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Subject[PATCH v5 0/6] block-layer interposer
Hi all.

I'm joyful to suggest the block-layer interposer (blk_interposer) v5.
blk_interposer allows to intercept bio requests, remap bio to another
devices or add new bios.

This patch series adds support blk_interposer for dm-linear.

In the first patch, I suggest the remap_and_filter.rst file.
Yes, Mike, it's probably too early for documentation, but maybe it will be
interesting for someone. In the documentation I tried to explain
the purpose of blk_interposer and what prospects it opens up.

The second patch adds the function blk_mq_is_queue_frozen(). It allows to
assert a queue state.

The third patch is dedicated to blk_interposer itself, which provides
the ability to intercept bio.

The fourth one adds support for blk_interposer from the device mapper.
Added ioctl DM_DEV_REMAP_CMD.

In the fifth - added the 'noexcl' option for dm-linear, which allows
to open the underlying block-device without the FMODE_EXCL mode.
This allows to create a dm device to which can redirect bio requests

The latest patch changes linear.rst with the description of the 'noexcl'
option that is added for dm-linear.

A little history of changes:

v5 - current patch set
* rebase for v5.11-rc7;
* patch set organization;
* fix defects in documentation;
* add some comments;
* change mutex names for better code readability;
* remove calling bd_unlink_disk_holder() for targets with non-exclusive
* change type for struct dm_remap_param from uint8_t to __u8.

v4 -
Mostly changes were made, due to Damien's comments:
* on the design of the code;
* by the patch set organization;
* bug with passing a wrong parameter to dm_get_device();
* description of the 'noexcl' parameter in the linear.rst.
Also added remap_and_filter.rst.

v3 -
In this version, I already suggested blk_interposer to apply to dm-linear.
Problems were solved:
* Interception of bio requests from a specific device on the disk, not
from the entire disk. To do this, we added the dm_interposed_dev
structure and an interval tree to store these structures.
* Implemented ioctl DM_DEV_REMAP_CMD. A patch with changes in the lvm2
project was sent to the team
* Added the 'noexcl' option for dm-linear, which allows you to open
the underlying block-device without FMODE_EXCL mode.

v2 -
I tried to suggest blk_interposer without using it in device mapper,
but with the addition of a sample of its use. It was then that I learned
about the maintainers' attitudes towards the samples directory :).

v1 -
This Hannes's patch can be considered as a starting point, since this is
where the interception mechanism and the term blk_interposer itself
appeared. It became clear that blk_interposer can be useful for
device mapper.

before v1 -
I tried to offer a rather cumbersome blk-filter and a monster-like
blk-snap module for creating snapshots.

Thank you to everyone who was able to take the time to review
the previous versions.
I hope that this time I achieved the required quality.


Sergei Shtepa (6):
docs: device-mapper: add remap_and_filter
block: add blk_mq_is_queue_frozen()
block: add blk_interposer
dm: new ioctl DM_DEV_REMAP_CMD
dm: add 'noexcl' option for dm-linear
docs: device-mapper: 'noexcl' option for dm-linear

.../admin-guide/device-mapper/index.rst | 1 +
.../admin-guide/device-mapper/linear.rst | 26 +-
.../device-mapper/remap_and_filter.rst | 132 ++++++
block/bio.c | 2 +
block/blk-core.c | 35 ++
block/blk-mq.c | 13 +
block/genhd.c | 86 ++++
drivers/md/dm-core.h | 20 +
drivers/md/dm-ioctl.c | 35 ++
drivers/md/dm-linear.c | 14 +-
drivers/md/dm-table.c | 14 +-
drivers/md/dm.c | 401 +++++++++++++++++-
drivers/md/dm.h | 2 +-
include/linux/blk-mq.h | 1 +
include/linux/blk_types.h | 6 +-
include/linux/device-mapper.h | 7 +
include/linux/genhd.h | 18 +
include/uapi/linux/dm-ioctl.h | 15 +-
18 files changed, 796 insertions(+), 32 deletions(-)
create mode 100644 Documentation/admin-guide/device-mapper/remap_and_filter.rst


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