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scsi: sd: Improve sd_completed_bytes
Re-shuffle the code to be more efficient by not initializing variables upfront (i.e. do it only when necessary). Also replace the do_div calls with calls to sectors_to_logical(). No functional change is introduced by this patch. [mkp: bytes_to_logical()] Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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@ -1758,41 +1758,44 @@ static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
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static unsigned int sd_completed_bytes(struct scsi_cmnd *scmd)
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{
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u64 start_lba = blk_rq_pos(scmd->request);
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u64 end_lba = blk_rq_pos(scmd->request) + (scsi_bufflen(scmd) / 512);
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u64 factor = scmd->device->sector_size / 512;
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u64 bad_lba;
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int info_valid;
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struct request *req = scmd->request;
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struct scsi_device *sdev = scmd->device;
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unsigned int transferred, good_bytes;
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u64 start_lba, end_lba, bad_lba;
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/*
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* Some commands have a payload smaller than the device logical
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* block size (e.g. INQUIRY on a 4K disk).
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*/
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if (scsi_bufflen(scmd) <= sdev->sector_size)
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return 0;
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/* Check if we have a 'bad_lba' information */
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if (!scsi_get_sense_info_fld(scmd->sense_buffer,
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SCSI_SENSE_BUFFERSIZE,
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&bad_lba))
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return 0;
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/*
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* If the bad lba was reported incorrectly, we have no idea where
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* the error is.
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*/
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start_lba = sectors_to_logical(sdev, blk_rq_pos(req));
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end_lba = start_lba + bytes_to_logical(sdev, scsi_bufflen(scmd));
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if (bad_lba < start_lba || bad_lba >= end_lba)
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return 0;
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/*
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* resid is optional but mostly filled in. When it's unused,
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* its value is zero, so we assume the whole buffer transferred
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*/
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unsigned int transferred = scsi_bufflen(scmd) - scsi_get_resid(scmd);
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unsigned int good_bytes;
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transferred = scsi_bufflen(scmd) - scsi_get_resid(scmd);
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info_valid = scsi_get_sense_info_fld(scmd->sense_buffer,
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SCSI_SENSE_BUFFERSIZE,
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&bad_lba);
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if (!info_valid)
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return 0;
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if (scsi_bufflen(scmd) <= scmd->device->sector_size)
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return 0;
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/* be careful ... don't want any overflows */
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do_div(start_lba, factor);
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do_div(end_lba, factor);
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/* The bad lba was reported incorrectly, we have no idea where
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* the error is.
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/* This computation should always be done in terms of the
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* resolution of the device's medium.
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*/
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if (bad_lba < start_lba || bad_lba >= end_lba)
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return 0;
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good_bytes = logical_to_bytes(sdev, bad_lba - start_lba);
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/* This computation should always be done in terms of
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* the resolution of the device's medium.
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*/
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good_bytes = (bad_lba - start_lba) * scmd->device->sector_size;
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return min(good_bytes, transferred);
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}
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@ -169,6 +169,11 @@ static inline unsigned int logical_to_bytes(struct scsi_device *sdev, sector_t b
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return blocks * sdev->sector_size;
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}
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static inline sector_t bytes_to_logical(struct scsi_device *sdev, unsigned int bytes)
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{
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return bytes >> ilog2(sdev->sector_size);
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}
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static inline sector_t sectors_to_logical(struct scsi_device *sdev, sector_t sector)
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{
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return sector >> (ilog2(sdev->sector_size) - 9);
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