[dm-devel] [PATCH 2/7] dm: add reserved_rq_based_ios module parameter
Mike Snitzer
snitzer at redhat.com
Thu Sep 12 22:24:53 UTC 2013
Allow user to change the number of IOs that are reserved by
request-based DM's mempools by writing to this file:
/sys/module/dm_mod/parameters/reserved_rq_based_ios
The default value is RESERVED_REQUEST_BASED_IOS (256).
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
drivers/md/dm.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 48 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 47bac14..8553d03 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -216,6 +216,38 @@ struct dm_md_mempools {
static struct kmem_cache *_io_cache;
static struct kmem_cache *_rq_tio_cache;
+/*
+ * Request-based DM's mempools' reserved IOs set by the user
+ */
+static unsigned reserved_rq_based_ios;
+
+/*
+ * A copy of reserved_rq_based_ios because it can change anytime.
+ * If values disagree, the user has changed reserved_rq_based_ios.
+ */
+static unsigned reserved_rq_based_ios_latch;
+
+/*
+ * This mutex protects reserved_rq_based_ios_latch.
+ */
+static DEFINE_MUTEX(dm_mempools_lock);
+
+static void __reserved_request_based_ios_refresh(void)
+{
+ BUG_ON(!mutex_is_locked(&dm_mempools_lock));
+
+ reserved_rq_based_ios_latch = ACCESS_ONCE(reserved_rq_based_ios);
+
+ /*
+ * If the user uses "0", it means default. Modify
+ * reserved_rq_based_ios to report the default to the user.
+ */
+ if (!reserved_rq_based_ios_latch) {
+ (void)cmpxchg(&reserved_rq_based_ios, 0, RESERVED_REQUEST_BASED_IOS);
+ reserved_rq_based_ios_latch = reserved_rq_based_ios;
+ }
+}
+
static int __init local_init(void)
{
int r = -ENOMEM;
@@ -241,6 +273,10 @@ static int __init local_init(void)
if (!_major)
_major = r;
+ mutex_lock(&dm_mempools_lock);
+ __reserved_request_based_ios_refresh();
+ mutex_unlock(&dm_mempools_lock);
+
return 0;
out_uevent_exit:
@@ -2867,7 +2903,14 @@ struct dm_md_mempools *dm_alloc_md_mempools(unsigned type, unsigned integrity, u
front_pad = roundup(per_bio_data_size, __alignof__(struct dm_target_io)) + offsetof(struct dm_target_io, clone);
} else if (type == DM_TYPE_REQUEST_BASED) {
cachep = _rq_tio_cache;
- pool_size = RESERVED_REQUEST_BASED_IOS;
+
+ mutex_lock(&dm_mempools_lock);
+ /* Check if reserved_rq_based_ios changed. */
+ if (reserved_rq_based_ios != reserved_rq_based_ios_latch)
+ __reserved_request_based_ios_refresh();
+ pool_size = reserved_rq_based_ios_latch;
+ mutex_unlock(&dm_mempools_lock);
+
front_pad = offsetof(struct dm_rq_clone_bio_info, clone);
/* per_bio_data_size is not used. See __bind_mempools(). */
WARN_ON(per_bio_data_size != 0);
@@ -2925,6 +2968,10 @@ module_exit(dm_exit);
module_param(major, uint, 0);
MODULE_PARM_DESC(major, "The major number of the device mapper");
+
+module_param(reserved_rq_based_ios, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(reserved_rq_based_ios, "Reserved IOs in request-based mempools");
+
MODULE_DESCRIPTION(DM_NAME " driver");
MODULE_AUTHOR("Joe Thornber <dm-devel at redhat.com>");
MODULE_LICENSE("GPL");
--
1.8.1.4
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