[pbs-devel] applied: [PATCH proxmox-backup v2] tape: work around buggy changer implementations

[Dietmar Maurer]

applied

On 12/13/23 10:00, Dominik Csapak wrote:
> allocation length for read element status is a 3 byte field, but it
> seems some changers only look at the bottom two bytes. Since we used
> 0x010000 for it, those changers did not return any data and the calls
> failed.
>
> To work around it, request one byte less (0xFFFF) which should still be
> enough for the data, but should now work with those buggy
> implementations.
>
> Reported by a user in the forum: https://forum.proxmox.com/threads/137391/
>
> Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
> ---
> changes from v1:
> * add a comment to make sure we know why we set this value
>   pbs-tape/src/sg_pt_changer.rs | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/pbs-tape/src/sg_pt_changer.rs b/pbs-tape/src/sg_pt_changer.rs
> index cfddbf9a..5b8596f0 100644
> --- a/pbs-tape/src/sg_pt_changer.rs
> +++ b/pbs-tape/src/sg_pt_changer.rs
> @@ -369,7 +369,7 @@ pub fn read_element_status<F: AsRawFd>(file: &mut F) -> Result<MtxStatus, Error>
>       // first, request address assignment (used for sanity checks)
>       let setup = read_element_address_assignment(file)?;
>   
> -    let allocation_len: u32 = 0x10000;
> +    let allocation_len: u32 = 0xFFFF; // some changer only use the lower 2 bytes
>   
>       let mut sg_raw = SgRaw::new(file, allocation_len as usize)?;
>       sg_raw.set_timeout(SCSI_CHANGER_DEFAULT_TIMEOUT);