From 169e2cc279c443085f7e423561eb1fe6158ade44 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@redhat.com>
Date: Thu, 22 Aug 2013 18:21:38 -0400
Subject: [PATCH] dm: allow error target to replace bio-based and request-based
targets
It may be useful to switch a request-based table to the "error" target.
Enhance the DM core to allow a hybrid target_type which is capable of
handling either bios (via .map) or requests (via .map_rq).
Add a request-based map function (.map_rq) to the "error" target_type;
making it DM's first hybrid target. Train dm_table_set_type() to prefer
the mapped device's established type (request-based or bio-based). If
the mapped device doesn't have an established type default to making the
table with the hybrid target(s) bio-based.
Tested 'dmsetup wipe_table' to work on both bio-based and request-based
devices.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---
drivers/md/dm-table.c | 22 ++++++++++++++++++++--
drivers/md/dm-target.c | 9 ++++++++-
drivers/md/dm.h | 11 +++++++++++
3 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f221812b7dbc..f309477d7efe 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -860,14 +860,17 @@ 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;
+ unsigned live_md_type;
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 +882,21 @@ 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.
+ * Default to bio-based if device is new.
+ */
+ dm_lock_md_type(t->md);
+ live_md_type = dm_get_md_type(t->md);
+ dm_unlock_md_type(t->md);
+ if (live_md_type == DM_TYPE_REQUEST_BASED)
+ request_based = 1;
+ else
+ bio_based = 1;
+ }
+
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 37ba5db71cd9..242e3cec397a 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 45b97da1bd06..8b4c075d9a2f 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -88,11 +88,22 @@ 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.
*---------------------------------------------------------------*/
--
2.34.1