Author: alc
Date: Wed Sep 10 05:52:30 2014
New Revision: 271351
URL: http://svnweb.freebsd.org/changeset/base/271351
Log:
Fix a boundary case error in vm_reserv_alloc_contig(): If a reservation
isn't being allocated for the last of the requested pages, because a
reservation won't fit in the gap between allocated pages, then the
reservation structure shouldn't be initialized.
While I'm here, improve the nearby comments.
Reported by: jeff, pho
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
Modified:
head/sys/vm/vm_reserv.c
Modified: head/sys/vm/vm_reserv.c
==============================================================================
--- head/sys/vm/vm_reserv.c Wed Sep 10 05:44:15 2014 (r271350)
+++ head/sys/vm/vm_reserv.c Wed Sep 10 05:52:30 2014 (r271351)
@@ -364,7 +364,7 @@ vm_reserv_populate(vm_reserv_t rv, int i
/*
* Allocates a contiguous set of physical pages of the given size "npages"
- * from an existing or newly-created reservation. All of the physical pages
+ * from existing or newly created reservations. All of the physical pages
* must be at or above the given physical address "low" and below the given
* physical address "high". The given value "alignment" determines the
* alignment of the first physical page in the set. If the given value
@@ -436,8 +436,8 @@ vm_reserv_alloc_contig(vm_object_t objec
/*
* Could at least one reservation fit between the first index to the
- * left that can be used and the first index to the right that cannot
- * be used?
+ * left that can be used ("leftcap") and the first index to the right
+ * that cannot be used ("rightcap")?
*/
first = pindex - VM_RESERV_INDEX(object, pindex);
if (mpred != NULL) {
@@ -459,6 +459,13 @@ vm_reserv_alloc_contig(vm_object_t objec
if (first + maxpages > rightcap) {
if (maxpages == VM_LEVEL_0_NPAGES)
return (NULL);
+
+ /*
+ * At least one reservation will fit between "leftcap"
+ * and "rightcap". However, a reservation for the
+ * last of the requested pages will not fit. Reduce
+ * the size of the upcoming allocation accordingly.
+ */
allocpages = minpages;
}
}
@@ -482,16 +489,23 @@ vm_reserv_alloc_contig(vm_object_t objec
}
/*
- * Allocate and populate the new reservations. The alignment and
- * boundary specified for this allocation may be different from the
- * alignment and boundary specified for the requested pages. For
- * instance, the specified index may not be the first page within the
- * first new reservation.
+ * Allocate the physical pages. The alignment and boundary specified
+ * for this allocation may be different from the alignment and
+ * boundary specified for the requested pages. For instance, the
+ * specified index may not be the first page within the first new
+ * reservation.
*/
m = vm_phys_alloc_contig(allocpages, low, high, ulmax(alignment,
VM_LEVEL_0_SIZE), boundary > VM_LEVEL_0_SIZE ? boundary : 0);
if (m == NULL)
return (NULL);
+
+ /*
+ * The allocated physical pages always begin at a reservation
+ * boundary, but they do not always end at a reservation boundary.
+ * Initialize every reservation that is completely covered by the
+ * allocated physical pages.
+ */
m_ret = NULL;
index = VM_RESERV_INDEX(object, pindex);
do {
@@ -525,7 +539,7 @@ vm_reserv_alloc_contig(vm_object_t objec
m += VM_LEVEL_0_NPAGES;
first += VM_LEVEL_0_NPAGES;
allocpages -= VM_LEVEL_0_NPAGES;
- } while (allocpages > 0);
+ } while (allocpages >= VM_LEVEL_0_NPAGES);
return (m_ret);
/*
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