1 files changed, 37 insertions, 11 deletions

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 0a537a0515ca..d055450c2a4a 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -439,10 +439,7 @@ static int fill_from_dev_buffer(struct scsi_cmnd *scp, unsigned char *arr,
 
         act_len = sg_copy_from_buffer(sdb->table.sgl, sdb->table.nents,
                                       arr, arr_len);
-        if (sdb->resid)
-                sdb->resid -= act_len;
-        else
-                sdb->resid = scsi_bufflen(scp) - act_len;
+        sdb->resid = scsi_bufflen(scp) - act_len;
 
         return 0;
 }
@@ -1693,24 +1690,48 @@ static int check_device_access_params(struct sdebug_dev_info *devi,
         return 0;
 }
 
+/* Returns number of bytes copied or -1 if error. */
 static int do_device_access(struct scsi_cmnd *scmd,
                             struct sdebug_dev_info *devi,
                             unsigned long long lba, unsigned int num, int write)
 {
         int ret;
         unsigned long long block, rest = 0;
-        int (*func)(struct scsi_cmnd *, unsigned char *, int);
+        struct scsi_data_buffer *sdb;
+        enum dma_data_direction dir;
+        size_t (*func)(struct scatterlist *, unsigned int, void *, size_t,
+                       off_t);
+
+        if (write) {
+                sdb = scsi_out(scmd);
+                dir = DMA_TO_DEVICE;
+                func = sg_pcopy_to_buffer;
+        } else {
+                sdb = scsi_in(scmd);
+                dir = DMA_FROM_DEVICE;
+                func = sg_pcopy_from_buffer;
+        }
 
-        func = write ? fetch_to_dev_buffer : fill_from_dev_buffer;
+        if (!sdb->length)
+                return 0;
+        if (!(scsi_bidi_cmnd(scmd) || scmd->sc_data_direction == dir))
+                return -1;
 
         block = do_div(lba, sdebug_store_sectors);
         if (block + num > sdebug_store_sectors)
                 rest = block + num - sdebug_store_sectors;
 
-        ret = func(scmd, fake_storep + (block * scsi_debug_sector_size),
-                   (num - rest) * scsi_debug_sector_size);
-        if (!ret && rest)
-                ret = func(scmd, fake_storep, rest * scsi_debug_sector_size);
+        ret = func(sdb->table.sgl, sdb->table.nents,
+                   fake_storep + (block * scsi_debug_sector_size),
+                   (num - rest) * scsi_debug_sector_size, 0);
+        if (ret != (num - rest) * scsi_debug_sector_size)
+                return ret;
+
+        if (rest) {
+                ret += func(sdb->table.sgl, sdb->table.nents,
+                            fake_storep, rest * scsi_debug_sector_size,
+                            (num - rest) * scsi_debug_sector_size);
+        }
 
         return ret;
 }
@@ -1849,7 +1870,12 @@ static int resp_read(struct scsi_cmnd *SCpnt, unsigned long long lba,
         read_lock_irqsave(&atomic_rw, iflags);
         ret = do_device_access(SCpnt, devip, lba, num, 0);
         read_unlock_irqrestore(&atomic_rw, iflags);
-        return ret;
+        if (ret == -1)
+                return DID_ERROR << 16;
+
+        scsi_in(SCpnt)->resid = scsi_bufflen(SCpnt) - ret;
+
+        return 0;
 }
 
 void dump_sector(unsigned char *buf, int len)