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Wed, 9 Dec 2020 14:36:11 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8A9215275D; Wed, 9 Dec 2020 14:36:07 +0000 (UTC) Date: Wed, 9 Dec 2020 09:36:06 -0500 From: Mike Snitzer To: Sergei Shtepa Cc: axboe@kernel.dk, johannes.thumshirn@wdc.com, koct9i@gmail.com, ming.lei@redhat.com, hare@suse.de, josef@toxicpanda.com, steve@sk2.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, pavel.tide@veeam.com Subject: Re: [PATCH 2/3] block: blk_interposer - sample Message-ID: <20201209143606.GA494@redhat.com> References: <1607518911-30692-1-git-send-email-sergei.shtepa@veeam.com> <1607518911-30692-3-git-send-email-sergei.shtepa@veeam.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1607518911-30692-3-git-send-email-sergei.shtepa@veeam.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 09 2020 at 8:01am -0500, Sergei Shtepa wrote: > This sample demonstrates how to use blk_interposer. > It show how to properly connect the interposer module to kernel, > and perform the simplest monitoring of the number of bio. > > Signed-off-by: Sergei Shtepa > --- > samples/blk_interposer/Makefile | 2 + > samples/blk_interposer/blk-interposer.c | 276 ++++++++++++++++++++++++ > 2 files changed, 278 insertions(+) > create mode 100644 samples/blk_interposer/Makefile > create mode 100644 samples/blk_interposer/blk-interposer.c > > diff --git a/samples/blk_interposer/Makefile b/samples/blk_interposer/Makefile > new file mode 100644 > index 000000000000..b11aefde2b1c > --- /dev/null > +++ b/samples/blk_interposer/Makefile > @@ -0,0 +1,2 @@ > +# SPDX-License-Identifier: GPL-2.0 > +obj-$(CONFIG_SAMPLE_BLK_INTERPOSER) += blk-interposer.o > diff --git a/samples/blk_interposer/blk-interposer.c b/samples/blk_interposer/blk-interposer.c > new file mode 100644 > index 000000000000..92b4c1fcf8f7 > --- /dev/null > +++ b/samples/blk_interposer/blk-interposer.c > @@ -0,0 +1,276 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +/* > + * Block layer interposer allow to interpose bio requests from kernel module. > + * This allows you to monitor requests, modify requests, add new request, > + * or even redirect requests to another devices. > + * > + * This sample demonstrates how to use blk_interposer. > + * It show how to properly connect the interposer module to kernel, > + * and perform the simplest monitoring of the number of bio. > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include > +#include > +#include > +#include > +#include > +#include > + > +int device_major = 8; > +int device_minor; > +int fmode = FMODE_READ | FMODE_WRITE; > + > +/* > + * Each interposer must have a common part in the form of the blk_interposer structure, > + * as well as its own unique data. > + */ > +struct my_interposer { > + /* > + * Common part of block device interposer. > + */ > + struct blk_interposer interposer; > + /* > + * Specific part for our interposer data. > + */ > + atomic_t counter; > +}; > + > +struct my_interposer my_ip; > + > +/** > + * blk_interposer_attach - Attach interposer to disk > + * @disk: target disk > + * @interposer: block device interposer > + */ > +static int blk_interposer_attach(struct gendisk *disk, struct blk_interposer *interposer) > +{ > + int ret = 0; > + > + /* > + * Stop disks queue processing. > + */ > + blk_mq_freeze_queue(disk->queue); > + blk_mq_quiesce_queue(disk->queue); > + > + /* > + * Check if the interposer is already busy. > + * The interposer will only connect if it is not busy. > + */ > + if (blk_has_interposer(disk)) { > + pr_info("The interposer is already busy.\n"); > + ret = -EBUSY; > + goto out; > + } > + > + /* > + * Attach the interposer. > + */ > + disk->interposer = interposer; > + /* > + * And while the queue is stopped, we can do something specific for our module. > + */ > + pr_info("Block device interposer attached successfully.\n"); > + > +out: > + /* > + * Resume disks queue processing > + */ > + blk_mq_unquiesce_queue(disk->queue); > + blk_mq_unfreeze_queue(disk->queue); > + > + return ret; > +} > + > +/** > + * blk_interposer_detach - Detach interposer from disk > + * @disk: target disk > + * @interposer: block device interposer > + */ > +static int blk_interposer_detach(struct gendisk *disk, struct blk_interposer *interposer) > +{ > + int ret = 0; > + > + if (WARN_ON(!disk)) > + return -EINVAL; > + > + /* > + * Stop disks queue processing. > + */ > + blk_mq_freeze_queue(disk->queue); > + blk_mq_quiesce_queue(disk->queue); > + > + /* > + * Check if the interposer is still available. > + */ > + if (!disk->interposer) { > + pr_info("The interposer is not available.\n"); > + return -ENOENT; > + goto out; > + } > + /* > + * Check if it is really our interposer. > + */ > + if (disk->interposer->ip_submit_bio != interposer->ip_submit_bio) { > + pr_info("The interposer found is not ours.\n"); > + return -EPERM; > + goto out; > + } > + > + /* > + * Detach interposer. > + */ > + disk->interposer = NULL; > + /* > + * And while the queue is stopped, we can do something specific for our module. > + */ > + pr_info("Block device interposer detached successfully.\n"); > + > +out: > + /* > + * Resume disks queue processing. > + */ > + blk_mq_unquiesce_queue(disk->queue); > + blk_mq_unfreeze_queue(disk->queue); > + > + return ret; > +} This attach and detach code needs to be elevated out of samples so that any future consumer of blk_interposer doesn't reinvent it. It is far too fundamental. The way you've proposed this be merged is very much unacceptable. Nacked-by: Mike Snitzer