xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

nbd: handle discard requests

Browse Source 
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>
This commit is contained in:
Paul Clements
2012-10-04 17:16:18 -07:00
committed by Linus Torvalds
parent 2f01250888
commit a336d29870
2 changed files with 19 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/nbd.h
View File

@@ -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])