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VOP_GETPAGES(9) | Kernel Developer's Manual | VOP_GETPAGES(9) |
NAME¶
VOP_GETPAGES
,
VOP_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 *ma,
int count,
int reqpage,
vm_ooffset_t
offset);
int
VOP_PUTPAGES
(struct
vnode *vp,
vm_page_t *ma,
int count,
int sync,
int *rtvals,
vm_ooffset_t
offset);
DESCRIPTION¶
TheVOP_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:
- vp
- The file to access.
- ma
- Pointer to the first element of an array of pages representing a contiguous region of the file to be read or written.
- count
- The number of bytes that should be read into the pages of the array.
- sync
VM_PAGER_PUT_SYNC
if the write should be synchronous.- rtvals
- An array of VM system result codes indicating the status of each page
written by
VOP_PUTPAGES
(). - reqpage
- The index in the page array of the requested page; i.e., the one page which the implementation of this method must handle.
- offset
- Offset in the file at which the mapped pages begin.
VOP_PUTPAGES
() method is
returned on a page-by-page basis in the array
rtvals[]. The possible status values are as
follows:
VM_PAGER_OK
- The page was successfully written. The implementation must call vm_page_undirty(9) 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_wakeup(9) and vm_page_sunbusy(9) to clear the busy flag and awaken any other threads waiting for this page, in addition to calling vm_page_undirty(9).
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.
VOP_GETPAGES
() method is expected to
release any pages in ma that it does not
successfully handle, by calling vm_page_free(9).
When it succeeds, VOP_GETPAGES
() must set
the valid bits appropriately.
VOP_GETPAGES
() must keep
reqpage busy. It must unbusy all other
successfully handled pages and put them on appropriate page queue(s). For
example, VOP_GETPAGES
() may either activate
a page (if its wanted bit is set) or deactivate it (otherwise), and finally
call vm_page_xunbusy(9) to arouse any threads
currently waiting for the page to be faulted in.
RETURN VALUES¶
If it successfully reads ma[reqpage],VOP_GETPAGES
() returns
VM_PAGER_OK
; otherwise,
VM_PAGER_ERROR
. By convention, the return
value of VOP_PUTPAGES
() is
rtvals[0].
SEE ALSO¶
vm_object_pip_wakeup(9), vm_page_free(9), vm_pagge_sunbusy(9), vm_page_undirty(9), vm_page_xunbusy(9), vnode(9)AUTHORS¶
This manual page was written by Doug Rabson and then substantially rewritten byGarrett Wollman.
September 27, 2003 | Debian |