[SRU][B][PULL v2] bcache: fix hung task timeout in bch_bucket_alloc()

[Andrea Righi]

On Wed, Aug 07, 2019 at 02:29:05PM +0200, Andrea Righi wrote:
...
> [Regression Potential]
> 
> The upstream fixes are all clean cherry picks from stable (most of them
> are small cleanups), so regression potential is minimal.
> 
> The only special patch is "UBUNTU: SAUCE: bcache: fix deadlock in
> bcache_allocator" that is addressing the main deadlock bug (that seems
> to be a mainline bug - not fixed yet). We should spend more time trying
> to reproduce this deadlock with a mainline kernel and post the patch to
> the LKML for review / feedback.
> 
> However, considering that this patch seems to fix/prevent the specific
> deadlock problem reported in this bug (tested on the affected platform),
> it should be considered safe to apply it as it is for now, to prevent
> potential hung task timeout conditions.

Sorry, this comment is not valid anymore. The bug has been reproduced
with the latest mainline kernel (from Linus' git) and the fix has been
successfully tested, so we can confirm that it's definitely a mainline
bug.

-Andrea