[PATCH 4.9 100/102] Revert "mtip32xx: use runtime tag to initialize command header"

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Kroah-Hartman <gre...@linuxfoundation.org>

This reverts commit db54facd56a40e7766bf7f7cda1ae138e72a691c which was
commit a4e84aae8139aca9fbfbced1f45c51ca81b57488 upstream.

Ben writes:
    MQ IO schedulers were introduced in 4.11, so this shouldn't be
    needed in older branches.  It also causes a performance
    regression (fixed upstream).  Please revert this for 4.4 and
    4.9.

So let's revert it!

Reported-by: Ben Hutchings <ben.hutchi...@codethink.co.uk>
Cc: Ming Lei <ming....@redhat.com>
Cc: Jens Axboe <ax...@fb.com>
Cc: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/block/mtip32xx/mtip32xx.c |   36 ++++++++++++------------------------
 1 file changed, 12 insertions(+), 24 deletions(-)

--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -169,25 +169,6 @@ static bool mtip_check_surprise_removal(
        return false; /* device present */
 }
 
-/* we have to use runtime tag to setup command header */
-static void mtip_init_cmd_header(struct request *rq)
-{
-       struct driver_data *dd = rq->q->queuedata;
-       struct mtip_cmd *cmd = blk_mq_rq_to_pdu(rq);
-       u32 host_cap_64 = readl(dd->mmio + HOST_CAP) & HOST_CAP_64;
-
-       /* Point the command headers at the command tables. */
-       cmd->command_header = dd->port->command_list +
-                               (sizeof(struct mtip_cmd_hdr) * rq->tag);
-       cmd->command_header_dma = dd->port->command_list_dma +
-                               (sizeof(struct mtip_cmd_hdr) * rq->tag);
-
-       if (host_cap_64)
-               cmd->command_header->ctbau = __force_bit2int 
cpu_to_le32((cmd->command_dma >> 16) >> 16);
-
-       cmd->command_header->ctba = __force_bit2int 
cpu_to_le32(cmd->command_dma & 0xFFFFFFFF);
-}
-
 static struct mtip_cmd *mtip_get_int_command(struct driver_data *dd)
 {
        struct request *rq;
@@ -199,9 +180,6 @@ static struct mtip_cmd *mtip_get_int_com
        if (IS_ERR(rq))
                return NULL;
 
-       /* Internal cmd isn't submitted via .queue_rq */
-       mtip_init_cmd_header(rq);
-
        return blk_mq_rq_to_pdu(rq);
 }
 
@@ -3833,8 +3811,6 @@ static int mtip_queue_rq(struct blk_mq_h
        struct request *rq = bd->rq;
        int ret;
 
-       mtip_init_cmd_header(rq);
-
        if (unlikely(mtip_check_unal_depth(hctx, rq)))
                return BLK_MQ_RQ_QUEUE_BUSY;
 
@@ -3866,6 +3842,7 @@ static int mtip_init_cmd(void *data, str
 {
        struct driver_data *dd = data;
        struct mtip_cmd *cmd = blk_mq_rq_to_pdu(rq);
+       u32 host_cap_64 = readl(dd->mmio + HOST_CAP) & HOST_CAP_64;
 
        /*
         * For flush requests, request_idx starts at the end of the
@@ -3882,6 +3859,17 @@ static int mtip_init_cmd(void *data, str
 
        memset(cmd->command, 0, CMD_DMA_ALLOC_SZ);
 
+       /* Point the command headers at the command tables. */
+       cmd->command_header = dd->port->command_list +
+                               (sizeof(struct mtip_cmd_hdr) * request_idx);
+       cmd->command_header_dma = dd->port->command_list_dma +
+                               (sizeof(struct mtip_cmd_hdr) * request_idx);
+
+       if (host_cap_64)
+               cmd->command_header->ctbau = __force_bit2int 
cpu_to_le32((cmd->command_dma >> 16) >> 16);
+
+       cmd->command_header->ctba = __force_bit2int 
cpu_to_le32(cmd->command_dma & 0xFFFFFFFF);
+
        sg_init_table(cmd->sg, MTIP_MAX_SG);
        return 0;
 }