From: Mikulas Patocka Remove queue_io return value and a loop in dm_request. IO may be submitted to a worker thread with queue_io(). queue_io() sets DMF_QUEUE_IO_TO_THREAD so that all further IO is queued for the thread. When the thread finishes its work, it clears DMF_QUEUE_IO_TO_THREAD and from this point on, requests are submitted from dm_request again. This will be used for processing barriers. Remove the loop in dm_request. queue_io() can submit I/Os to the worker thread even if DMF_QUEUE_IO_TO_THREAD was not set. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- drivers/md/dm.c | 22 +++++++--------------- 1 files changed, 7 insertions(+), 15 deletions(-) Index: linux-2.6.30-rc1/drivers/md/dm.c =================================================================== --- linux-2.6.30-rc1.orig/drivers/md/dm.c 2009-04-08 22:28:06.000000000 +0100 +++ linux-2.6.30-rc1/drivers/md/dm.c 2009-04-08 22:28:08.000000000 +0100 @@ -436,21 +436,18 @@ static void end_io_acct(struct dm_io *io /* * Add the bio to the list of deferred io. */ -static int queue_io(struct mapped_device *md, struct bio *bio) +static void queue_io(struct mapped_device *md, struct bio *bio) { down_write(&md->io_lock); - if (!test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) { - up_write(&md->io_lock); - return 1; - } - spin_lock_irq(&md->deferred_lock); bio_list_add(&md->deferred, bio); spin_unlock_irq(&md->deferred_lock); + if (!test_and_set_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) + queue_work(md->wq, &md->work); + up_write(&md->io_lock); - return 0; /* deferred successfully */ } /* @@ -953,7 +950,7 @@ static int dm_request(struct request_que * If we're suspended or the thread is processing barriers * we have to queue this io for later. */ - while (test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags)) { + if (unlikely(test_bit(DMF_QUEUE_IO_TO_THREAD, &md->flags))) { up_read(&md->io_lock); if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) && @@ -962,14 +959,9 @@ static int dm_request(struct request_que return 0; } - if (!queue_io(md, bio)) - return 0; + queue_io(md, bio); - /* - * We're in a while loop, because someone could suspend - * before we get to the following read lock. - */ - down_read(&md->io_lock); + return 0; } __split_and_process_bio(md, bio);