Hello Mike,
On 08/23/13 09:17, Mike Snitzer wrote:
>> I do like the idea of a single error target that is hybrid (supports
>> both bio-based and request-based) but the DM core would need to be
>> updated to support this.
>>
>> Specifically, we'd need to check if the device (and active table) is
>> already bio-based or request-based and select the appropriate type. If
>> it is a new device, default to selecting bio-based.
>>
>> There are some wrappers and other logic thoughout DM core that will need
>> auditing too.
>
> Here is a patch that should work for your needs (I tested it to work
> with 'dmsetup wipe_table' on both request-based and bio-based devices):
How about moving the default handling in dm_table_set_type() outside of
the for-each-target loop, like the modified patch below?
For example, if a table has 2 targets, hybrid and request_based,
and live_md_type is DM_TYPE_NONE, the table should be considered as
request_based, not inconsistent.
Though the end result is same as such a table is rejected by other
constraint anyway, I think it's good to keep the semantics clean
and error messages consistent.
I.e. for the above case, the error message should be
"Request-based dm doesn't support multiple targets yet",
not "Inconsistent table: different target types can't be mixed up".
---
Jun'ichi Nomura, NEC Corporation
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f221812..6e683c8 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -860,14 +860,16 @@ EXPORT_SYMBOL(dm_consume_args);
static int dm_table_set_type(struct dm_table *t)
{
unsigned i;
- unsigned bio_based = 0, request_based = 0;
+ unsigned bio_based = 0, request_based = 0, hybrid = 0;
struct dm_target *tgt;
struct dm_dev_internal *dd;
struct list_head *devices;
for (i = 0; i < t->num_targets; i++) {
tgt = t->targets + i;
- if (dm_target_request_based(tgt))
+ if (dm_target_hybrid(tgt))
+ hybrid = 1;
+ else if (dm_target_request_based(tgt))
request_based = 1;
else
bio_based = 1;
@@ -879,6 +881,25 @@ static int dm_table_set_type(struct dm_table *t)
}
}
+ if (hybrid && !bio_based && !request_based) {
+ /*
+ * The targets can work either way.
+ * Determine the type from the live device.
+ */
+ unsigned live_md_type;
+ dm_lock_md_type(t->md);
+ live_md_type = dm_get_md_type(t->md);
+ dm_unlock_md_type(t->md);
+ switch (live_md_type) {
+ case DM_TYPE_REQUEST_BASED:
+ request_based = 1;
+ break;
+ default:
+ bio_based = 1;
+ break;
+ }
+ }
+
if (bio_based) {
/* We must use this table as bio-based */
t->type = DM_TYPE_BIO_BASED;
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 37ba5db..242e3ce 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -131,12 +131,19 @@ static int io_err_map(struct dm_target *tt, struct bio *bio)
return -EIO;
}
+static int io_err_map_rq(struct dm_target *ti, struct request *clone,
+ union map_info *map_context)
+{
+ return -EIO;
+}
+
static struct target_type error_target = {
.name = "error",
- .version = {1, 1, 0},
+ .version = {1, 2, 0},
.ctr = io_err_ctr,
.dtr = io_err_dtr,
.map = io_err_map,
+ .map_rq = io_err_map_rq,
};
int __init dm_target_init(void)
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 45b97da..8b4c075 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -89,10 +89,21 @@ int dm_setup_md_queue(struct mapped_device *md);
#define dm_target_is_valid(t) ((t)->table)
/*
+ * To check whether the target type is bio-based or not (request-based).
+ */
+#define dm_target_bio_based(t) ((t)->type->map != NULL)
+
+/*
* To check whether the target type is request-based or not (bio-based).
*/
#define dm_target_request_based(t) ((t)->type->map_rq != NULL)
+/*
+ * To check whether the target type is a hybrid (capable of being
+ * either request-based or bio-based).
+ */
+#define dm_target_hybrid(t) (dm_target_bio_based(t) && dm_target_request_based(t))
+
/*-----------------------------------------------------------------
* A registry of target types.
*---------------------------------------------------------------*/
--
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