diff mbox

block/iscsi: add support for request timeouts

Message ID 558C6DBE.5000903@redhat.com
State New
Headers show

Commit Message

Paolo Bonzini June 25, 2015, 9:08 p.m. UTC
On 16/06/2015 13:45, Peter Lieven wrote:
> libiscsi starting with 1.15 will properly support timeout of iscsi
> commands. The default will remain no timeout, but this can
> be changed via cmdline parameters, e.g.:
> 
> qemu -iscsi timeout=30 -drive file=iscsi://...
> 
> If a timeout occurs a reconnect is scheduled and the timed out command
> will be requeued for processing after a successful reconnect.
> 
> The required API call iscsi_set_timeout is present since libiscsi
> 1.10 which was released in October 2013. However, due to some bugs
> in the libiscsi code the use is not recommended before version 1.15.

If so, QEMU should not allow it if libiscsi is older than 1.15.

> Please note that this patch bumps the libiscsi requirement to 1.10
> to have all function and macros defined.

This is not acceptable, unfortunately.  I explained this two months ago
(https://lists.gnu.org/archive/html/qemu-devel/2015-04/msg01847.html)
and it is still true.

libiscsi keeps breaking ABI compatibility and for a while did not even
bump the soname when they do.  This makes it completely impossible for
distros to upgrade to a newer libiscsi, and RHEL7 is thus stuck with 1.9.

Yes, it is 2 years old.  It doesn't matter.  If libiscsi upstream only
_tried_ to preserve ABI compatibility, they wouldn't be in this
situation.  And I know that it is not even trying, because it broke
again sometime between 1.11 and 1.14 for a totally trivial reason:



This is the only change between these releases that breaks the ABI, but
it is already one too much. :(

(Also, the parsing of URLs into iscsi_url doesn't even try to obey the
RFCs...).

> The patch fixes also a
> off-by-one error in the NOP timeout calculation which was fixed
> while touching these code parts.

Can you please separate this part anyway?

Paolo

Comments

Peter Lieven June 25, 2015, 9:21 p.m. UTC | #1
Am 25.06.2015 um 23:08 schrieb Paolo Bonzini:
>
> On 16/06/2015 13:45, Peter Lieven wrote:
>> libiscsi starting with 1.15 will properly support timeout of iscsi
>> commands. The default will remain no timeout, but this can
>> be changed via cmdline parameters, e.g.:
>>
>> qemu -iscsi timeout=30 -drive file=iscsi://...
>>
>> If a timeout occurs a reconnect is scheduled and the timed out command
>> will be requeued for processing after a successful reconnect.
>>
>> The required API call iscsi_set_timeout is present since libiscsi
>> 1.10 which was released in October 2013. However, due to some bugs
>> in the libiscsi code the use is not recommended before version 1.15.
> If so, QEMU should not allow it if libiscsi is older than 1.15.

Not accept a timeout parameter or ignore it and print a warning?

>
>> Please note that this patch bumps the libiscsi requirement to 1.10
>> to have all function and macros defined.
> This is not acceptable, unfortunately.  I explained this two months ago
> (https://lists.gnu.org/archive/html/qemu-devel/2015-04/msg01847.html)
> and it is still true.

Sorry, i missed that. Can you verify if 1.15.0 has a soname that
makes it possible to jump to 1.15.0 at some point in the future?

>
> libiscsi keeps breaking ABI compatibility and for a while did not even
> bump the soname when they do.  This makes it completely impossible for
> distros to upgrade to a newer libiscsi, and RHEL7 is thus stuck with 1.9.
>
> Yes, it is 2 years old.  It doesn't matter.  If libiscsi upstream only
> _tried_ to preserve ABI compatibility, they wouldn't be in this
> situation.  And I know that it is not even trying, because it broke
> again sometime between 1.11 and 1.14 for a totally trivial reason:
>
> --- a/iscsi/iscsi.h
> +++ b/iscsi/iscsi.h
> @@ -91,6 +136,8 @@ struct iscsi_url {
>         char target[MAX_STRING_SIZE + 1];
>         char user[MAX_STRING_SIZE + 1];
>         char passwd[MAX_STRING_SIZE + 1];
> +       char target_user[MAX_STRING_SIZE + 1];
> +       char target_passwd[MAX_STRING_SIZE + 1];
>         int lun;
>         struct iscsi_context *iscsi;
>  };
>
>
> This is the only change between these releases that breaks the ABI, but
> it is already one too much. :(
>
> (Also, the parsing of URLs into iscsi_url doesn't even try to obey the
> RFCs...).
>
>> The patch fixes also a
>> off-by-one error in the NOP timeout calculation which was fixed
>> while touching these code parts.
> Can you please separate this part anyway?

Sure.

I will send a v2 that is compatible with 1.9.0 and enables the timeout
stuff only for libiscsi >= 1.15.0

Peter
Paolo Bonzini June 26, 2015, 9:07 a.m. UTC | #2
On 25/06/2015 23:21, Peter Lieven wrote:
> I will send a v2 that is compatible with 1.9.0 and enables the timeout
> stuff only for libiscsi >= 1.15.0

Since Stefan has already applied the patch, restoring 1.9.0
compatibility (and disabling timeouts between 1.9.0 and 1.14.x) on top
of this patch would be enough.

Thanks for your understanding!

Paolo
diff mbox

Patch

--- a/iscsi/iscsi.h
+++ b/iscsi/iscsi.h
@@ -91,6 +136,8 @@  struct iscsi_url {
        char target[MAX_STRING_SIZE + 1];
        char user[MAX_STRING_SIZE + 1];
        char passwd[MAX_STRING_SIZE + 1];
+       char target_user[MAX_STRING_SIZE + 1];
+       char target_passwd[MAX_STRING_SIZE + 1];
        int lun;
        struct iscsi_context *iscsi;
 };