On Wed, Sep 7, 2011 at 10:41 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> When the feature is enabled, set QUEUE_FLAG_DISCARD and transmit those as
> NBD_CMD_TRIM requests.
>
> I used "trim" instead of "discard" to avoid confusion with the existing
> NBD_CMD_DISC that is used for disconnect.
This patchset looks good to me.
--
Paul
> Cc: Paul Clements <Paul.Clements@xxxxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> drivers/block/nbd.c | 15 ++++++++++++---
> include/linux/nbd.h | 4 +++-
> 2 files changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index c4fe9c8..71ebaab 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -98,6 +98,7 @@ static const char *nbdcmd_to_ascii(int cmd)
> case NBD_CMD_READ: return "read";
> case NBD_CMD_WRITE: return "write";
> case NBD_CMD_DISC: return "disconnect";
> + case NBD_CMD_TRIM: return "trim (discard)";
> }
> return "invalid";
> }
> @@ -454,9 +455,13 @@ static void nbd_handle_req(struct nbd_device *lo, struct request *req)
> if (req->cmd_type != REQ_TYPE_FS)
> goto error_out;
>
> - if (rq_data_dir(req) == WRITE)
> - nbd_cmd(req) = NBD_CMD_WRITE;
> - else
> + if (rq_data_dir(req) == WRITE) {
> + if ((req->cmd_flags & REQ_DISCARD)) {
> + WARN_ON(!(lo->flags & NBD_FEATURE_TRIM));
> + nbd_cmd(req) = NBD_CMD_TRIM;
> + } else
> + nbd_cmd(req) = NBD_CMD_WRITE;
> + } else
> nbd_cmd(req) = NBD_CMD_READ;
>
> req->errors = 0;
> @@ -659,6 +664,9 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *lo,
> return -EINVAL;
>
> mutex_unlock(&lo->tx_lock);
> + if (lo->flags & NBD_FEATURE_TRIM)
> + queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
> + lo->disk->queue);
>
> thread = kthread_create(nbd_thread, lo, lo->disk->disk_name);
> if (IS_ERR(thread)) {
> @@ -677,6 +685,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *lo,
> lo->file = NULL;
> nbd_clear_que(lo);
> printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
> + queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, lo->disk->queue);
> if (file)
> fput(file);
> lo->flags = 0;
> @@ -796,6 +805,9 @@ static int __init nbd_init(void)
> * Tell the block layer that we are not a rotational device
> */
> queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
> + disk->queue->limits.discard_granularity = 512;
> + disk->queue->limits.max_discard_sectors = UINT_MAX;
> + disk->queue->limits.discard_zeroes_data = 0;
> }
>
> if (register_blkdev(NBD_MAJOR, "nbd")) {
> diff --git a/include/linux/nbd.h b/include/linux/nbd.h
> index 926f19d..7048463 100644
> --- a/include/linux/nbd.h
> +++ b/include/linux/nbd.h
> @@ -33,11 +33,13 @@
> * not want any overlap. Bits 32-63 are reserved because they
> * are inaccessible on 32-bit platforms. */
> #define NBD_FEATURE_RESERVED 0xFFFFFFFF00000003LL
> +#define NBD_FEATURE_TRIM (1 << 2)
>
> enum {
> NBD_CMD_READ = 0,
> NBD_CMD_WRITE = 1,
> - NBD_CMD_DISC = 2
> + NBD_CMD_DISC = 2,
> + NBD_CMD_TRIM = 3
> };
>
> #define nbd_cmd(req) ((req)->cmd[0])
> --
> 1.7.6
>
>
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