Hi all, This is the tenth revision of a patchset that adds to XFS kernel support for mapping multiple file logical blocks to the same physical block (reflink/deduplication). There shouldn't be any incompatible on-disk format changes, pending a thorough review of the patches within. NOTE: This patchset contains all the review fixes from the v9 posting, and no other changes. If you were in the middle of reviewing patches, you can continue from wherever you left off. The reflink implementation features a simple per-AG b+tree containing tuples of (physical block, blockcount, refcount) with the key being the physical block. Copy on Write (CoW) is implemented by creating a separate CoW extent mapping fork and using the existing delayed allocation mechanism to try to allocate as large of a replacement extent as possible before committing the new data to media. A CoW extent size hint allows administrators to influence the size of the replacement extents, and certain writes can be "promoted" to CoW when it would be advantageous to reduce fragmentation. The userspace interface to reflink and dedupe are the VFS FICLONE, FICLONERANGE, and FIDEDUPERANGE ioctls, which were previously private to btrfs. Next comes the reference count B+tree, which tracks the reference counts of shared extents (refcount > 1) and extents being used to stage a copy-on-write operation (refcount == 1). We define new log redo item pairs both for refcount updates and for inode fork updates; these plug into the deferred ops framework created for the reverse mapping patches. After that comes the reflink code, which handles the actual copy-on-write behavior that is required for block sharing; and connections to the VFS file ops for reflink, dedupe, and copy_file_range. At the very end of the patchset is a reimplementation of the swap extents code that uses reverse mapping and block mapping deferred ops to implement xfs_swap_extent for filesystems with reverse-mapping. The patches contained within are also available as git trees. The kernel patches[1] apply against Dave Chinner's for-next branch, and for user tools you'll want to use the xfsprogs dev branch[2]. I do not intend to mail out userspace patches until after the merge window and libxfs-apply resync happens. The clone group xfstests should all pass. This is an extraordinary way to eat your data. Enjoy! Comments and questions are, as always, welcome. --D [1] https://github.com/djwong/linux/tree/for-dave-for-4.9-8 [2] https://github.com/djwong/xfsprogs/tree/for-dave-for-4.9-8 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
