On 05/05/2015 06:49 AM, Ming Lei wrote:
> Documentation/workqueue.txt:
> If there is dependency among multiple work items used
> during memory reclaim, they should be queued to separate
> wq each with WQ_MEM_RECLAIM.
>
> Loop devices can be stacked, so we have to convert to per-device
> workqueue. One example is Fedora live CD.
I'm just now looking at this, but I found a minor nit. I'm not sure if
it's worth replacing the patch or just fixing it with a trivial cleanup
patch.
>
> Fixes: b5dd2f6047ca108001328aac0e8588edd15f1778
> Cc: stable@xxxxxxxxxxxxxxx (v4.0)
> Cc: Justin M. Forbes <jforbes@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
> ---
> drivers/block/loop.c | 30 ++++++++++++++----------------
> drivers/block/loop.h | 1 +
> 2 files changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index ae3fcb4..3dc1598 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -86,8 +86,6 @@ static DEFINE_MUTEX(loop_index_mutex);
> static int max_part;
> static int part_shift;
>
> -static struct workqueue_struct *loop_wq;
> -
> static int transfer_xor(struct loop_device *lo, int cmd,
> struct page *raw_page, unsigned raw_off,
> struct page *loop_page, unsigned loop_off,
> @@ -725,6 +723,12 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
> size = get_loop_size(lo, file);
> if ((loff_t)(sector_t)size != size)
> goto out_putf;
> + error = -ENOMEM;
> + lo->wq = alloc_workqueue("kloopd%d",
> + WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 0,
> + lo->lo_number);
> + if (!lo->wq)
> + goto out_putf;
>
> error = 0;
>
> @@ -872,6 +876,8 @@ static int loop_clr_fd(struct loop_device *lo)
> lo->lo_flags = 0;
> if (!part_shift)
> lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
> + destroy_workqueue(lo->wq);
> + lo->wq = NULL;
> mutex_unlock(&lo->lo_ctl_mutex);
> /*
> * Need not hold lo_ctl_mutex to fput backing file.
> @@ -1425,9 +1431,13 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
> const struct blk_mq_queue_data *bd)
> {
> struct loop_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
> + struct loop_device *lo = cmd->rq->q->queuedata;
>
> blk_mq_start_request(bd->rq);
>
> + if (lo->lo_state != Lo_bound)
> + return -EIO;
> +
> if (cmd->rq->cmd_flags & REQ_WRITE) {
> struct loop_device *lo = cmd->rq->q->queuedata;
The above definition of lo becomes redundant now.
> bool need_sched = true;
> @@ -1441,9 +1451,9 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
> spin_unlock_irq(&lo->lo_lock);
>
> if (need_sched)
> - queue_work(loop_wq, &lo->write_work);
> + queue_work(lo->wq, &lo->write_work);
> } else {
> - queue_work(loop_wq, &cmd->read_work);
> + queue_work(lo->wq, &cmd->read_work);
> }
>
> return BLK_MQ_RQ_QUEUE_OK;
> @@ -1455,9 +1465,6 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
> struct loop_device *lo = cmd->rq->q->queuedata;
> int ret = -EIO;
>
> - if (lo->lo_state != Lo_bound)
> - goto failed;
> -
> if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY))
> goto failed;
>
> @@ -1806,13 +1813,6 @@ static int __init loop_init(void)
> goto misc_out;
> }
>
> - loop_wq = alloc_workqueue("kloopd",
> - WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 0);
> - if (!loop_wq) {
> - err = -ENOMEM;
> - goto misc_out;
> - }
> -
> blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
> THIS_MODULE, loop_probe, NULL, NULL);
>
> @@ -1850,8 +1850,6 @@ static void __exit loop_exit(void)
> blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
> unregister_blkdev(LOOP_MAJOR, "loop");
>
> - destroy_workqueue(loop_wq);
> -
> misc_deregister(&loop_misc);
> }
>
> diff --git a/drivers/block/loop.h b/drivers/block/loop.h
> index 301c27f..49564ed 100644
> --- a/drivers/block/loop.h
> +++ b/drivers/block/loop.h
> @@ -54,6 +54,7 @@ struct loop_device {
> gfp_t old_gfp_mask;
>
> spinlock_t lo_lock;
> + struct workqueue_struct *wq;
> struct list_head write_cmd_head;
> struct work_struct write_work;
> bool write_started;
>
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