From 45cbcd798354251b99694086af9d57c99e89bb43 Mon Sep 17 00:00:00 2001 From: Kiyoshi Ueda Date: Fri, 8 Dec 2006 02:41:05 -0800 Subject: [PATCH] [PATCH] dm: map and endio return code clarification Tighten the use of return values from the target map and end_io functions. Values of 2 and above are now explictly reserved for future use. There are no existing targets using such values. The patch has no effect on existing behaviour. o Reserve return values of 2 and above from target map functions. Any positive value currently indicates "mapping complete", but all existing drivers use the value 1. We now make that a requirement so we can assign new meaning to higher values in future. The new definition of return values from target map functions is: < 0 : error = 0 : The target will handle the io (DM_MAPIO_SUBMITTED). = 1 : Mapping completed (DM_MAPIO_REMAPPED). > 1 : Reserved (undefined). Previously this was the same as '= 1'. o Reserve return values of 2 and above from target end_io functions for similar reasons. DM_ENDIO_INCOMPLETE is introduced for a return value of 1. Test results: I have tested by using the multipath target. I/Os succeed when valid paths exist. I/Os are queued in the multipath target when there are no valid paths and queue_if_no_path is set. I/Os fail when there are no valid paths and queue_if_no_path is not set. Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Signed-off-by: Alasdair G Kergon Cc: dm-devel@redhat.com Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/dm.c | 13 ++++++++++--- drivers/md/dm.h | 11 +++++++++++ include/linux/device-mapper.h | 2 +- 3 files changed, 22 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index b42e71bb9e67..d8544e1a4c1f 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -482,9 +482,13 @@ static int clone_endio(struct bio *bio, unsigned int done, int error) 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 *ti, struct bio *clone, 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 *ti, struct bio *clone, 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 --git a/drivers/md/dm.h b/drivers/md/dm.h index 81c98d6e35e9..293d5ce62a21 100644 --- a/drivers/md/dm.h +++ b/drivers/md/dm.h @@ -32,6 +32,17 @@ #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 */ diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h index 9194ff2d08c0..2e5c42346c38 100644 --- a/include/linux/device-mapper.h +++ b/include/linux/device-mapper.h @@ -39,7 +39,7 @@ typedef void (*dm_dtr_fn) (struct dm_target *ti); * 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); -- 2.20.1