Re: [RESEND PATCH v5 2/2] bio: add limit_bio_size sysfs

[Changheun Lee]

> On 3/16/21 12:44 AM, Changheun Lee wrote:
> > Add limit_bio_size block sysfs node to limit bio size.
> > Queue flag QUEUE_FLAG_LIMIT_BIO_SIZE will be set if limit_bio_size is set.
> > And bio max size will be limited by queue max sectors via
> > QUEUE_FLAG_LIMIT_BIO_SIZE set.
> > 
> > Signed-off-by: Changheun Lee <nanich.lee@xxxxxxxxxxx>
> > ---
> >  Documentation/ABI/testing/sysfs-block | 10 ++++++++++
> >  Documentation/block/queue-sysfs.rst   |  7 +++++++
> >  block/blk-sysfs.c                     |  3 +++
> >  3 files changed, 20 insertions(+)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
> > index e34cdeeeb9d4..86a7b15410cf 100644
> > --- a/Documentation/ABI/testing/sysfs-block
> > +++ b/Documentation/ABI/testing/sysfs-block
> > @@ -316,3 +316,13 @@ Description:
> >  		does not complete in this time then the block driver timeout
> >  		handler is invoked. That timeout handler can decide to retry
> >  		the request, to fail it or to start a device recovery strategy.
> > +
> > +What:		/sys/block/<disk>/queue/limit_bio_size
> > +Date:		Feb, 2021
> > +Contact:	Changheun Lee <nanich.lee@xxxxxxxxxxx>
> > +Description:
> > +		(RW) Toggle for set/clear QUEUE_FLAG_LIMIT_BIO_SIZE queue flag.
> > +		Queue flag QUEUE_FLAG_LIMIT_BIO_SIZE will be set if limit_bio_size
> > +		is set. And bio max size will be limited by queue max sectors.
> > +		QUEUE_FLAG_LIMIT_BIO_SIZE will be cleared if limit_bio_size is
> > +		cleard. And limit of bio max size will be cleard.
> > diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
> > index 2638d3446b79..cd371a821855 100644
> > --- a/Documentation/block/queue-sysfs.rst
> > +++ b/Documentation/block/queue-sysfs.rst
> > @@ -273,4 +273,11 @@ devices are described in the ZBC (Zoned Block Commands) and ZAC
> >  do not support zone commands, they will be treated as regular block devices
> >  and zoned will report "none".
> >  
> > +limit_bio_size (RW)
> > +-------------------
> > +This indicates QUEUE_FLAG_LIMIT_BIO_SIZE queue flag value. And
> > +QUEUE_FLAG_LIMIT_BIO_SIZE can be changed via set(1)/clear(0) this node.
> > +bio max size will be limited by queue max sectors via set this node. And
> > +limit of bio max size will be cleard via clear this node.
> > +
> >  Jens Axboe <jens.axboe@xxxxxxxxxx>, February 2009
> > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> > index b513f1683af0..840d97f427e6 100644
> > --- a/block/blk-sysfs.c
> > +++ b/block/blk-sysfs.c
> > @@ -288,6 +288,7 @@ QUEUE_SYSFS_BIT_FNS(nonrot, NONROT, 1);
> >  QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
> >  QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
> >  QUEUE_SYSFS_BIT_FNS(stable_writes, STABLE_WRITES, 0);
> > +QUEUE_SYSFS_BIT_FNS(limit_bio_size, LIMIT_BIO_SIZE, 0);
> >  #undef QUEUE_SYSFS_BIT_FNS
> >  
> >  static ssize_t queue_zoned_show(struct request_queue *q, char *page)
> > @@ -615,6 +616,7 @@ QUEUE_RW_ENTRY(queue_nonrot, "rotational");
> >  QUEUE_RW_ENTRY(queue_iostats, "iostats");
> >  QUEUE_RW_ENTRY(queue_random, "add_random");
> >  QUEUE_RW_ENTRY(queue_stable_writes, "stable_writes");
> > +QUEUE_RW_ENTRY(queue_limit_bio_size, "limit_bio_size");
> >  
> >  static struct attribute *queue_attrs[] = {
> >  	&queue_requests_entry.attr,
> > @@ -648,6 +650,7 @@ static struct attribute *queue_attrs[] = {
> >  	&queue_rq_affinity_entry.attr,
> >  	&queue_iostats_entry.attr,
> >  	&queue_stable_writes_entry.attr,
> > +	&queue_limit_bio_size_entry.attr,
> >  	&queue_random_entry.attr,
> >  	&queue_poll_entry.attr,
> >  	&queue_wc_entry.attr,
> 
> Has it been considered to introduce a function to set the BIO size limit
> instead of introducing a new sysfs attribute? See also
> blk_queue_max_hw_sectors().

A function to set has been not considered yet.
But sysfs attribute should be supported I think. Because it can be
different depending on each system environment including policy.

> 
> Thanks,
> 
> Bart.

Thanks,

Changheun Lee