From: "Michael S. Tsirkin" <[email protected]>

virtio fs tunnels fuse over a virtio channel.  One issue is two sides might
be speaking different endian-ness. To detects this, host side looks at the
opcode value in the FUSE_INIT command.  Works fine at the moment but might
fail if a future version of fuse will use such an opcode for
initialization.  Let's reserve this opcode so we remember and don't do
this.

Same for CUSE_INIT.

Signed-off-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Miklos Szeredi <[email protected]>
---
 include/uapi/linux/fuse.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 2971d29a42e4..df2e12fb3381 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -425,6 +425,10 @@ enum fuse_opcode {
 
        /* CUSE specific operations */
        CUSE_INIT               = 4096,
+
+       /* Reserved opcodes: helpful to detect structure endian-ness */
+       CUSE_INIT_BSWAP_RESERVED        = 1048576,      /* CUSE_INIT << 8 */
+       FUSE_INIT_BSWAP_RESERVED        = 436207616,    /* FUSE_INIT << 24 */
 };
 
 enum fuse_notify_code {
-- 
2.21.0

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