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Commit 2c561246 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Jens Axboe
Browse files

block: Simplify bsg complete all 



It took me a few tries to figure out what this code did; lets rewrite
it into a more regular form.

The thing that makes this one 'special' is the BSG_F_BLOCK flag, if
that is not set we're not supposed/allowed to block and should spin
wait for completion.

The (new) io_wait_event() will never see a false condition in case of
the spinning and we will therefore not block.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent b7f120b2

block/bsg.c

+25 −47
Original line number Diff line number Diff line
@@ -136,42 +136,6 @@ static inline struct hlist_head *bsg_dev_idx_hash(int index) 
	return &bsg_device_list[index & (BSG_LIST_ARRAY_SIZE - 1)];

}



static int bsg_io_schedule(struct bsg_device *bd)

{

	DEFINE_WAIT(wait);

	int ret = 0;



	spin_lock_irq(&bd->lock);



	BUG_ON(bd->done_cmds > bd->queued_cmds);



	/*

	 * -ENOSPC or -ENODATA?  I'm going for -ENODATA, meaning "I have no

	 * work to do", even though we return -ENOSPC after this same test

	 * during bsg_write() -- there, it means our buffer can't have more

	 * bsg_commands added to it, thus has no space left.

	 */

	if (bd->done_cmds == bd->queued_cmds) {

		ret = -ENODATA;

		goto unlock;

	}



	if (!test_bit(BSG_F_BLOCK, &bd->flags)) {

		ret = -EAGAIN;

		goto unlock;

	}



	prepare_to_wait(&bd->wq_done, &wait, TASK_UNINTERRUPTIBLE);

	spin_unlock_irq(&bd->lock);

	io_schedule();

	finish_wait(&bd->wq_done, &wait);



	return ret;

unlock:

	spin_unlock_irq(&bd->lock);

	return ret;

}



static int blk_fill_sgv4_hdr_rq(struct request_queue *q, struct request *rq,

				struct sg_io_v4 *hdr, struct bsg_device *bd,

				fmode_t has_write_perm)
@@ -482,6 +446,30 @@ static int blk_complete_sgv4_hdr_rq(struct request *rq, struct sg_io_v4 *hdr, 
	return ret;

}



static bool bsg_complete(struct bsg_device *bd)

{

	bool ret = false;

	bool spin;



	do {

		spin_lock_irq(&bd->lock);



		BUG_ON(bd->done_cmds > bd->queued_cmds);



		/*

		 * All commands consumed.

		 */

		if (bd->done_cmds == bd->queued_cmds)

			ret = true;



		spin = !test_bit(BSG_F_BLOCK, &bd->flags);



		spin_unlock_irq(&bd->lock);

	} while (!ret && spin);



	return ret;

}



static int bsg_complete_all_commands(struct bsg_device *bd)

{

	struct bsg_command *bc;
@@ -492,17 +480,7 @@ static int bsg_complete_all_commands(struct bsg_device *bd) 
	/*

	 * wait for all commands to complete

	 */

	ret = 0;

	do {

		ret = bsg_io_schedule(bd);

		/*

		 * look for -ENODATA specifically -- we'll sometimes get

		 * -ERESTARTSYS when we've taken a signal, but we can't

		 * return until we're done freeing the queue, so ignore

		 * it.  The signal will get handled when we're done freeing

		 * the bsg_device.

		 */

	} while (ret != -ENODATA);

	io_wait_event(bd->wq_done, bsg_complete(bd));



	/*

	 * discard done commands

include/linux/wait.h

+15 −0
Original line number Diff line number Diff line
@@ -267,6 +267,21 @@ do { \ 
	__wait_event(wq, condition);					\

} while (0)



#define __io_wait_event(wq, condition)					\

	(void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0,	\

			    io_schedule())



/*

 * io_wait_event() -- like wait_event() but with io_schedule()

 */

#define io_wait_event(wq, condition)					\

do {									\

	might_sleep();							\

	if (condition)							\

		break;							\

	__io_wait_event(wq, condition);					\

} while (0)



#define __wait_event_freezable(wq, condition)				\

	___wait_event(wq, condition, TASK_INTERRUPTIBLE, 0, 0,		\

			    schedule(); try_to_freeze())