| Message ID | 1607518911-30692-3-git-send-email-sergei.shtepa@veeam.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: blk_interposer - Block Layer Interposer | expand |
On Wed, Dec 09 2020 at 8:01am -0500, Sergei Shtepa <sergei.shtepa@veeam.com> 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 <sergei.shtepa@veeam.com> > --- > 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 <linux/module.h> > +#include <linux/types.h> > +#include <linux/errno.h> > +#include <linux/blkdev.h> > +#include <linux/genhd.h> > +#include <linux/blk-mq.h> > + > +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 <snitzer@redhat.com>
The 12/09/2020 17:36, Mike Snitzer wrote: > On Wed, Dec 09 2020 at 8:01am -0500, > Sergei Shtepa <sergei.shtepa@veeam.com> 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 <sergei.shtepa@veeam.com> > > --- > > 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 <linux/module.h> > > +#include <linux/types.h> > > +#include <linux/errno.h> > > +#include <linux/blkdev.h> > > +#include <linux/genhd.h> > > +#include <linux/blk-mq.h> > > + > > +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 <snitzer@redhat.com> > Yes, but on the other hand, while the queue is suspended, the module can perform some other actions specific to it. And since the functions blk_mq_freeze_queue(), blk_mq_quiesce_queue(), blk_mq_unquiesce_queue() and blk_mq_unfreeze_queue() are public, the module creator can implement its module connection functionality regardless of whether we make the functions blk_interposer_attach() and blk_interposer_detach() in the kernel or not. I'll think about it and try to come up with a better solution.
On Thu, Dec 10 2020 at 10:54am -0500, Sergei Shtepa <sergei.shtepa@veeam.com> wrote: > The 12/09/2020 17:36, Mike Snitzer wrote: > > On Wed, Dec 09 2020 at 8:01am -0500, > > Sergei Shtepa <sergei.shtepa@veeam.com> 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 <sergei.shtepa@veeam.com> > > > --- > > > 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 <linux/module.h> > > > +#include <linux/types.h> > > > +#include <linux/errno.h> > > > +#include <linux/blkdev.h> > > > +#include <linux/genhd.h> > > > +#include <linux/blk-mq.h> > > > + > > > +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 <snitzer@redhat.com> > > > Yes, but on the other hand, while the queue is suspended, the module can perform > some other actions specific to it. > > And since the functions blk_mq_freeze_queue(), blk_mq_quiesce_queue(), > blk_mq_unquiesce_queue() and blk_mq_unfreeze_queue() are public, > the module creator can implement its module connection functionality regardless of > whether we make the functions blk_interposer_attach() and blk_interposer_detach() > in the kernel or not. > > I'll think about it and try to come up with a better solution. This practice of sprinkling code in samples/ subdir and getting a minimalist hook into the kernel (with no actual in-kernel consumer) is _not_ how we do things. I'm not well-versed on the samples/ subdir nor when it came into existence; but it should die in a fire! Mike
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 <linux/module.h> +#include <linux/types.h> +#include <linux/errno.h> +#include <linux/blkdev.h> +#include <linux/genhd.h> +#include <linux/blk-mq.h> + +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; +} + +/** + * blk_interposer_submit_bio - Interpose bio + * @interposer: block device interposer + * @bio: interposed bio + */ +static void blk_interposer_submit_bio(struct blk_interposer *interposer, struct bio *bio) +{ + struct my_interposer *ip = container_of(interposer, struct my_interposer, interposer); + + atomic_inc(&ip->counter); + if (atomic_read(&ip->counter) < 10) + pr_info("%s - %d", __func__, atomic_read(&ip->counter)); + else if (atomic_read(&ip->counter) == 10) + pr_info("%s the flooding of log has stopped", __func__); + + /* + * Here we can submit a new child bio requests before the original. + * If the new bio should not be interposed, set BIO_INTERPOSED flag. + */ + + /* + * We can resubmit the original bio or just add it to the current->bio_list. + * In the second case, we do not call submit_bio_checks() twice. + */ + bio_list_add(¤t->bio_list[0], bio); + + /* + * Here we can submit a new bio requests after the original, + * although I don't know how it might be useful. + */ + + /* + * All submitted bio will be just placed in the current->bio_list. + * We can't wait for the bio request to complete. + */ + + /* + * The function doesn't return anything, because it can only return BLK_QC_T_NONE. + */ +} + +static int __init blk_interposer_init(void) +{ + int ret = 0; + dev_t dev_id; + struct block_device *bdev; + + pr_info("Loading module\n"); + + pr_info("Tracking device: %d:%d\n", device_major, device_minor); + dev_id = MKDEV(device_major, device_minor); + + /* + * Open block device + */ + bdev = blkdev_get_by_dev(dev_id, fmode, &my_ip); + if (IS_ERR(bdev)) { + ret = PTR_ERR(bdev); + pr_err("Unable to open device [%d:%d]: blkdev_get_by_dev return %d\n", + MAJOR(dev_id), MINOR(dev_id), 0-ret); + return ret; + } + + /* + * Initialize block device interposer fields. + */ + my_ip.interposer.ip_submit_bio = blk_interposer_submit_bio; + + /* + * Initialize our interposer specific fields + */ + atomic_set(&my_ip.counter, 0); + + /* + * Attach interposer to disk + */ + ret = blk_interposer_attach(bdev->bd_disk, &my_ip.interposer); + if (ret) + pr_info("Failed to attach the block device interposer.\n"); + /* + * Close device + */ + blkdev_put(bdev, fmode); + + return ret; +} + +static void __exit blk_interposer_exit(void) +{ + int ret; + dev_t dev_id; + struct block_device *bdev; + + pr_info("Unloading module\n"); + + dev_id = MKDEV(device_major, device_minor); + + /* + * Open block device + */ + bdev = blkdev_get_by_dev(dev_id, fmode, &my_ip); + if (IS_ERR(bdev)) { + ret = PTR_ERR(bdev); + pr_err("Unable to open device [%d:%d]: blkdev_get_by_dev return %d\n", + MAJOR(dev_id), MINOR(dev_id), 0-ret); + return; + } + + /* + * Detach interposer from disk + */ + ret = blk_interposer_detach(bdev->bd_disk, &my_ip.interposer); + if (ret) + pr_info("Failed to detach the block device interposer.\n"); + /* + * Close device + */ + blkdev_put(bdev, fmode); + + /* + * The counter shows how much bio was interposed. + */ + pr_info("%d bio was interposed.\n", atomic_read(&my_ip.counter)); +} + +module_init(blk_interposer_init); +module_exit(blk_interposer_exit); + +MODULE_DESCRIPTION("Block Layer Interposer Sample kernel module"); +MODULE_AUTHOR("Veeam Software Group GmbH"); +MODULE_LICENSE("GPL"); + +module_param_named(device_major, device_major, int, 0644); +MODULE_PARM_DESC(device_major, "Tracking device major number"); +module_param_named(device_minor, device_minor, int, 0644); +MODULE_PARM_DESC(device_minor, "Tracking device minor number");
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 <sergei.shtepa@veeam.com> --- 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