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Move the increment of vm object generation count into

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vm_object_set_writeable_dirty().

Fix an issue where restart of the scan in vm_object_page_clean() did
not removed write permissions for newly added pages or, if the mapping
for some already scanned page changed to writeable due to fault.
Merge the two loops in vm_object_page_clean(), doing the remove of
write permission and cleaning in the same loop. The restart of the
loop then correctly downgrade writeable mappings.

Fix an issue where a second caller to msync() might actually return
before the first caller had actually completed flushing the
pages. Clear the OBJ_MIGHTBEDIRTY flag after the cleaning loop, not
before.

Calls to pmap_is_modified() are not needed after pmap_remove_write()
there.

Proposed, reviewed and tested by:	alc
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2010-12-29 12:53:53 +00:00
parent a738d4cf20
commit 3280870dca
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=216799
2 changed files with 34 additions and 32 deletions
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65
sys/vm/vm_object.c
View File

@ -101,7 +101,9 @@ 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 pagerflags, int flags, int *clearobjflags);
static boolean_t vm_object_page_remove_write(vm_page_t p, int flags,
int *clearobjflags);
static void vm_object_qcollapse(vm_object_t object);
static void vm_object_vndeallocate(vm_object_t object);
@ -753,6 +755,24 @@ vm_object_terminate(vm_object_t object)
vm_object_destroy(object);
}
static boolean_t
vm_object_page_remove_write(vm_page_t p, int flags, int *clearobjflags)
{
/*
* If we have been asked to skip nosync pages and this is a
* nosync page, skip it. Note that the object flags were not
* cleared in this case so we do not have to set them.
*/
if ((flags & OBJPC_NOSYNC) != 0 && (p->oflags & VPO_NOSYNC) != 0) {
*clearobjflags = 0;
return (FALSE);
} else {
pmap_remove_write(p);
return (p->dirty != 0);
}
}
/*
* vm_object_page_clean
*
@ -799,17 +819,6 @@ vm_object_page_clean(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
* object flags.
*/
clearobjflags = 1;
for (p = vm_page_find_least(object, start);
p != NULL && p->pindex < tend; p = TAILQ_NEXT(p, listq)) {
if ((flags & OBJPC_NOSYNC) != 0 &&
(p->oflags & VPO_NOSYNC) != 0)
clearobjflags = 0;
else
pmap_remove_write(p);
}
if (clearobjflags && (start == 0) && (tend == object->size))
vm_object_clear_flag(object, OBJ_MIGHTBEDIRTY);
rescan:
curgeneration = object->generation;
@ -827,20 +836,11 @@ vm_object_page_clean(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
np = vm_page_find_least(object, pi);
continue;
}
vm_page_test_dirty(p);
if (p->dirty == 0)
if (!vm_object_page_remove_write(p, flags, &clearobjflags))
continue;
/*
* If we have been asked to skip nosync pages and this is a
* nosync page, skip it. Note that the object flags were
* not cleared in this case so we do not have to set them.
*/
if ((flags & OBJPC_NOSYNC) != 0 &&
(p->oflags & VPO_NOSYNC) != 0)
continue;
n = vm_object_page_collect_flush(object, p, pagerflags);
n = vm_object_page_collect_flush(object, p, pagerflags,
flags, &clearobjflags);
if (object->generation != curgeneration)
goto rescan;
np = vm_page_find_least(object, pi + n);
@ -850,10 +850,13 @@ vm_object_page_clean(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
#endif
vm_object_clear_flag(object, OBJ_CLEANING);
if (clearobjflags && start == 0 && tend == object->size)
vm_object_clear_flag(object, OBJ_MIGHTBEDIRTY);
}
static int
vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags)
vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags,
int flags, int *clearobjflags)
{
vm_page_t ma[vm_pageout_page_count], p_first, tp;
int count, i, mreq, runlen;
@ -869,8 +872,7 @@ vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags)
tp = vm_page_next(tp);
if (tp == NULL || tp->busy != 0 || (tp->oflags & VPO_BUSY) != 0)
break;
vm_page_test_dirty(tp);
if (tp->dirty == 0)
if (!vm_object_page_remove_write(tp, flags, clearobjflags))
break;
}
@ -878,8 +880,7 @@ vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags)
tp = vm_page_prev(p_first);
if (tp == NULL || tp->busy != 0 || (tp->oflags & VPO_BUSY) != 0)
break;
vm_page_test_dirty(tp);
if (tp->dirty == 0)
if (!vm_object_page_remove_write(tp, flags, clearobjflags))
break;
p_first = tp;
mreq++;
@ -1985,8 +1986,10 @@ vm_object_set_writeable_dirty(vm_object_t object)
{
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
if (object->type != OBJT_VNODE ||
(object->flags & OBJ_MIGHTBEDIRTY) != 0)
if (object->type != OBJT_VNODE)
return;
object->generation++;
if ((object->flags & OBJ_MIGHTBEDIRTY) != 0)
return;
vm_object_set_flag(object, OBJ_MIGHTBEDIRTY);
}

1
sys/vm/vm_page.c
View File

@ -811,7 +811,6 @@ vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
}
}
object->root = m;
object->generation++;
/*
* show that the object has one more resident page.