On Mon, 2017-03-20 at 16:43 -0400, Christoph Hellwig wrote:
> We're never touching the contents of the page, so save a memory
> allocation for these cases.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> drivers/scsi/sd.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index c18fe9ff1f8f..af632e350ab4 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -756,7 +756,7 @@ static int sd_setup_write_same16_cmnd(struct scsi_cmnd *cmd)
> u32 nr_sectors = blk_rq_sectors(rq) >> (ilog2(sdp->sector_size) - 9);
> u32 data_len = sdp->sector_size;
>
> - rq->special_vec.bv_page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
> + rq->special_vec.bv_page = ZERO_PAGE(0);
> if (!rq->special_vec.bv_page)
> return BLKPREP_DEFER;
> rq->special_vec.bv_offset = 0;
> @@ -785,7 +785,7 @@ static int sd_setup_write_same10_cmnd(struct scsi_cmnd *cmd, bool unmap)
> u32 nr_sectors = blk_rq_sectors(rq) >> (ilog2(sdp->sector_size) - 9);
> u32 data_len = sdp->sector_size;
>
> - rq->special_vec.bv_page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
> + rq->special_vec.bv_page = ZERO_PAGE(0);
> if (!rq->special_vec.bv_page)
> return BLKPREP_DEFER;
> rq->special_vec.bv_offset = 0;
> @@ -1256,7 +1256,8 @@ static void sd_uninit_command(struct scsi_cmnd *SCpnt)
> {
> struct request *rq = SCpnt->request;
>
> - if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
> + if ((rq->rq_flags & RQF_SPECIAL_PAYLOAD) &&
> + rq->special_vec.bv_page != ZERO_PAGE(0))
> __free_page(rq->special_vec.bv_page);
>
> if (SCpnt->cmnd != scsi_req(rq)->cmd) {
Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
