
fs.m = NULL;
cnt.v_cow_optim++;
} else {
/*
* Oh, well, lets copy it.
*/
vm_page_copy(fs.m, fs.first_m);
}
if (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);
/*
* Only use the new page below...
*/
cnt.v_cow_faults++;
fs.m = fs.first_m;
fs.object = fs.first_object;
fs.pindex = fs.first_pindex;
} else {
prot &= ~VM_PROT_WRITE;
}
}
/*
* We must verify that the maps have not changed since our last
* lookup.
*/
if (!fs.lookup_still_valid &&
(fs.map->timestamp != map_generation)) {
vm_object_t retry_object;
vm_pindex_t retry_pindex;
vm_prot_t retry_prot;
/*
* Since map entries may be pageable, make sure we can take a
* page fault on them.
*/
/*
* Unlock vnode before the lookup to avoid deadlock. E.G.
* avoid a deadlock between the inode and exec_map that can
* occur due to locks being obtained in different orders.
*/
if (fs.vp != NULL) {
vput(fs.vp);
fs.vp = NULL;
}
if (fs.map->infork) {
release_page(&fs);
unlock_and_deallocate(&fs);
goto RetryFault;
}
/*
* To avoid trying to write_lock the map while another process
* has it read_locked (in vm_map_pageable), we do not try for
* write permission. If the page is still writable, we will
* get write permission. If it is not, or has been marked
* needs_copy, we enter the mapping without write permission,
* and will merely take another fault.
*/
result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE,
&fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
map_generation = fs.map->timestamp;
/*
* If we don't need the page any longer, put it on the active
* 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);
mtx_unlock(&Giant);
return (result);
}
fs.lookup_still_valid = TRUE;
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;
}
/*
* Put this page into the physical map. We had to do the unlock above
* because pmap_enter may cause other faults. We don't put the page
* back on the active queue until later so that the page-out daemon
* won't find us (yet).
*/
if (prot & VM_PROT_WRITE) {
vm_page_flag_set(fs.m, PG_WRITEABLE);
vm_object_set_writeable_dirty(fs.m->object);
/*
* 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.
*
* If this is a NOSYNC mmap we do not want to set PG_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.
*
* Also tell the backing pager, if any, that it should remove
* any swap backing since the page is now dirty.
*/
if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
if (fs.m->dirty == 0)
vm_page_flag_set(fs.m, PG_NOSYNC);
} else {
vm_page_flag_clear(fs.m, PG_NOSYNC);
}
if (fault_flags & VM_FAULT_DIRTY) {
int s;
vm_page_dirty(fs.m);
s = splvm();
vm_pager_page_unswapped(fs.m);
splx(s);
}
}
/*
* Page had better still be busy
*/
KASSERT(fs.m->flags & PG_BUSY,
("vm_fault: page %p not busy!", fs.m));
unlock_things(&fs);
/*
* Sanity check: page must be completely valid or it is not fit to
* map into user space. vm_pager_get_pages() ensures this.
*/
if (fs.m->valid != VM_PAGE_BITS_ALL) {
vm_page_zero_invalid(fs.m, TRUE);
printf("Warning: page %p partially invalid on fault\n", fs.m);
}
pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired);
if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) {
pmap_prefault(fs.map->pmap, vaddr, fs.entry);
}
vm_page_lock_queues();
vm_page_flag_clear(fs.m, PG_ZERO);
vm_page_flag_set(fs.m, PG_REFERENCED);
/*
* If the page is not wired down, then put it where the pageout daemon
* can find it.
*/
if (fault_flags & VM_FAULT_WIRE_MASK) {
if (wired)
vm_page_wire(fs.m);
else
vm_page_unwire(fs.m, 1);
} else {
vm_page_activate(fs.m);
}
vm_page_wakeup(fs.m);
vm_page_unlock_queues();
mtx_lock_spin(&sched_lock);
if (curproc && (curproc->p_sflag & PS_INMEM) && curproc->p_stats) {
if (hardfault) {
curproc->p_stats->p_ru.ru_majflt++;
} else {
curproc->p_stats->p_ru.ru_minflt++;
}
}
mtx_unlock_spin(&sched_lock);
/*
* Unlock everything, and return
*/
vm_object_deallocate(fs.first_object);
mtx_unlock(&Giant);
return (KERN_SUCCESS);
}
/*
* vm_fault_wire:
*
* Wire down a range of virtual addresses in a map.
*/
int
vm_fault_wire(map, start, end, user_wire)
vm_map_t map;
vm_offset_t start, end;
boolean_t user_wire;
{
vm_offset_t va;
int rv;
/*
* We simulate a fault to get the page and enter it in the physical
* map. For user wiring, we only ask for read access on currently
* read-only sections.
*/
for (va = start; va < end; va += PAGE_SIZE) {
rv = vm_fault(map, va,
user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE,
user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING);
if (rv) {
if (va != start)
vm_fault_unwire(map, start, va);
return (rv);
}
}
return (KERN_SUCCESS);
}
/*
* vm_fault_unwire:
*
* Unwire a range of virtual addresses in a map.
*/
void
vm_fault_unwire(map, start, end)
vm_map_t map;
vm_offset_t start, end;
{
vm_offset_t va, pa;
pmap_t pmap;
pmap = vm_map_pmap(map);
mtx_lock(&Giant);
/*
* Since the pages are wired down, we must be able to get their
* mappings from the physical map system.
*/
for (va = start; va < end; va += PAGE_SIZE) {
pa = pmap_extract(pmap, va);
if (pa != (vm_offset_t) 0) {
pmap_change_wiring(pmap, va, FALSE);
vm_page_lock_queues();
vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
vm_page_unlock_queues();
}
}
mtx_unlock(&Giant);
}
/*
* Routine:
* vm_fault_copy_entry
* Function:
* Copy all of the pages from a wired-down map entry to another.
*
* 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(dst_map, src_map, dst_entry, src_entry)
vm_map_t dst_map;
vm_map_t src_map;
vm_map_entry_t dst_entry;
vm_map_entry_t src_entry;
{
vm_object_t dst_object;
vm_object_t src_object;
vm_ooffset_t dst_offset;
vm_ooffset_t src_offset;
vm_prot_t prot;
vm_offset_t vaddr;
vm_page_t dst_m;
vm_page_t src_m;
#ifdef lint
src_map++;
#endif /* lint */
src_object = src_entry->object.vm_object;
src_offset = src_entry->offset;
/*
* 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,
(vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start));
dst_entry->object.vm_object = dst_object;
dst_entry->offset = 0;
prot = dst_entry->max_protection;
/*
* Loop through all of the pages in the entry's range, copying each
* one from the source object (it should be there) to the destination
* object.
*/
for (vaddr = dst_entry->start, dst_offset = 0;
vaddr < dst_entry->end;
vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
/*
* Allocate a page in the destination object
*/
do {
dst_m = vm_page_alloc(dst_object,
OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
if (dst_m == NULL) {
VM_WAIT;
}
} while (dst_m == NULL);
/*
* Find the page in the source object, and copy it in.
* (Because the source is wired down, the page will be in
* memory.)
*/
src_m = vm_page_lookup(src_object,
OFF_TO_IDX(dst_offset + src_offset));
if (src_m == NULL)
panic("vm_fault_copy_wired: page missing");
vm_page_copy(src_m, dst_m);
/*
* Enter it in the pmap...
*/
vm_page_flag_clear(dst_m, PG_ZERO);
pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
vm_page_lock_queues();
vm_page_flag_set(dst_m, PG_WRITEABLE);
/*
* Mark it no longer busy, and put it on the active list.
*/
vm_page_activate(dst_m);
vm_page_wakeup(dst_m);
vm_page_unlock_queues();
}
}
/*
* 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
*
* This routine can't block.
*/
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;
GIANT_REQUIRED;
object = m->object;
pindex = m->pindex;
/*
* we don't fault-ahead for device pager
*/
if (object->type == OBJT_DEVICE) {
*reqpage = 0;
marray[0] = m;
return 1;
}
/*
* 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;
}
/*
* try to do any readahead that we might have free pages for.
*/
if ((rahead + rbehind) >
((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) {
pagedaemon_wakeup();
marray[0] = m;
*reqpage = 0;
return 1;
}
/*
* scan backward for the read behind pages -- in memory
*/
if (pindex > 0) {
if (rbehind > pindex) {
rbehind = pindex;
startpindex = 0;
} else {
startpindex = pindex - rbehind;
}
for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) {
if (vm_page_lookup(object, tpindex)) {
startpindex = tpindex + 1;
break;
}
if (tpindex == 0)
break;
}
for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) {
rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
if (rtm == NULL) {
vm_page_lock_queues();
for (j = 0; j < i; j++) {
vm_page_free(marray[j]);
}
vm_page_unlock_queues();
marray[0] = m;
*reqpage = 0;
return 1;
}
marray[i] = 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 (endpindex > object->size)
endpindex = object->size;
for (; tpindex < endpindex; i++, tpindex++) {
if (vm_page_lookup(object, tpindex)) {
break;
}
rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
if (rtm == NULL) {
break;
}
marray[i] = rtm;
}
/* return number of bytes of pages */
return i;
}
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