NAME

biomodified - check if a buffer is modified

SYNOPSIS

#include <sys/ddi.h>

#include <sys/sunddi.h>

int biomodified(struct buf * bp);

INTERFACE LEVEL

Solaris DDI specific (Solaris DDI).

ARGUMENTS

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.

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.

EXAMPLES

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.

SEE ALSO

bp_mapin(9F), buf(9S)

Writing Device Drivers