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| author | Paul Clements <paul.clements@steeleye.com> | 2012-10-04 17:16:18 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-06 03:05:24 +0900 |
| commit | a336d29870f8a1f8e5f10d9f1aa95531c4edeabe (patch) | |
| tree | 9957b7a2dbdc5047fe1f2be7907f90f5bdb6fbf0 /drivers/block/nbd.c | |
| parent | 2f012508880f8037590372c24ca6e8b6af8fffb6 (diff) | |
| download | lwn-a336d29870f8a1f8e5f10d9f1aa95531c4edeabe.tar.gz lwn-a336d29870f8a1f8e5f10d9f1aa95531c4edeabe.zip | |
nbd: handle discard requests
Add discard support to nbd. If the nbd-server supports discard, it will
send NBD_FLAG_SEND_TRIM to the client. The client will then set the flag
in the kernel via NBD_SET_FLAGS, which tells the kernel to enable discards
for the device (QUEUE_FLAG_DISCARD).
If discard support is enabled, then when the nbd client system receives a
discard request, this will be passed along to the nbd-server. When the
discard request is received by the nbd-server, it will perform:
fallocate(.. FALLOC_FL_PUNCH_HOLE ..)
To punch a hole in the backend storage, which is no longer needed.
Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/block/nbd.c')
| -rw-r--r-- | drivers/block/nbd.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 68fe7514413d..043ddcca4abf 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"; } @@ -469,7 +470,11 @@ static void nbd_handle_req(struct nbd_device *nbd, struct request *req) nbd_cmd(req) = NBD_CMD_READ; if (rq_data_dir(req) == WRITE) { - nbd_cmd(req) = NBD_CMD_WRITE; + if ((req->cmd_flags & REQ_DISCARD)) { + WARN_ON(!(nbd->flags & NBD_FLAG_SEND_TRIM)); + nbd_cmd(req) = NBD_CMD_TRIM; + } else + nbd_cmd(req) = NBD_CMD_WRITE; if (nbd->flags & NBD_FLAG_READ_ONLY) { dev_err(disk_to_dev(nbd->disk), "Write on read-only\n"); @@ -676,6 +681,10 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, mutex_unlock(&nbd->tx_lock); + if (nbd->flags & NBD_FLAG_SEND_TRIM) + queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, + nbd->disk->queue); + thread = kthread_create(nbd_thread, nbd, nbd->disk->disk_name); if (IS_ERR(thread)) { mutex_lock(&nbd->tx_lock); @@ -693,6 +702,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, nbd->file = NULL; nbd_clear_que(nbd); dev_warn(disk_to_dev(nbd->disk), "queue cleared\n"); + queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue); if (file) fput(file); nbd->bytesize = 0; @@ -811,6 +821,9 @@ 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")) { |