git: d47d3a94bb2d - main - vm_fault: Factor out per-object operations into vm_fault_object()
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Date: Wed, 24 Nov 2021 19:03:12 UTC
The branch main has been updated by markj:
URL: https://cgit.FreeBSD.org/src/commit/?id=d47d3a94bb2d873b1c3a5cdfe9cc00e4619f649b
commit d47d3a94bb2d873b1c3a5cdfe9cc00e4619f649b
Author: Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2021-11-24 18:43:38 +0000
Commit: Mark Johnston <markj@FreeBSD.org>
CommitDate: 2021-11-24 19:02:56 +0000
vm_fault: Factor out per-object operations into vm_fault_object()
No functional change intended.
Obtained from: jeff (object_concurrency patches)
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D33018
---
sys/vm/vm_fault.c | 213 ++++++++++++++++++++++++++++++------------------------
1 file changed, 118 insertions(+), 95 deletions(-)
diff --git a/sys/vm/vm_fault.c b/sys/vm/vm_fault.c
index 0e4d9fd33c6f..a929351257ce 100644
--- a/sys/vm/vm_fault.c
+++ b/sys/vm/vm_fault.c
@@ -166,6 +166,7 @@ enum fault_status {
FAULT_OUT_OF_BOUNDS, /* Invalid address for pager. */
FAULT_HARD, /* Performed I/O. */
FAULT_SOFT, /* Found valid page. */
+ FAULT_PROTECTION_FAILURE, /* Invalid access. */
};
static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
@@ -1350,6 +1351,96 @@ vm_fault_busy_sleep(struct faultstate *fs)
vm_object_deallocate(fs->first_object);
}
+/*
+ * Handle page lookup, populate, allocate, page-in for the current
+ * object.
+ *
+ * The object is locked on entry and will remain locked with a return
+ * code of FAULT_CONTINUE so that fault may follow the shadow chain.
+ * Otherwise, the object will be unlocked upon return.
+ */
+static enum fault_status
+vm_fault_object(struct faultstate *fs, int *behindp, int *aheadp)
+{
+ enum fault_status res;
+ bool dead;
+
+ /*
+ * If the object is marked for imminent termination, we retry
+ * here, since the collapse pass has raced with us. Otherwise,
+ * if we see terminally dead object, return fail.
+ */
+ if ((fs->object->flags & OBJ_DEAD) != 0) {
+ dead = fs->object->type == OBJT_DEAD;
+ unlock_and_deallocate(fs);
+ if (dead)
+ return (FAULT_PROTECTION_FAILURE);
+ pause("vmf_de", 1);
+ return (FAULT_RESTART);
+ }
+
+ /*
+ * See if the page is resident.
+ */
+ fs->m = vm_page_lookup(fs->object, fs->pindex);
+ if (fs->m != NULL) {
+ if (!vm_page_tryxbusy(fs->m)) {
+ vm_fault_busy_sleep(fs);
+ return (FAULT_RESTART);
+ }
+
+ /*
+ * The page is marked busy for other processes and the
+ * pagedaemon. If it is still completely valid we are
+ * done.
+ */
+ if (vm_page_all_valid(fs->m)) {
+ VM_OBJECT_WUNLOCK(fs->object);
+ return (FAULT_SOFT);
+ }
+ }
+ VM_OBJECT_ASSERT_WLOCKED(fs->object);
+
+ /*
+ * Page is not resident. If the pager might contain the page
+ * or this is the beginning of the search, allocate a new
+ * page. (Default objects are zero-fill, so there is no real
+ * pager for them.)
+ */
+ if (fs->m == NULL && (fs->object->type != OBJT_DEFAULT ||
+ fs->object == fs->first_object)) {
+ res = vm_fault_allocate(fs);
+ if (res != FAULT_CONTINUE)
+ return (res);
+ }
+
+ /*
+ * Default objects have no pager so no exclusive busy exists
+ * to protect this page in the chain. Skip to the next
+ * object without dropping the lock to preserve atomicity of
+ * shadow faults.
+ */
+ if (fs->object->type != OBJT_DEFAULT) {
+ /*
+ * At this point, we have either allocated a new page
+ * or found an existing page that is only partially
+ * valid.
+ *
+ * We hold a reference on the current object and the
+ * page is exclusive busied. The exclusive busy
+ * prevents simultaneous faults and collapses while
+ * the object lock is dropped.
+ */
+ VM_OBJECT_WUNLOCK(fs->object);
+ res = vm_fault_getpages(fs, behindp, aheadp);
+ if (res == FAULT_CONTINUE)
+ VM_OBJECT_WLOCK(fs->object);
+ } else {
+ res = FAULT_CONTINUE;
+ }
+ return (res);
+}
+
int
vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
int fault_flags, vm_page_t *m_hold)
@@ -1357,7 +1448,7 @@ vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
struct faultstate fs;
int ahead, behind, faultcount, rv;
enum fault_status res;
- bool dead, hardfault;
+ bool hardfault;
VM_CNT_INC(v_vm_faults);
@@ -1452,98 +1543,29 @@ RetryFault:
while (TRUE) {
KASSERT(fs.m == NULL,
("page still set %p at loop start", fs.m));
- /*
- * If the object is marked for imminent termination,
- * we retry here, since the collapse pass has raced
- * with us. Otherwise, if we see terminally dead
- * object, return fail.
- */
- if ((fs.object->flags & OBJ_DEAD) != 0) {
- dead = fs.object->type == OBJT_DEAD;
- unlock_and_deallocate(&fs);
- if (dead)
- return (KERN_PROTECTION_FAILURE);
- pause("vmf_de", 1);
- goto RetryFault;
- }
-
- /*
- * See if page is resident
- */
- fs.m = vm_page_lookup(fs.object, fs.pindex);
- if (fs.m != NULL) {
- if (vm_page_tryxbusy(fs.m) == 0) {
- vm_fault_busy_sleep(&fs);
- goto RetryFault;
- }
-
- /*
- * The page is marked busy for other processes and the
- * pagedaemon. If it still is completely valid we
- * are done.
- */
- if (vm_page_all_valid(fs.m)) {
- VM_OBJECT_WUNLOCK(fs.object);
- break; /* break to PAGE HAS BEEN FOUND. */
- }
- }
- VM_OBJECT_ASSERT_WLOCKED(fs.object);
-
- /*
- * Page is not resident. If the pager might contain the page
- * or this is the beginning of the search, allocate a new
- * page. (Default objects are zero-fill, so there is no real
- * pager for them.)
- */
- if (fs.m == NULL && (fs.object->type != OBJT_DEFAULT ||
- fs.object == fs.first_object)) {
- res = vm_fault_allocate(&fs);
- switch (res) {
- case FAULT_RESTART:
- goto RetryFault;
- case FAULT_SUCCESS:
- return (KERN_SUCCESS);
- case FAULT_FAILURE:
- return (KERN_FAILURE);
- case FAULT_OUT_OF_BOUNDS:
- return (KERN_OUT_OF_BOUNDS);
- case FAULT_CONTINUE:
- break;
- default:
- panic("vm_fault: Unhandled status %d", res);
- }
- }
- /*
- * Default objects have no pager so no exclusive busy exists
- * to protect this page in the chain. Skip to the next
- * object without dropping the lock to preserve atomicity of
- * shadow faults.
- */
- if (fs.object->type != OBJT_DEFAULT) {
- /*
- * At this point, we have either allocated a new page
- * or found an existing page that is only partially
- * valid.
- *
- * We hold a reference on the current object and the
- * page is exclusive busied. The exclusive busy
- * prevents simultaneous faults and collapses while
- * the object lock is dropped.
- */
- VM_OBJECT_WUNLOCK(fs.object);
-
- res = vm_fault_getpages(&fs, &behind, &ahead);
- if (res == FAULT_SUCCESS) {
- faultcount = behind + 1 + ahead;
- hardfault = true;
- break; /* break to PAGE HAS BEEN FOUND. */
- }
- if (res == FAULT_RESTART)
- goto RetryFault;
- if (res == FAULT_OUT_OF_BOUNDS)
- return (KERN_OUT_OF_BOUNDS);
- VM_OBJECT_WLOCK(fs.object);
+ res = vm_fault_object(&fs, &behind, &ahead);
+ switch (res) {
+ case FAULT_SOFT:
+ goto found;
+ case FAULT_HARD:
+ faultcount = behind + 1 + ahead;
+ hardfault = true;
+ goto found;
+ case FAULT_RESTART:
+ goto RetryFault;
+ case FAULT_SUCCESS:
+ return (KERN_SUCCESS);
+ case FAULT_FAILURE:
+ return (KERN_FAILURE);
+ case FAULT_OUT_OF_BOUNDS:
+ return (KERN_OUT_OF_BOUNDS);
+ case FAULT_PROTECTION_FAILURE:
+ return (KERN_PROTECTION_FAILURE);
+ case FAULT_CONTINUE:
+ break;
+ default:
+ panic("vm_fault: Unhandled status %d", res);
}
/*
@@ -1563,12 +1585,13 @@ RetryFault:
vm_fault_zerofill(&fs);
/* Don't try to prefault neighboring pages. */
faultcount = 1;
- break; /* break to PAGE HAS BEEN FOUND. */
+ break;
}
+found:
/*
- * PAGE HAS BEEN FOUND. A valid page has been found and exclusively
- * busied. The object lock must no longer be held.
+ * A valid page has been found and exclusively busied. The
+ * object lock must no longer be held.
*/
vm_page_assert_xbusied(fs.m);
VM_OBJECT_ASSERT_UNLOCKED(fs.object);