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_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.
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
August 22, 2023 BIOMODIFIED(9F)
NAME
biomodified - check if a buffer is modified
SYNOPSIS
#include <sys/ddi.h>
#include <sys/sunddi.h>
int biomodified(struct buf *bp);
INTERFACE LEVEL
illumos DDI specific (illumos 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
August 22, 2023 BIOMODIFIED(9F)