linux-kernel - Re: [PATCH 5.5 072/176] bcache: ignore pending signals when creating gc and allocator thread

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Date:   Tue, 3 Mar 2020 19:14:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Coly Li <colyli@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.5 072/176] bcache: ignore pending signals when creating
 gc and allocator thread

On Tue, Mar 03, 2020 at 10:58:29AM -0700, Jens Axboe wrote:
> On 3/3/20 10:42 AM, Greg Kroah-Hartman wrote:
> > From: Coly Li <colyli@...e.de>
> > 
> > [ Upstream commit 0b96da639a4874311e9b5156405f69ef9fc3bef8 ]
> > 
> > When run a cache set, all the bcache btree node of this cache set will
> > be checked by bch_btree_check(). If the bcache btree is very large,
> > iterating all the btree nodes will occupy too much system memory and
> > the bcache registering process might be selected and killed by system
> > OOM killer. kthread_run() will fail if current process has pending
> > signal, therefore the kthread creating in run_cache_set() for gc and
> > allocator kernel threads are very probably failed for a very large
> > bcache btree.
> > 
> > Indeed such OOM is safe and the registering process will exit after
> > the registration done. Therefore this patch flushes pending signals
> > during the cache set start up, specificly in bch_cache_allocator_start()
> > and bch_gc_thread_start(), to make sure run_cache_set() won't fail for
> > large cahced data set.
> 
> Ditto this one, of course.
> 
> Did someone send this in for stable? It's not marked stable in the
> original commit.

I think the autobot grabbed it.