Hi all.
I'm joyful to suggest the block-layer interposer (blk_interposer) v6.
blk_interposer allows to intercept bio requests, remap bio to another
devices or add new bios.
This series of patches adds the ability to use blk_interposer for
any dm-target using the DM_INTERPOSED_FLAG flag.
The first patch adds the function blk_mq_is_queue_frozen(). It allows to
assert a queue state.
The second patch is dedicated to blk_interposer itself, which provides
the ability to intercept bio.
The third one adds support for blk_interposer from the device mapper.
The fourth patch adds the DM_INTERPOSED_FLAG flag. When this flag is
applied with the ioctl DM_TABLE_LOAD_CMD, the underlying devices are
opened without the FMODE_EXCL flag and connected via blk_interposer.
Changes:
v6 - current patch set
* designed for 5.12;
* thanks to the new design of the bio structure in v5.12, it is
possible to perform interception not for the entire disk, but
for each block device;
* instead of the new ioctl DM_DEV_REMAP_CMD and the 'noexcl' option,
the DM_INTERPOSED_FLAG flag for the ioctl DM_TABLE_LOAD_CMD is
applied.
v5 - https://patchwork.kernel.org/project/linux-block/cover/1612881028-7878-1-git-send-email-sergei.shtepa@xxxxxxxxx/
* 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
flag;
* change type for struct dm_remap_param from uint8_t to __u8.
v4 - https://patchwork.kernel.org/project/linux-block/cover/1612367638-3794-1-git-send-email-sergei.shtepa@xxxxxxxxx/
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 - https://patchwork.kernel.org/project/linux-block/cover/1611853955-32167-1-git-send-email-sergei.shtepa@xxxxxxxxx/
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 lvm-devel@xxxxxxxxxx.
* Added the 'noexcl' option for dm-linear, which allows you to open
the underlying block-device without FMODE_EXCL mode.
v2 - https://patchwork.kernel.org/project/linux-block/cover/1607518911-30692-1-git-send-email-sergei.shtepa@xxxxxxxxx/
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 - https://lwn.net/ml/linux-block/20201119164924.74401-1-hare@xxxxxxx/
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 - https://patchwork.kernel.org/project/linux-block/cover/1603271049-20681-1-git-send-email-sergei.shtepa@xxxxxxxxx/
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.
Thanks,
Sergei.
Sergei Shtepa (4):
block: add blk_mq_is_queue_frozen()
block: add blk_interposer
dm: introduce dm-interposer
dm: add DM_INTERPOSED_FLAG
block/bio.c | 2 +
block/blk-core.c | 36 +++++
block/blk-mq.c | 12 ++
block/genhd.c | 93 ++++++++++++
drivers/md/Makefile | 2 +-
drivers/md/dm-core.h | 6 +
drivers/md/dm-interposer.c | 258 ++++++++++++++++++++++++++++++++++
drivers/md/dm-interposer.h | 40 ++++++
drivers/md/dm-ioctl.c | 9 ++
drivers/md/dm-table.c | 115 +++++++++++++--
drivers/md/dm.c | 38 +++--
include/linux/blk-mq.h | 1 +
include/linux/blk_types.h | 4 +
include/linux/blkdev.h | 17 +++
include/linux/device-mapper.h | 1 +
include/uapi/linux/dm-ioctl.h | 6 +
16 files changed, 618 insertions(+), 22 deletions(-)
create mode 100644 drivers/md/dm-interposer.c
create mode 100644 drivers/md/dm-interposer.h
--
2.20.1
