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

biomodified - check if a buffer is modified

#include <sys/ddi.h>
#include <sys/sunddi.h>
int biomodified(struct buf *bp);

illumos DDI specific (illumos DDI).

bp
Pointer to the buffer header structure.

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_PAGEIOflag 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.

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.

biomodified() can be called from any context.

bp_mapin(9F), buf(9S)

Writing Device Drivers

November 20, 1996 OmniOS