The patch titled
dm: map and endio return code clarification
has been added to the -mm tree. Its filename is
dm-map-and-endio-return-code-clarification.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: dm: map and endio return code clarification
From: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Cc: dm-devel@xxxxxxxxxx
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/md/dm.c | 13 ++++++++++---
drivers/md/dm.h | 11 +++++++++++
include/linux/device-mapper.h | 2 +-
3 files changed, 22 insertions(+), 4 deletions(-)
diff -puN drivers/md/dm.c~dm-map-and-endio-return-code-clarification drivers/md/dm.c
--- a/drivers/md/dm.c~dm-map-and-endio-return-code-clarification
+++ a/drivers/md/dm.c
@@ -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 -puN drivers/md/dm.h~dm-map-and-endio-return-code-clarification drivers/md/dm.h
--- a/drivers/md/dm.h~dm-map-and-endio-return-code-clarification
+++ a/drivers/md/dm.h
@@ -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 -puN include/linux/device-mapper.h~dm-map-and-endio-return-code-clarification include/linux/device-mapper.h
--- a/include/linux/device-mapper.h~dm-map-and-endio-return-code-clarification
+++ a/include/linux/device-mapper.h
@@ -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);
_
Patches currently in -mm which might be from k-ueda@xxxxxxxxxxxxx are
dm-tidy-core-formatting.patch
dm-suspend-parameter-change.patch
dm-map-and-endio-return-code-clarification.patch
dm-map-and-endio-symbolic-return-codes.patch
dm-ioctl-add-noflush-suspend.patch
dm-suspend-add-noflush-pushback.patch
dm-mpath-use-noflush-suspending.patch
-
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