sd: Reject optimal transfer length smaller than page size
Eryu Guan reported that loading scsi_debug would fail. This turned out to be caused by scsi_debug reporting an optimal I/O size of 32KB which is smaller than the 64KB page size on the PowerPC system in question. Add a check to ensure that we only use the device-reported OPTIMAL TRANSFER LENGTH if it is bigger than or equal to the page cache size. Reported-by: Eryu Guan <guaneryu@gmail.com> Reported-by: Ming Lei <tom.leiming@gmail.com> Reviewed-by: Douglas Gilbert <dgilbert@interlog.com> Reviewed-by: Ewan Milne <emilne@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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@ -2885,10 +2885,13 @@ static int sd_revalidate_disk(struct gendisk *disk)
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/*
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* Use the device's preferred I/O size for reads and writes
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* unless the reported value is unreasonably large (or garbage).
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* unless the reported value is unreasonably small, large, or
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* garbage.
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*/
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if (sdkp->opt_xfer_blocks && sdkp->opt_xfer_blocks <= dev_max &&
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sdkp->opt_xfer_blocks <= SD_DEF_XFER_BLOCKS)
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if (sdkp->opt_xfer_blocks &&
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sdkp->opt_xfer_blocks <= dev_max &&
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sdkp->opt_xfer_blocks <= SD_DEF_XFER_BLOCKS &&
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sdkp->opt_xfer_blocks * sdp->sector_size >= PAGE_CACHE_SIZE)
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rw_max = q->limits.io_opt =
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logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
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else
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