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.\" $FreeBSD: release/9.1.0/share/man/man9/vm_page_bits.9 211397 2010-08-16 15:18:30Z joel $
.\"
.Dd December 1, 2001
.Dt VM_PAGE_BITS 9
.Os
.Sh NAME
.Nm vm_page_bits ,
.Nm vm_page_set_validclean ,
.Nm vm_page_clear_dirty ,
.Nm vm_page_set_invalid ,
.Nm vm_page_zero_invalid ,
.Nm vm_page_is_valid ,
.Nm vm_page_test_dirty ,
.Nm vm_page_dirty ,
.Nm vm_page_undirty
.Nd "manage page clean and dirty bits"
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/vm_page.h
.Ft int
.Fn vm_page_bits "int base" "int size"
.Ft void
.Fn vm_page_set_validclean "vm_page_t m" "int base" "int size"
.Ft void
.Fn vm_page_clear_dirty "vm_page_t m" "int base" "int size"
.Ft void
.Fn vm_page_set_invalid "vm_page_t m" "int base" "int size"
.Ft void
.Fn vm_page_zero_invalid "vm_page_t m" "boolean_t setvalid"
.Ft int
.Fn vm_page_is_valid "vm_page_t m" "int base" "int size"
.Ft void
.Fn vm_page_test_dirty "vm_page_t m"
.Ft void
.Fn vm_page_dirty "vm_page_t m"
.Ft void
.Fn vm_page_undirty "vm_page_t m"
.Sh DESCRIPTION
.Fn vm_page_bits
calculates the bits representing the
.Dv DEV_BSIZE
range of bytes between
.Fa base
and
.Fa size .
The byte range is expected to be within a single page, and if
.Fa size
is zero, no bits will be set.
.Pp
.Fn vm_page_set_validclean
flags the byte range between
.Fa base
and
.Fa size
as valid and clean.
The range is expected to be
.Dv DEV_BSIZE
aligned and no larger than
.Dv PAGE_SIZE .
If it is not properly aligned, any unaligned chunks of the
.Dv DEV_BSIZE
blocks at the beginning and end of the range will be zeroed.
.Pp
If
.Fa base
is zero and
.Fa size
is one page, the modified bit in the page map is cleared; as well,
the
.Dv VPO_NOSYNC
flag is cleared.
.Pp
.Fn vm_page_clear_dirty
clears the dirty bits within a page in the range between
.Fa base
and
.Fa size .
The bits representing the range are calculated by calling
.Fn vm_page_bits .
.Pp
.Fn vm_page_set_invalid
clears the bits in both the valid and dirty flags representing
the
.Dv DEV_BSIZE
blocks between
.Fa base
and
.Fa size
in the page.
The bits are calculated by calling
.Fn vm_page_bits .
As well as clearing the bits within the page, the generation
number within the object holding the page is incremented.
.Pp
.Fn vm_page_zero_invalid
zeroes all of the blocks within the page that are currently
flagged as invalid.
If
.Fa setvalid
is
.Dv TRUE ,
all of the valid bits within the page are set.
.Pp
In some cases, such as NFS, the valid bits cannot be set
in order to maintain cache consistency.
.Pp
.Fn vm_page_is_valid
checks to determine if the all of the
.Dv DEV_BSIZE
blocks between
.Fa base
and
.Fa size
of the page are valid.
If
.Fa size
is zero and the page is entirely invalid
.Fn vm_page_is_valid
will return
.Dv TRUE ,
in all other cases a size of zero will return
.Dv FALSE .
.Pp
.Fn vm_page_test_dirty
checks if a page has been modified via any of its physical maps,
and if so, flags the entire page as dirty.
.Fn vm_page_dirty
is called to modify the dirty bits.
.Pp
.Fn vm_page_dirty
flags the entire page as dirty.
It is expected that the page is not currently on the cache queue.
.Pp
.Fn vm_page_undirty
clears all of the dirty bits in a page.
.Sh NOTES
None of these functions are allowed to block.
.Sh AUTHORS
This manual page was written by
.An Chad David Aq davidc@acns.ab.ca .