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    Subject[ 008/135] [SCSI] mpt2sas: Fix for Driver oops, when loading driver with max_queue_depth command line option to a very small value
    3.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: "sreekanth.reddy@lsi.com" <sreekanth.reddy@lsi.com>

    commit 338b131a3269881c7431234855c93c219b0979b6 upstream.

    If the specified max_queue_depth setting is less than the
    expected number of internal commands, then driver will calculate
    the queue depth size to a negitive number. This negitive number
    is actually a very large number because variable is unsigned
    16bit integer. So, the driver will ask for a very large amount of
    memory for message frames and resulting into oops as memory
    allocation routines will not able to handle such a large request.

    So, in order to limit this kind of oops, The driver need to set
    the max_queue_depth to a scsi mid layer's can_queue value. Then
    the overall message frames required for IO is minimum of either
    (max_queue_depth plus internal commands) or the IOC global
    credits.

    Signed-off-by: Sreekanth Reddy <sreekanth.reddy@lsi.com>
    Signed-off-by: James Bottomley <JBottomley@Parallels.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/scsi/mpt2sas/mpt2sas_base.c | 13 ++++++++-----
    1 file changed, 8 insertions(+), 5 deletions(-)

    diff --git a/drivers/scsi/mpt2sas/mpt2sas_base.c b/drivers/scsi/mpt2sas/mpt2sas_base.c
    index 9d46fcb..b25757d 100644
    --- a/drivers/scsi/mpt2sas/mpt2sas_base.c
    +++ b/drivers/scsi/mpt2sas/mpt2sas_base.c
    @@ -2424,10 +2424,13 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc, int sleep_flag)
    }

    /* command line tunables for max controller queue depth */
    - if (max_queue_depth != -1)
    - max_request_credit = (max_queue_depth < facts->RequestCredit)
    - ? max_queue_depth : facts->RequestCredit;
    - else
    + if (max_queue_depth != -1 && max_queue_depth != 0) {
    + max_request_credit = min_t(u16, max_queue_depth +
    + ioc->hi_priority_depth + ioc->internal_depth,
    + facts->RequestCredit);
    + if (max_request_credit > MAX_HBA_QUEUE_DEPTH)
    + max_request_credit = MAX_HBA_QUEUE_DEPTH;
    + } else
    max_request_credit = min_t(u16, facts->RequestCredit,
    MAX_HBA_QUEUE_DEPTH);

    @@ -2502,7 +2505,7 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc, int sleep_flag)
    /* set the scsi host can_queue depth
    * with some internal commands that could be outstanding
    */
    - ioc->shost->can_queue = ioc->scsiio_depth - (2);
    + ioc->shost->can_queue = ioc->scsiio_depth;
    dinitprintk(ioc, printk(MPT2SAS_INFO_FMT "scsi host: "
    "can_queue depth (%d)\n", ioc->name, ioc->shost->can_queue));




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