skd: Optimize locking

Only take skdev->lock if necessary.

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 a732bb8..bcd8df0 100644 (file)
--- a/drivers/block/skd_main.c
+++ b/drivers/block/skd_main.c
@@ -490,7 +490,7 @@ static void skd_process_request(struct request *req, bool last)
        const u32 tag = blk_mq_unique_tag(req);
        struct skd_request_context *const skreq = blk_mq_rq_to_pdu(req);
        struct skd_scsi_request *scsi_req;
-       unsigned long flags;
+       unsigned long flags = 0;
        const u32 lba = blk_rq_pos(req);
        const u32 count = blk_rq_sectors(req);
        const int data_dir = rq_data_dir(req);
@@ -525,9 +525,13 @@ static void skd_process_request(struct request *req, bool last)
                                   sizeof(struct fit_sg_descriptor),
                                   DMA_TO_DEVICE);
 
-       spin_lock_irqsave(&skdev->lock, flags);
        /* Either a FIT msg is in progress or we have to start one. */
-       skmsg = skdev->skmsg;
+       if (skd_max_req_per_msg == 1) {
+               skmsg = NULL;
+       } else {
+               spin_lock_irqsave(&skdev->lock, flags);
+               skmsg = skdev->skmsg;
+       }
        if (!skmsg) {
                skmsg = &skdev->skmsg_table[tag];
                skdev->skmsg = skmsg;
@@ -574,11 +578,16 @@ static void skd_process_request(struct request *req, bool last)
        /*
         * If the FIT msg buffer is full send it.
         */
-       if (last || fmh->num_protocol_cmds_coalesced >= skd_max_req_per_msg) {
+       if (skd_max_req_per_msg == 1) {
                skd_send_fitmsg(skdev, skmsg);
-               skdev->skmsg = NULL;
+       } else {
+               if (last ||
+                   fmh->num_protocol_cmds_coalesced >= skd_max_req_per_msg) {
+                       skd_send_fitmsg(skdev, skmsg);
+                       skdev->skmsg = NULL;
+               }
+               spin_unlock_irqrestore(&skdev->lock, flags);
        }
-       spin_unlock_irqrestore(&skdev->lock, flags);
 }
 
 static blk_status_t skd_mq_queue_rq(struct blk_mq_hw_ctx *hctx,