block: Export max number of segments and max segment size in sysfs
These two values are useful when debugging issues surrounding maximum
I/O size. Put them in sysfs with the rest of the queue limits.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index e8544241..fad8655 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -106,6 +106,19 @@
return queue_var_show(max_sectors_kb, (page));
}
+static ssize_t queue_max_segments_show(struct request_queue *q, char *page)
+{
+ return queue_var_show(queue_max_segments(q), (page));
+}
+
+static ssize_t queue_max_segment_size_show(struct request_queue *q, char *page)
+{
+ if (test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
+ return queue_var_show(queue_max_segment_size(q), (page));
+
+ return queue_var_show(PAGE_CACHE_SIZE, (page));
+}
+
static ssize_t queue_logical_block_size_show(struct request_queue *q, char *page)
{
return queue_var_show(queue_logical_block_size(q), page);
@@ -280,6 +293,16 @@
.show = queue_max_hw_sectors_show,
};
+static struct queue_sysfs_entry queue_max_segments_entry = {
+ .attr = {.name = "max_segments", .mode = S_IRUGO },
+ .show = queue_max_segments_show,
+};
+
+static struct queue_sysfs_entry queue_max_segment_size_entry = {
+ .attr = {.name = "max_segment_size", .mode = S_IRUGO },
+ .show = queue_max_segment_size_show,
+};
+
static struct queue_sysfs_entry queue_iosched_entry = {
.attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
.show = elv_iosched_show,
@@ -355,6 +378,8 @@
&queue_ra_entry.attr,
&queue_max_hw_sectors_entry.attr,
&queue_max_sectors_entry.attr,
+ &queue_max_segments_entry.attr,
+ &queue_max_segment_size_entry.attr,
&queue_iosched_entry.attr,
&queue_hw_sector_size_entry.attr,
&queue_logical_block_size_entry.attr,
