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fix amap_extend() to handle amaps where we previously failed to allocate

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the ppref memory.
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chs 2020-08-18 10:40:20 +00:00
parent daaf9b06cf
commit 752f40af2e
1 changed files with 33 additions and 3 deletions
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36
sys/uvm/uvm_amap.c
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@ -1,4 +1,4 @@
/* $NetBSD: uvm_amap.c,v 1.122 2020/07/09 05:57:15 skrll Exp $ */
/* $NetBSD: uvm_amap.c,v 1.123 2020/08/18 10:40:20 chs Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
@ -35,7 +35,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.122 2020/07/09 05:57:15 skrll Exp $");
__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.123 2020/08/18 10:40:20 chs Exp $");
#include "opt_uvmhist.h"
@ -353,7 +353,7 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize, int flags)
struct vm_amap *amap = entry->aref.ar_amap;
int slotoff = entry->aref.ar_pageoff;
int slotmapped, slotadd, slotneed, slotadded, slotalloc;
int slotadj, slotarea;
int slotadj, slotarea, slotendoff;
int oldnslots;
#ifdef UVM_AMAP_PPREF
int *newppref, *oldppref;
@ -387,6 +387,36 @@ amap_extend(struct vm_map_entry *entry, vsize_t addsize, int flags)
slotarea = amap->am_maxslot - slotmapped;
}
/*
* Because this amap only has 1 ref, we know that there is
* only one vm_map_entry pointing to it, and the one entry is
* using slots between slotoff and slotoff + slotmapped. If
* we have been using ppref then we know that only slots in
* the one map entry's range can have anons, since ppref
* allowed us to free any anons outside that range as other map
* entries which used this amap were removed. But without ppref,
* we couldn't know which slots were still needed by other map
* entries, so we couldn't free any anons as we removed map
* entries, and so any slot from 0 to am_nslot can have an
* anon. But now that we know there is only one map entry
* left and we know its range, we can free up any anons
* outside that range. This is necessary because the rest of
* this function assumes that there are no anons in the amap
* outside of the one map entry's range.
*/
slotendoff = slotoff + slotmapped;
if (amap->am_ppref == PPREF_NONE) {
amap_wiperange(amap, 0, slotoff);
amap_wiperange(amap, slotendoff, amap->am_nslot - slotendoff);
}
for (i = 0; i < slotoff; i++) {
KASSERT(amap->am_anon[i] == NULL);
}
for (i = slotendoff; i < amap->am_nslot - slotendoff; i++) {
KASSERT(amap->am_anon[i] == NULL);
}
/*
* case 1: we already have enough slots in the map and thus
* only need to bump the reference counts on the slots we are