mtip32xx: avoid using semaphores

The "cmd_slot_unal" semaphore is never used in a blocking way
but only as an atomic counter. Change the code to using
atomic_dec_if_positive() as a better API.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index 2b0ac9d..d7dc307 100644 (file)
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -2680,7 +2680,7 @@ static void mtip_softirq_done_fn(struct request *rq)
                                                        cmd->direction);
 
        if (unlikely(cmd->unaligned))
-               up(&dd->port->cmd_slot_unal);
+               atomic_inc(&dd->port->cmd_slot_unal);
 
        blk_mq_end_request(rq, cmd->status);
 }
@@ -2990,7 +2990,7 @@ static int mtip_hw_init(struct driver_data *dd)
        else
                dd->unal_qdepth = 0;
 
-       sema_init(&dd->port->cmd_slot_unal, dd->unal_qdepth);
+       atomic_set(&dd->port->cmd_slot_unal, dd->unal_qdepth);
 
        /* Spinlock to prevent concurrent issue */
        for (i = 0; i < MTIP_MAX_SLOT_GROUPS; i++)
@@ -3533,7 +3533,7 @@ static bool mtip_check_unal_depth(struct blk_mq_hw_ctx *hctx,
                        cmd->unaligned = 1;
        }
 
-       if (cmd->unaligned && down_trylock(&dd->port->cmd_slot_unal))
+       if (cmd->unaligned && atomic_dec_if_positive(&dd->port->cmd_slot_unal) >= 0)
                return true;
 
        return false;

diff --git a/drivers/block/mtip32xx/mtip32xx.h b/drivers/block/mtip32xx/mtip32xx.h
index c33f8c3..abce25f 100644 (file)
--- a/drivers/block/mtip32xx/mtip32xx.h
+++ b/drivers/block/mtip32xx/mtip32xx.h
@@ -433,8 +433,8 @@ struct mtip_port {
         */
        unsigned long ic_pause_timer;
 
-       /* Semaphore to control queue depth of unaligned IOs */
-       struct semaphore cmd_slot_unal;
+       /* Counter to control queue depth of unaligned IOs */
+       atomic_t cmd_slot_unal;
 
        /* Spinlock for working around command-issue bug. */
        spinlock_t cmd_issue_lock[MTIP_MAX_SLOT_GROUPS];