disksort(9F)
NAME
disksort − single direction elevator seek sort for buffers
SYNOPSIS
#include <sys/conf.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
void disksort(struct diskhd ∗dp, struct buf ∗bp)
INTERFACE LEVEL
SPARC architecture specific (SPARC DDI).
DESCRIPTION
The function disksort() sorts a pointer to a buffer into a single forward linked list headed by the av_forw element of the argument ∗dp.
The sort algorithm is a one-way elevator algorithm that sorts buffers into the queue in ascending order based upon a key value held in the argument buffer structure element b_resid.
This value can either be the driver calculated cylinder number for the I/O request described by the buffer argument, or simply the absolute logical block for the I/O request, depending on how fine grained the sort is desired to be or how applicable either quantity is to the device in question.
The head of the linked list is found by use of the av_forw structure element of the argument ∗dp. The tail of the linked list is found by use of the av_back structure element of the argument ∗dp. The av_forw element of the ∗bp argument is used by disksort() to maintain the forward linkage.
ARGUMENTS
dp A pointer to a diskhd structure. A diskhd structure is essentially identical to head of a buffer structure (see buf(9S)). The only defined items of interest for this structure are the av_forw and av_back structure elements which are used to maintain the front and tail pointers of the forward linked I/O request queue.
bp A pointer to a buffer structure. Typically this is the I/O request that the driver receives in its strategy routine (see strategy(9E)). The driver is responsible for initializes the b_resid structure element to a meaningful sort key value prior to calling disksort().
WARNING
disksort() does no locking. Therefore, any locking is completely the responsibility of the caller.
CONTEXT
This function can be called from user or interrupt context.
SEE ALSO
BUGS
This function is simplistic and has been around for about twenty years and should be replaced with something a bit more flexible and snazzy.
SunOS 5.1 — Last change: 4 Nov 1991