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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 /include/linux/nbd.h | |
| parent | 2f012508880f8037590372c24ca6e8b6af8fffb6 (diff) | |
| download | linux-exynos-a336d29870f8a1f8e5f10d9f1aa95531c4edeabe.tar.gz linux-exynos-a336d29870f8a1f8e5f10d9f1aa95531c4edeabe.tar.bz2 linux-exynos-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 'include/linux/nbd.h')
| -rw-r--r-- | include/linux/nbd.h | 6 |
1 files changed, 5 insertions, 1 deletions
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]) |