From 45cbcd798354251b99694086af9d57c99e89bb43 Mon Sep 17 00:00:00 2001 From: Kiyoshi Ueda Date: Fri, 8 Dec 2006 02:41:05 -0800 Subject: [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 --- include/linux/device-mapper.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/device-mapper.h') 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); -- cgit v1.2.3