block: Add test-iosched scheduler

The test scheduler allows testing a block device by dispatching
specific requests according to the test case and declare PASS/FAIL
according to the requests completion error code

Change-Id: Ief91f9fed6e3c3c75627d27264d5252ea14f10ad
Signed-off-by: Maya Erez <merez@codeaurora.org>

Documentation/block/test-iosched.txt

@@ -0,0 +1,39 @@
+Test IO scheduler
+==================
+
+The test scheduler allows testing a block device by dispatching
+specific requests according to the test case and declare PASS/FAIL
+according to the requests completion error code.
+
+The test IO scheduler implements the no-op scheduler operations, and uses
+them in order to dispatch the non-test requests when no test is running.
+This will allow to keep a normal FS operation in parallel to the test
+capability.
+The test IO scheduler keeps two different queues, one for real-world requests
+(inserted by the FS) and the other for the test requests.
+The test IO scheduler chooses the queue for dispatch requests according to the
+test state (IDLE/RUNNING).
+
+the test IO scheduler is compiled by default as a dynamic module and enabled
+only if CONFIG_DEBUG_FS is defined.
+
+Each block device test utility that would like to use the test-iosched test
+services, should register as a blk_dev_test_type and supply an init and exit
+callbacks. Those callback are called upon selection (or removal) of the
+test-iosched as the active scheduler. From that point the block device test
+can start a test and supply its own callbacks for preparing, running, result
+checking and cleanup of the test.
+
+Each test is exposed via debugfs and can be triggered by writing to
+the debugfs file. In order to add a new test one should expose a new debugfs
+file for the new test.
+
+Selecting IO schedulers
+-----------------------
+Refer to Documentation/block/switching-sched.txt for information on
+selecting an io scheduler on a per-device basis.
+
+
+May 10 2012, maya Erez <merez@codeaurora.org>
+
+

block/Kconfig.iosched

@@ -12,6 +12,17 @@ config IOSCHED_NOOP
 	  that do their own scheduling and require only minimal assistance from
 	  the kernel.
 
+config IOSCHED_TEST
+	tristate "Test I/O scheduler"
+	depends on DEBUG_FS
+	default m
+	---help---
+	  The test I/O scheduler is a duplicate of the noop scheduler with
+	  addition of test utlity.
+	  It allows testing a block device by dispatching specific requests
+	  according to the test case and declare PASS/FAIL according to the
+	  requests completion error code.
+
 config IOSCHED_DEADLINE
 	tristate "Deadline I/O scheduler"
 	default y

block/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_BLK_DEV_THROTTLING)	+= blk-throttle.o
 obj-$(CONFIG_IOSCHED_NOOP)	+= noop-iosched.o
 obj-$(CONFIG_IOSCHED_DEADLINE)	+= deadline-iosched.o
 obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
+obj-$(CONFIG_IOSCHED_TEST)	+= test-iosched.o
 
 obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
 obj-$(CONFIG_BLK_CMDLINE_PARSER)	+= cmdline-parser.o

block/blk-core.c

@@ -1275,8 +1275,6 @@ static struct request *blk_old_get_request(struct request_queue *q, int rw,
 {
 	struct request *rq;
 
-	BUG_ON(rw != READ && rw != WRITE);
-
 	/* create ioc upfront */
 	create_io_context(gfp_mask, q->node);
 
@@ -1696,6 +1694,7 @@ void init_request_from_bio(struct request *req, struct bio *bio)
 	req->ioprio = bio_prio(bio);
 	blk_rq_bio_prep(req->q, req, bio);
 }
+EXPORT_SYMBOL(init_request_from_bio);
 
 static blk_qc_t blk_queue_bio(struct request_queue *q, struct bio *bio)
 {