From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Jens Axboe <axboe@kernel.dk>, Dongyun Liu <dongyun.liu3@gmail.com>
Cc: minchan@kernel.org, senozhatsky@chromium.org,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
lincheng.yang@transsion.com, jiajun.ling@transsion.com,
ldys2014@foxmail.com, Dongyun Liu <dongyun.liu@transsion.com>
Subject: Re: [PATCH] zram: Using GFP_ATOMIC instead of GFP_KERNEL to allocate bitmap memory in backing_dev_store
Date: Sat, 2 Dec 2023 00:28:22 +0900 [thread overview]
Message-ID: <20231201152822.GA404241@google.com> (raw)
In-Reply-To: <b26ab8d0-c719-4bf6-b909-26f4c014574b@kernel.dk>
On (23/12/01 07:19), Jens Axboe wrote:
> >> IOW, you have a slew of GFP_KERNEL allocations in there, and you
> >> probably just patched the largest one. But the core issue remains.
> >>
> >> The whole handling of backing_dev_store() looks pretty broken.
> >>
> >
> > Indeed, this patch only solves the biggest problem and does not
> > fundamentally solve it, because there are many processes for holding
> > zram->init_lock before allocation memory in backing_dev_store that
> > need to be fully modified, and I did not consider it thoroughly.
> > Obviously, a larger and better patch is needed to eliminate this risk,
> > but it is currently not necessary.
>
> You agree that it doesn't fix the issue, it just happens to fix the one
> that you hit. And then you jump to the conclusion that this is all
> that's needed to fix it. Ehm, confused?
Yeah.
zram is very sensitive to memory - zsmalloc pool needs physical pages
(allocated on demand) to keep data written to zram. zram probably simply
should not be used on systems under such heavy memory pressure. Throwing
GPF_ATOMICs at zram isn't going to fix anything.
Jens, you said that zram's backing device handling is broken. Got a minute
to elaborate?
next prev parent reply other threads:[~2023-12-01 15:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-30 15:20 [PATCH] zram: Using GFP_ATOMIC instead of GFP_KERNEL to allocate bitmap memory in backing_dev_store Dongyun Liu
2023-11-30 15:37 ` Jens Axboe
2023-12-01 6:51 ` Dongyun Liu
2023-12-01 14:19 ` Jens Axboe
2023-12-01 15:28 ` Sergey Senozhatsky [this message]
2023-12-02 13:54 ` Dongyun Liu
2023-12-01 15:39 ` Sergey Senozhatsky
2023-12-02 15:50 ` Dongyun Liu
2023-12-03 1:23 ` Sergey Senozhatsky
2023-12-03 14:45 ` Dongyun Liu
2023-12-01 18:41 ` Minchan Kim
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