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Move vm_fault busy logic into its own function for clarity and re-use by

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later changes.

Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D22820
This commit is contained in:
jeff 2019-12-22 04:21:16 +00:00
parent 73773fcda9
commit f0e23b70a0
1 changed files with 36 additions and 35 deletions
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71
sys/vm/vm_fault.c
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@ -684,6 +684,41 @@ vm_fault_lock_vnode(struct faultstate *fs)
return (KERN_RESOURCE_SHORTAGE);
}
/*
* Wait/Retry if the page is busy. We have to do this if the page is
* either exclusive or shared busy because the vm_pager may be using
* read busy for pageouts (and even pageins if it is the vnode pager),
* and we could end up trying to pagein and pageout the same page
* simultaneously.
*
* We can theoretically allow the busy case on a read fault if the page
* is marked valid, but since such pages are typically already pmap'd,
* putting that special case in might be more effort then it is worth.
* We cannot under any circumstances mess around with a shared busied
* page except, perhaps, to pmap it.
*/
static void
vm_fault_busy_sleep(struct faultstate *fs)
{
/*
* Reference the page before unlocking and
* sleeping so that the page daemon is less
* likely to reclaim it.
*/
vm_page_aflag_set(fs->m, PGA_REFERENCED);
if (fs->object != fs->first_object) {
fault_page_release(&fs->first_m);
vm_object_pip_wakeup(fs->first_object);
}
vm_object_pip_wakeup(fs->object);
unlock_map(fs);
if (fs->m == vm_page_lookup(fs->object, fs->pindex))
vm_page_sleep_if_busy(fs->m, "vmpfw");
VM_OBJECT_WUNLOCK(fs->object);
VM_CNT_INC(v_intrans);
vm_object_deallocate(fs->first_object);
}
int
vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
int fault_flags, vm_page_t *m_hold)
@ -822,42 +857,8 @@ RetryFault_oom:
*/
fs.m = vm_page_lookup(fs.object, fs.pindex);
if (fs.m != NULL) {
/*
* Wait/Retry if the page is busy. We have to do this
* if the page is either exclusive or shared busy
* because the vm_pager may be using read busy for
* pageouts (and even pageins if it is the vnode
* pager), and we could end up trying to pagein and
* pageout the same page simultaneously.
*
* We can theoretically allow the busy case on a read
* fault if the page is marked valid, but since such
* pages are typically already pmap'd, putting that
* special case in might be more effort then it is
* worth. We cannot under any circumstances mess
* around with a shared busied page except, perhaps,
* to pmap it.
*/
if (vm_page_tryxbusy(fs.m) == 0) {
/*
* Reference the page before unlocking and
* sleeping so that the page daemon is less
* likely to reclaim it.
*/
vm_page_aflag_set(fs.m, PGA_REFERENCED);
if (fs.object != fs.first_object) {
fault_page_release(&fs.first_m);
vm_object_pip_wakeup(fs.first_object);
}
unlock_map(&fs);
vm_object_pip_wakeup(fs.object);
if (fs.m == vm_page_lookup(fs.object,
fs.pindex)) {
vm_page_sleep_if_busy(fs.m, "vmpfw");
}
VM_OBJECT_WUNLOCK(fs.object);
VM_CNT_INC(v_intrans);
vm_object_deallocate(fs.first_object);
vm_fault_busy_sleep(&fs);
goto RetryFault;
}