Re: [PATCH] lightnvm: limit get chunk meta request size

[Matias BjÃrling]

On 07/03/2018 09:10 PM, Javier Gonzalez wrote:
> > On 2 Jul 2018, at 10.02, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> >
> > 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.
> >
> > Signed-off-by: Matias BjÃrling <mb@xxxxxxxxxxx>
> > ---
> > drivers/nvme/host/lightnvm.c | 10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > 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 = 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 = min_t(unsigned int, ctrl->max_hw_sectors << 9, 256 * 1024);
> >
> > 	/* Normalize lba address space to obtain log offset */
> > 	ppa.ppa = slba;
> > @@ -596,7 +602,7 @@ static int nvme_nvm_get_chk_meta(struct nvm_dev *ndev,
> > 	offset = log_pos * sizeof(struct nvme_nvm_chk_meta);
> >
> > 	while (left) {
> > -		len = min_t(unsigned int, left, ctrl->max_hw_sectors << 9);
> > +		len = min_t(unsigned int, left, max_len);
> >
> > 		ret = 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 GonzÃlez <javier@xxxxxxxxxxxx>

I changed the title. Since it didn't touch pblk. Thanks.