BIOMODIFIED(9F)BIOMODIFIED(9F)NAMEbiomodified - 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).
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_PAGEIOflag must be set in the b_flags field of
the buf(9S) structure. The biomodified() function will check the mem‐
ory pages associated with this buffer whether the Virtual Memory sys‐
tem's modification bit is set. If at least one of these pages is modi‐
fied, 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 applica‐
tion 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.
CONTEXTbiomodified() can be called from any context.
SEE ALSObp_mapin(9F), buf(9S)
Writing Device Drivers
Nov 20, 1996 BIOMODIFIED(9F)
