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>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index c385d90..1cc5dd2 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1758,41 +1758,44 @@ static int sd_eh_action(struct scsi_cmnd *scmd, int eh_disp)
 
 static unsigned int sd_completed_bytes(struct scsi_cmnd *scmd)
 {
-       u64 start_lba = blk_rq_pos(scmd->request);
-       u64 end_lba = blk_rq_pos(scmd->request) + (scsi_bufflen(scmd) / 512);
-       u64 factor = scmd->device->sector_size / 512;
-       u64 bad_lba;
-       int info_valid;
+       struct request *req = scmd->request;
+       struct scsi_device *sdev = scmd->device;
+       unsigned int transferred, good_bytes;
+       u64 start_lba, end_lba, bad_lba;
+
        /*
-        * resid is optional but mostly filled in.  When it's unused,
-        * its value is zero, so we assume the whole buffer transferred
+        * Some commands have a payload smaller than the device logical
+        * block size (e.g. INQUIRY on a 4K disk).
         */
-       unsigned int transferred = scsi_bufflen(scmd) - scsi_get_resid(scmd);
-       unsigned int good_bytes;
-
-       info_valid = scsi_get_sense_info_fld(scmd->sense_buffer,
-                                            SCSI_SENSE_BUFFERSIZE,
-                                            &bad_lba);
-       if (!info_valid)
+       if (scsi_bufflen(scmd) <= sdev->sector_size)
                return 0;
 
-       if (scsi_bufflen(scmd) <= scmd->device->sector_size)
+       /* Check if we have a 'bad_lba' information */
+       if (!scsi_get_sense_info_fld(scmd->sense_buffer,
+                                    SCSI_SENSE_BUFFERSIZE,
+                                    &bad_lba))
                return 0;
 
-       /* be careful ... don't want any overflows */
-       do_div(start_lba, factor);
-       do_div(end_lba, factor);
-
-       /* The bad lba was reported incorrectly, we have no idea where
+       /*
+        * If the bad lba was reported incorrectly, we have no idea where
         * the error is.
         */
-       if (bad_lba < start_lba  || bad_lba >= end_lba)
+       start_lba = sectors_to_logical(sdev, blk_rq_pos(req));
+       end_lba = start_lba + bytes_to_logical(sdev, scsi_bufflen(scmd));
+       if (bad_lba < start_lba || bad_lba >= end_lba)
                return 0;
 
-       /* This computation should always be done in terms of
-        * the resolution of the device's medium.
+       /*
+        * resid is optional but mostly filled in.  When it's unused,
+        * its value is zero, so we assume the whole buffer transferred
         */
-       good_bytes = (bad_lba - start_lba) * scmd->device->sector_size;
+       transferred = scsi_bufflen(scmd) - scsi_get_resid(scmd);
+
+       /* This computation should always be done in terms of the
+        * resolution of the device's medium.
+        */
+       good_bytes = logical_to_bytes(sdev, bad_lba - start_lba);
+
        return min(good_bytes, transferred);
 }
 

diff --git a/drivers/scsi/sd.h b/drivers/scsi/sd.h
index 0cf9680..e6241c4 100644 (file)
--- a/drivers/scsi/sd.h
+++ b/drivers/scsi/sd.h
@@ -169,6 +169,11 @@ static inline unsigned int logical_to_bytes(struct scsi_device *sdev, sector_t b
        return blocks * sdev->sector_size;
 }
 
+static inline sector_t bytes_to_logical(struct scsi_device *sdev, unsigned int bytes)
+{
+       return bytes >> ilog2(sdev->sector_size);
+}
+
 static inline sector_t sectors_to_logical(struct scsi_device *sdev, sector_t sector)
 {
        return sector >> (ilog2(sdev->sector_size) - 9);