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(fault 3/9) Move map relookup into a dedicated function.

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Add a new VM return code KERN_RESTART which means, deallocate and restart in
fault.

Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D23303
This commit is contained in:
Jeff Roberson 2020-01-23 05:07:01 +00:00
parent c308a3a6c9
commit fcb0475833
2 changed files with 57 additions and 51 deletions
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107
sys/vm/vm_fault.c
View File

@ -795,6 +795,57 @@ vm_fault_lookup(struct faultstate *fs)
return (KERN_SUCCESS);
}
static int
vm_fault_relookup(struct faultstate *fs)
{
vm_object_t retry_object;
vm_pindex_t retry_pindex;
vm_prot_t retry_prot;
int result;
if (!vm_map_trylock_read(fs->map))
return (KERN_RESTART);
fs->lookup_still_valid = true;
if (fs->map->timestamp == fs->map_generation)
return (KERN_SUCCESS);
result = vm_map_lookup_locked(&fs->map, fs->vaddr, fs->fault_type,
&fs->entry, &retry_object, &retry_pindex, &retry_prot,
&fs->wired);
if (result != KERN_SUCCESS) {
/*
* If retry of map lookup would have blocked then
* retry fault from start.
*/
if (result == KERN_FAILURE)
return (KERN_RESTART);
return (result);
}
if (retry_object != fs->first_object ||
retry_pindex != fs->first_pindex)
return (KERN_RESTART);
/*
* Check whether the protection has changed or the object has
* been copied while we left the map unlocked. Changing from
* read to write permission is OK - we leave the page
* write-protected, and catch the write fault. Changing from
* write to read permission means that we can't mark the page
* write-enabled after all.
*/
fs->prot &= retry_prot;
fs->fault_type &= retry_prot;
if (fs->prot == 0)
return (KERN_RESTART);
/* Reassert because wired may have changed. */
KASSERT(fs->wired || (fs->fault_flags & VM_FAULT_WIRE) == 0,
("!wired && VM_FAULT_WIRE"));
return (KERN_SUCCESS);
}
/*
* 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
@ -837,10 +888,8 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
{
struct faultstate fs;
struct domainset *dset;
vm_object_t next_object, retry_object;
vm_object_t next_object;
vm_offset_t e_end, e_start;
vm_pindex_t retry_pindex;
vm_prot_t retry_prot;
int ahead, alloc_req, behind, cluster_offset, faultcount;
int nera, oom, result, rv;
u_char behavior;
@ -1363,56 +1412,12 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
* lookup.
*/
if (!fs.lookup_still_valid) {
if (!vm_map_trylock_read(fs.map)) {
result = vm_fault_relookup(&fs);
if (result != KERN_SUCCESS) {
fault_deallocate(&fs);
goto RetryFault;
}
fs.lookup_still_valid = true;
if (fs.map->timestamp != fs.map_generation) {
result = vm_map_lookup_locked(&fs.map, vaddr, fs.fault_type,
&fs.entry, &retry_object, &retry_pindex, &retry_prot,
&fs.wired);
/*
* If we don't need the page any longer, put it on the inactive
* list (the easiest thing to do here). If no one needs it,
* pageout will grab it eventually.
*/
if (result != KERN_SUCCESS) {
fault_deallocate(&fs);
/*
* If retry of map lookup would have blocked then
* retry fault from start.
*/
if (result == KERN_FAILURE)
goto RetryFault;
return (result);
}
if ((retry_object != fs.first_object) ||
(retry_pindex != fs.first_pindex)) {
fault_deallocate(&fs);
if (result == KERN_RESTART)
goto RetryFault;
}
/*
* Check whether the protection has changed or the object has
* been copied while we left the map unlocked. Changing from
* read to write permission is OK - we leave the page
* write-protected, and catch the write fault. Changing from
* write to read permission means that we can't mark the page
* write-enabled after all.
*/
fs.prot &= retry_prot;
fs.fault_type &= retry_prot;
if (fs.prot == 0) {
fault_deallocate(&fs);
goto RetryFault;
}
/* Reassert because wired may have changed. */
KASSERT(fs.wired || (fs.fault_flags & VM_FAULT_WIRE) == 0,
("!wired && VM_FAULT_WIRE"));
return (result);
}
}
VM_OBJECT_ASSERT_UNLOCKED(fs.object);

1
sys/vm/vm_param.h
View File

@ -114,6 +114,7 @@ struct xswdev {
#define KERN_NOT_RECEIVER 7
#define KERN_NO_ACCESS 8
#define KERN_OUT_OF_BOUNDS 9
#define KERN_RESTART 10
#ifndef PA_LOCK_COUNT
#ifdef SMP