From: Manuel Bentele <development@xxxxxxxxxxxxxxxxx> Hi Regarding to the following discussion [1] on the mailing list I show you the result of my work as announced at the end of the discussion [2]. The discussion was about the project topic of how to implement the reading/writing of QCOW2 in the kernel. The project focuses on an read-only in-kernel QCOW2 implementation to increase the read/write performance and tries to avoid nbd. Furthermore, the project is part of a project series to develop a in-kernel network boot infrastructure that has no need for any user space interaction (e.g. nbd) anymore. During the discussion, it turned out that the implementation as device mapper target is not applicable. The device mapper stacks different functionality such as compression or encryption on multiple block device layers whereas an implementation for the QCOW2 container format provides these functionalities on one block device layer. Using FUSE is also not possible due to performance reasons and user space interaction. Therefore, I propose the extension of the loop device module. I created a new file format subsystem which is part of the loop device module. The file format subsystem abstracts the direct file access and provides an driver API to implement various disk file formats such as QCOW2, VDI and VMDK. File format drivers are implemented as kernel modules and can be registered by the file format subsystem. The patch series contains documentation for the file format subsystem and the loop device module, too. Also, it provides a default RAW file format driver and a read-only QCOW2 driver. The RAW file format driver is based on the file specific parts of the existing loop device implementation and preserves the default behaviour of a loop device. More specific information can be found in the commit logs of the following patches. Regards, Manuel [1] https://www.spinics.net/lists/linux-block/msg39538.html [2] https://www.spinics.net/lists/linux-block/msg40479.html Manuel Bentele (5): block: loop: add file format subsystem for loop devices doc: admin-guide: add loop block device documentation doc: driver-api: add loop file format subsystem API documentation block: loop: add QCOW2 loop file format driver (read-only) doc: admin-guide: add QCOW2 file format to loop device documentation Documentation/admin-guide/blockdev/index.rst | 1 + Documentation/admin-guide/blockdev/loop.rst | 85 ++ Documentation/driver-api/index.rst | 1 + Documentation/driver-api/loop-file-fmt.rst | 137 +++ arch/alpha/configs/defconfig | 1 + arch/arc/configs/axs103_defconfig | 1 + arch/arc/configs/axs103_smp_defconfig | 1 + arch/arm/configs/am200epdkit_defconfig | 1 + arch/arm/configs/aspeed_g4_defconfig | 1 + arch/arm/configs/aspeed_g5_defconfig | 1 + arch/arm/configs/assabet_defconfig | 1 + arch/arm/configs/at91_dt_defconfig | 1 + 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arch/sparc/configs/sparc64_defconfig | 1 + arch/um/configs/i386_defconfig | 1 + arch/um/configs/x86_64_defconfig | 1 + arch/unicore32/configs/defconfig | 1 + arch/x86/configs/i386_defconfig | 1 + arch/x86/configs/x86_64_defconfig | 1 + arch/xtensa/configs/audio_kc705_defconfig | 1 + arch/xtensa/configs/cadence_csp_defconfig | 1 + arch/xtensa/configs/generic_kc705_defconfig | 1 + arch/xtensa/configs/nommu_kc705_defconfig | 1 + arch/xtensa/configs/smp_lx200_defconfig | 1 + arch/xtensa/configs/virt_defconfig | 1 + drivers/block/Kconfig | 73 +- drivers/block/Makefile | 4 +- drivers/block/loop/Kconfig | 93 ++ drivers/block/loop/Makefile | 13 + drivers/block/{ => loop}/cryptoloop.c | 2 +- drivers/block/loop/loop_file_fmt.c | 328 ++++++ drivers/block/loop/loop_file_fmt.h | 351 +++++++ drivers/block/loop/loop_file_fmt_qcow_cache.c | 218 ++++ drivers/block/loop/loop_file_fmt_qcow_cache.h | 51 + .../block/loop/loop_file_fmt_qcow_cluster.c | 270 +++++ .../block/loop/loop_file_fmt_qcow_cluster.h | 23 + drivers/block/loop/loop_file_fmt_qcow_main.c | 945 ++++++++++++++++++ drivers/block/loop/loop_file_fmt_qcow_main.h | 417 ++++++++ drivers/block/loop/loop_file_fmt_raw.c | 449 +++++++++ drivers/block/{loop.c => loop/loop_main.c} | 567 ++++------- drivers/block/{loop.h => loop/loop_main.h} | 14 +- include/uapi/linux/loop.h | 14 +- 248 files changed, 3861 insertions(+), 422 deletions(-) create mode 100644 Documentation/admin-guide/blockdev/loop.rst create mode 100644 Documentation/driver-api/loop-file-fmt.rst create mode 100644 drivers/block/loop/Kconfig create mode 100644 drivers/block/loop/Makefile rename drivers/block/{ => loop}/cryptoloop.c (99%) create mode 100644 drivers/block/loop/loop_file_fmt.c create mode 100644 drivers/block/loop/loop_file_fmt.h create mode 100644 drivers/block/loop/loop_file_fmt_qcow_cache.c create mode 100644 drivers/block/loop/loop_file_fmt_qcow_cache.h create mode 100644 drivers/block/loop/loop_file_fmt_qcow_cluster.c create mode 100644 drivers/block/loop/loop_file_fmt_qcow_cluster.h create mode 100644 drivers/block/loop/loop_file_fmt_qcow_main.c create mode 100644 drivers/block/loop/loop_file_fmt_qcow_main.h create mode 100644 drivers/block/loop/loop_file_fmt_raw.c rename drivers/block/{loop.c => loop/loop_main.c} (86%) rename drivers/block/{loop.h => loop/loop_main.h} (92%) -- 2.23.0
