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    SubjectRe: kernel BUG at ide-cd.c:1726 in 2.6.24-03863-g0ba6c33 && -g8561b089
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    On Thu, Jan 31, 2008 at 02:05:58PM +0100, Jens Axboe wrote:
    > On Thu, Jan 31 2008, Nai Xia wrote:
    > > My dmesg relevant info is quite similar:
    > >
    > > [ 6.875041] Freeing unused kernel memory: 320k freed
    > > [ 8.143120] ide-cd: rq still having bio: dev hdc: type=2, flags=114c8
    > > [ 8.144439]
    > > [ 8.144439] sector 10824201199534213, nr/cnr 0/0
    > > [ 8.144439] bio cf029280, biotail cf029280, buffer 00000000, data
    > > 00000000, len 158
    > > [ 8.144439] cdb: 12 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
    > > [ 8.144439] backup: data_len=158 bi_size=158
    > > [ 8.160756] ide-cd: rq still having bio: dev hdc: type=2, flags=114c8
    > > [ 8.160756]
    > > [ 8.160756] sector 2669858, nr/cnr 0/0
    > > [ 8.160756] bio cf029300, biotail cf029300, buffer 00000000, data
    > > 00000000, len 158
    > > [ 8.160756] cdb: 12 01 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
    > > [ 8.160756] backup: data_len=158 bi_size=158
    > > [ 14.851101] eth0: link up
    > > [ 27.121883] eth0: no IPv6 routers present
    > >
    > >
    > > And by the way, Kiyoshi,
    > > This can be reproduced in a typical setup vmware workstation 6.02 with
    > > a vritual IDE cdrom,
    > > in case you wanna catch that with your own eyes. :-)
    > > Thanks for your trying hard to correct this annoying bug.
    >
    > The below fix should be enough. It's perfectly legal to have leftover
    > byte counts when the drive signals completion, happens all the time for
    > eg user issued commands where you don't know an exact byte count.

    Actually, this behavior has been the case even before the __blk_end_request()
    changes. I did test plain 2.6.24 with the following


    --- linux-2.6/drivers/ide/ide-cd.c 2008-01-31 22:18:59.000000000 +0100
    +++ linux-2.6/drivers/ide/ide-cd.c-new 2008-01-31 22:18:50.000000000 +0100
    @@ -1711,8 +1711,12 @@ static ide_startstop_t cdrom_newpc_intr(
    /*
    * If DRQ is clear, the command has completed.
    */
    - if ((stat & DRQ_STAT) == 0)
    + if ((stat & DRQ_STAT) == 0) {
    + blk_dump_rq_flags(rq, "ide-cd: rq still having bio");
    + printk("backup: data_len=%u bi_size=%u\n",
    + rq->data_len, rq->bio->bi_size);
    goto end_request;
    + }

    /*
    * check which way to transfer data

    to see whether we've been getting residual byte counts:

    Jan 31 22:10:06 gollum kernel: [ 26.702877] ide-cd: rq still having bio: dev hdc: type=2, flags=114c8
    Jan 31 22:10:06 gollum kernel: [ 26.702945]
    Jan 31 22:10:06 gollum kernel: [ 26.702946] sector 2673511, nr/cnr 0/0
    Jan 31 22:10:06 gollum kernel: [ 26.703052] bio dfa8ec40, biotail dfa8ec40, buffer 00000000, data 00000000, len 158
    Jan 31 22:10:06 gollum kernel: [ 26.703122] cdb: 12 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
    Jan 31 22:10:06 gollum kernel: [ 26.703877] backup: data_len=158 bi_size=158
    ... so we've been simply silently ignoring this until now so i guess we don't
    need to BUG() for something that's totally benign.

    --
    Regards/Gruß,
    Boris.
    --
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