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Date: Mon, 26 Jan 2015 12:57:53 -0500 From: Jeff Moyer <jmoyer@...hat.com> To: Ming Lei <ming.lei@...onical.com> Cc: linux-kernel@...r.kernel.org, Dave Kleikamp <dave.kleikamp@...cle.com>, Jens Axboe <axboe@...nel.dk>, Zach Brown <zab@...bo.net>, Christoph Hellwig <hch@...radead.org>, Maxim Patlasov <mpatlasov@...allels.com>, Andrew Morton <akpm@...ux-foundation.org>, Alexander Viro <viro@...iv.linux.org.uk>, Benjamin LaHaise <bcrl@...ck.org> Subject: Re: [PATCH v2 3/4] block: loop: introduce 'use_aio' sysfs file Ming Lei <ming.lei@...onical.com> writes: > So that users can control if kernel aio is used to submit I/O. How would a user know to choose aio or, um, /not/ aio? At the very least, documentation is required for this. I'd rather see the option disappear completely, though. Cheers, Jeff > > Signed-off-by: Ming Lei <ming.lei@...onical.com> > --- > drivers/block/loop.c | 33 +++++++++++++++++++++++++++++++++ > drivers/block/loop.h | 1 + > 2 files changed, 34 insertions(+) > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index d1f168b..47af456 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -659,6 +659,38 @@ static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf) > return sprintf(buf, "%s\n", partscan ? "1" : "0"); > } > > +static ssize_t loop_attr_do_show_use_aio(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + struct gendisk *disk = dev_to_disk(dev); > + struct loop_device *lo = disk->private_data; > + > + return sprintf(buf, "%s\n", lo->use_aio ? "1" : "0"); > +} > + > +ssize_t loop_attr_do_store_use_aio(struct device *dev, > + struct device_attribute *attr, const char *buf, > + size_t count) > +{ > + struct gendisk *disk = dev_to_disk(dev); > + struct loop_device *lo = disk->private_data; > + int err; > + unsigned long v; > + > + err = kstrtoul(buf, 10, &v); > + if (err < 0) > + return err; > + if (v) > + lo->use_aio = true; > + else > + lo->use_aio = false; > + return count; > +} > + > +static struct device_attribute loop_attr_use_aio = > + __ATTR(use_aio, S_IRUGO | S_IWUSR, loop_attr_do_show_use_aio, > + loop_attr_do_store_use_aio); > + > LOOP_ATTR_RO(backing_file); > LOOP_ATTR_RO(offset); > LOOP_ATTR_RO(sizelimit); > @@ -671,6 +703,7 @@ static struct attribute *loop_attrs[] = { > &loop_attr_sizelimit.attr, > &loop_attr_autoclear.attr, > &loop_attr_partscan.attr, > + &loop_attr_use_aio.attr, > NULL, > }; > > diff --git a/drivers/block/loop.h b/drivers/block/loop.h > index 301c27f..15049e9 100644 > --- a/drivers/block/loop.h > +++ b/drivers/block/loop.h > @@ -57,6 +57,7 @@ struct loop_device { > struct list_head write_cmd_head; > struct work_struct write_work; > bool write_started; > + bool use_aio; > int lo_state; > struct mutex lo_ctl_mutex; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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