bcache: a cache for arbitrary block devices using an SSD. Short overview: Bcache does both writethrough and writeback caching. It presents itself as a new block device, a bit like say md. You can cache an arbitrary number of block devices with a single cache device, and attach and detach things at runtime - it's quite flexible.
It's very fast. It uses a b+ tree for the index, along with a journal to coalesce index updates, and a bunch of other cool tricks like auxiliary binary search trees with software floating point keys for searching within btree nodes. CURRENT STATUS: Bcache is solid, production ready code. I think there's still a bug or two related to bcache + dm, but nothing I've been able to reproduce. I'm running it on this machine in writeback mode for awhile now - subjectively, it's just as good as running on an SSD. It's been running on various servers in production, I have no clue how many. This patch series is based on my block_stuff branch, available at git://evilpiepirate.org/~kent/linux-bcache.org http://evilpiepirate.org/git/linux-bcache.git/log/?h=block_stuff and that branch is in turn based on v3.5. CHANGES SINCE v14: Almost 500 lines of new code documentation, most of it high level design docs. Start at the top of bcache.h - most of the header files now start with some high level documentation, and alloc.c since it doesn't have its own header. Suggestions on what else to document would be most welcome. I think the high level design documentation is in pretty good shape (except perhaps for non btree metadata stuff), but I've started on function level documentation. So, if there's a function and you can't figure out wtf it does, please let me know. Incorporated Joe Perches' feedback. CHANGES SINCE v13: I lost the cover letter I was writing just as I was about to send out v14, and in a fit of frustration sent it out with just the shortlog. Anyways, v14 had all a ton of review feedback incorporated; if there's anything anyone pointed out that hasn't been fixed or responded to I probably missed it. Incorporated feedback from Tejun, Vivek, and Joe Perches'. Though it's quite possible I missed some bits. I also refactored a lot of the trickiest code; the refcounting and flow control in request.c (around request_write) in particular is massively improved, and I changed the way bio splits are refcounted, which is now much more consistent. The btree in memory cache code was also significantly improved. I rebased onto my patches for the generic block layer that make generic_make_request() take arbitrary sized bios, which cleaned up a lot of bcache code and let me delete like 400 lines of code from bcache. Merged in the moving garbage collector. It needs more work (needs generational garbage collection, rate limiting) but it does currently work. It's for flash only volumes, and ultimately for making bcache a full blown FTL. TODO/KNOWN ISSUES (Incomplete): * More documentation * My patch for adding human readable units to vsnprintf() isn't going to work because of gcc printf typechecking. Probably going to end up reverting that. The current code works fine, gcc just complains a lot. * I need to get better at responding to emails. Kent Overstreet (16): Revert "rw_semaphore: remove up/down_read_non_owner" Fix ratelimit macro to compile in c99 mode Export get_random_int() Export blk_fill_rwbs() Export __lockdep_no_validate__ Add human-readable units modifier to vsnprintf() Closures bcache: Generic utility code bcache: Documentation, and changes to generic code bcache: Superblock/initialization/sysfs code bcache: Core btree code bcache: Bset code (lookups within a btree node) bcache: Journalling bcache: Request, io and allocation code bcache: Writeback, copying garbage collection bcache: Debug and tracing code Documentation/ABI/testing/sysfs-block-bcache | 156 ++ Documentation/bcache.txt | 255 +++ drivers/char/random.c | 1 + drivers/md/Kconfig | 2 + drivers/md/Makefile | 1 + drivers/md/bcache/Kconfig | 41 + drivers/md/bcache/Makefile | 14 + drivers/md/bcache/alloc.c | 615 +++++++ drivers/md/bcache/bcache.h | 1142 ++++++++++++ drivers/md/bcache/bset.c | 1165 ++++++++++++ drivers/md/bcache/bset.h | 372 ++++ drivers/md/bcache/btree.c | 2508 ++++++++++++++++++++++++++ drivers/md/bcache/btree.h | 423 +++++ drivers/md/bcache/debug.c | 576 ++++++ drivers/md/bcache/debug.h | 54 + drivers/md/bcache/io.c | 136 ++ drivers/md/bcache/journal.c | 703 ++++++++ drivers/md/bcache/journal.h | 159 ++ drivers/md/bcache/movinggc.c | 245 +++ drivers/md/bcache/request.c | 1366 ++++++++++++++ drivers/md/bcache/request.h | 61 + drivers/md/bcache/stats.c | 245 +++ drivers/md/bcache/stats.h | 58 + drivers/md/bcache/super.c | 1992 ++++++++++++++++++++ drivers/md/bcache/sysfs.c | 812 +++++++++ drivers/md/bcache/sysfs.h | 91 + drivers/md/bcache/trace.c | 26 + drivers/md/bcache/util.c | 392 ++++ drivers/md/bcache/util.h | 606 +++++++ drivers/md/bcache/writeback.c | 405 +++++ include/linux/cgroup_subsys.h | 6 + include/linux/closure.h | 88 +- include/linux/ratelimit.h | 2 +- include/linux/rwsem.h | 10 + include/linux/sched.h | 4 + include/trace/events/bcache.h | 271 +++ kernel/fork.c | 4 + kernel/lockdep.c | 1 + kernel/rwsem.c | 16 + kernel/trace/blktrace.c | 1 + lib/closure.c | 26 +- lib/vsprintf.c | 24 +- 42 files changed, 15022 insertions(+), 53 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-block-bcache create mode 100644 Documentation/bcache.txt create mode 100644 drivers/md/bcache/Kconfig create mode 100644 drivers/md/bcache/Makefile create mode 100644 drivers/md/bcache/alloc.c create mode 100644 drivers/md/bcache/bcache.h create mode 100644 drivers/md/bcache/bset.c create mode 100644 drivers/md/bcache/bset.h create mode 100644 drivers/md/bcache/btree.c create mode 100644 drivers/md/bcache/btree.h create mode 100644 drivers/md/bcache/debug.c create mode 100644 drivers/md/bcache/debug.h create mode 100644 drivers/md/bcache/io.c create mode 100644 drivers/md/bcache/journal.c create mode 100644 drivers/md/bcache/journal.h create mode 100644 drivers/md/bcache/movinggc.c create mode 100644 drivers/md/bcache/request.c create mode 100644 drivers/md/bcache/request.h create mode 100644 drivers/md/bcache/stats.c create mode 100644 drivers/md/bcache/stats.h create mode 100644 drivers/md/bcache/super.c create mode 100644 drivers/md/bcache/sysfs.c create mode 100644 drivers/md/bcache/sysfs.h create mode 100644 drivers/md/bcache/trace.c create mode 100644 drivers/md/bcache/util.c create mode 100644 drivers/md/bcache/util.h create mode 100644 drivers/md/bcache/writeback.c create mode 100644 include/trace/events/bcache.h -- 1.7.7.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
