Re: [PATCH v4 2/2] libata-scsi: avoid repeated calculation of number of TRIM ranges

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I decided not to define a macro (e.g. ATA_MAX_TRIM_RSIZE) for all the
0xffff / 65535 in the various functions in libata-scsi.c / ata.h. Let
me know if you think I should.

On 7 July 2016 at 00:55,  <tom.ty89@xxxxxxxxx> wrote:
> From: Tom Yan <tom.ty89@xxxxxxxxx>
>
> Currently libata statically allows only 1-block (512-byte) payload
> for each TRIM command. Each payload can carry 64 TRIM ranges since
> each range requires 8 bytes.
>
> It is silly to keep doing the calculation (512 / 8) in different
> places. Hence, define the new ATA_MAX_TRIM_RNUM for the result.
>
> Signed-off-by: Tom Yan <tom.ty89@xxxxxxxxx>
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index a1f061a..82739be 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -2314,7 +2314,7 @@ static unsigned int ata_scsiop_inq_b0(struct ata_scsi_args *args, u8 *rbuf)
>          * with the unmap bit set.
>          */
>         if (ata_id_has_trim(args->id)) {
> -               put_unaligned_be64(65535 * 512 / 8, &rbuf[36]);
> +               put_unaligned_be64(65535 * ATA_MAX_TRIM_RNUM, &rbuf[36]);
>                 put_unaligned_be32(1, &rbuf[28]);
>         }
>
> @@ -3306,8 +3306,8 @@ static unsigned int ata_scsi_write_same_xlat(struct ata_queued_cmd *qc)
>
>         buf = page_address(sg_page(scsi_sglist(scmd)));
>
> -       if (n_block <= 65535 * 512 / 8)
> -               size = ata_set_lba_range_entries(buf, 512, block, n_block);
> +       if (n_block <= 65535 * ATA_MAX_TRIM_RNUM)
> +               size = ata_set_lba_range_entries(buf, ATA_MAX_TRIM_RNUM, block, n_block);
>         else
>                 goto invalid_fld;
>
> diff --git a/include/linux/ata.h b/include/linux/ata.h
> index 99346be..ce59500 100644
> --- a/include/linux/ata.h
> +++ b/include/linux/ata.h
> @@ -48,6 +48,7 @@ enum {
>         ATA_MAX_SECTORS_1024    = 1024,
>         ATA_MAX_SECTORS_LBA48   = 65535,/* TODO: 65536? */
>         ATA_MAX_SECTORS_TAPE    = 65535,
> +       ATA_MAX_TRIM_RNUM       = 64,   /* 512-byte payload / (6-byte LBA + 2-byte range per entry) */
>
>         ATA_ID_WORDS            = 256,
>         ATA_ID_CONFIG           = 0,
> @@ -1071,7 +1072,7 @@ static inline unsigned ata_set_lba_range_entries(void *_buffer,
>         __le64 *buffer = _buffer;
>         unsigned i = 0, used_bytes;
>
> -       while (i < buf_size / 8 ) { /* 6-byte LBA + 2-byte range per entry */
> +       while (i < buf_size) {
>                 u64 entry = sector |
>                         ((u64)(count > 0xffff ? 0xffff : count) << 48);
>                 buffer[i++] = __cpu_to_le64(entry);
> --
> 2.9.0
>
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