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SubjectRe: [PATCH 1/2] mpt2sas: Refcount sas_device objects and fix unsafe list usage
On 07/12/2015 12:24 AM, Calvin Owens wrote:
> These objects can be referenced concurrently throughout the driver, we
> need a way to make sure threads can't delete them out from under each
> other. This patch adds the refcount, and refactors the code to use it.
>
> Additionally, we cannot iterate over the sas_device_list without
> holding the lock, or we risk corrupting random memory if items are
> added or deleted as we iterate. This patch refactors _scsih_probe_sas()
> to use the sas_device_list in a safe way.
>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Bart Van Assche <bart.vanassche@sandisk.com>
> Signed-off-by: Calvin Owens <calvinowens@fb.com>
> ---
> drivers/scsi/mpt2sas/mpt2sas_base.h | 22 +-
> drivers/scsi/mpt2sas/mpt2sas_scsih.c | 434 ++++++++++++++++++++-----------
> drivers/scsi/mpt2sas/mpt2sas_transport.c | 12 +-
> 3 files changed, 315 insertions(+), 153 deletions(-)

[ ... snip ... ]

> @@ -2078,7 +2150,7 @@ _scsih_slave_configure(struct scsi_device *sdev)
> }
>
> spin_lock_irqsave(&ioc->sas_device_lock, flags);
> - sas_device = mpt2sas_scsih_sas_device_find_by_sas_address(ioc,
> + sas_device = __mpt2sas_get_sdev_by_addr(ioc,
> sas_device_priv_data->sas_target->sas_address);
> if (!sas_device) {
> spin_unlock_irqrestore(&ioc->sas_device_lock, flags);
> @@ -2116,13 +2188,14 @@ _scsih_slave_configure(struct scsi_device *sdev)
> if (!ssp_target)
> _scsih_display_sata_capabilities(ioc, handle, sdev);
>
> -
> _scsih_change_queue_depth(sdev, qdepth);
>
> if (ssp_target) {
> sas_read_port_mode_page(sdev);
> _scsih_enable_tlr(ioc, sdev);
> }
> +
> + sas_device_put(sas_device);
> return 0;
> }

Hi Calvin,

Any reason why this sas_device_put is placed outside the sas_device
lock? Most other instances in this patch were called just before unlocking.

BTW I attempted testing, but needed to port to mpt3 and ended up with a
driver that didn't boot :( Hopefully I can retry later this week, or
find an older mpt2 box lying around.

-- Joe


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