This aims to fix write hole issue on btrfs raid5/6 setup by adding a separate disk as a journal (aka raid5/6 log), so that after unclean shutdown we can make sure data and parity are consistent on the raid array by replaying the journal.
The idea and the code are similar to the write-through mode of md raid5-cache, so ppl(partial parity log) is also feasible to implement. (If you've been familiar with md, you may find this patch set is boring to read...) Patch 1-3 are about adding a log disk, patch 5-8 are the main part of the implementation, the rest patches are improvements and bugfixes, eg. readahead for recovery, checksum. Two btrfs-progs patches are required to play with this patch set, one is to enhance 'btrfs device add' to add a disk as raid5/6 log with the option '-L', the other is to teach 'btrfs-show-super' to show %journal_tail. This is currently based on 4.12-rc3. The patch set is tagged with RFC, and comments are always welcome, thanks. Known limitations: - Deleting a log device is not implemented yet. Liu Bo (14): Btrfs: raid56: add raid56 log via add_dev v2 ioctl Btrfs: raid56: do not allocate chunk on raid56 log Btrfs: raid56: detect raid56 log on mount Btrfs: raid56: add verbose debug Btrfs: raid56: add stripe log for raid5/6 Btrfs: raid56: add reclaim support Btrfs: raid56: load r5log Btrfs: raid56: log recovery Btrfs: raid56: add readahead for recovery Btrfs: raid56: use the readahead helper to get page Btrfs: raid56: add csum support Btrfs: raid56: fix error handling while adding a log device Btrfs: raid56: initialize raid5/6 log after adding it Btrfs: raid56: maintain IO order on raid5/6 log fs/btrfs/ctree.h | 16 +- fs/btrfs/disk-io.c | 16 + fs/btrfs/ioctl.c | 48 +- fs/btrfs/raid56.c | 1429 ++++++++++++++++++++++++++++++++++----- fs/btrfs/raid56.h | 82 +++ fs/btrfs/transaction.c | 2 + fs/btrfs/volumes.c | 56 +- fs/btrfs/volumes.h | 7 +- include/uapi/linux/btrfs.h | 3 + include/uapi/linux/btrfs_tree.h | 4 + 10 files changed, 1487 insertions(+), 176 deletions(-) -- 2.9.4 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html