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    SubjectRe: kernel BUG at ide-cd.c:1726 in 2.6.24-03863-g0ba6c33 && -g8561b089
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    Hi Jens,

    On Thu, 31 Jan 2008 19:16:54 +0100, Jens Axboe wrote:
    > On 31/01/2008, at 18.04, Kiyoshi Ueda <k-ueda@ct.jp.nec.com> wrote:
    > > On Thu, 31 Jan 2008 14:05:58 +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.
    > >>
    > >> diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
    > >> index 74c6087..bee05a3 100644
    > >> --- a/drivers/ide/ide-cd.c
    > >> +++ b/drivers/ide/ide-cd.c
    > >> @@ -1722,7 +1722,7 @@ static ide_startstop_t cdrom_newpc_intr
    > >> (ide_drive_t *drive)
    > >> */
    > >> if ((stat & DRQ_STAT) == 0) {
    > >> spin_lock_irqsave(&ide_lock, flags);
    > >> - if (__blk_end_request(rq, 0, 0))
    > >> + if (__blk_end_request(rq, 0, rq->data_len))
    > >> BUG();
    > >> HWGROUP(drive)->rq = NULL;
    > >> spin_unlock_irqrestore(&ide_lock, flags);
    > >
    > > OK, I undarstand the leftover is legal.
    > >
    > > By the way, is it safe to always return success if there is a
    > > leftover?
    > > I thought we might have to complete the rq with -EIO in such case.
    >
    > data_len being non zero should pass the residual count back to the
    > issuer.

    Aah, so the issuer can know how many bytes of the I/Os are not done,
    and the error status of the bio which is completed by
    end_that_request_first() in __blk_end_request() don't matter
    for the issuer.
    OK, thanks. I think the patch is fine.

    Thanks,
    Kiyoshi Ueda


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