* [PATCH] fuse: reserve byteswapped init opcodes
@ 2019-09-04 12:36 Michael S. Tsirkin
2019-09-04 14:22 ` Dr. David Alan Gilbert
2019-09-04 18:53 ` Stefan Hajnoczi
0 siblings, 2 replies; 3+ messages in thread
From: Michael S. Tsirkin @ 2019-09-04 12:36 UTC (permalink / raw)
To: linux-kernel; +Cc: Miklos Szeredi, linux-fsdevel, stefanha, dgilbert
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 <mst@redhat.com>
---
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..f042e63f4aa0 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 */
+ FUSE_INIT_BSWAP_RESERVED = 26 << 24,
+ CUSE_INIT_BSWAP_RESERVED = 16 << 16,
};
enum fuse_notify_code {
--
MST
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] fuse: reserve byteswapped init opcodes
2019-09-04 12:36 [PATCH] fuse: reserve byteswapped init opcodes Michael S. Tsirkin
@ 2019-09-04 14:22 ` Dr. David Alan Gilbert
2019-09-04 18:53 ` Stefan Hajnoczi
1 sibling, 0 replies; 3+ messages in thread
From: Dr. David Alan Gilbert @ 2019-09-04 14:22 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: linux-kernel, Miklos Szeredi, linux-fsdevel, stefanha
* Michael S. Tsirkin (mst@redhat.com) wrote:
> 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.
I think in theory that works even for normal fuse.
> Same for CUSE_INIT.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 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..f042e63f4aa0 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 */
> + FUSE_INIT_BSWAP_RESERVED = 26 << 24,
FUSE_INIT << 24 probably works?
> + CUSE_INIT_BSWAP_RESERVED = 16 << 16,
Dave
> };
>
> enum fuse_notify_code {
> --
> MST
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] fuse: reserve byteswapped init opcodes
2019-09-04 12:36 [PATCH] fuse: reserve byteswapped init opcodes Michael S. Tsirkin
2019-09-04 14:22 ` Dr. David Alan Gilbert
@ 2019-09-04 18:53 ` Stefan Hajnoczi
1 sibling, 0 replies; 3+ messages in thread
From: Stefan Hajnoczi @ 2019-09-04 18:53 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: linux-kernel, Miklos Szeredi, linux-fsdevel, dgilbert
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On Wed, Sep 04, 2019 at 08:36:33AM -0400, Michael S. Tsirkin wrote:
> 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 <mst@redhat.com>
> ---
> include/uapi/linux/fuse.h | 4 ++++
> 1 file changed, 4 insertions(+)
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-09-04 12:36 [PATCH] fuse: reserve byteswapped init opcodes Michael S. Tsirkin
2019-09-04 14:22 ` Dr. David Alan Gilbert
2019-09-04 18:53 ` Stefan Hajnoczi
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