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>
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2f01250888
Коммит
a336d29870
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@ -98,6 +98,7 @@ static const char *nbdcmd_to_ascii(int cmd)
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case NBD_CMD_READ: return "read";
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case NBD_CMD_WRITE: return "write";
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case NBD_CMD_DISC: return "disconnect";
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case NBD_CMD_TRIM: return "trim/discard";
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}
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return "invalid";
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}
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@ -469,7 +470,11 @@ static void nbd_handle_req(struct nbd_device *nbd, struct request *req)
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nbd_cmd(req) = NBD_CMD_READ;
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if (rq_data_dir(req) == WRITE) {
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nbd_cmd(req) = NBD_CMD_WRITE;
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if ((req->cmd_flags & REQ_DISCARD)) {
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WARN_ON(!(nbd->flags & NBD_FLAG_SEND_TRIM));
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nbd_cmd(req) = NBD_CMD_TRIM;
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} else
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nbd_cmd(req) = NBD_CMD_WRITE;
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if (nbd->flags & NBD_FLAG_READ_ONLY) {
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dev_err(disk_to_dev(nbd->disk),
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"Write on read-only\n");
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@ -676,6 +681,10 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
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mutex_unlock(&nbd->tx_lock);
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if (nbd->flags & NBD_FLAG_SEND_TRIM)
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queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
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nbd->disk->queue);
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thread = kthread_create(nbd_thread, nbd, nbd->disk->disk_name);
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if (IS_ERR(thread)) {
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mutex_lock(&nbd->tx_lock);
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@ -693,6 +702,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
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nbd->file = NULL;
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nbd_clear_que(nbd);
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dev_warn(disk_to_dev(nbd->disk), "queue cleared\n");
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queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
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if (file)
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fput(file);
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nbd->bytesize = 0;
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@ -811,6 +821,9 @@ static int __init nbd_init(void)
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* Tell the block layer that we are not a rotational device
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*/
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queue_flag_set_unlocked(QUEUE_FLAG_NONROT, disk->queue);
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disk->queue->limits.discard_granularity = 512;
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disk->queue->limits.max_discard_sectors = UINT_MAX;
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disk->queue->limits.discard_zeroes_data = 0;
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}
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if (register_blkdev(NBD_MAJOR, "nbd")) {
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@ -32,12 +32,16 @@
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enum {
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NBD_CMD_READ = 0,
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NBD_CMD_WRITE = 1,
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NBD_CMD_DISC = 2
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NBD_CMD_DISC = 2,
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/* there is a gap here to match userspace */
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NBD_CMD_TRIM = 4
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};
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/* values for flags field */
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#define NBD_FLAG_HAS_FLAGS (1 << 0) /* nbd-server supports flags */
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#define NBD_FLAG_READ_ONLY (1 << 1) /* device is read-only */
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/* there is a gap here to match userspace */
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#define NBD_FLAG_SEND_TRIM (1 << 5) /* send trim/discard */
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#define nbd_cmd(req) ((req)->cmd[0])
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