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Message-ID: <20220217125901.GA3781@test-zns>
Date: Thu, 17 Feb 2022 18:29:01 +0530
From: Nitesh Shetty <nj.shetty@...sung.com>
To: Luis Chamberlain <mcgrof@...nel.org>
Cc: hch@....de, javier@...igon.com, chaitanyak@...dia.com,
linux-block@...r.kernel.org, linux-scsi@...r.kernel.org,
dm-devel@...hat.com, linux-nvme@...ts.infradead.org,
linux-fsdevel@...r.kernel.org, axboe@...nel.dk,
msnitzer@...hat.com, bvanassche@....org,
martin.petersen@...cle.com, hare@...e.de, kbusch@...nel.org,
Frederick.Knight@...app.com, osandov@...com,
lsf-pc@...ts.linux-foundation.org, djwong@...nel.org,
josef@...icpanda.com, clm@...com, dsterba@...e.com, tytso@....edu,
jack@...e.com, joshi.k@...sung.com, arnav.dawn@...sung.com,
nitheshshetty@...il.com, SelvaKumar S <selvakuma.s1@...sung.com>,
Alasdair Kergon <agk@...hat.com>,
Mike Snitzer <snitzer@...hat.com>,
Sagi Grimberg <sagi@...mberg.me>,
James Smart <james.smart@...adcom.com>,
Chaitanya Kulkarni <kch@...dia.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/10] block: Introduce queue limits for copy-offload
support
Thu, Feb 17, 2022 at 01:07:00AM -0800, Luis Chamberlain wrote:
> The subject says limits for copy-offload...
>
> On Mon, Feb 14, 2022 at 01:29:52PM +0530, Nitesh Shetty wrote:
> > Add device limits as sysfs entries,
> > - copy_offload (RW)
> > - copy_max_bytes (RW)
> > - copy_max_hw_bytes (RO)
> > - copy_max_range_bytes (RW)
> > - copy_max_range_hw_bytes (RO)
> > - copy_max_nr_ranges (RW)
> > - copy_max_nr_ranges_hw (RO)
>
> Some of these seem like generic... and also I see a few more max_hw ones
> not listed above...
>
queue_limits and sysfs entries are differently named.
All sysfs entries start with copy_* prefix. Also it makes easy to lookup
all copy sysfs.
For queue limits naming, I tried to following existing queue limit
convention (like discard).
> > --- a/block/blk-settings.c
> > +++ b/block/blk-settings.c
> > +/**
> > + * blk_queue_max_copy_sectors - set max sectors for a single copy payload
> > + * @q: the request queue for the device
> > + * @max_copy_sectors: maximum number of sectors to copy
> > + **/
> > +void blk_queue_max_copy_sectors(struct request_queue *q,
> > + unsigned int max_copy_sectors)
> > +{
> > + q->limits.max_hw_copy_sectors = max_copy_sectors;
> > + q->limits.max_copy_sectors = max_copy_sectors;
> > +}
> > +EXPORT_SYMBOL(blk_queue_max_copy_sectors);
>
> Please use EXPORT_SYMBOL_GPL() for all new things.
>
acked.
> Why is this setting both? The documentation does't seem to say.
> What's the point?
>
This function is used only by driver, while intializing request queue.
I will put this as part of description next time.
> > +
> > +/**
> > + * blk_queue_max_copy_range_sectors - set max sectors for a single range, in a copy payload
> > + * @q: the request queue for the device
> > + * @max_copy_range_sectors: maximum number of sectors to copy in a single range
> > + **/
> > +void blk_queue_max_copy_range_sectors(struct request_queue *q,
> > + unsigned int max_copy_range_sectors)
> > +{
> > + q->limits.max_hw_copy_range_sectors = max_copy_range_sectors;
> > + q->limits.max_copy_range_sectors = max_copy_range_sectors;
> > +}
> > +EXPORT_SYMBOL(blk_queue_max_copy_range_sectors);
>
> Same here.
>
> > +/**
> > + * blk_queue_max_copy_nr_ranges - set max number of ranges, in a copy payload
> > + * @q: the request queue for the device
> > + * @max_copy_nr_ranges: maximum number of ranges
> > + **/
> > +void blk_queue_max_copy_nr_ranges(struct request_queue *q,
> > + unsigned int max_copy_nr_ranges)
> > +{
> > + q->limits.max_hw_copy_nr_ranges = max_copy_nr_ranges;
> > + q->limits.max_copy_nr_ranges = max_copy_nr_ranges;
> > +}
> > +EXPORT_SYMBOL(blk_queue_max_copy_nr_ranges);
>
> Same.
>
> > +
> > /**
> > * blk_queue_max_write_same_sectors - set max sectors for a single write same
> > * @q: the request queue for the device
> > @@ -541,6 +592,14 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
> > t->max_segment_size = min_not_zero(t->max_segment_size,
> > b->max_segment_size);
> >
> > + t->max_copy_sectors = min(t->max_copy_sectors, b->max_copy_sectors);
> > + t->max_hw_copy_sectors = min(t->max_hw_copy_sectors, b->max_hw_copy_sectors);
> > + t->max_copy_range_sectors = min(t->max_copy_range_sectors, b->max_copy_range_sectors);
> > + t->max_hw_copy_range_sectors = min(t->max_hw_copy_range_sectors,
> > + b->max_hw_copy_range_sectors);
> > + t->max_copy_nr_ranges = min(t->max_copy_nr_ranges, b->max_copy_nr_ranges);
> > + t->max_hw_copy_nr_ranges = min(t->max_hw_copy_nr_ranges, b->max_hw_copy_nr_ranges);
> > +
> > t->misaligned |= b->misaligned;
> >
> > alignment = queue_limit_alignment_offset(b, start);
> > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> > index 9f32882ceb2f..9ddd07f142d9 100644
> > --- a/block/blk-sysfs.c
> > +++ b/block/blk-sysfs.c
> > @@ -212,6 +212,129 @@ static ssize_t queue_discard_zeroes_data_show(struct request_queue *q, char *pag
> > return queue_var_show(0, page);
> > }
> >
> > +static ssize_t queue_copy_offload_show(struct request_queue *q, char *page)
> > +{
> > + return queue_var_show(blk_queue_copy(q), page);
> > +}
> > +
> > +static ssize_t queue_copy_offload_store(struct request_queue *q,
> > + const char *page, size_t count)
> > +{
> > + unsigned long copy_offload;
> > + ssize_t ret = queue_var_store(©_offload, page, count);
> > +
> > + if (ret < 0)
> > + return ret;
> > +
> > + if (copy_offload && !q->limits.max_hw_copy_sectors)
> > + return -EINVAL;
>
>
> If the kernel schedules, copy_offload may still be true and
> max_hw_copy_sectors may be set to 0. Is that an issue?
>
This check ensures that, we dont enable offload if device doesnt support
offload. I feel it shouldn't be an issue.
> > +
> > + if (copy_offload)
> > + blk_queue_flag_set(QUEUE_FLAG_COPY, q);
> > + else
> > + blk_queue_flag_clear(QUEUE_FLAG_COPY, q);
>
> The flag may be set but the queue flag could be set. Is that an issue?
>
> > @@ -597,6 +720,14 @@ QUEUE_RO_ENTRY(queue_nr_zones, "nr_zones");
> > QUEUE_RO_ENTRY(queue_max_open_zones, "max_open_zones");
> > QUEUE_RO_ENTRY(queue_max_active_zones, "max_active_zones");
> >
> > +QUEUE_RW_ENTRY(queue_copy_offload, "copy_offload");
> > +QUEUE_RO_ENTRY(queue_copy_max_hw, "copy_max_hw_bytes");
> > +QUEUE_RW_ENTRY(queue_copy_max, "copy_max_bytes");
> > +QUEUE_RO_ENTRY(queue_copy_range_max_hw, "copy_max_range_hw_bytes");
> > +QUEUE_RW_ENTRY(queue_copy_range_max, "copy_max_range_bytes");
> > +QUEUE_RO_ENTRY(queue_copy_nr_ranges_max_hw, "copy_max_nr_ranges_hw");
> > +QUEUE_RW_ENTRY(queue_copy_nr_ranges_max, "copy_max_nr_ranges");
>
> Seems like you need to update Documentation/ABI/stable/sysfs-block.
>
acked.
> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > index efed3820cbf7..792e6d556589 100644
> > --- a/include/linux/blkdev.h
> > +++ b/include/linux/blkdev.h
> > @@ -254,6 +254,13 @@ struct queue_limits {
> > unsigned int discard_alignment;
> > unsigned int zone_write_granularity;
> >
> > + unsigned long max_hw_copy_sectors;
> > + unsigned long max_copy_sectors;
> > + unsigned int max_hw_copy_range_sectors;
> > + unsigned int max_copy_range_sectors;
> > + unsigned short max_hw_copy_nr_ranges;
> > + unsigned short max_copy_nr_ranges;
>
> Before limits start growing more.. I wonder if we should just
> stuff hw offload stuff to its own struct within queue_limits.
>
> Christoph?
>
> Luis
>
Yeah, would like to know community opinion on this.
-- Nitesh
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