Author: alc
Date: Fri Oct 12 03:09:59 2012
New Revision: 241478
URL: http://svn.freebsd.org/changeset/base/241478
Log:
MFC r241155
Update some of the comments. In particular, use "sleep" in preference
to "block" where appropriate.
Eliminate some unnecessary casts.
Make a few whitespace changes for consistency.
Modified:
stable/9/sys/vm/vm_page.c
Modified: stable/9/sys/vm/vm_page.c
==============================================================================
--- stable/9/sys/vm/vm_page.c Fri Oct 12 02:12:53 2012 (r241477)
+++ stable/9/sys/vm/vm_page.c Fri Oct 12 03:09:59 2012 (r241478)
@@ -904,11 +904,10 @@ vm_page_splay(vm_pindex_t pindex, vm_pag
*
* The pagetables are not updated but will presumably fault the page
* in if necessary, or if a kernel page the caller will at some point
- * enter the page into the kernel's pmap. We are not allowed to block
+ * enter the page into the kernel's pmap. We are not allowed to sleep
* here so we *can't* do this anyway.
*
- * The object and page must be locked.
- * This routine may not block.
+ * The object must be locked.
*/
void
vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
@@ -952,14 +951,15 @@ vm_page_insert(vm_page_t m, vm_object_t
object->root = m;
/*
- * show that the object has one more resident page.
+ * Show that the object has one more resident page.
*/
object->resident_page_count++;
+
/*
* Hold the vnode until the last page is released.
*/
if (object->resident_page_count == 1 && object->type == OBJT_VNODE)
- vhold((struct vnode *)object->handle);
+ vhold(object->handle);
/*
* Since we are inserting a new and possibly dirty page,
@@ -971,15 +971,14 @@ vm_page_insert(vm_page_t m, vm_object_t
/*
* vm_page_remove:
- * NOTE: used by device pager as well -wfj
*
* Removes the given mem entry from the object/offset-page
* table and the object page list, but do not invalidate/terminate
* the backing store.
*
- * The object and page must be locked.
* The underlying pmap entry (if any) is NOT removed here.
- * This routine may not block.
+ *
+ * The object must be locked. The page must be locked if it is managed.
*/
void
vm_page_remove(vm_page_t m)
@@ -1042,11 +1041,12 @@ vm_page_remove(vm_page_t m)
* And show that the object has one fewer resident page.
*/
object->resident_page_count--;
+
/*
* The vnode may now be recycled.
*/
if (object->resident_page_count == 0 && object->type == OBJT_VNODE)
- vdrop((struct vnode *)object->handle);
+ vdrop(object->handle);
m->object = NULL;
}
@@ -1058,8 +1058,6 @@ vm_page_remove(vm_page_t m)
* pair specified; if none is found, NULL is returned.
*
* The object must be locked.
- * This routine may not block.
- * This is a critical path routine
*/
vm_page_t
vm_page_lookup(vm_object_t object, vm_pindex_t pindex)
@@ -1082,7 +1080,6 @@ vm_page_lookup(vm_object_t object, vm_pi
* greater than or equal to the parameter pindex, or NULL.
*
* The object must be locked.
- * The routine may not block.
*/
vm_page_t
vm_page_find_least(vm_object_t object, vm_pindex_t pindex)
@@ -1142,9 +1139,6 @@ vm_page_prev(vm_page_t m)
* Move the given memory entry from its
* current object to the specified target object/offset.
*
- * The object must be locked.
- * This routine may not block.
- *
* Note: swap associated with the page must be invalidated by the move. We
* have to do this for several reasons: (1) we aren't freeing the
* page, (2) we are dirtying the page, (3) the VM system is probably
@@ -1156,6 +1150,8 @@ vm_page_prev(vm_page_t m)
* swap. If the page is on the cache, we have to deactivate it
* or vm_page_dirty() will panic. Dirty pages are not allowed
* on the cache.
+ *
+ * The objects must be locked. The page must be locked if it is managed.
*/
void
vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex)
@@ -1675,7 +1671,7 @@ vm_page_alloc_freelist(int flind, int re
/*
* vm_wait: (also see VM_WAIT macro)
*
- * Block until free pages are available for allocation
+ * Sleep until free pages are available for allocation.
* - Called in various places before memory allocations.
*/
void
@@ -1700,7 +1696,7 @@ vm_wait(void)
/*
* vm_waitpfault: (also see VM_WAITPFAULT macro)
*
- * Block until free pages are available for allocation
+ * Sleep until free pages are available for allocation.
* - Called only in vm_fault so that processes page faulting
* can be easily tracked.
* - Sleeps at a lower priority than vm_wait() so that vm_wait()ing
@@ -1767,7 +1763,6 @@ vm_page_queue_remove(int queue, vm_page_
* Remove a page from its queue.
*
* The given page must be locked.
- * This routine may not block.
*/
void
vm_pageq_remove(vm_page_t m)
@@ -1809,7 +1804,6 @@ vm_page_enqueue(int queue, vm_page_t m)
* mess with it.
*
* The page must be locked.
- * This routine may not block.
*/
void
vm_page_activate(vm_page_t m)
@@ -1844,7 +1838,6 @@ vm_page_activate(vm_page_t m)
* queues.
*
* The page queues must be locked.
- * This routine may not block.
*/
static inline void
vm_page_free_wakeup(void)
@@ -1877,10 +1870,8 @@ vm_page_free_wakeup(void)
* Returns the given page to the free list,
* disassociating it with any VM object.
*
- * Object and page must be locked prior to entry.
- * This routine may not block.
+ * The object must be locked. The page must be locked if it is managed.
*/
-
void
vm_page_free_toq(vm_page_t m)
{
@@ -1898,7 +1889,7 @@ vm_page_free_toq(vm_page_t m)
panic("vm_page_free: freeing busy page %p", m);
/*
- * unqueue, then remove page. Note that we cannot destroy
+ * Unqueue, then remove page. Note that we cannot destroy
* the page here because we do not want to call the pager's
* callback routine until after we've put the page on the
* appropriate free queue.
@@ -1964,7 +1955,6 @@ vm_page_free_toq(vm_page_t m)
* If the page is fictitious, then its wire count must remain one.
*
* The page must be locked.
- * This routine may not block.
*/
void
vm_page_wire(vm_page_t m)
@@ -2053,7 +2043,7 @@ vm_page_unwire(vm_page_t m, int activate
* to 1 if we want this page to be 'as if it were placed in the cache',
* except without unmapping it from the process address space.
*
- * This routine may not block.
+ * The page must be locked.
*/
static inline void
_vm_page_deactivate(vm_page_t m, int athead)
@@ -2145,7 +2135,7 @@ vm_page_try_to_free(vm_page_t m)
*
* Put the specified page onto the page cache queue (if appropriate).
*
- * This routine may not block.
+ * The object and page must be locked.
*/
void
vm_page_cache(vm_page_t m)
@@ -2302,6 +2292,8 @@ vm_page_cache(vm_page_t m)
* system to balance the queues, potentially recovering other unrelated
* space from active. The idea is to not force this to happen too
* often.
+ *
+ * The object and page must be locked.
*/
void
vm_page_dontneed(vm_page_t m)
@@ -2365,7 +2357,10 @@ vm_page_dontneed(vm_page_t m)
* The caller must always specify the VM_ALLOC_RETRY flag. This is intended
* to facilitate its eventual removal.
*
- * This routine may block.
+ * This routine may sleep.
+ *
+ * The object must be locked on entry. The lock will, however, be released
+ * and reacquired if the routine sleeps.
*/
vm_page_t
vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
@@ -2413,8 +2408,7 @@ retrylookup:
}
/*
- * Mapping function for valid bits or for dirty bits in
- * a page. May not block.
+ * Mapping function for valid or dirty bits in a page.
*
* Inputs are required to range within a page.
*/
@@ -2553,8 +2547,6 @@ vm_page_clear_dirty_mask(vm_page_t m, vm
* of any partial chunks touched by the range. The invalid portion of
* such chunks will be zero'd.
*
- * This routine may not block.
- *
* (base + size) must be less then or equal to PAGE_SIZE.
*/
void
@@ -2647,8 +2639,6 @@ vm_page_clear_dirty(vm_page_t m, int bas
*
* Invalidates DEV_BSIZE'd chunks within a page. Both the
* valid and dirty bits for the effected areas are cleared.
- *
- * May not block.
*/
void
vm_page_set_invalid(vm_page_t m, int base, int size)
@@ -2717,8 +2707,6 @@ vm_page_zero_invalid(vm_page_t m, boolea
* Is (partial) page valid? Note that the case where size == 0
* will return FALSE in the degenerate case where the page is
* entirely invalid, and TRUE otherwise.
- *
- * May not block.
*/
int
vm_page_is_valid(vm_page_t m, int base, int size)
@@ -2734,7 +2722,7 @@ vm_page_is_valid(vm_page_t m, int base,
}
/*
- * update dirty bits from pmap/mmu. May not block.
+ * Set the page's dirty bits if the page is modified.
*/
void
vm_page_test_dirty(vm_page_t m)
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