On Wed, Apr 23, 2025 at 11:13:13AM +0300, Leon Romanovsky wrote:
> From: Christoph Hellwig <hch@xxxxxx>
>
> There is plenty of unused space in the iod next to nr_descriptors.
> Add a separate flag to encode that the transfer is using the full
> page sized pool, and use a normal 0..n count for the number of
> descriptors.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Tested-by: Jens Axboe <axboe@xxxxxxxxx>
> [ Leon: changed original bool variable to be flag as was proposed by Kanchan ]
> Signed-off-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> ---
> drivers/nvme/host/pci.c | 93 ++++++++++++++++++++---------------------
> 1 file changed, 46 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 638e759b29ad..7e93536d01cb 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -44,6 +44,7 @@
> #define NVME_MAX_SEGS 128
> #define NVME_MAX_META_SEGS 15
> #define NVME_MAX_NR_DESCRIPTORS 5
> +#define NVME_SMALL_DESCRIPTOR_SIZE 256
>
> static int use_threaded_interrupts;
> module_param(use_threaded_interrupts, int, 0444);
> @@ -219,6 +220,10 @@ struct nvme_queue {
> struct completion delete_done;
> };
>
> +enum {
> + IOD_LARGE_DESCRIPTORS = 1, /* uses the full page sized descriptor pool */
This is used as a ORable flag, I'd make that explicit:
/* uses the full page sized descriptor pool */
IOD_LARGE_DESCRIPTORS = 1U << 0,
and similar for the next flag added in the next patch.
> struct nvme_request req;
> struct nvme_command cmd;
> bool aborted;
> - /* # of PRP/SGL descriptors: (0 for small pool) */
> - s8 nr_descriptors;
> + u8 nr_descriptors; /* # of PRP/SGL descriptors */
> + unsigned int flags;
And this should be limited to a u16 to not bloat the structure.
