[pbs-devel] [PATCH proxmox-backup] tape: fix read element status for some changers

[pbs-devel] [PATCH proxmox-backup] tape: fix read element status for some changers

[Dominik Csapak]

It seems some changers are setting the PVolTag/AVolTag flags in the
ELEMENT STATUS page response, but don't include the actual fields then.
To make it work with such changers, downgrade the errors to warnings, so
we can continue to decode the remaining data.

This is OK since one volume tag is optional and the other is skipped
anyway.

Reported in the forum:
https://forum.proxmox.com/threads/hpe-storeonce-vtl.152547/

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 pbs-tape/src/sg_pt_changer.rs | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/pbs-tape/src/sg_pt_changer.rs b/pbs-tape/src/sg_pt_changer.rs
index b600a49d..940eed4a 100644
--- a/pbs-tape/src/sg_pt_changer.rs
+++ b/pbs-tape/src/sg_pt_changer.rs
@@ -746,9 +746,18 @@ fn decode_element_status_page(
                     let desc: TransportDescriptor = unsafe { reader.read_be_value()? };
 
                     let full = (desc.flags1 & 1) != 0;
-                    let volume_tag = subhead.parse_optional_volume_tag(&mut reader, full)?;
 
-                    subhead.skip_alternate_volume_tag(&mut reader)?;
+                    let volume_tag = match subhead.parse_optional_volume_tag(&mut reader, full) {
+                        Ok(tag) => tag,
+                        Err(err) => {
+                            log::warn!("could not read optional volume tag: {err}");
+                            None
+                        }
+                    };
+
+                    if let Err(err) = subhead.skip_alternate_volume_tag(&mut reader) {
+                        log::warn!("could not skip alternate volume tag: {err}");
+                    }
 
                     result.last_element_address = Some(desc.element_address);
 
-- 
2.39.2



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Re: [pbs-devel] [PATCH proxmox-backup] tape: fix read element status for some changers

[Dietmar Maurer]

> It seems some changers are setting the PVolTag/AVolTag flags in the
> ELEMENT STATUS page response, but don't include the actual fields then.
> To make it work with such changers, downgrade the errors to warnings, so
> we can continue to decode the remaining data.

cant we simply check if there is remaining data in the reader?


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Re: [pbs-devel] [PATCH proxmox-backup] tape: fix read element status for some changers

[Dominik Csapak]

On 9/3/24 07:26, Dietmar Maurer wrote:
>> It seems some changers are setting the PVolTag/AVolTag flags in the
>> ELEMENT STATUS page response, but don't include the actual fields then.
>> To make it work with such changers, downgrade the errors to warnings, so
>> we can continue to decode the remaining data.
> 
> cant we simply check if there is remaining data in the reader?


yes we could, but we have to do it outside the functions, because
we don't have access to the reader there, only to something that
implements `read`

should i send a patch that checks the remaining size beforehand?


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