On 4/16/21 8:02 PM, Jens Axboe wrote: > On 4/13/21 11:46 PM, Coly Li wrote: >> Hi Jens, >> >> This is the 2nd wave of bcache patches for Linux v5.13. This series are >> patches to use NVDIMM to store bcache journal, which is the first effort >> to support NVDIMM for bcache [EXPERIMENTAL]. >> >> All concerns from Linux v5.12 merge window are fixed, especially the >> data type defined in include/uapi/linux/bcache-nvm.h. And in this >> series, all the lists defined in bcache-nvm.h uapi file are stored and >> accessed directly on NVDIMM as memory objects. >> >> Intel developers Jianpeng Ma and Qiaowei Ren compose the initial code of >> nvm-pages, the related patches are, >> - bcache: initialize the nvm pages allocator >> - bcache: initialization of the buddy >> - bcache: bch_nvm_alloc_pages() of the buddy >> - bcache: bch_nvm_free_pages() of the buddy >> - bcache: get allocated pages from specific owner >> All the code depends on Linux libnvdimm and dax drivers, the bcache nvm- >> pages allocator can be treated as user of these two drivers. >> >> The nvm-pages allocator is a buddy-like allocator, which allocates size >> in power-of-2 pages from the NVDIMM namespace. User space tool 'bcache' >> has a new added '-M' option to format a NVDIMM namespace and register it >> via sysfs interface as a bcache meta device. The nvm-pages kernel code >> does a DAX mapping to map the whole namespace into system's memory >> address range, and allocating the pages to requestion like typical buddy >> allocator does. The major difference is nvm-pages allocator maintains >> the pages allocated to each requester by a owner list which stored on >> NVDIMM too. Owner list of different requester is tracked by a pre- >> defined UUID, all the pages tracked in all owner lists are treated as >> allocated busy pages and won't be initialized into buddy system after >> the system reboot. >> >> I modify the bcache code to recognize the nvm meta device feature, >> initialize journal on NVDIMM, and do journal I/Os on NVDIMM in the >> following patches, >> - bcache: add initial data structures for nvm pages >> - bcache: use bucket index to set GC_MARK_METADATA for journal buckets >> in bch_btree_gc_finish() >> - bcache: add BCH_FEATURE_INCOMPAT_NVDIMM_META into incompat feature set >> - bcache: initialize bcache journal for NVDIMM meta device >> - bcache: support storing bcache journal into NVDIMM meta device >> - bcache: read jset from NVDIMM pages for journal replay >> - bcache: add sysfs interface register_nvdimm_meta to register NVDIMM >> meta device >> - bcache: use div_u64() in init_owner_info() >> >> The bcache journal code may request a block of power-of-2 size pages >> from the nvm-pages allocator, normally it is a range of 256MB or 512MB >> continuous pages range. During meta data journaling, the in-memory jsets >> go into the calculated nvdimm pages location by kernel memcpy routine. >> So the journaling I/Os won't go into block device (e.g. SSD) anymore, >> the write and read for journal jsets happen on NVDIMM. >> >> The whole series is testing for a while and all addressed issues are >> verified to be fixed. Now it is time to consider this series as an >> initial code base of a commnity cooperation and have them in bcache >> upstream for future development. >> >> Thanks in advance for taking this. > > Applied, with 13/13 folded in. > Thank you for doing this. Coly Li
