Anons: the pages a process has written to, in one of its mappings. More...

#include <core/system.h>
#include <core/panic.h>
#include <mm/vm.h>

Functions
static int	vm_aref_eq (void _a, void _b)
	Says whether an aref is the one for an offset (_b, a size_t *), for the anon's hashmap.
struct vm_anon *	vm_anon_new (void)
	Makes a new, empty anon.
void	vm_aref_destroy (struct vm_aref *vm_aref)
	Releases what an aref holds.
void	vm_aref_decref (struct vm_aref *vm_aref)
	Drops a reference to an aref.
void	vm_anon_destroy (struct vm_anon *vm_anon)
	Releases an anon's arefs, and the pages of those that no other anon shares.
void	vm_anon_incref (struct vm_anon *vm_anon)
	Adds a reference to an anon: another mapping shares it (a fork).
void	vm_anon_decref (struct vm_anon *vm_anon)
	Drops a reference to an anon, and frees it with the last one.
static int	vm_anon_copy_arefs (struct vm_anon src, struct vm_anon dst)
	Puts all of src's arefs in dst as well, shared: each gets one more reference.
struct vm_anon *	vm_anon_copy (struct vm_anon *vm_anon)
	Makes a copy of an anon that shares its arefs, and so its pages, when a mapping's shared anon is written to after a fork.

Detailed Description

Anons: the pages a process has written to, in one of its mappings.

An anon (struct vm_anon) holds a mapping's private pages, each through an aref (struct vm_aref), keyed by its offset in the mapping. A fork shares the anon, and its arefs, between parent and child, copy on write: the first one to write a shared page gets its own copy (mm/fault.c). This is a simplified form of NetBSD's UVM amaps and anons.

Definition in file vm_anon.c.

Function Documentation

◆ vm_anon_copy()

struct vm_anon * vm_anon_copy ( struct vm_anon * vm_anon )

Makes a copy of an anon that shares its arefs, and so its pages, when a mapping's shared anon is written to after a fork.

The pages themselves are copied later, one by one, as they are written to.

Parameters

vm_anon the anon to copy

Returns: the new anon, with one reference, or NULL if there was no memory for it

Definition at line 174 of file vm_anon.c.

References vm_anon::flags, kfree(), NULL, vm_anon::ref, vm_anon_copy(), vm_anon_copy_arefs(), vm_anon_destroy(), vm_anon_new(), and VM_COPY.

Referenced by pf_anon(), and vm_anon_copy().

◆ vm_anon_copy_arefs()

int vm_anon_copy_arefs	(	struct vm_anon *	src,
		struct vm_anon *	dst )

static

Puts all of src's arefs in dst as well, shared: each gets one more reference.

Returns 0, -EINVAL, or -ENOMEM if there was no memory for one; the arefs put in dst before that have their reference, and go with vm_anon_destroy(dst).

Definition at line 147 of file vm_anon.c.

References vm_anon::arefs, hashmap_node::entry, hashmap_node::hash, hashmap_for, vm_aref::ref, qnode::value, and vm_anon_copy_arefs().

Referenced by vm_anon_copy(), and vm_anon_copy_arefs().