Re: [Jfs-discussion] ssd+3.7 kernel trim: problems, read-only.

[Dave K. <dav...@or...>]

On 02/07/2015 10:54 AM, Uwe Brauer wrote:
> Hello
> 
> 
> I tried to send this email via gmane, but I never saw it on that list,
> so I resend it.
> 
> 
> 
> Using a Thinkpad Laptop with a new Samsung ssd, I have installed kubuntu
> 10.04 and chosen jfs. Since 10.04 is too old to support trimming, I
> compiled and installed kernel 3.7 and complied fstrim.
> 
> The relevant entry of my fstab reads as follows.
> 
> 
> UUID=8e06979b-2dbf-4192-8513-957bafa74a1e /               jfs
> nodiratime,noatime,errors=remount-ro 0       
> 
> The recommendation to use nodiratime and noatime for ssd I found
> for example in http://askubuntu.com/questions/1400/how-do-i-optimize-the-os-for-ssds
> 
> I run fstrim periodically via cron and everything seems fine.
> 
> However from time to time by system ends up to be mounted *read-only*.
> 
>  dmesg  gives errors like this:
> 
> [105074.721310] ERROR: (device sda5): dbDiscardAG: no memory for trim array
>  
> (I could send the complete result of dmesg, but it is large. I obtained
> it by dmesg | pastebinit).
> 
> Since the fstab entry states errors=remount-ro I presumed this is the
> source for the read only remount.

Yeah, that would explain it. The error should be a warning. No harm is
done if the trim fails and there is no danger continuing to using the
filesystem.

> 
> I can remount my hard disk and continue as if nothing has happened or I
> can reboot. 
> 
> In any case I would like to know:
> 
>     -  what can I do to prevent this problem, since it is annoying and
>        might result in  loss.

The quick fix might be to change to fstab entry to errors=continue

The real fix is to change the error to a warning. I'll go ahead and make
that change.

> 
>     -  is it safe just to remount or should I reboot?

Just remounting is safe. This error is not the result of any filesystem
corruption.

> 
> Thanks and regards
> 
> Uwe Brauer