Commit 45cbcd798354251b99694086af9d57c99e89bb43
Committed by
Linus Torvalds
Linus Torvalds
1 parent
a3d77d35be
Exists in
master
and in
20 other branches
[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 <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Showing 3 changed files with 22 additions and 4 deletions Side-by-side Diff
drivers/md/dm.c
| ... | ... | @@ -482,9 +482,13 @@ |
| 482 | 482 | r = endio(tio->ti, bio, error, &tio->info); |
| 483 | 483 | if (r < 0) |
| 484 | 484 | error = r; |
| 485 | - else if (r > 0) | |
| 486 | - /* the target wants another shot at the io */ | |
| 485 | + else if (r == DM_ENDIO_INCOMPLETE) | |
| 486 | + /* The target will handle the io */ | |
| 487 | 487 | return 1; |
| 488 | + else if (r) { | |
| 489 | + DMWARN("unimplemented target endio return value: %d", r); | |
| 490 | + BUG(); | |
| 491 | + } | |
| 488 | 492 | } |
| 489 | 493 | |
| 490 | 494 | dec_pending(tio->io, error); |
| ... | ... | @@ -542,7 +546,7 @@ |
| 542 | 546 | atomic_inc(&tio->io->io_count); |
| 543 | 547 | sector = clone->bi_sector; |
| 544 | 548 | r = ti->type->map(ti, clone, &tio->info); |
| 545 | - if (r > 0) { | |
| 549 | + if (r == DM_MAPIO_REMAPPED) { | |
| 546 | 550 | /* the bio has been remapped so dispatch it */ |
| 547 | 551 | |
| 548 | 552 | blk_add_trace_remap(bdev_get_queue(clone->bi_bdev), clone, |
| ... | ... | @@ -560,6 +564,9 @@ |
| 560 | 564 | clone->bi_private = md->bs; |
| 561 | 565 | bio_put(clone); |
| 562 | 566 | free_tio(md, tio); |
| 567 | + } else if (r) { | |
| 568 | + DMWARN("unimplemented target map return value: %d", r); | |
| 569 | + BUG(); | |
| 563 | 570 | } |
| 564 | 571 | } |
| 565 | 572 |
drivers/md/dm.h
| ... | ... | @@ -33,6 +33,17 @@ |
| 33 | 33 | #define SECTOR_SHIFT 9 |
| 34 | 34 | |
| 35 | 35 | /* |
| 36 | + * Definitions of return values from target end_io function. | |
| 37 | + */ | |
| 38 | +#define DM_ENDIO_INCOMPLETE 1 | |
| 39 | + | |
| 40 | +/* | |
| 41 | + * Definitions of return values from target map function. | |
| 42 | + */ | |
| 43 | +#define DM_MAPIO_SUBMITTED 0 | |
| 44 | +#define DM_MAPIO_REMAPPED 1 | |
| 45 | + | |
| 46 | +/* | |
| 36 | 47 | * Suspend feature flags |
| 37 | 48 | */ |
| 38 | 49 | #define DM_SUSPEND_LOCKFS_FLAG (1 << 0) |
include/linux/device-mapper.h
| ... | ... | @@ -39,7 +39,7 @@ |
| 39 | 39 | * The map function must return: |
| 40 | 40 | * < 0: error |
| 41 | 41 | * = 0: The target will handle the io by resubmitting it later |
| 42 | - * > 0: simple remap complete | |
| 42 | + * = 1: simple remap complete | |
| 43 | 43 | */ |
| 44 | 44 | typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio, |
| 45 | 45 | union map_info *map_context); |