VOP_GETPAGESVOP_PUTPAGES
- read or write VM pages from a file
SYNOPSIS
#include <sys/param.h>
#include <sys/vnode.h>
#include <vm/vm.h> int
VOP_GETPAGES (struct vnode *vp vm_page_t *m int count int reqpage vm_ooffset_t offset); int
VOP_PUTPAGES (struct vnode *vp vm_page_t *m int count int sync int *rtvals vm_ooffset_t offset);
DESCRIPTION
The
VOP_GETPAGES ();
method is called to read in pages of virtual memory which are backed by
ordinary files.
If other adjacent pages are backed by adjacent regions of the same file,
VOP_GETPAGES ();
is requested to read those pages as well, although it is not required to
do so.
The
VOP_PUTPAGES ();
method does the converse; that is to say, it writes out adjacent dirty
pages of virtual memory.
On entry, the vnode lock is held but neither the page queue nor VM object
locks are held.
Both methods return in the same state on both success and error returns.
The arguments are:
Fa vp
The file to access.
Fa m
Pointer to the first element of an array of contiguous pages representing a
contiguous region of the file to be read or written.
Fa count
The number of pages in the array.
Fa sync
VM_PAGER_PUT_SYNC
if the write should be synchronous.
Fa rtvals
An array of VM system result codes indicating the status of each
page written by
VOP_PUTPAGES (.);
Fa reqpage
The index in the page array of the requested page; i.e., the one page which
the implementation of this method must handle.
Fa offset
Offset in the file at which the mapped pages begin.
The status of the
VOP_PUTPAGES ();
method is returned on a page-by-page basis in the array
Fa rtvals[] .
The possible status values are as follows:
VM_PAGER_OK
The page was successfully written.
The implementation must call
vm_page_undirty9
to mark the page as clean.
VM_PAGER_PEND
The page was scheduled to be written asynchronously.
When the write completes, the completion callback should
call
vm_object_pip_wakeup9
and
vm_page_io_finish9
to clear the busy flag and awaken any other threads waiting for this page,
in addition to calling
vm_page_undirty9.
VM_PAGER_BAD
The page was entirely beyond the end of the backing file.
This condition should not be possible if the vnode's file system
is correctly implemented.
VM_PAGER_ERROR
The page could not be written because of an error on the underlying storage
medium or protocol.
VM_PAGER_FAIL
Treated identically to
VM_PAGER_ERROR
VM_PAGER_AGAIN
The page was not handled by this request.
The
VOP_GETPAGES ();
method is expected to release any pages in
Fa m
that it does not successfully handle, by calling
vm_page_free9.
When it succeeds,
VOP_GETPAGES ();
must set the valid bits appropriately, clear the dirty bit
(using
vm_page_undirty9),
either activate the page (if its wanted bit is set)
or deactivate it (otherwise), and finally call
vm_page_wakeup9
to arouse any threads currently waiting for the page to be faulted in,
for each page read.
RETURN VALUES
If it successfully reads
Fa m[reqpage] ,
VOP_GETPAGES ();
returns
VM_PAGER_OK
otherwise,
VM_PAGER_ERROR
By convention, the return value of
VOP_PUTPAGES ();
is
Fa rtvals[0] .
