Hi, everyone. About 1 years ago, we implemented the chunk tree recover function, but it has not been applied till now because that implementation need change the disk format. (http://marc.info/?l=linux-btrfs&m=129914269932543&w=2 http://marc.info/?l=linux-btrfs&m=130976668006281&w=2 http://marc.info/?l=linux-btrfs&m=129914269932543&w=2)
Recently, I reconsidered the implementation of this function, and found a new approach that needn't change the disk format. That is the external chunk tree backup, just like external journal device of ext4. The basic idea is: - specify a external file or device which is used to backup the chunk tree when mount. - When mount, compare the super block in the external file/device with the super block of the btrfs, if the checksum of the super block in the externel file/device is right, and the FS UUID and generation are the same as the fs, it means the chunk tree in the external file/device is valid, needn't rebuild it. Otherwise, we will rebuild the chunk tree in the external file/device according to the chunk tree of the fs. - When we allocate a new chunk, we will log the new chunk information into the external file/device - sync the external file/device when committing the transaction - If the chunk tree of the fs is corrupted, we use the information in the external file/device to recover it. By this way, we needn't change disk format and also needn't do a block device scan which need lots of time, and is very hard to find the start address and length of a chunk. Any comment for this idea? Thanks Miao -- 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
