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From:   Javier Gonzalez <javier@cnexlabs.com>
To:     =?utf-8?B?TWF0aWFzIEJqw7hybGluZw==?= <mb@lightnvm.io>
CC:     "Konopko, Igor J" <igor.j.konopko@intel.com>,
        Marcin Dziegielewski <marcin.dziegielewski@intel.com>,
        Hans Holmberg <hans.holmberg@cnexlabs.com>,
        Heiner Litz <hlitz@ucsc.edu>,
        Young Tack Tack Jin <youngtack.jin@circuitblvd.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lightnvm: limit get chunk meta request size
Thread-Topic: [PATCH] lightnvm: limit get chunk meta request size
Thread-Index: AQHUEdsSzTW28Ywxt0+HVRJbpGneyqR931SAgAABMACAAlttgA==
Date:   Thu, 5 Jul 2018 07:14:38 +0000
Message-ID: <FA6B99A4-5CDA-4F43-81B1-F05303F63EC1@cnexlabs.com>
References: <20180702080223.13214-1-mb@lightnvm.io>
 <C0B26672-CFD1-4058-A979-48341CD40F8D@cnexlabs.com>
 <dd3b8963-1f11-59a6-dc60-e0171687a727@lightnvm.io>
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> On 3 Jul 2018, at 21.14, Matias Bj=C3=B8rling <mb@lightnvm.io> wrote:
>=20
> On 07/03/2018 09:10 PM, Javier Gonzalez wrote:
>>> On 2 Jul 2018, at 10.02, Matias Bj=C3=B8rling <mb@lightnvm.io> =
wrote:
>>>=20
>>> For devices that does not specify a limit on its transfer size, the
>>> get_chk_meta command may send down a single I/O retrieving the full
>>> chunk metadata table. Resulting in large 2-4MB I/O requests. =
Instead,
>>> split up the I/Os to a maximum of 256KB and issue them separately to
>>> reduce memory requirements.
>>>=20
>>> Signed-off-by: Matias Bj=C3=B8rling <mb@lightnvm.io>
>>> ---
>>> drivers/nvme/host/lightnvm.c | 10 ++++++++--
>>> 1 file changed, 8 insertions(+), 2 deletions(-)
>>>=20
>>> diff --git a/drivers/nvme/host/lightnvm.c =
b/drivers/nvme/host/lightnvm.c
>>> index b9989717418d..3b644b0e9713 100644
>>> --- a/drivers/nvme/host/lightnvm.c
>>> +++ b/drivers/nvme/host/lightnvm.c
>>> @@ -583,7 +583,13 @@ static int nvme_nvm_get_chk_meta(struct nvm_dev =
*ndev,
>>> 	struct ppa_addr ppa;
>>> 	size_t left =3D nchks * sizeof(struct nvme_nvm_chk_meta);
>>> 	size_t log_pos, offset, len;
>>> -	int ret, i;
>>> +	int ret, i, max_len;
>>> +
>>> +	/*
>>> +	 * limit requests to maximum 256K to avoid issuing arbitrary =
large
>>> +	 * requests when the device does not specific a maximum transfer =
size.
>>> +	 */
>>> +	max_len =3D min_t(unsigned int, ctrl->max_hw_sectors << 9, 256 * =
1024);
>>>=20
>>> 	/* Normalize lba address space to obtain log offset */
>>> 	ppa.ppa =3D slba;
>>> @@ -596,7 +602,7 @@ static int nvme_nvm_get_chk_meta(struct nvm_dev =
*ndev,
>>> 	offset =3D log_pos * sizeof(struct nvme_nvm_chk_meta);
>>>=20
>>> 	while (left) {
>>> -		len =3D min_t(unsigned int, left, ctrl->max_hw_sectors =
<< 9);
>>> +		len =3D min_t(unsigned int, left, max_len);
>>>=20
>>> 		ret =3D nvme_get_log_ext(ctrl, ns, =
NVME_NVM_LOG_REPORT_CHUNK,
>>> 				dev_meta, len, offset);
>>> --
>>> 2.11.0
>> Is this a v2? I remember seeing this patch being posted before [1]. =
It
>> still looks good to me :)
>> [1] https://lkml.org/lkml/2018/6/12/466
>> Reviewed-by: Javier Gonz=C3=A1lez <javier@cnexlabs.com>
>=20
> I changed the title. Since it didn't touch pblk. Thanks.

Makes sense. Thanks!


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