On Thu, Oct 18 2007, Jeff Garzik wrote:
> Jens Axboe wrote:
>> index 4df8311..b858183 100644
>> --- a/drivers/ata/sata_mv.c
>> +++ b/drivers/ata/sata_mv.c
>> @@ -1139,6 +1139,7 @@ static void mv_fill_sg(struct ata_queued_cmd *qc)
>>      struct mv_port_priv *pp = qc->ap->private_data;
>>      struct scatterlist *sg;
>>      struct mv_sg *mv_sg;
>> +    int end_marked = 0;
>>      mv_sg = pp->sg_tbl;
>>      ata_for_each_sg(sg, qc) {
>> @@ -1159,13 +1160,15 @@ static void mv_fill_sg(struct ata_queued_cmd *qc)
>>                      sg_len -= len;
>>                      addr += len;
>>  -                   if (!sg_len && ata_sg_is_last(sg, qc))
>> +                    if (!sg_len && ata_sg_is_last(sg, qc)) {
>>                              mv_sg->flags_size |= 
>> cpu_to_le32(EPRD_FLAG_END_OF_TBL);
>> +                            end_marked++;
>> +                    }
>>                      mv_sg++;
>>              }
>> -
>>      }
>> +    BUG_ON(end_marked != 1);
>
>
> Your BUG_ON() does indeed trip, here.
>
> Its surprising that other folks don't explode, considering that 
> mv_fill_sg() intentionally mirrors the logic in ata_fill_sg().

The sata_mv construct looks a bit odd. Does this work? That last
end_mv_sg test should always be true, just being paranoid...

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index 4df8311..5397eea 100644
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -1138,8 +1138,9 @@ static void mv_fill_sg(struct ata_queued_cmd *qc)
 {
        struct mv_port_priv *pp = qc->ap->private_data;
        struct scatterlist *sg;
-       struct mv_sg *mv_sg;
+       struct mv_sg *mv_sg, *end_mv_sg;
 
+       end_mv_sg = NULL;
        mv_sg = pp->sg_tbl;
        ata_for_each_sg(sg, qc) {
                dma_addr_t addr = sg_dma_address(sg);
@@ -1158,14 +1159,12 @@ static void mv_fill_sg(struct ata_queued_cmd *qc)
 
                        sg_len -= len;
                        addr += len;
-
-                       if (!sg_len && ata_sg_is_last(sg, qc))
-                               mv_sg->flags_size |= 
cpu_to_le32(EPRD_FLAG_END_OF_TBL);
-
+                       end_mv_sg = mv_sg;
                        mv_sg++;
                }
-
        }
+       if (end_mv_sg)
+               end_mv_sg->flags_size |= cpu_to_le32(EPRD_FLAG_END_OF_TBL);
 }
 
 static inline void mv_crqb_pack_cmd(__le16 *cmdw, u8 data, u8 addr, unsigned 
last)

-- 
Jens Axboe

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