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30.Dd April 8, 2021
31.Dt VNODE_PAGER_SETSIZE 9
32.Os
33.Sh NAME
34.Nm vnode_pager_setsize
35.Nd "notify the VM system about updates in the file size"
36.Sh SYNOPSIS
37.In sys/param.h
38.In vm/vm.h
39.In vm/vm_extern.h
40.Ft void
41.Fn vnode_pager_setsize "struct vnode *vp" "vm_ooffset_t nsize"
42.Sh DESCRIPTION
43.Nm
44lets the VM system know about a change in size for a file,
45and updates the object size and vnode pager size of the vm object in
46.Fa vp
47with
48.Fa nsize .
49Page faults on the object mapping with offset beyond the new object
50size results in
51.Va SIGBUS .
52.Pp
53Pages between the old EOF and the new EOF are removed from the object queue
54if the file size shrinks.
55In case the new EOF specified by the
56.Fa nsize
57argument is not aligned to page boundary,
58partial-page area starting beyond the EOF is zeroed and marked invalid.
59if the page exists resident.
60.Pp
61In case the vnode
62.Fa vp
63does not have a VM object allocated, the effect of calling this function is no-op.
64.Pp
65This function must be used within file system code to implement truncation
66if the file system allocates vm objects for vnodes.
67.Sh LOCKS
68The vnode should be exclusively locked on entry and will still be locked on exit.
69.Sh SEE ALSO
70.Xr vnode 9
71.Sh HISTORY
72The
73.Nm
74manual page first appeared in
75.Fx 14 .
76.Sh AUTHORS
77This
78manual page was written by
79.An Ka Ho Ng Aq Mt khng@FreeBSD.org .
80