skd: Convert several per-device scalar variables into atomics

Convert the per-device scalar variables that are protected by the
queue lock into atomics such that it becomes safe to access these
variables without holding the queue lock.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/skd_main.c b/drivers/block/skd_main.c
index 35343fb..4b92d71 100644 (file)
--- a/drivers/block/skd_main.c
+++ b/drivers/block/skd_main.c
@@ -243,7 +243,7 @@ struct skd_device {
        enum skd_drvr_state state;
        u32 drive_state;
 
-       u32 in_flight;
+       atomic_t in_flight;
        u32 cur_max_queue_depth;
        u32 queue_low_water_mark;
        u32 dev_max_queue_depth;
@@ -251,8 +251,8 @@ struct skd_device {
        u32 num_fitmsg_context;
        u32 num_req_context;
 
-       u32 timeout_slot[SKD_N_TIMEOUT_SLOT];
-       u32 timeout_stamp;
+       atomic_t timeout_slot[SKD_N_TIMEOUT_SLOT];
+       atomic_t timeout_stamp;
        struct skd_fitmsg_context *skmsg_table;
 
        struct skd_request_context *skreq_table;
@@ -517,7 +517,8 @@ static void skd_request_fn(struct request_queue *q)
        }
 
        if (blk_queue_stopped(skdev->queue)) {
-               if (skdev->in_flight >= skdev->queue_low_water_mark)
+               if (atomic_read(&skdev->in_flight) >=
+                   skdev->queue_low_water_mark)
                        /* There is still some kind of shortage */
                        return;
 
@@ -559,9 +560,11 @@ static void skd_request_fn(struct request_queue *q)
                /* At this point we know there is a request */
 
                /* Are too many requets already in progress? */
-               if (skdev->in_flight >= skdev->cur_max_queue_depth) {
+               if (atomic_read(&skdev->in_flight) >=
+                   skdev->cur_max_queue_depth) {
                        dev_dbg(&skdev->pdev->dev, "qdepth %d, limit %d\n",
-                               skdev->in_flight, skdev->cur_max_queue_depth);
+                               atomic_read(&skdev->in_flight),
+                               skdev->cur_max_queue_depth);
                        break;
                }
 
@@ -647,12 +650,12 @@ static void skd_request_fn(struct request_queue *q)
                 * Update the active request counts.
                 * Capture the timeout timestamp.
                 */
-               skreq->timeout_stamp = skdev->timeout_stamp;
+               skreq->timeout_stamp = atomic_read(&skdev->timeout_stamp);
                timo_slot = skreq->timeout_stamp & SKD_TIMEOUT_SLOT_MASK;
-               skdev->timeout_slot[timo_slot]++;
-               skdev->in_flight++;
+               atomic_inc(&skdev->timeout_slot[timo_slot]);
+               atomic_inc(&skdev->in_flight);
                dev_dbg(&skdev->pdev->dev, "req=0x%x busy=%d\n", skreq->id,
-                       skdev->in_flight);
+                       atomic_read(&skdev->in_flight));
 
                /*
                 * If the FIT msg buffer is full send it.
@@ -805,22 +808,24 @@ static void skd_timer_tick(ulong arg)
                skd_timer_tick_not_online(skdev);
                goto timer_func_out;
        }
-       skdev->timeout_stamp++;
-       timo_slot = skdev->timeout_stamp & SKD_TIMEOUT_SLOT_MASK;
+       timo_slot = atomic_inc_return(&skdev->timeout_stamp) &
+               SKD_TIMEOUT_SLOT_MASK;
 
        /*
         * All requests that happened during the previous use of
         * this slot should be done by now. The previous use was
         * over 7 seconds ago.
         */
-       if (skdev->timeout_slot[timo_slot] == 0)
+       if (atomic_read(&skdev->timeout_slot[timo_slot]) == 0)
                goto timer_func_out;
 
        /* Something is overdue */
        dev_dbg(&skdev->pdev->dev, "found %d timeouts, draining busy=%d\n",
-               skdev->timeout_slot[timo_slot], skdev->in_flight);
+               atomic_read(&skdev->timeout_slot[timo_slot]),
+               atomic_read(&skdev->in_flight));
        dev_err(&skdev->pdev->dev, "Overdue IOs (%d), busy %d\n",
-               skdev->timeout_slot[timo_slot], skdev->in_flight);
+               atomic_read(&skdev->timeout_slot[timo_slot]),
+               atomic_read(&skdev->in_flight));
 
        skdev->timer_countdown = SKD_DRAINING_TIMO;
        skdev->state = SKD_DRVR_STATE_DRAINING_TIMEOUT;
@@ -900,10 +905,10 @@ static void skd_timer_tick_not_online(struct skd_device *skdev)
                dev_dbg(&skdev->pdev->dev,
                        "draining busy [%d] tick[%d] qdb[%d] tmls[%d]\n",
                        skdev->timo_slot, skdev->timer_countdown,
-                       skdev->in_flight,
-                       skdev->timeout_slot[skdev->timo_slot]);
+                       atomic_read(&skdev->in_flight),
+                       atomic_read(&skdev->timeout_slot[skdev->timo_slot]));
                /* if the slot has cleared we can let the I/O continue */
-               if (skdev->timeout_slot[skdev->timo_slot] == 0) {
+               if (atomic_read(&skdev->timeout_slot[skdev->timo_slot]) == 0) {
                        dev_dbg(&skdev->pdev->dev,
                                "Slot drained, starting queue.\n");
                        skdev->state = SKD_DRVR_STATE_ONLINE;
@@ -1310,7 +1315,7 @@ static void skd_send_fitmsg(struct skd_device *skdev,
        u64 qcmd;
 
        dev_dbg(&skdev->pdev->dev, "dma address 0x%llx, busy=%d\n",
-               skmsg->mb_dma_address, skdev->in_flight);
+               skmsg->mb_dma_address, atomic_read(&skdev->in_flight));
        dev_dbg(&skdev->pdev->dev, "msg_buf %p\n", skmsg->msg_buf);
 
        qcmd = skmsg->mb_dma_address;
@@ -1550,12 +1555,12 @@ static void skd_release_skreq(struct skd_device *skdev,
         * Decrease the number of active requests.
         * Also decrements the count in the timeout slot.
         */
-       SKD_ASSERT(skdev->in_flight > 0);
-       skdev->in_flight -= 1;
+       SKD_ASSERT(atomic_read(&skdev->in_flight) > 0);
+       atomic_dec(&skdev->in_flight);
 
        timo_slot = skreq->timeout_stamp & SKD_TIMEOUT_SLOT_MASK;
-       SKD_ASSERT(skdev->timeout_slot[timo_slot] > 0);
-       skdev->timeout_slot[timo_slot] -= 1;
+       SKD_ASSERT(atomic_read(&skdev->timeout_slot[timo_slot]) > 0);
+       atomic_dec(&skdev->timeout_slot[timo_slot]);
 
        /*
         * Reset backpointer
@@ -1615,8 +1620,8 @@ static int skd_isr_completion_posted(struct skd_device *skdev,
                dev_dbg(&skdev->pdev->dev,
                        "cycle=%d ix=%d got cycle=%d cmdctxt=0x%x stat=%d busy=%d rbytes=0x%x proto=%d\n",
                        skdev->skcomp_cycle, skdev->skcomp_ix, cmp_cycle,
-                       cmp_cntxt, cmp_status, skdev->in_flight, cmp_bytes,
-                       skdev->proto_ver);
+                       cmp_cntxt, cmp_status, atomic_read(&skdev->in_flight),
+                       cmp_bytes, skdev->proto_ver);
 
                if (cmp_cycle != skdev->skcomp_cycle) {
                        dev_dbg(&skdev->pdev->dev, "end of completions\n");
@@ -1707,8 +1712,8 @@ static int skd_isr_completion_posted(struct skd_device *skdev,
                }
        }
 
-       if ((skdev->state == SKD_DRVR_STATE_PAUSING)
-               && (skdev->in_flight) == 0) {
+       if (skdev->state == SKD_DRVR_STATE_PAUSING &&
+           atomic_read(&skdev->in_flight) == 0) {
                skdev->state = SKD_DRVR_STATE_PAUSED;
                wake_up_interruptible(&skdev->waitq);
        }
@@ -2053,9 +2058,9 @@ static void skd_recover_requests(struct skd_device *skdev)
        }
 
        for (i = 0; i < SKD_N_TIMEOUT_SLOT; i++)
-               skdev->timeout_slot[i] = 0;
+               atomic_set(&skdev->timeout_slot[i], 0);
 
-       skdev->in_flight = 0;
+       atomic_set(&skdev->in_flight, 0);
 }
 
 static void skd_isr_msg_from_dev(struct skd_device *skdev)
@@ -3714,10 +3719,11 @@ static void skd_log_skdev(struct skd_device *skdev, const char *event)
                skd_drive_state_to_str(skdev->drive_state), skdev->drive_state,
                skd_skdev_state_to_str(skdev->state), skdev->state);
        dev_dbg(&skdev->pdev->dev, "  busy=%d limit=%d dev=%d lowat=%d\n",
-               skdev->in_flight, skdev->cur_max_queue_depth,
+               atomic_read(&skdev->in_flight), skdev->cur_max_queue_depth,
                skdev->dev_max_queue_depth, skdev->queue_low_water_mark);
        dev_dbg(&skdev->pdev->dev, "  timestamp=0x%x cycle=%d cycle_ix=%d\n",
-               skdev->timeout_stamp, skdev->skcomp_cycle, skdev->skcomp_ix);
+               atomic_read(&skdev->timeout_stamp), skdev->skcomp_cycle,
+               skdev->skcomp_ix);
 }
 
 static void skd_log_skreq(struct skd_device *skdev,