Module Name: src
Committed By: rmind
Date: Thu Jun 23 17:36:59 UTC 2011
Modified Files:
src/sys/uvm: uvm_fault.c
Log Message:
uvmfault_anonget: clean-up, improve some comments, misc.
To generate a diff of this commit:
cvs rdiff -u -r1.186 -r1.187 src/sys/uvm/uvm_fault.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_fault.c
diff -u src/sys/uvm/uvm_fault.c:1.186 src/sys/uvm/uvm_fault.c:1.187
--- src/sys/uvm/uvm_fault.c:1.186 Sun Jun 12 03:36:02 2011
+++ src/sys/uvm/uvm_fault.c Thu Jun 23 17:36:59 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: uvm_fault.c,v 1.186 2011/06/12 03:36:02 rmind Exp $ */
+/* $NetBSD: uvm_fault.c,v 1.187 2011/06/23 17:36:59 rmind Exp $ */
/*
* Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -32,7 +32,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.186 2011/06/12 03:36:02 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.187 2011/06/23 17:36:59 rmind Exp $");
#include "opt_uvmhist.h"
@@ -255,58 +255,60 @@
* uvmfault_anonget: get data in an anon into a non-busy, non-released
* page in that anon.
*
- * => maps, amap, and anon locked by caller.
- * => if we fail (result != 0) we unlock everything.
- * => if we are successful, we return with everything still locked.
- * => we don't move the page on the queues [gets moved later]
- * => if we allocate a new page [we_own], it gets put on the queues.
- * either way, the result is that the page is on the queues at return time
- * => for pages which are on loan from a uvm_object (and thus are not
- * owned by the anon): if successful, we return with the owning object
- * locked. the caller must unlock this object when it unlocks everything
- * else.
+ * => Map, amap and thus anon should be locked by caller.
+ * => If we fail, we unlock everything and error is returned.
+ * => If we are successful, return with everything still locked.
+ * => We do not move the page on the queues [gets moved later]. If we
+ * allocate a new page [we_own], it gets put on the queues. Either way,
+ * the result is that the page is on the queues at return time
+ * => For pages which are on loan from a uvm_object (and thus are not owned
+ * by the anon): if successful, return with the owning object locked.
+ * The caller must unlock this object when it unlocks everything else.
*/
int
uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
struct vm_anon *anon)
{
- bool we_own; /* we own anon's page? */
- bool locked; /* did we relock? */
struct vm_page *pg;
int error;
- UVMHIST_FUNC("uvmfault_anonget"); UVMHIST_CALLED(maphist);
+ UVMHIST_FUNC("uvmfault_anonget"); UVMHIST_CALLED(maphist);
KASSERT(mutex_owned(anon->an_lock));
KASSERT(amap == NULL || anon->an_lock == amap->am_lock);
- error = 0;
+ /* Increment the counters.*/
uvmexp.fltanget++;
- /* bump rusage counters */
- if (anon->an_page)
+ if (anon->an_page) {
curlwp->l_ru.ru_minflt++;
- else
+ } else {
curlwp->l_ru.ru_majflt++;
+ }
+ error = 0;
/*
- * loop until we get it, or fail.
+ * Loop until we get the anon data, or fail.
*/
for (;;) {
- we_own = false; /* true if we set PG_BUSY on a page */
+ bool we_own, locked;
+ /*
+ * Note: 'we_own' will become true if we set PG_BUSY on a page.
+ */
+ we_own = false;
pg = anon->an_page;
/*
- * if there is a resident page and it is loaned, then anon
- * may not own it. call out to uvm_anon_lockpage() to ensure
- * the real owner of the page has been identified and locked.
+ * If there is a resident page and it is loaned, then anon
+ * may not own it. Call out to uvm_anon_lockloanpg() to
+ * identify and lock the real owner of the page.
*/
if (pg && pg->loan_count)
pg = uvm_anon_lockloanpg(anon);
/*
- * page there? make sure it is not busy/released.
+ * Is page resident? Make sure it is not busy/released.
*/
if (pg) {
@@ -320,42 +322,43 @@
if ((pg->flags & PG_BUSY) == 0) {
UVMHIST_LOG(maphist, "<- OK",0,0,0,0);
- return (0);
+ return 0;
}
pg->flags |= PG_WANTED;
uvmexp.fltpgwait++;
/*
- * the last unlock must be an atomic unlock+wait on
- * the owner of page
+ * The last unlock must be an atomic unlock and wait
+ * on the owner of page.
*/
- if (pg->uobject) { /* owner is uobject ? */
+ if (pg->uobject) {
+ /* Owner of page is UVM object. */
uvmfault_unlockall(ufi, amap, NULL);
UVMHIST_LOG(maphist, " unlock+wait on uobj",0,
0,0,0);
UVM_UNLOCK_AND_WAIT(pg,
pg->uobject->vmobjlock,
- false, "anonget1",0);
+ false, "anonget1", 0);
} else {
- /* anon owns page */
+ /* Owner of page is anon. */
uvmfault_unlockall(ufi, NULL, NULL);
UVMHIST_LOG(maphist, " unlock+wait on anon",0,
0,0,0);
- UVM_UNLOCK_AND_WAIT(pg, anon->an_lock, 0,
- "anonget2",0);
+ UVM_UNLOCK_AND_WAIT(pg, anon->an_lock,
+ false, "anonget2", 0);
}
} else {
#if defined(VMSWAP)
-
/*
- * no page, we must try and bring it in.
+ * No page, therefore allocate one.
*/
pg = uvm_pagealloc(NULL,
ufi != NULL ? ufi->orig_rvaddr : 0,
anon, ufi != NULL ? UVM_FLAG_COLORMATCH : 0);
- if (pg == NULL) { /* out of RAM. */
+ if (pg == NULL) {
+ /* Out of memory. Wait a little. */
uvmfault_unlockall(ufi, amap, NULL);
uvmexp.fltnoram++;
UVMHIST_LOG(maphist, " noram -- UVM_WAIT",0,
@@ -365,33 +368,33 @@
}
uvm_wait("flt_noram1");
} else {
- /* we set the PG_BUSY bit */
+ /* PG_BUSY bit is set. */
we_own = true;
uvmfault_unlockall(ufi, amap, NULL);
/*
- * we are passing a PG_BUSY+PG_FAKE+PG_CLEAN
- * page into the uvm_swap_get function with
- * all data structures unlocked. note that
- * it is ok to read an_swslot here because
- * we hold PG_BUSY on the page.
+ * Pass a PG_BUSY+PG_FAKE+PG_CLEAN page into
+ * the uvm_swap_get() function with all data
+ * structures unlocked. Note that it is OK
+ * to read an_swslot here, because we hold
+ * PG_BUSY on the page.
*/
uvmexp.pageins++;
error = uvm_swap_get(pg, anon->an_swslot,
PGO_SYNCIO);
/*
- * we clean up after the i/o below in the
- * "we_own" case
+ * We clean up after the I/O below in the
+ * 'we_own' case.
*/
}
-#else /* defined(VMSWAP) */
+#else
panic("%s: no page", __func__);
#endif /* defined(VMSWAP) */
}
/*
- * now relock and try again
+ * Re-lock the map and anon.
*/
locked = uvmfault_relock(ufi);
@@ -400,14 +403,14 @@
}
/*
- * if we own the page (i.e. we set PG_BUSY), then we need
- * to clean up after the I/O. there are three cases to
+ * If we own the page (i.e. we set PG_BUSY), then we need
+ * to clean up after the I/O. There are three cases to
* consider:
- * [1] page released during I/O: free anon and ReFault.
- * [2] I/O not OK. free the page and cause the fault
- * to fail.
- * [3] I/O OK! activate the page and sync with the
- * non-we_own case (i.e. drop anon lock if not locked).
+ *
+ * 1) Page was released during I/O: free anon and ReFault.
+ * 2) I/O not OK. Free the page and cause the fault to fail.
+ * 3) I/O OK! Activate the page and sync with the non-we_own
+ * case (i.e. drop anon lock if not locked).
*/
if (we_own) {
@@ -418,31 +421,34 @@
if (error) {
/*
- * remove the swap slot from the anon
- * and mark the anon as having no real slot.
- * don't free the swap slot, thus preventing
+ * Remove the swap slot from the anon and
+ * mark the anon as having no real slot.
+ * Do not free the swap slot, thus preventing
* it from being used again.
*/
- if (anon->an_swslot > 0)
+ if (anon->an_swslot > 0) {
uvm_swap_markbad(anon->an_swslot, 1);
+ }
anon->an_swslot = SWSLOT_BAD;
- if ((pg->flags & PG_RELEASED) != 0)
+ if ((pg->flags & PG_RELEASED) != 0) {
goto released;
+ }
/*
- * note: page was never !PG_BUSY, so it
- * can't be mapped and thus no need to
- * pmap_page_protect it...
+ * Note: page was never !PG_BUSY, so it
+ * cannot be mapped and thus no need to
+ * pmap_page_protect() it.
*/
mutex_enter(&uvm_pageqlock);
uvm_pagefree(pg);
mutex_exit(&uvm_pageqlock);
- if (locked)
+ if (locked) {
uvmfault_unlockall(ufi, NULL, NULL);
+ }
mutex_exit(anon->an_lock);
UVMHIST_LOG(maphist, "<- ERROR", 0,0,0,0);
return error;
@@ -453,12 +459,12 @@
KASSERT(anon->an_ref == 0);
/*
- * released while we unlocked amap.
+ * Released while we had unlocked amap.
*/
- if (locked)
+ if (locked) {
uvmfault_unlockall(ufi, NULL, NULL);
-
+ }
uvm_anon_release(anon);
if (error) {
@@ -472,7 +478,7 @@
}
/*
- * we've successfully read the page, activate it.
+ * We have successfully read the page, activate it.
*/
mutex_enter(&uvm_pageqlock);
@@ -480,13 +486,13 @@
mutex_exit(&uvm_pageqlock);
pg->flags &= ~(PG_WANTED|PG_BUSY|PG_FAKE);
UVM_PAGE_OWN(pg, NULL);
-#else /* defined(VMSWAP) */
+#else
panic("%s: we_own", __func__);
#endif /* defined(VMSWAP) */
}
/*
- * we were not able to relock. restart fault.
+ * We were not able to re-lock the map - restart the fault.
*/
if (!locked) {
@@ -494,11 +500,12 @@
mutex_exit(anon->an_lock);
}
UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0);
- return (ERESTART);
+ return ERESTART;
}
/*
- * verify no one has touched the amap and moved the anon on us.
+ * Verify that no one has touched the amap and moved
+ * the anon on us.
*/
if (ufi != NULL && amap_lookup(&ufi->entry->aref,
@@ -506,11 +513,11 @@
uvmfault_unlockall(ufi, amap, NULL);
UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0);
- return (ERESTART);
+ return ERESTART;
}
/*
- * try it again!
+ * Retry..
*/
uvmexp.fltanretry++;
