vm_object.c File Reference

The page cache: a file's pages in memory, for mmap(). More...

#include <core/system.h>
#include <core/string.h>
#include <mm/vm.h>
#include <mm/pmap.h>

Go to the source code of this file.

Functions
static int	vm_page_eq (void *_a, void *_b)
	Says whether a cached page is the one at the offset _b points to.
struct vm_object *	vm_object_vnode (struct vnode *vnode)
	Gets a vnode's vm object, making it the first time.
struct vm_page *	vnode_page_in (struct vm_object *vm_object, size_t off)
	Reads a page of a file into its vm object: the vnode pager's page in.
void	vnode_pages_update (struct vnode *vnode, off_t start, off_t end)
	Reads a file's cached pages again after a write or a truncation changed a range of it.
void	vnode_pages_free (struct vnode *vnode)
	Frees a vnode's vm object and its cached pages, when the vnode itself is freed.

Variables
static struct vm_pager	vnode_pager

Detailed Description

The page cache: a file's pages in memory, for mmap().

A vnode that is mapped has a vm object, which keeps the file's pages by their offset; its pager reads a page in the first time a process touches it (see mm/fault.c), and every process that maps the file shares it.

Definition in file vm_object.c.

Function Documentation

vm_object_vnode()

struct vm_object * vm_object_vnode

(

struct vnode *

vnode

)

Gets a vnode's vm object, making it the first time.

Parameters

vnode

the vnode

Returns

its vm object, or NULL if vnode is NULL or there was no memory

Definition at line 31 of file vm_object.c.

References kfree(), kmalloc(), M_ZERO, NULL, vm_object::p, vm_object::pager, vm_object::pages, vm_object::type, vnode::vm_object, vm_object_vnode(), vm_page_eq(), VMOBJ_FILE, and vnode_pager.

Referenced by binfmt_elf_load_segments(), sys_mmap(), and vm_object_vnode().

vm_page_eq()

int vm_page_eq ( void * _a, void * _b )

static

Says whether a cached page is the one at the offset _b points to.

Definition at line 16 of file vm_object.c.

References vm_page::off, and vm_page_eq().

vnode_page_in()

struct vm_page * vnode_page_in	(	struct vm_object *	vm_object,
		size_t	off )

Reads a page of a file into its vm object: the vnode pager's page in.

Past the end of the file, the page reads as zeros.

Parameters

vm_object	the file's vm object
off	the page's offset in the file

Returns

the page, or NULL if there was no memory or the read failed

Definition at line 67 of file vm_object.c.

References hashmap_node::entry, hashmap_node::hash, kfree(), kmalloc(), M_ZERO, mm_page_alloc(), mm_page_dealloc(), NULL, vm_page::off, vm_object::p, vm_page::paddr, PAGE_ALIGN, PAGE_SIZE, vm_object::pages, pmap_page_write(), vm_page::ref, vfs_read(), vm_page::vm_object, vm_object_page_insert(), and vnode_page_in().

Referenced by vnode_page_in().

vnode_pages_free()

void vnode_pages_free

(

struct vnode *

vnode

)

Frees a vnode's vm object and its cached pages, when the vnode itself is freed.

Nothing maps them then, since a mapping holds the vnode (vm_object_incref()).

Parameters

vnode

the vnode

Definition at line 172 of file vm_object.c.

References hashmap_node::entry, hashmap_for, kfree(), mm_page_dealloc(), NULL, vm_page::paddr, vm_object::pages, qnode::value, vnode::vm_object, and vnode_pages_free().

Referenced by ext2_close(), procfs_close(), pseudofs_close(), and vnode_pages_free().

vnode_pages_update()

void vnode_pages_update	(	struct vnode *	vnode,
		off_t	start,
		off_t	end )

Reads a file's cached pages again after a write or a truncation changed a range of it.

A page stays where it is, mapped by every process that maps the file, so its contents change but not the page; past the file's end it reads zeros. A private mapping's copies, made when it wrote to a page, are its own and don't change.

Parameters

vnode	the file
start	the start of the range that changed
end	its end (exclusive)

Definition at line 128 of file vm_object.c.

References hashmap::count, hashmap_node::entry, hashmap_node::hash, kfree(), kmalloc(), memset(), NULL, vm_page::off, vm_page::paddr, PAGE_ALIGN, PAGE_SIZE, vm_object::pages, pmap_page_write(), printk(), vfs_read(), vnode::vm_object, and vnode_pages_update().

Referenced by vfs_trunc(), vfs_write_io(), and vnode_pages_update().

Variable Documentation

vnode_pager

struct vm_pager vnode_pager

static

Initial value:

                     = {
    .in = vnode_page_in,
    .out = NULL,
}

Definition at line 13 of file vm_object.c.

Referenced by vm_object_vnode().