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    Subject[PATCH 3.16 031/134] scsi: scsi_error: count medium access timeout only once per EH run
    3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Hannes Reinecke <hare@suse.de>

    commit 7a38dc0bfb4cc39ed57e120e2224673f3d4d200f upstream.

    The current medium access timeout counter will be increased for
    each command, so if there are enough failed commands we'll hit
    the medium access timeout for even a single device failure and
    the following kernel message is displayed:

    sd H:C:T:L: [sdXY] Medium access timeout failure. Offlining disk!

    Fix this by making the timeout per EH run, ie the counter will
    only be increased once per device and EH run.

    Fixes: 18a4d0a ("[SCSI] Handle disk devices which can not process medium access commands")
    Cc: Ewan Milne <emilne@redhat.com>
    Cc: Lawrence Obermann <loberman@redhat.com>
    Cc: Benjamin Block <bblock@linux.vnet.ibm.com>
    Cc: Steffen Maier <maier@linux.vnet.ibm.com>
    Signed-off-by: Hannes Reinecke <hare@suse.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    [bwh: Backported to 3.16:
    - Open-code blk_rq_is_passthrough()
    - Adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/scsi/scsi_error.c | 18 ++++++++++++++++++
    drivers/scsi/sd.c | 27 ++++++++++++++++++++++++++-
    drivers/scsi/sd.h | 1 +
    include/scsi/scsi_driver.h | 1 +
    4 files changed, 46 insertions(+), 1 deletion(-)

    --- a/drivers/scsi/scsi_error.c
    +++ b/drivers/scsi/scsi_error.c
    @@ -224,6 +224,23 @@ scsi_abort_command(struct scsi_cmnd *scm
    }

    /**
    + * scsi_eh_reset - call into ->eh_action to reset internal counters
    + * @scmd: scmd to run eh on.
    + *
    + * The scsi driver might be carrying internal state about the
    + * devices, so we need to call into the driver to reset the
    + * internal state once the error handler is started.
    + */
    +static void scsi_eh_reset(struct scsi_cmnd *scmd)
    +{
    + if (scmd->request->cmd_type == REQ_TYPE_FS) {
    + struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
    + if (sdrv->eh_reset)
    + sdrv->eh_reset(scmd);
    + }
    +}
    +
    +/**
    * scsi_eh_scmd_add - add scsi cmd to error handling.
    * @scmd: scmd to run eh on.
    * @eh_flag: optional SCSI_EH flag.
    @@ -252,6 +269,7 @@ int scsi_eh_scmd_add(struct scsi_cmnd *s
    if (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED)
    eh_flag &= ~SCSI_EH_CANCEL_CMD;
    scmd->eh_eflags |= eh_flag;
    + scsi_eh_reset(scmd);
    list_add_tail(&scmd->eh_entry, &shost->eh_cmd_q);
    shost->host_failed++;
    scsi_eh_wakeup(shost);
    --- a/drivers/scsi/sd.c
    +++ b/drivers/scsi/sd.c
    @@ -112,6 +112,7 @@ static void sd_rescan(struct device *);
    static int sd_init_command(struct scsi_cmnd *SCpnt);
    static void sd_uninit_command(struct scsi_cmnd *SCpnt);
    static int sd_done(struct scsi_cmnd *);
    +static void sd_eh_reset(struct scsi_cmnd *);
    static int sd_eh_action(struct scsi_cmnd *, int);
    static void sd_read_capacity(struct scsi_disk *sdkp, unsigned char *buffer);
    static void scsi_disk_release(struct device *cdev);
    @@ -509,6 +510,7 @@ static struct scsi_driver sd_template =
    .uninit_command = sd_uninit_command,
    .done = sd_done,
    .eh_action = sd_eh_action,
    + .eh_reset = sd_eh_reset,
    };

    /*
    @@ -1536,6 +1538,26 @@ static const struct block_device_operati
    };

    /**
    + * sd_eh_reset - reset error handling callback
    + * @scmd: sd-issued command that has failed
    + *
    + * This function is called by the SCSI midlayer before starting
    + * SCSI EH. When counting medium access failures we have to be
    + * careful to register it only only once per device and SCSI EH run;
    + * there might be several timed out commands which will cause the
    + * 'max_medium_access_timeouts' counter to trigger after the first
    + * SCSI EH run already and set the device to offline.
    + * So this function resets the internal counter before starting SCSI EH.
    + **/
    +static void sd_eh_reset(struct scsi_cmnd *scmd)
    +{
    + struct scsi_disk *sdkp = scsi_disk(scmd->request->rq_disk);
    +
    + /* New SCSI EH run, reset gate variable */
    + sdkp->ignore_medium_access_errors = false;
    +}
    +
    +/**
    * sd_eh_action - error handling callback
    * @scmd: sd-issued command that has failed
    * @eh_disp: The recovery disposition suggested by the midlayer
    @@ -1564,7 +1586,10 @@ static int sd_eh_action(struct scsi_cmnd
    * process of recovering or has it suffered an internal failure
    * that prevents access to the storage medium.
    */
    - sdkp->medium_access_timed_out++;
    + if (!sdkp->ignore_medium_access_errors) {
    + sdkp->medium_access_timed_out++;
    + sdkp->ignore_medium_access_errors = true;
    + }

    /*
    * If the device keeps failing read/write commands but TEST UNIT
    --- a/drivers/scsi/sd.h
    +++ b/drivers/scsi/sd.h
    @@ -90,6 +90,7 @@ struct scsi_disk {
    unsigned lbpvpd : 1;
    unsigned ws10 : 1;
    unsigned ws16 : 1;
    + unsigned ignore_medium_access_errors : 1;
    };
    #define to_scsi_disk(obj) container_of(obj,struct scsi_disk,dev)

    --- a/include/scsi/scsi_driver.h
    +++ b/include/scsi/scsi_driver.h
    @@ -17,6 +17,7 @@ struct scsi_driver {
    void (*uninit_command)(struct scsi_cmnd *);
    int (*done)(struct scsi_cmnd *);
    int (*eh_action)(struct scsi_cmnd *, int);
    + void (*eh_reset)(struct scsi_cmnd *);
    };
    #define to_scsi_driver(drv) \
    container_of((drv), struct scsi_driver, gendrv)
    \
     
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