Copyright (c) 1996 Doug Rabson Copyright 2003, Garrett A. Wollman All rights reserved. This program is free software. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditi...
NAMEVOP_GETPAGES VOP_PUTPAGES - read or write VM pages from a file
SYNOPSISIn sys/param.h In sys/vnode.h In vm/vm.h Ft int Fn VOP_GETPAGES struct vnode *vp vm_page_t *ma int count int *rbehind int *rahead Ft int Fn VOP_PUTPAGES struct vnode *vp vm_page_t *ma int count int sync int *rtvals
DESCRIPTIONThe Fn 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, Fn VOP_GETPAGES is requested to read those pages as well, although it is not required to do so. The Fn 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 ma
- Pointer to the first element of an array of pages representing a contiguous region of the file to be read or written.
- Fa count
- The number of bytes that should be read into the pages of 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 Fn VOP_PUTPAGES .
- Fa rbehind
- Optional pointer to integer specifying number of pages to be read behind, if possible. If the filesystem supports that feature, number of actually read pages is reported back, otherwise zero is returned.
- Fa rahead
- Optional pointer to integer specifying number of pages to be read ahead, if possible. If the filesystem supports that feature, number of actually read pages is reported back, otherwise zero is returned.
The status of the Fn VOP_PUTPAGES method is returned on a page-by-page basis in the array Fa rtvals . The possible status values are as follows:
- The page was successfully written. The implementation must call vm_page_undirty9 to mark the page as clean.
- The page was scheduled to be written asynchronously. When the write completes, the completion callback should call vm_object_pip_wakeup9 and vm_page_sunbusy9 to clear the busy flag and awaken any other threads waiting for this page, in addition to calling vm_page_undirty9.
- 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.
- The page could not be written because of an error on the underlying storage medium or protocol.
- Treated identically to VM_PAGER_ERROR
- The page was not handled by this request.
The Fn VOP_GETPAGES method is expected to release any pages in Fa ma that it does not successfully handle, by calling vm_page_free9. When it succeeds, Fn VOP_GETPAGES must set the valid bits appropriately. Fn VOP_GETPAGES must keep Fa reqpage busy. It must unbusy all other successfully handled pages and put them on appropriate page queue(s). For example, Fn VOP_GETPAGES may either activate a page (if its wanted bit is set) or deactivate it (otherwise), and finally call vm_page_xunbusy9 to arouse any threads currently waiting for the page to be faulted in.