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 chunks 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
       VPO_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  object  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 zero 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 expected 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@acns.ab.ca>.

Debian                                          December 1, 2001                                 VM_PAGE_BITS(9)