Re: ata timeout exceptions

[Niklas Cassel <cassel@kernel.org>]

On Fri, Nov 14, 2025 at 03:32:20PM +1100, Eyal Lebedinsky wrote:
> > For the last few weeks it started to log timeout errors (not always) like this:
> 
> For the last two weeks I was monitoring the activity on the disk and here is what I did:
> 
> - added to boot command line:	libata.force=2.00:noncq
> 	now smartmon sees no more Command_Timeout errors since

To be honest, I don't think you should need to disable NCQ.


> This disk was used for a few years without such errors. The first report is recent (from 25/Oct this year).

Which kernel version are you running?

> 12:15:14+11:00 kernel: ata2.00: failed command: WRITE DMA EXT
> 12:15:14+11:00 kernel: ata2.00: cmd 35/00:00:00:68:4e/00:20:77:00:00/e0 tag 28 dma 4194304 out
>                                 res 40/00:00:00:4f:c2/00:00:00:00:00/40 Emask 0x4 (timeout)
> 12:15:14+11:00 kernel: ata2.00: status: { DRDY }
> 12:15:14+11:00 kernel: ata2: hard resetting link
> 12:15:15+11:00 kernel: ata2: SATA link up 6.0 Gbps (SStatus 133 SControl 300)
> 12:15:15+11:00 kernel: ata2.00: configured for UDMA/133
> 12:15:15+11:00 kernel: ata2: EH complete

It is a 4194304 byte write that is failing, i.e. 4 MiB write.

This sounds very much like a recent bug report we have received:
https://bugzilla.kernel.org/show_bug.cgi?id=220693

In fact, a lot of the failing commands in that bug report is also a read
or write of size 4 MiB.

I guess you could try reverting 459779d04ae8 ("block: Improve read ahead
size for rotational devices") and see if that improves things for you
(while keeping NCQ enabled).


Kind regards,
Niklas