3w-9xxx: don't unmap bounce buffered commands

commit 15e3d5a285ab9283136dba34bbf72886d9146706 upstream.

3w controller don't dma map small single SGL entry commands but instead
bounce buffer them.  Add a helper to identify these commands and don't
call scsi_dma_unmap for them.

Based on an earlier patch from James Bottomley.

Fixes: 118c85 ("3w-9xxx: fix command completion race")
Reported-by: Tóth Attila <atoth@atoth.sote.hu>
Tested-by: Tóth Attila <atoth@atoth.sote.hu>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Adam Radford <aradford@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/scsi/3w-9xxx.c b/drivers/scsi/3w-9xxx.c
index 5f57e3d35e26d4aad0e3620759e7ee253bccce92..6adf9abdf955ed67a3f62ea8ae657e4215bfbe9f 100644 (file)
--- a/drivers/scsi/3w-9xxx.c
+++ b/drivers/scsi/3w-9xxx.c
@@ -225,6 +225,17 @@ static const struct file_operations twa_fops = {
        .llseek         = noop_llseek,
 };
 
+/*
+ * The controllers use an inline buffer instead of a mapped SGL for small,
+ * single entry buffers.  Note that we treat a zero-length transfer like
+ * a mapped SGL.
+ */
+static bool twa_command_mapped(struct scsi_cmnd *cmd)
+{
+       return scsi_sg_count(cmd) != 1 ||
+               scsi_bufflen(cmd) >= TW_MIN_SGL_LENGTH;
+}
+
 /* This function will complete an aen request from the isr */
 static int twa_aen_complete(TW_Device_Extension *tw_dev, int request_id)
 {
@@ -1351,7 +1362,8 @@ static irqreturn_t twa_interrupt(int irq, void *dev_instance)
                                }
 
                                /* Now complete the io */
-                               scsi_dma_unmap(cmd);
+                               if (twa_command_mapped(cmd))
+                                       scsi_dma_unmap(cmd);
                                cmd->scsi_done(cmd);
                                tw_dev->state[request_id] = TW_S_COMPLETED;
                                twa_free_request_id(tw_dev, request_id);
@@ -1594,7 +1606,8 @@ static int twa_reset_device_extension(TW_Device_Extension *tw_dev)
                                struct scsi_cmnd *cmd = tw_dev->srb[i];
 
                                cmd->result = (DID_RESET << 16);
-                               scsi_dma_unmap(cmd);
+                               if (twa_command_mapped(cmd))
+                                       scsi_dma_unmap(cmd);
                                cmd->scsi_done(cmd);
                        }
                }
@@ -1777,12 +1790,14 @@ static int twa_scsi_queue_lck(struct scsi_cmnd *SCpnt, void (*done)(struct scsi_
        retval = twa_scsiop_execute_scsi(tw_dev, request_id, NULL, 0, NULL);
        switch (retval) {
        case SCSI_MLQUEUE_HOST_BUSY:
-               scsi_dma_unmap(SCpnt);
+               if (twa_command_mapped(SCpnt))
+                       scsi_dma_unmap(SCpnt);
                twa_free_request_id(tw_dev, request_id);
                break;
        case 1:
                SCpnt->result = (DID_ERROR << 16);
-               scsi_dma_unmap(SCpnt);
+               if (twa_command_mapped(SCpnt))
+                       scsi_dma_unmap(SCpnt);
                done(SCpnt);
                tw_dev->state[request_id] = TW_S_COMPLETED;
                twa_free_request_id(tw_dev, request_id);
@@ -1843,8 +1858,7 @@ static int twa_scsiop_execute_scsi(TW_Device_Extension *tw_dev, int request_id,
                /* Map sglist from scsi layer to cmd packet */
 
                if (scsi_sg_count(srb)) {
-                       if ((scsi_sg_count(srb) == 1) &&
-                           (scsi_bufflen(srb) < TW_MIN_SGL_LENGTH)) {
+                       if (!twa_command_mapped(srb)) {
                                if (srb->sc_data_direction == DMA_TO_DEVICE ||
                                    srb->sc_data_direction == DMA_BIDIRECTIONAL)
                                        scsi_sg_copy_to_buffer(srb,
@@ -1917,7 +1931,7 @@ static void twa_scsiop_execute_scsi_complete(TW_Device_Extension *tw_dev, int re
 {
        struct scsi_cmnd *cmd = tw_dev->srb[request_id];
 
-       if (scsi_bufflen(cmd) < TW_MIN_SGL_LENGTH &&
+       if (!twa_command_mapped(cmd) &&
            (cmd->sc_data_direction == DMA_FROM_DEVICE ||
             cmd->sc_data_direction == DMA_BIDIRECTIONAL)) {
                if (scsi_sg_count(cmd) == 1) {