Re: [bug] ata subsystem related crash with latest -git

Jens Axboe
2007-10-18T09:17:55Z

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