[PATCH 11/19] btrfs: add bps discard rate limit

[Dennis Zhou <dennis@kernel.org>]

Provide an ability to rate limit based on mbps in addition to the iops
delay calculated from number of discardable extents.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/ctree.h   |  2 ++
 fs/btrfs/discard.c | 11 +++++++++++
 fs/btrfs/sysfs.c   | 30 ++++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b0823961d049..e81f699347e0 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -447,10 +447,12 @@ struct btrfs_discard_ctl {
 	spinlock_t lock;
 	struct btrfs_block_group_cache *cache;
 	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
+	u64 prev_discard;
 	atomic_t discard_extents;
 	atomic64_t discardable_bytes;
 	atomic_t delay;
 	atomic_t iops_limit;
+	atomic64_t bps_limit;
 };
 
 /* delayed seq elem */
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index c7afb5f8240d..072c73f48297 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -176,6 +176,13 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
 	cache = find_next_cache(discard_ctl, now);
 	if (cache) {
 		u64 delay = atomic_read(&discard_ctl->delay);
+		s64 bps_limit = atomic64_read(&discard_ctl->bps_limit);
+
+		if (bps_limit)
+			delay = max_t(u64, delay,
+				      msecs_to_jiffies(MSEC_PER_SEC *
+						discard_ctl->prev_discard /
+						bps_limit));
 
 		if (now < cache->discard_delay)
 			delay = max_t(u64, delay,
@@ -213,6 +220,8 @@ static void btrfs_discard_workfn(struct work_struct *work)
 		btrfs_trim_block_group(cache, &trimmed, cache->discard_cursor,
 				       btrfs_block_group_end(cache), 0, true);
 
+	discard_ctl->prev_discard = trimmed;
+
 	if (cache->discard_cursor >= btrfs_block_group_end(cache)) {
 		if (btrfs_discard_bitmaps(cache)) {
 			remove_from_discard_list(discard_ctl, cache);
@@ -324,10 +333,12 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
 	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++)
 		 INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
 
+	discard_ctl->prev_discard = 0;
 	atomic_set(&discard_ctl->discard_extents, 0);
 	atomic64_set(&discard_ctl->discardable_bytes, 0);
 	atomic_set(&discard_ctl->delay, BTRFS_DISCARD_MAX_DELAY);
 	atomic_set(&discard_ctl->iops_limit, BTRFS_DISCARD_MAX_IOPS);
+	atomic64_set(&discard_ctl->bps_limit, 0);
 }
 
 void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index b9a62e470316..6fc4d644401b 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -522,10 +522,40 @@ static ssize_t btrfs_discard_iops_limit_store(struct kobject *kobj,
 BTRFS_ATTR_RW(discard, iops_limit, btrfs_discard_iops_limit_show,
 	      btrfs_discard_iops_limit_store);
 
+static ssize_t btrfs_discard_bps_limit_show(struct kobject *kobj,
+					     struct kobj_attribute *a,
+					     char *buf)
+{
+	struct btrfs_fs_info *fs_info = to_fs_info(kobj->parent);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+			atomic64_read(&fs_info->discard_ctl.bps_limit));
+}
+
+static ssize_t btrfs_discard_bps_limit_store(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info = to_fs_info(kobj->parent);
+	s64 bps_limit;
+	int ret;
+
+	ret = kstrtos64(buf, 10, &bps_limit);
+	if (ret || bps_limit < 0)
+		return -EINVAL;
+
+	atomic64_set(&fs_info->discard_ctl.bps_limit, bps_limit);
+
+	return len;
+}
+BTRFS_ATTR_RW(discard, bps_limit, btrfs_discard_bps_limit_show,
+	      btrfs_discard_bps_limit_store);
+
 static const struct attribute *discard_attrs[] = {
 	BTRFS_ATTR_PTR(discard, discard_extents),
 	BTRFS_ATTR_PTR(discard, discardable_bytes),
 	BTRFS_ATTR_PTR(discard, iops_limit),
+	BTRFS_ATTR_PTR(discard, bps_limit),
 	NULL,
 };
 
-- 
2.17.1