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authorGao Xiang <gaoxiang25@huawei.com>2019-06-24 15:22:51 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-26 09:44:39 +0800
commitec8c24420501d4cf3ed495c4d026984194897276 (patch)
tree9ecde9f14e9b774cd311059f78e710afe756b816 /drivers/staging/erofs/Makefile
parentstaging: comedi: use dma_mmap_coherent for DMA-able buffer mmap (diff)
downloadlinux-dev-ec8c24420501d4cf3ed495c4d026984194897276.tar.xz
linux-dev-ec8c24420501d4cf3ed495c4d026984194897276.zip
staging: erofs: add compacted ondisk compression indexes
This patch introduces new compacted compression indexes. In contract to legacy compression indexes that each 4k logical cluster has an 8-byte index, compacted ondisk compression indexes will have amortized 2 bytes for each 4k logical cluster (compacted 2B) amortized 4 bytes for each 4k logical cluster (compacted 4B) In detail, several continuous clusters will be encoded in a compacted pack with cluster types, offsets, and one blkaddr at the end of the pack to leave 4-byte margin for better decoding performance, as illustrated below: _____________________________________________ |___@_____ encoded bits __________|_ blkaddr _| 0 . amortized * vcnt . . . . amortized * vcnt - 4 . . .___________________. |_type_|_clusterofs_| Note that compacted 2 / 4B should be aligned with 32 / 8 bytes in order to avoid each pack crossing page boundary. Reviewed-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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