This patch explicitly defines the use of return values from target map/end_io functions. Values more than 1 are reserved for future use. I have confirmed existing upstream target drivers don't use the reserved values. Should have no effect on the behavior. Corresponding changes in target drivers will follow. Details are below. o Reserve return values more than 1 from target map function. Current target drivers can use more than 0 to tell map complete to the dm core, but all target drivers are using 1 for that now. So reserve more than 1 explicitly so that target drivers can tell other things to the dm core in the future. New definition is below. < 0 : error = 0 : The target will handle the io (symbol: DM_MAPIO_SUBMITTED) = 1 : map complete (symbol: DM_MAPIO_REMAPPED) > 1 : reserved (undefined) o Reserve return values more than 1 from target end_io function. More than 1 is not defined and actually target drivers can use more than 1 instead of 1. So reserve it explicitly. Test results: I have tested by using multipath target. I/Os succeed when valid paths are existing. I/Os are queued in the multipath target when no valid paths and queue_if_no_path is set. I/Os fail when no valid paths and no queue_if_no_path setting. The patch is for: 2.6.18-mm2 + patch 1-2 Signed-off-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx> diff -rupN 2-susp-iface-change/drivers/md/dm.c 3-core-rval-iface-change/drivers/md/dm.c --- 2-susp-iface-change/drivers/md/dm.c 2006-10-05 10:26:33.000000000 -0400 +++ 3-core-rval-iface-change/drivers/md/dm.c 2006-10-05 13:48:34.000000000 -0400 @@ -482,9 +482,13 @@ static int clone_endio(struct bio *bio, r = endio(tio->ti, bio, error, &tio->info); if (r < 0) error = r; - else if (r > 0) - /* the target wants another shot at the io */ + else if (r == DM_ENDIO_INCOMPLETE) + /* The target will handle the io */ return 1; + else if (r) { + DMWARN("unimplemented target endio return value: %d", r); + BUG(); + } } dec_pending(tio->io, error); @@ -542,7 +546,7 @@ static void __map_bio(struct dm_target * atomic_inc(&tio->io->io_count); sector = clone->bi_sector; r = ti->type->map(ti, clone, &tio->info); - if (r > 0) { + if (r == DM_MAPIO_REMAPPED) { /* the bio has been remapped so dispatch it */ blk_add_trace_remap(bdev_get_queue(clone->bi_bdev), clone, @@ -560,6 +564,9 @@ static void __map_bio(struct dm_target * clone->bi_private = md->bs; bio_put(clone); free_tio(md, tio); + } else if (r) { + DMWARN("unimplemented target map return value: %d", r); + BUG(); } } diff -rupN 2-susp-iface-change/drivers/md/dm.h 3-core-rval-iface-change/drivers/md/dm.h --- 2-susp-iface-change/drivers/md/dm.h 2006-10-05 10:26:33.000000000 -0400 +++ 3-core-rval-iface-change/drivers/md/dm.h 2006-10-05 10:45:08.000000000 -0400 @@ -33,6 +33,17 @@ #define SECTOR_SHIFT 9 /* + * Definitions of return values from target end_io function. + */ +#define DM_ENDIO_INCOMPLETE 1 + +/* + * Definitions of return values from target map function. + */ +#define DM_MAPIO_SUBMITTED 0 +#define DM_MAPIO_REMAPPED 1 + +/* * Suspend feature flags */ #define DM_SUSPEND_LOCKFS_FLAG (1 << 0) diff -rupN 2-susp-iface-change/include/linux/device-mapper.h 3-core-rval-iface-change/include/linux/device-mapper.h --- 2-susp-iface-change/include/linux/device-mapper.h 2006-10-05 10:26:33.000000000 -0400 +++ 3-core-rval-iface-change/include/linux/device-mapper.h 2006-10-05 10:41:27.000000000 -0400 @@ -39,7 +39,7 @@ typedef void (*dm_dtr_fn) (struct dm_tar * The map function must return: * < 0: error * = 0: The target will handle the io by resubmitting it later - * > 0: simple remap complete + * = 1: simple remap complete */ typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio, union map_info *map_context); -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel