linux-kernel - Re: [PATCH 5.4 062/152] bcache: ignore pending signals when creating gc and allocator thread

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Date:   Tue, 3 Mar 2020 11:19:28 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Coly Li <colyli@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.4 062/152] bcache: ignore pending signals when creating
 gc and allocator thread

On 3/3/20 11:12 AM, Greg Kroah-Hartman wrote:
> On Tue, Mar 03, 2020 at 10:55:04AM -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.
>>
>> Please drop this one, it's being reverted in mainline.
> 
> Dropped from all trees now, thanks.

Thanks!

-- 
Jens Axboe