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[Qemu-devel] [PULL 16/16] qemu-nbd: only send a limited number of errno
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 16/16] qemu-nbd: only send a limited number of errno codes on the wire |
Date: |
Fri, 8 May 2015 14:08:01 +0200 |
Right now, NBD includes potentially platform-specific error values in
the wire protocol.
Luckily, most common error values are more or less universal: in
particular, of all errno values <= 34 (up to ERANGE), they are all the
same on supported platforms except for 11 (which is EAGAIN on Windows and
Linux, but EDEADLK on Darwin and the *BSDs). So, in order to guarantee
some portability, only keep a handful of possible error codes and squash
everything else to EINVAL.
This patch defines a limited set of errno values that are valid for the
NBD protocol, and specifies recommendations for what error to return
in specific corner cases. The set of errno values is roughly based on
the errors listed in the read(2) and write(2) man pages, with some
exceptions:
- ENOMEM is added for servers that implement copy-on-write or other
formats that require dynamic allocation.
- EDQUOT is not part of the universal set of errors; it can be changed
to ENOSPC on the wire format.
- EFBIG is part of the universal set of errors, but it is also changed
to ENOSPC because it is pretty similar to ENOSPC or EDQUOT.
Incoming values will in general match system errno values, but not
on the Hurd which has different errno values (they have a "subsystem
code" equal to 0x10 in bits 24-31). The Hurd is probably not something
to which QEMU has been ported, but still do the right thing and
reverse-map the NBD errno values to the system errno values.
The corresponding patch to the NBD protocol description can be found at
http://article.gmane.org/gmane.linux.drivers.nbd.general/3154.
Signed-off-by: Paolo Bonzini <address@hidden>
---
nbd.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 52 insertions(+)
diff --git a/nbd.c b/nbd.c
index cb1b9bb..57d71b2 100644
--- a/nbd.c
+++ b/nbd.c
@@ -86,6 +86,54 @@
#define NBD_OPT_ABORT (2)
#define NBD_OPT_LIST (3)
+/* NBD errors are based on errno numbers, so there is a 1:1 mapping,
+ * but only a limited set of errno values is specified in the protocol.
+ * Everything else is squashed to EINVAL.
+ */
+#define NBD_EPERM 1
+#define NBD_EIO 5
+#define NBD_ENOMEM 12
+#define NBD_EINVAL 22
+#define NBD_ENOSPC 28
+
+static int system_errno_to_nbd_errno(int err)
+{
+ switch (err) {
+ case EPERM:
+ return NBD_EPERM;
+ case EIO:
+ return NBD_EIO;
+ case ENOMEM:
+ return NBD_ENOMEM;
+#ifdef EDQUOT
+ case EDQUOT:
+#endif
+ case EFBIG:
+ case ENOSPC:
+ return NBD_ENOSPC;
+ case EINVAL:
+ default:
+ return NBD_EINVAL;
+ }
+}
+
+static int nbd_errno_to_system_errno(int err)
+{
+ switch (err) {
+ case NBD_EPERM:
+ return EPERM;
+ case NBD_EIO:
+ return EIO;
+ case NBD_ENOMEM:
+ return ENOMEM;
+ case NBD_ENOSPC:
+ return ENOSPC;
+ case NBD_EINVAL:
+ default:
+ return EINVAL;
+ }
+}
+
/* Definitions for opaque data types */
typedef struct NBDRequest NBDRequest;
@@ -856,6 +904,8 @@ ssize_t nbd_receive_reply(int csock, struct nbd_reply
*reply)
reply->error = be32_to_cpup((uint32_t*)(buf + 4));
reply->handle = be64_to_cpup((uint64_t*)(buf + 8));
+ reply->error = nbd_errno_to_system_errno(reply->error);
+
TRACE("Got reply: "
"{ magic = 0x%x, .error = %d, handle = %" PRIu64" }",
magic, reply->error, reply->handle);
@@ -872,6 +922,8 @@ static ssize_t nbd_send_reply(int csock, struct nbd_reply
*reply)
uint8_t buf[NBD_REPLY_SIZE];
ssize_t ret;
+ reply->error = system_errno_to_nbd_errno(reply->error);
+
/* Reply
[ 0 .. 3] magic (NBD_REPLY_MAGIC)
[ 4 .. 7] error (0 == no error)
--
2.3.5
- [Qemu-devel] [PULL 05/16] kvm: add support for memory transaction attributes, (continued)
- [Qemu-devel] [PULL 05/16] kvm: add support for memory transaction attributes, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 06/16] exec: move rcu_read_lock/unlock to address_space_translate callers, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 07/16] configure: require __thread support, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 09/16] qom: document user creatable object types in help text, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 08/16] qom: fix typename of 'policy' enum property in hostmem obj, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 10/16] qom: create objects in two phases, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 12/16] qom: make enum string tables const-correct, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 11/16] qom: add object_new_propv / object_new_proplist constructors, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 13/16] qom: add a object_property_add_enum helper method, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 14/16] qom: don't pass string table to object_get_enum method, Paolo Bonzini, 2015/05/08
- [Qemu-devel] [PULL 16/16] qemu-nbd: only send a limited number of errno codes on the wire,
Paolo Bonzini <=
- Re: [Qemu-devel] [PULL 00/16] KVM, QOM, NBD, build fixes for 2015-05-08, Andreas Färber, 2015/05/08
- Re: [Qemu-devel] [PULL 00/16] KVM, QOM, NBD, build fixes for 2015-05-08, Daniel P. Berrange, 2015/05/08
- Re: [Qemu-devel] [PULL 00/16] KVM, QOM, NBD, build fixes for 2015-05-08, Andreas Färber, 2015/05/08
- Re: [Qemu-devel] [PULL 00/16] KVM, QOM, NBD, build fixes for 2015-05-08, Daniel P. Berrange, 2015/05/08
- Re: [Qemu-devel] [PULL 00/16] KVM, QOM, NBD, build fixes for 2015-05-08, Daniel P. Berrange, 2015/05/12