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SubjectRe: Linux 2.6.14: Badness in as-iosched
On Thu, Nov 10 2005, Brice Goglin wrote:
> Hi Jens,
>
> I just hit a badness (actually, tons of badness like this) in as-iosched
> while ripping
> an audio CD with ripperX (with cdparanoia as a backend).
> I was using 2.6.14 on an IBM Thinkpad R52. The kernel has been compiled with
> gcc-4.0.2-2 (Debian testing).
>
> The first badness in dmesg is:
>
> cdrom: dropping to single frame dma
> arq->state: 4
> Badness in as_insert_request at drivers/block/as-iosched.c:1519
> [<c0237410>] as_insert_request+0x70/0x1d0
> [<c022dc25>] __elv_add_request+0xa5/0xe0
> [<c022dc8b>] elv_add_request+0x2b/0x40
> [<c0230fe6>] blk_execute_rq_nowait+0x46/0x60
> [<c023107a>] blk_execute_rq+0x7a/0xe0
> [<c0231310>] blk_end_sync_rq+0x0/0x30
> [<c0160b77>] bio_phys_segments+0x27/0x30
> [<c0232610>] blk_rq_bio_prep+0x40/0xb0
> [<c0230dc7>] blk_rq_map_user+0xb7/0xf0
> [<c026bc32>] cdrom_read_cdda_bpc+0x182/0x210
> [<c026bd1b>] cdrom_read_cdda+0x5b/0xc0

Similar case was posted yesterday (I realize yours is older, just missed
it the first time around), see my explanation here:

http://lkml.org/lkml/2005/11/20/119

And work-around below.

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index 1539603..7540d27 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -2089,7 +2089,7 @@ static int cdrom_read_cdda_bpc(struct cd
int lba, int nframes)
{
request_queue_t *q = cdi->disk->queue;
- struct request *rq;
+ struct request *rq = NULL;
struct bio *bio;
unsigned int len;
int nr, ret = 0;
@@ -2097,13 +2097,13 @@ static int cdrom_read_cdda_bpc(struct cd
if (!q)
return -ENXIO;

- rq = blk_get_request(q, READ, GFP_KERNEL);
- if (!rq)
- return -ENOMEM;
-
cdi->last_sense = 0;

while (nframes) {
+ rq = blk_get_request(q, READ, GFP_KERNEL);
+ if (!rq)
+ return -ENOMEM;
+
nr = nframes;
if (cdi->cdda_method == CDDA_BPC_SINGLE)
nr = 1;
@@ -2151,9 +2151,13 @@ static int cdrom_read_cdda_bpc(struct cd
nframes -= nr;
lba += nr;
ubuf += len;
+ blk_put_request(rq);
+ rq = NULL;
}

- blk_put_request(rq);
+ if (rq)
+ blk_put_request(rq);
+
return ret;
}

--
Jens Axboe

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