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@xxxxxxxxxx> --- 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@xxxxxxxxxx>"); MODULE_LICENSE("GPL"); -- 1.8.1.4 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel