modified

biomodified(9F) 					   Kernel Functions for Drivers 					   biomodified(9F)

NAME

       biomodified - check if a buffer is modified

SYNOPSIS

       #include <sys/ddi.h>
       #include <sys/sunddi.h>

       intbiomodified(struct buf *bp);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       bp	Pointer to the buffer header structure.

DESCRIPTION

       The  biomodified()  function returns status to indicate if the buffer is modified. The  biomodified() function is only supported for paged-
       I/O request, that is the B_PAGEIO flag must be set in the b_flags field of the buf(9S) structure.  The  biomodified() function  will  check
       the  memory  pages associated with this buffer whether the Virtual Memory system's modification bit is set.  If at least one of these pages
       is modified, the buffer is indicated as modified.  A filesystem will mark the pages  unmodified when it writes the  pages  to  the  backing
       store.  The  biomodified() function can be used to detect any modifications to the memory pages while I/O is in progress.

       A  device  driver  can use biomodified() for disk mirroring.  An application is allowed to mmap a file which can  reside on a disk which is
       mirrored by multiple submirrors. If the file system writes the file to the backing store, it is written to all  submirrors in parallel.	It
       must  be ensured that the copies on all submirrors are identical. The biomodified() function can be used in the device driver to detect any
       modifications to  the buffer by the user program during the time the buffer is written to multiple submirrors.

RETURN VALUES

       The  biomodified() function returns the following values:

       1	Buffer is modified.

       0	Buffer is not modified.

       -1	Buffer is not used for paged I/O request.

CONTEXT

       biomodified() can be called from any context.

SEE ALSO

       bp_mapin(9F), buf(9S)

       Writing Device Drivers

SunOS 5.10							    20 Nov 1996 						   biomodified(9F)