Re: [PATCH 4.19 153/306] block: fix the DISCARD request merge (4.19.87+ crash)

[Jack Wang]

Andre Tomt <andre@xxxxxxxx> ä2019å12æ16æåä äå10:18åéï
>
> On 16.12.2019 08:42, Jack Wang wrote:
> > Andre Tomt <andre@xxxxxxxx> ä2019å12æ14æåå äå3:24åéï
> >>
> >> 4.19.87, 4.19.88, 4.19.89 all lock up frequently on some of my systems.
> >> The same systems run 5.4.3 fine, so the newer trees are probably OK.
> >> Reverting this commit on top of 4.19.87 makes everything stable.
> >>
> >> To trigger it all I have to do is re-rsyncing a directory tree with some
> >> changed files churn, it will usually crash in 10 to 30 minutes.
> >>
> >> The systems crashing has ext4 filesystem on a two ssd md raid1 mounted
> >> with the mount option discard. If mounting it without discard, the
> >> crashes no longer seem to occur.
> >>
> >> No oops/panic made it to the ipmi console. I suspect the console is just
> >> misbehaving and it didnt really livelock. At one point one line of the
> >> crash made it to the console (kernel BUG at block/blk-core.c:1776), and
> >> it was enough to pinpoint this commit. Note that the line number might
> >> be off, as I was attempting a bisect at the time.
> >>
> >> This commit also made it to 4.14.x, but I have not tested it.
> > Hi Andre,
> >
> > I noticed one fix is missing for discard merge in 4.19.y
> > 2a5cf35cd6c5 ("block: fix single range discard merge")
> >
> > Can you try if it helps? just "git cherry-pick 2a5cf35cd6c5"
>
> Indeed, adding this commit on top a clean 4.19.89 fixes the issue. So
> far survived about an hour of rsyncing file churn.
>
Glad to hear it!

Greg, Sasha,

Can you apply the fix 2a5cf35cd6c5 ("block: fix single range discard
merge") for 4.19 tree.

Regards,
Jack Wang