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uvmfault_anonget: clean-up, improve some comments, misc.

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rmind 2011-06-23 17:36:59 +00:00
parent 281288535e
commit df10270871
1 changed files with 79 additions and 72 deletions
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149
sys/uvm/uvm_fault.c
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@ -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_amapcopy(struct uvm_faultinfo *ufi)
* 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) {
@ -320,17 +322,18 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
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);
@ -338,24 +341,24 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
pg->uobject->vmobjlock,
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 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
}
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 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
}
/*
* 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 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
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 @@ released:
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 @@ released:
}
/*
* we've successfully read the page, activate it.
* We have successfully read the page, activate it.
*/
mutex_enter(&uvm_pageqlock);
@ -480,13 +486,13 @@ released:
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 @@ released:
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 @@ released:
uvmfault_unlockall(ufi, amap, NULL);
UVMHIST_LOG(maphist, "<- REFAULT", 0,0,0,0);
return (ERESTART);
return ERESTART;
}
/*
* try it again!
* Retry..
*/
uvmexp.fltanretry++;