vm_page_bits(9)

NAME

vm_page_bits, vm_page_set_validclean, vm_page_clear_dirty, vm_page_set_invalid, vm_page_zero_invalid, vm_page_is_valid, vm_page_test_dirty, vm_page_dirty, vm_page_undirty - manage

page clean
and dirty bits

SYNOPSIS

#include <sys/param.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
int
vm_page_bits(int base, int size);
void
vm_page_set_validclean(vm_page_t m, int base, int size);
void
vm_page_clear_dirty(vm_page_t m, int base, int size);
void
vm_page_set_invalid(vm_page_t m, int base, int size);
void
vm_page_zero_invalid(vm_page_t m, boolean_t setvalid);
int
vm_page_is_valid(vm_page_t m, int base, int size);
void
vm_page_test_dirty(vm_page_t m);
void
vm_page_dirty(vm_page_t m);
void
vm_page_undirty(vm_page_t m);

DESCRIPTION

vm_page_bits() calculates the bits representing the

DEV_BSIZE range of
bytes between base and size. The byte range is expected to

be within a
single page, and if size is zero, no bits will be set.

vm_page_set_validclean() flags the byte range between base

and size as
valid and clean. The range is expected to be DEV_BSIZE

aligned and no
larger than PAGE_SIZE. If it is not properly aligned, any

unaligned
chucks of the DEV_BSIZE blocks at the beginning and end of

the range will
be zeroed.

If base is zero and size is one page, the modified bit in

the page map is
cleared; as well, the PG_NOSYNC flag is cleared.

vm_page_clear_dirty() clears the dirty bits within a page in

the range
between base and size. The bits representing the range are

calculated by
calling vm_page_bits().

vm_page_set_invalid() clears the bits in both the valid and

dirty flags
representing the DEV_BSIZE blocks between base and size in

the page. The
bits are calculated by calling vm_page_bits(). As well as

clearing the
bits within the page, the generation number within the ob

ject holding the
page is incremented.

vm_page_zero_invalid() zeroes all of the blocks within the

page that are
currently flagged as invalid. If setvalid is TRUE, all of

the valid bits
within the page are set.

In some cases, such as NFS, the valid bits cannot be set in

order to
maintain cache consistency.

vm_page_is_valid() checks to determine if the all of the

DEV_BSIZE blocks
between base and size of the page are valid. If size is ze

ro and the
page is entirely invalid vm_page_is_valid() will return

TRUE, in all
other cases a size of zero will return FALSE.

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.
vm_page_dirty() is called to modify the dirty bits.

vm_page_dirty() flags the entire page as dirty. It is ex

pected that the
page is not currently on the cache queue.

vm_page_undirty() clears all of the dirty bits in a page.

NOTES

None of these functions are allowed to block.

AUTHORS

This manual page was written by Chad David <davidc@ac

ns.ab.ca>.

BSD December 1, 2001

BSD