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    SubjectRe: [PATCH] Don't change direction flags in struct request.
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    On Tue, 2010-03-02 at 01:54 -0600, Mike Christie wrote:
    > On 03/01/2010 11:26 PM, James Bottomley wrote:
    > > On Thu, 2010-03-18 at 22:31 -0700, Hugh Daschbach wrote:
    > >> The EMC multipath device handler should not change the I/O direction
    > >> flags of its trespass command request.
    > >>
    > >> The CFQ elevator may BUG if the direction flags on an I/O request are
    > >> changed after allocation. cfq_set_request() and cfq_put_request()
    > >> count READ and WRITE requests separately. Changing the I/O request
    > >> direction after blk_get_request() allocates the request throws off
    > >> this CFQ accounting.
    > >
    > > This description doesn't really match what the problem seems to be
    > > below:
    > >
    > >> Signed-off-by: Hugh Daschbach<hdasch@broadcom.com>
    > >> ---
    > >> drivers/scsi/device_handler/scsi_dh_emc.c | 8 ++++----
    > >> 1 files changed, 4 insertions(+), 4 deletions(-)
    > >>
    > >> diff --git a/drivers/scsi/device_handler/scsi_dh_emc.c b/drivers/scsi/device_handler/scsi_dh_emc.c
    > >> index 6196675..3709342 100644
    > >> --- a/drivers/scsi/device_handler/scsi_dh_emc.c
    > >> +++ b/drivers/scsi/device_handler/scsi_dh_emc.c
    > >> @@ -269,10 +269,12 @@ static struct request *get_req(struct scsi_device *sdev, int cmd,
    > >> unsigned char *buffer)
    > >> {
    > >> struct request *rq;
    > >> + int mode = READ;
    > >> int len = 0;
    > >>
    > >> - rq = blk_get_request(sdev->request_queue,
    > >> - (cmd == MODE_SELECT) ? WRITE : READ, GFP_NOIO);
    > >> + if (cmd == MODE_SELECT || cmd == MODE_SELECT_10)
    > >> + mode = WRITE;
    > >> + rq = blk_get_request(sdev->request_queue, mode, GFP_NOIO);
    > >
    > > So the actual bug is failure to set WRITE for MODE_SELECT_10.
    > >
    >
    > I think we have a fix for this and some len issues in that module that
    > was sent here:
    > http://marc.info/?l=linux-scsi&m=125978574800618&w=2

    Yes, you did ... the need to change the From: field caused me to mark it
    in a different way and ultimately lose it ... I'll add it this time ...

    James




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