blk-mq: expose write hints through debugfs

Useful to verify that things are working the way they should.
Reading the file will return number of kb written with each
write hint. Writing the file will reset the statistics. No care
is taken to ensure that we don't race on updates.

Drivers will write to q->write_hints[] if they handle a given
write hint.

Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 9edebbdce0bdfc22ee9ba8319bb3cc58923bbfa7..9ebc2945f991e9ff5d50c5191de45ca1025f1201 100644 (file)
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -135,6 +135,29 @@ static void print_stat(struct seq_file *m, struct blk_rq_stat *stat)
        }
 }
 
+static int queue_write_hint_show(void *data, struct seq_file *m)
+{
+       struct request_queue *q = data;
+       int i;
+
+       for (i = 0; i < BLK_MAX_WRITE_HINTS; i++)
+               seq_printf(m, "hint%d: %llu\n", i, q->write_hints[i]);
+
+       return 0;
+}
+
+static ssize_t queue_write_hint_store(void *data, const char __user *buf,
+                                     size_t count, loff_t *ppos)
+{
+       struct request_queue *q = data;
+       int i;
+
+       for (i = 0; i < BLK_MAX_WRITE_HINTS; i++)
+               q->write_hints[i] = 0;
+
+       return count;
+}
+
 static int queue_poll_stat_show(void *data, struct seq_file *m)
 {
        struct request_queue *q = data;
@@ -730,6 +753,7 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_queue_attrs[] = {
        {"poll_stat", 0400, queue_poll_stat_show},
        {"requeue_list", 0400, .seq_ops = &queue_requeue_list_seq_ops},
        {"state", 0600, queue_state_show, queue_state_write},
+       {"write_hints", 0600, queue_write_hint_show, queue_write_hint_store},
        {},
 };
 

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0eebd3bcfd8581a37b538970b851df6766fd51b2..e1e289ab66b91f1f6997d7060f34f8cb33915568 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -596,6 +596,9 @@ struct request_queue {
        void                    *rq_alloc_data;
 
        struct work_struct      release_work;
+
+#define BLK_MAX_WRITE_HINTS    5
+       u64                     write_hints[BLK_MAX_WRITE_HINTS];
 };
 
 #define QUEUE_FLAG_QUEUED      1       /* uses generic tag queueing */