On 23/10/20(Fri) 10:31, Martin Pieuchot wrote:
> More refactoring. This time let's introduce a helper to manipulate
> references. The goal is to reduce the upcoming diff adding locking.
>
> This is extracted from a bigger diff from guenther@ as well as some
> bits from NetBSD.
Now with the correct diff, ok?
Index: uvm/uvm_amap.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_amap.c,v
retrieving revision 1.85
diff -u -p -r1.85 uvm_amap.c
--- uvm/uvm_amap.c 12 Oct 2020 08:44:45 -0000 1.85
+++ uvm/uvm_amap.c 23 Oct 2020 08:23:59 -0000
@@ -68,7 +68,23 @@ static inline void amap_list_remove(stru
struct vm_amap_chunk *amap_chunk_get(struct vm_amap *, int, int, int);
void amap_chunk_free(struct vm_amap *, struct vm_amap_chunk *);
-void amap_wiperange_chunk(struct vm_amap *, struct vm_amap_chunk *, int, int);
+
+/*
+ * if we enable PPREF, then we have a couple of extra functions that
+ * we need to prototype here...
+ */
+
+#ifdef UVM_AMAP_PPREF
+
+#define PPREF_NONE ((int *) -1) /* not using ppref */
+
+void amap_pp_adjref(struct vm_amap *, int, vsize_t, int);
+void amap_pp_establish(struct vm_amap *);
+void amap_wiperange_chunk(struct vm_amap *, struct vm_amap_chunk *, int,
+ int);
+void amap_wiperange(struct vm_amap *, int, int);
+
+#endif /* UVM_AMAP_PPREF */
static inline void
amap_list_insert(struct vm_amap *amap)
@@ -1153,6 +1169,32 @@ amap_unadd(struct vm_aref *aref, vaddr_t
}
/*
+ * amap_adjref_anons: adjust the reference count(s) on amap and its anons.
+ */
+static void
+amap_adjref_anons(struct vm_amap *amap, vaddr_t offset, vsize_t len,
+ int refv, boolean_t all)
+{
+#ifdef UVM_AMAP_PPREF
+ if (amap->am_ppref == NULL && !all && len != amap->am_nslot) {
+ amap_pp_establish(amap);
+ }
+#endif
+
+ amap->am_ref += refv;
+
+#ifdef UVM_AMAP_PPREF
+ if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
+ if (all) {
+ amap_pp_adjref(amap, 0, amap->am_nslot, refv);
+ } else {
+ amap_pp_adjref(amap, offset, len, refv);
+ }
+ }
+#endif
+}
+
+/*
* amap_ref: gain a reference to an amap
*
* => "offset" and "len" are in units of pages
@@ -1162,51 +1204,36 @@ void
amap_ref(struct vm_amap *amap, vaddr_t offset, vsize_t len, int flags)
{
- amap->am_ref++;
if (flags & AMAP_SHARED)
amap->am_flags |= AMAP_SHARED;
-#ifdef UVM_AMAP_PPREF
- if (amap->am_ppref == NULL && (flags & AMAP_REFALL) == 0 &&
- len != amap->am_nslot)
- amap_pp_establish(amap);
- if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
- if (flags & AMAP_REFALL)
- amap_pp_adjref(amap, 0, amap->am_nslot, 1);
- else
- amap_pp_adjref(amap, offset, len, 1);
- }
-#endif
+ amap_adjref_anons(amap, offset, len, 1, (flags & AMAP_REFALL) != 0);
}
/*
* amap_unref: remove a reference to an amap
*
- * => caller must remove all pmap-level references to this amap before
- * dropping the reference
- * => called from uvm_unmap_detach [only] ... note that entry is no
- * longer part of a map
+ * => All pmap-level references to this amap must be already removed.
+ * => Called from uvm_unmap_detach(); entry is already removed from the map.
*/
void
amap_unref(struct vm_amap *amap, vaddr_t offset, vsize_t len, boolean_t all)
{
+ KASSERT(amap->am_ref > 0);
- /* if we are the last reference, free the amap and return. */
- if (amap->am_ref-- == 1) {
- amap_wipeout(amap); /* drops final ref and frees */
+ if (amap->am_ref == 1) {
+ /*
+ * If the last reference - wipeout and destroy the amap.
+ */
+ amap->am_ref--;
+ amap_wipeout(amap);
return;
}
- /* otherwise just drop the reference count(s) */
- if (amap->am_ref == 1 && (amap->am_flags & AMAP_SHARED) != 0)
- amap->am_flags &= ~AMAP_SHARED; /* clear shared flag */
-#ifdef UVM_AMAP_PPREF
- if (amap->am_ppref == NULL && all == 0 && len != amap->am_nslot)
- amap_pp_establish(amap);
- if (amap->am_ppref && amap->am_ppref != PPREF_NONE) {
- if (all)
- amap_pp_adjref(amap, 0, amap->am_nslot, -1);
- else
- amap_pp_adjref(amap, offset, len, -1);
+ /*
+ * Otherwise, drop the reference count(s) on anons.
+ */
+ if (amap->am_ref == 2 && (amap->am_flags & AMAP_SHARED) != 0) {
+ amap->am_flags &= ~AMAP_SHARED;
}
-#endif
+ amap_adjref_anons(amap, offset, len, -1, all);
}
Index: uvm/uvm_amap.h
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_amap.h,v
retrieving revision 1.31
diff -u -p -r1.31 uvm_amap.h
--- uvm/uvm_amap.h 15 May 2019 06:12:19 -0000 1.31
+++ uvm/uvm_amap.h 23 Oct 2020 08:19:43 -0000
@@ -261,23 +261,6 @@ struct vm_amap {
#define amap_flags(AMAP) ((AMAP)->am_flags)
#define amap_refs(AMAP) ((AMAP)->am_ref)
-/*
- * if we enable PPREF, then we have a couple of extra functions that
- * we need to prototype here...
- */
-
-#ifdef UVM_AMAP_PPREF
-
-#define PPREF_NONE ((int *) -1) /* not using ppref */
-
- /* adjust references */
-void amap_pp_adjref(struct vm_amap *, int, vsize_t, int);
- /* establish ppref */
-void amap_pp_establish(struct vm_amap *);
- /* wipe part of an amap */
-void amap_wiperange(struct vm_amap *, int, int);
-#endif /* UVM_AMAP_PPREF */
-
#endif /* _KERNEL */
#endif /* _UVM_UVM_AMAP_H_ */
