ll_rw_blk: temporarily enable max_segments tweaking

Expose this setting for now, so that users can play with enabling
large commands without defaulting it to on globally. This is a debug
patch, it will be dropped for the final versions.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 36d205128f9a969a45d81b245f85842c117a4fb5..527bd8d4db501d79b75aad799f309686c6ab8490 100644 (file)
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -4072,7 +4072,23 @@ static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
        return queue_var_show(max_hw_sectors_kb, (page));
 }
 
+static ssize_t queue_max_segments_show(struct request_queue *q, char *page)
+{
+       return queue_var_show(q->max_phys_segments, page);
+}
+
+static ssize_t queue_max_segments_store(struct request_queue *q,
+                                       const char *page, size_t count)
+{
+       unsigned long segments;
+       ssize_t ret = queue_var_store(&segments, page, count);
 
+       spin_lock_irq(q->queue_lock);
+       q->max_phys_segments = segments;
+       spin_unlock_irq(q->queue_lock);
+
+       return ret;
+}
 static struct queue_sysfs_entry queue_requests_entry = {
        .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
        .show = queue_requests_show,
@@ -4096,6 +4112,12 @@ static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
        .show = queue_max_hw_sectors_show,
 };
 
+static struct queue_sysfs_entry queue_max_segments_entry = {
+       .attr = {.name = "max_segments", .mode = S_IRUGO | S_IWUSR },
+       .show = queue_max_segments_show,
+       .store = queue_max_segments_store,
+};
+
 static struct queue_sysfs_entry queue_iosched_entry = {
        .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
        .show = elv_iosched_show,
@@ -4107,6 +4129,7 @@ static struct attribute *default_attrs[] = {
        &queue_ra_entry.attr,
        &queue_max_hw_sectors_entry.attr,
        &queue_max_sectors_entry.attr,
+       &queue_max_segments_entry.attr,
        &queue_iosched_entry.attr,
        NULL,
 };