From a336d29870f8a1f8e5f10d9f1aa95531c4edeabe Mon Sep 17 00:00:00 2001 From: Paul Clements Date: Thu, 4 Oct 2012 17:16:18 -0700 Subject: 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/nbd.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'include/linux/nbd.h') diff --git a/include/linux/nbd.h b/include/linux/nbd.h index 4b8ed5a1cfb0..5c86e2b33e2d 100644 --- a/include/linux/nbd.h +++ b/include/linux/nbd.h @@ -32,12 +32,16 @@ enum { NBD_CMD_READ = 0, NBD_CMD_WRITE = 1, - NBD_CMD_DISC = 2 + NBD_CMD_DISC = 2, + /* there is a gap here to match userspace */ + NBD_CMD_TRIM = 4 }; /* values for flags field */ #define NBD_FLAG_HAS_FLAGS (1 << 0) /* nbd-server supports flags */ #define NBD_FLAG_READ_ONLY (1 << 1) /* device is read-only */ +/* there is a gap here to match userspace */ +#define NBD_FLAG_SEND_TRIM (1 << 5) /* send trim/discard */ #define nbd_cmd(req) ((req)->cmd[0]) -- cgit v1.2.3