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4 .\" Copyright 2003, Garrett A. Wollman
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32 .Dd September 27, 2003
38 .Nd read or write VM pages from a file
44 .Fn VOP_GETPAGES "struct vnode *vp" "vm_page_t *ma" "int count" "int reqpage" "vm_ooffset_t offset"
46 .Fn VOP_PUTPAGES "struct vnode *vp" "vm_page_t *ma" "int count" "int sync" "int *rtvals" "vm_ooffset_t offset"
50 method is called to read in pages of virtual memory which are backed by
52 If other adjacent pages are backed by adjacent regions of the same file,
54 is requested to read those pages as well, although it is not required to
58 method does the converse; that is to say, it writes out adjacent dirty
59 pages of virtual memory.
61 On entry, the vnode lock is held but neither the page queue nor VM object
63 Both methods return in the same state on both success and error returns.
66 .Bl -tag -width reqpage
70 Pointer to the first element of an array of pages representing a
71 contiguous region of the file to be read or written.
73 The number of bytes that should be read into the pages of the array.
76 if the write should be synchronous.
78 An array of VM system result codes indicating the status of each
82 The index in the page array of the requested page; i.e., the one page which
83 the implementation of this method must handle.
85 Offset in the file at which the mapped pages begin.
90 method is returned on a page-by-page basis in the array
92 The possible status values are as follows:
93 .Bl -tag -width VM_PAGER_ERROR
95 The page was successfully written.
96 The implementation must call
98 to mark the page as clean.
100 The page was scheduled to be written asynchronously.
101 When the write completes, the completion callback should
103 .Xr vm_object_pip_wakeup 9
105 .Xr vm_page_sunbusy 9
106 to clear the busy flag and awaken any other threads waiting for this page,
107 in addition to calling
108 .Xr vm_page_undirty 9 .
110 The page was entirely beyond the end of the backing file.
111 This condition should not be possible if the vnode's file system
112 is correctly implemented.
113 .It Dv VM_PAGER_ERROR
114 The page could not be written because of an error on the underlying storage
117 Treated identically to
119 .It Dv VM_PAGER_AGAIN
120 The page was not handled by this request.
125 method is expected to release any pages in
127 that it does not successfully handle, by calling
131 must set the valid bits appropriately.
136 It must unbusy all other successfully handled pages and put them
137 on appropriate page queue(s).
140 may either activate a page (if its wanted bit is set)
141 or deactivate it (otherwise), and finally call
142 .Xr vm_page_xunbusy 9
143 to arouse any threads currently waiting for the page to be faulted in.
145 If it successfully reads
152 By convention, the return value of
157 .Xr vm_object_pip_wakeup 9 ,
159 .Xr vm_pagge_sunbusy 9 ,
160 .Xr vm_page_undirty 9 ,
161 .Xr vm_page_xunbusy 9 ,
164 This manual page was written by
166 and then substantially rewritten by
167 .An Garrett Wollman .