[PATCH 2/3] nbd: add support for feature negotiation

Paolo Bonzini
2011-09-07T16:27:49Z

Add a IOCTL to negotiate features between the server and the
kernel module (mediated by the usermode client). Features are
stored in the pre-existing flags field.

Also zero out the flags when NBD_DO_IT completes.

Cc: Paul Clements <Paul.Clements@steeleye.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
drivers/block/nbd.c | 8 ++++++++
include/linux/nbd.h | 24 +++++++++++++++---------
2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index be23aec..c4fe9c8 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -85,6 +85,7 @@ static const char *ioctl_cmd_to_ascii(int cmd)
case NBD_PRINT_DEBUG: return "print-debug";
case NBD_SET_SIZE_BLOCKS: return "set-size-blocks";
case NBD_DISCONNECT: return "disconnect";
+ case NBD_SET_FEATURES: return "set-features";
case BLKROSET: return "set-read-only";
case BLKFLSBUF: return "flush-buffer-cache";
}
@@ -634,6 +635,12 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *lo,
lo->xmit_timeout = arg * HZ;
return 0;

+ case NBD_SET_FEATURES:
+ if (((u64) arg) & NBD_FEATURE_RESERVED)
+ return -EINVAL;
+ lo->flags = (lo->flags & NBD_FEATURE_RESERVED) | (u64)arg;
+ return 0;
+
case NBD_SET_SIZE_BLOCKS:
lo->bytesize = ((u64) arg) * lo->blksize;
bdev->bd_inode->i_size = lo->bytesize;
@@ -672,6 +679,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *lo,
printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
if (file)
fput(file);
+ lo->flags = 0;
lo->bytesize = 0;
bdev->bd_inode->i_size = 0;
set_capacity(lo->disk, 0);
diff --git a/include/linux/nbd.h b/include/linux/nbd.h
index 0582054..926f19d 100644
--- a/include/linux/nbd.h
+++ b/include/linux/nbd.h
@@ -17,16 +17,22 @@

#include <linux/types.h>

-#define NBD_SET_SOCK _IO( 0xab, 0 )
-#define NBD_SET_BLKSIZE _IO( 0xab, 1 )
-#define NBD_SET_SIZE _IO( 0xab, 2 )
-#define NBD_DO_IT _IO( 0xab, 3 )
-#define NBD_CLEAR_SOCK _IO( 0xab, 4 )
-#define NBD_CLEAR_QUE _IO( 0xab, 5 )
-#define NBD_PRINT_DEBUG _IO( 0xab, 6 )
-#define NBD_SET_SIZE_BLOCKS _IO( 0xab, 7 )
-#define NBD_DISCONNECT _IO( 0xab, 8 )
-#define NBD_SET_TIMEOUT _IO( 0xab, 9 )
+#define NBD_SET_SOCK _IO(0xab, 0)
+#define NBD_SET_BLKSIZE _IO(0xab, 1)
+#define NBD_SET_SIZE _IO(0xab, 2)
+#define NBD_DO_IT _IO(0xab, 3)
+#define NBD_CLEAR_SOCK _IO(0xab, 4)
+#define NBD_CLEAR_QUE _IO(0xab, 5)
+#define NBD_PRINT_DEBUG _IO(0xab, 6)
+#define NBD_SET_SIZE_BLOCKS _IO(0xab, 7)
+#define NBD_DISCONNECT _IO(0xab, 8)
+#define NBD_SET_TIMEOUT _IO(0xab, 9)
+#define NBD_SET_FEATURES _IO(0xab, 10)
+
+/* bits 0 and 1 are already used for flags in the protocol, we do
+ * not want any overlap. Bits 32-63 are reserved because they
+ * are inaccessible on 32-bit platforms. */
+#define NBD_FEATURE_RESERVED 0xFFFFFFFF00000003LL

enum {
NBD_CMD_READ = 0,
--
1.7.6