Module Name: src
Committed By: rmind
Date: Thu Jun 23 18:15:30 UTC 2011
Modified Files:
src/sys/uvm: uvm_amap.c
Log Message:
Clean-up, add asserts, slightly simplify.
To generate a diff of this commit:
cvs rdiff -u -r1.95 -r1.96 src/sys/uvm/uvm_amap.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/uvm/uvm_amap.c
diff -u src/sys/uvm/uvm_amap.c:1.95 src/sys/uvm/uvm_amap.c:1.96
--- src/sys/uvm/uvm_amap.c:1.95 Sat Jun 18 21:13:29 2011
+++ src/sys/uvm/uvm_amap.c Thu Jun 23 18:15:30 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: uvm_amap.c,v 1.95 2011/06/18 21:13:29 rmind Exp $ */
+/* $NetBSD: uvm_amap.c,v 1.96 2011/06/23 18:15:30 rmind 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 1.95 2011/06/18 21:13:29 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.96 2011/06/23 18:15:30 rmind Exp $");
#include "opt_uvmhist.h"
@@ -164,7 +164,7 @@
*
* => Note: lock is not set.
*/
-static inline struct vm_amap *
+static struct vm_amap *
amap_alloc1(int slots, int padslots, int flags)
{
const bool nowait = (flags & UVM_FLAG_NOWAIT) != 0;
@@ -763,34 +763,39 @@
amap_copy(struct vm_map *map, struct vm_map_entry *entry, int flags,
vaddr_t startva, vaddr_t endva)
{
+ const int waitf = (flags & AMAP_COPY_NOWAIT) ? UVM_FLAG_NOWAIT : 0;
struct vm_amap *amap, *srcamap;
struct vm_anon *tofree;
- int slots, lcv;
- vaddr_t chunksize;
- const int waitf = (flags & AMAP_COPY_NOWAIT) ? UVM_FLAG_NOWAIT : 0;
- const bool canchunk = (flags & AMAP_COPY_NOCHUNK) == 0;
kmutex_t *lock;
+ u_int slots, lcv;
+ vsize_t len;
+
UVMHIST_FUNC("amap_copy"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist, " (map=%p, entry=%p, flags=%d)",
map, entry, flags, 0);
KASSERT(map != kernel_map); /* we use nointr pool */
+ srcamap = entry->aref.ar_amap;
+ len = entry->end - entry->start;
+
/*
- * is there a map to copy? if not, create one from scratch.
+ * Is there an amap to copy? If not, create one.
*/
- if (entry->aref.ar_amap == NULL) {
+ if (srcamap == NULL) {
+ const bool canchunk = (flags & AMAP_COPY_NOCHUNK) == 0;
/*
- * check to see if we have a large amap that we can
- * chunk. we align startva/endva to chunk-sized
+ * Check to see if we have a large amap that we can
+ * chunk. We align startva/endva to chunk-sized
* boundaries and then clip to them.
*/
- if (canchunk && atop(entry->end - entry->start) >=
- UVM_AMAP_LARGE) {
- /* convert slots to bytes */
+ if (canchunk && atop(len) >= UVM_AMAP_LARGE) {
+ vsize_t chunksize;
+
+ /* Convert slots to bytes. */
chunksize = UVM_AMAP_CHUNK << PAGE_SHIFT;
startva = (startva / chunksize) * chunksize;
endva = roundup(endva, chunksize);
@@ -798,9 +803,11 @@
"to 0x%x->0x%x", entry->start, entry->end, startva,
endva);
UVM_MAP_CLIP_START(map, entry, startva, NULL);
- /* watch out for endva wrap-around! */
- if (endva >= startva)
+
+ /* Watch out for endva wrap-around! */
+ if (endva >= startva) {
UVM_MAP_CLIP_END(map, entry, endva, NULL);
+ }
}
if ((flags & AMAP_COPY_NOMERGE) == 0 &&
@@ -809,65 +816,66 @@
}
UVMHIST_LOG(maphist, "<- done [creating new amap 0x%x->0x%x]",
- entry->start, entry->end, 0, 0);
+ entry->start, entry->end, 0, 0);
+
+ /* Allocate an initialised amap and install it. */
entry->aref.ar_pageoff = 0;
- entry->aref.ar_amap = amap_alloc(entry->end - entry->start, 0,
- waitf);
- if (entry->aref.ar_amap != NULL)
+ entry->aref.ar_amap = amap_alloc(len, 0, waitf);
+ if (entry->aref.ar_amap != NULL) {
entry->etype &= ~UVM_ET_NEEDSCOPY;
+ }
return;
}
/*
- * first check and see if we are the only map entry
- * referencing the amap we currently have. if so, then we can
- * just take it over rather than copying it. note that we are
- * reading am_ref with the amap unlocked... the value can only
- * be one if we have the only reference to the amap (via our
- * locked map). if we are greater than one we fall through to
- * the next case (where we double check the value).
+ * First check and see if we are the only map entry referencing
+ * he amap we currently have. If so, then just take it over instead
+ * of copying it. Note that we are reading am_ref without lock held
+ * as the value value can only be one if we have the only reference
+ * to the amap (via our locked map). If the value is greater than
+ * one, then allocate amap and re-check the value.
*/
- if (entry->aref.ar_amap->am_ref == 1) {
+ if (srcamap->am_ref == 1) {
entry->etype &= ~UVM_ET_NEEDSCOPY;
UVMHIST_LOG(maphist, "<- done [ref cnt = 1, took it over]",
0, 0, 0, 0);
return;
}
+ UVMHIST_LOG(maphist," amap=%p, ref=%d, must copy it",
+ srcamap, srcamap->am_ref, 0, 0);
+
/*
- * looks like we need to copy the map.
+ * Allocate a new amap (note: not initialised, no lock set, etc).
*/
- UVMHIST_LOG(maphist," amap=%p, ref=%d, must copy it",
- entry->aref.ar_amap, entry->aref.ar_amap->am_ref, 0, 0);
- AMAP_B2SLOT(slots, entry->end - entry->start);
+ AMAP_B2SLOT(slots, len);
amap = amap_alloc1(slots, 0, waitf);
if (amap == NULL) {
UVMHIST_LOG(maphist, " amap_alloc1 failed", 0,0,0,0);
return;
}
- srcamap = entry->aref.ar_amap;
+
amap_lock(srcamap);
/*
- * need to double check reference count now that we've got the
- * src amap locked down. the reference count could have
- * changed while we were allocating. if the reference count
- * dropped down to one we take over the old map rather than
- * copying the amap.
+ * Re-check the reference count with the lock held. If it has
+ * dropped to one - we can take over the existing map.
*/
- if (srcamap->am_ref == 1) { /* take it over? */
+ if (srcamap->am_ref == 1) {
+ /* Just take over the existing amap. */
entry->etype &= ~UVM_ET_NEEDSCOPY;
- amap->am_ref--; /* drop final reference to map */
- amap_free(amap); /* dispose of new (unused) amap */
amap_unlock(srcamap);
+ /* Destroy the new (unused) amap. */
+ amap->am_ref--;
+ amap_free(amap);
return;
}
/*
- * we must copy it now.
+ * Copy the slots. Zero the padded part.
*/
UVMHIST_LOG(maphist, " copying amap now",0, 0, 0, 0);
@@ -886,28 +894,30 @@
(amap->am_maxslot - lcv) * sizeof(struct vm_anon *));
/*
- * drop our reference to the old amap (srcamap) and unlock.
- * we know that the reference count on srcamap is greater than
- * one (we checked above), so there is no way we could drop
- * the count to zero. [and no need to worry about freeing it]
+ * Drop our reference to the old amap (srcamap) and unlock.
+ * Since the reference count on srcamap is greater than one,
+ * (we checked above), it cannot drop to zero.
*/
srcamap->am_ref--;
- if (srcamap->am_ref == 1 && (srcamap->am_flags & AMAP_SHARED) != 0)
- srcamap->am_flags &= ~AMAP_SHARED; /* clear shared flag */
+ KASSERT(srcamap->am_ref > 0);
+
+ if (srcamap->am_ref == 1 && (srcamap->am_flags & AMAP_SHARED) != 0) {
+ srcamap->am_flags &= ~AMAP_SHARED;
+ }
tofree = NULL;
#ifdef UVM_AMAP_PPREF
if (srcamap->am_ppref && srcamap->am_ppref != PPREF_NONE) {
amap_pp_adjref(srcamap, entry->aref.ar_pageoff,
- (entry->end - entry->start) >> PAGE_SHIFT, -1, &tofree);
+ len >> PAGE_SHIFT, -1, &tofree);
}
#endif
uvm_anfree(tofree);
amap_unlock(srcamap);
/*
- * if we referenced any anons then share the source amap's lock.
- * otherwise we have nothing in common, so allocate a new one.
+ * If we referenced any anons, then share the source amap's lock.
+ * Otherwise, we have nothing in common, so allocate a new one.
*/
if (amap->am_nused != 0) {
@@ -920,7 +930,7 @@
amap_list_insert(amap);
/*
- * install new amap.
+ * Install new amap.
*/
entry->aref.ar_pageoff = 0;
@@ -1196,24 +1206,23 @@
}
/*
- * amap_wiperange: wipe out a range of an amap
- * [different from amap_wipeout because the amap is kept intact]
+ * amap_wiperange: wipe out a range of an amap.
+ * Note: different from amap_wipeout because the amap is kept intact.
*
- * => both map and amap must be locked by caller.
+ * => Both map and amap must be locked by caller.
*/
void
amap_wiperange(struct vm_amap *amap, int slotoff, int slots,
struct vm_anon **tofree)
{
- u_int lcv, stop, curslot, ptr, slotend;
- struct vm_anon *anon;
+ u_int lcv, stop, slotend;
bool byanon;
KASSERT(mutex_owned(amap->am_lock));
/*
- * we can either traverse the amap by am_anon or by am_slots depending
- * on which is cheaper. decide now.
+ * We can either traverse the amap by am_anon or by am_slots.
+ * Determine which way is less expensive.
*/
if (slots < amap->am_nused) {
@@ -1229,6 +1238,9 @@
}
while (lcv < stop) {
+ struct vm_anon *anon;
+ u_int curslot, ptr, last;
+
if (byanon) {
curslot = lcv++; /* lcv advances here */
if (amap->am_anon[curslot] == NULL)
@@ -1242,6 +1254,7 @@
stop--; /* drop stop, since anon will be removed */
}
anon = amap->am_anon[curslot];
+ KASSERT(anon->an_lock == amap->am_lock);
/*
* Remove anon from the amap.
@@ -1249,11 +1262,10 @@
amap->am_anon[curslot] = NULL;
ptr = amap->am_bckptr[curslot];
- if (ptr != (amap->am_nused - 1)) {
- amap->am_slots[ptr] =
- amap->am_slots[amap->am_nused - 1];
- amap->am_bckptr[amap->am_slots[ptr]] =
- ptr; /* back ptr. */
+ last = amap->am_nused - 1;
+ if (ptr != last) {
+ amap->am_slots[ptr] = amap->am_slots[last];
+ amap->am_bckptr[amap->am_slots[ptr]] = ptr;
}
amap->am_nused--;
