Re: [PATCH 3/3] nbd: map DISCARD requests to a new nbd request type
From: Paul Clements <hidden>
Date: 2011-09-08 01:13:50
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On Wed, Sep 7, 2011 at 10:41 AM, Paolo Bonzini [off-list ref] 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
quoted hunk ↗ jump to hunk
Cc: Paul Clements <Paul.Clements-G8/ITkJZaeZWk0Htik3J/w@public.gmane.org> Signed-off-by: Paolo Bonzini <redacted> --- 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