*friendly FUSE maintainer ping* :-) On Mon, Jan 25, 2021 at 12:24 AM Richard Weinberger <rich...@nod.at> wrote: > > I'm happy to announce the first non-RFC version of this patch set. > Over the xmas holidays I found some time to experiment with various userspace > implementations of MTDs and gave the kernel side more fine-tuning. > > Rationale: > ---------- > > When working with flash devices a common task is emulating them to run various > tests or inspect dumps from real hardware. To achieve that we have plenty of > emulators in the MTD subsystem: mtdram, block2mtd, nandsim. > > Each of them implements an ad-hoc MTD and have various drawbacks. > Over the last years some developers tried to extend them but these attempts > often got rejected because they added just more adhoc feature instead of > addressing overall problems. > > MUSE is a novel approach to address the need of advanced MTD emulators. > Advanced means in this context supporting different (vendor specific) image > formats, different ways for fault injection (fuzzing) and recoding/replaying > IOs to emulate power cuts. > > The core goal of MUSE is having the complexity on the userspace side and > only a small MTD driver in kernelspace. > While playing with different approaches I realized that FUSE offers everything > we need. So MUSE is a little like CUSE except that it does not implement a > bare character device but an MTD. > > Notes: > ------ > > - OOB support is currently limited. Currently MUSE has no support for > processing > in- and out-band in the same MTD operation. It is good enough to make JFFS2 > happy. This limitation is because FUSE has no support more than one variable > length buffer in a FUSE request. > At least I didn’t find a good way to pass more than one buffer to a request. > Maybe FUSE folks can correct me. :-) > > - Every MTD read/write operation maps 1:1 to a MUSE_READ/WRITE opcode. > Since FUSE requests are not cheap, the amount of read/written bytes in a MTD > operation as a huge impact on the performance. Especially when NOR style > MTDs > are implemented in userspace a large writebufsize should be requested to > gain > good write performance. > On the other hand, MTD operations with lengths larger than writesize are > *not* > split up into multiple MUSE_READ/WRITE requests. This means that userspace > has to split them manually when doing power-cut emulation. > > - MUSE is not super fast. On my i5 workstation nandsim is almost twice as fast > as a NAND flash in userspace. But MUSE is still magnitudes faster than any > real world MTD out there. So it is good enough for the use cases I have in > mind. > > Changelog: > ---------- > > Changes since v2 (RFC): > - OOB support > - MUSE_READ/WRITE opcodes are no longer a min IO MTD unit > - MTD partitions support via mtdparts string > - More code cleanup > - Code rebased to 5.11-rc4 > > Changes since v1 (RFC): > - Rewrote IO path, fuse_direct_io() is no longer used. > Instead of cheating fuse_direct_io() use custom ops to implement > reading and writing. That way MUSE no longer needs a dummy file object > nor a fuse file object. > In MTD all IO is synchronous and operations on kernel buffers, this > makes IO processing simple for MUSE. > - Support for bad blocks. > - No more (ab)use of FUSE ops such as FUSE_FSYNC. > - Major code cleanup. > > This series can also be found at: > git://git.kernel.org/pub/scm/linux/kernel/git/rw/misc.git muse_v3 > > Richard Weinberger (8): > fuse: Export fuse_simple_request > fuse: Export IO helpers > fuse: Make cuse_parse_one a common helper > mtd: Add MTD_MUSE flag > mtd: Allow passing a custom cmdline to cmdline line parser > fuse: Add MUSE specific defines FUSE interface > fuse: Implement MUSE - MTD in userspace > MAINTAINERS: Add entry for MUSE > > Documentation/ABI/testing/sysfs-class-mtd | 8 + > MAINTAINERS | 7 + > drivers/mtd/parsers/cmdlinepart.c | 73 +- > fs/fuse/Kconfig | 15 + > fs/fuse/Makefile | 2 + > fs/fuse/cuse.c | 58 +- > fs/fuse/dev.c | 1 + > fs/fuse/file.c | 16 +- > fs/fuse/fuse_i.h | 18 + > fs/fuse/helper.c | 70 ++ > fs/fuse/muse.c | 1086 +++++++++++++++++++++ > include/linux/mtd/partitions.h | 2 + > include/uapi/linux/fuse.h | 76 ++ > include/uapi/mtd/mtd-abi.h | 1 + > 14 files changed, 1346 insertions(+), 87 deletions(-) > create mode 100644 fs/fuse/helper.c > create mode 100644 fs/fuse/muse.c > > -- > 2.26.2 >
-- Thanks, //richard
