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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>
This commit is contained in:
Damien Le Moal 2017-04-24 16:51:10 +09:00 committed by Martin K. Petersen
parent 7529fbb008
commit 6eadc61224
2 changed files with 36 additions and 28 deletions
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59
drivers/scsi/sd.c
View File

@ -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;
/*
* Some commands have a payload smaller than the device logical
* block size (e.g. INQUIRY on a 4K disk).
*/
if (scsi_bufflen(scmd) <= sdev->sector_size)
return 0;
/* Check if we have a 'bad_lba' information */
if (!scsi_get_sense_info_fld(scmd->sense_buffer,
SCSI_SENSE_BUFFERSIZE,
&bad_lba))
return 0;
/*
* If the bad lba was reported incorrectly, we have no idea where
* the error is.
*/
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;
/*
* resid is optional but mostly filled in. When it's unused,
* its value is zero, so we assume the whole buffer transferred
*/
unsigned int transferred = scsi_bufflen(scmd) - scsi_get_resid(scmd);
unsigned int good_bytes;
transferred = scsi_bufflen(scmd) - scsi_get_resid(scmd);
info_valid = scsi_get_sense_info_fld(scmd->sense_buffer,
SCSI_SENSE_BUFFERSIZE,
&bad_lba);
if (!info_valid)
return 0;
if (scsi_bufflen(scmd) <= scmd->device->sector_size)
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
* the error is.
/* This computation should always be done in terms of the
* resolution of the device's medium.
*/
if (bad_lba < start_lba || bad_lba >= end_lba)
return 0;
good_bytes = logical_to_bytes(sdev, bad_lba - start_lba);
/* This computation should always be done in terms of
* the resolution of the device's medium.
*/
good_bytes = (bad_lba - start_lba) * scmd->device->sector_size;
return min(good_bytes, transferred);
}

5
drivers/scsi/sd.h
View File

@ -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);