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>

1 files changed, 23 insertions, 0 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 36d205128f9a..527bd8d4db50 100644
--- 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,
 };