* Boston, MA 021110-1307, USA.
*/
+/*
+ * Btrfs convert design:
+ *
+ * The overall design of btrfs convert is like the following:
+ *
+ * |<------------------Old fs----------------------------->|
+ * |<- used ->| |<- used ->| |<- used ->|
+ * ||
+ * \/
+ * |<---------------Btrfs fs------------------------------>|
+ * |<- Old data chunk ->|< new chunk (D/M/S)>|<- ODC ->|
+ * |<-Old-FE->| |<-Old-FE->|<- Btrfs extents ->|<-Old-FE->|
+ *
+ * ODC = Old data chunk, btrfs chunks containing old fs data
+ * Mapped 1:1 (logical address == device offset)
+ * Old-FE = file extents pointing to old fs.
+ *
+ * So old fs used space is (mostly) kept as is, while btrfs will insert
+ * its chunk (Data/Meta/Sys) into large enough free space.
+ * In this way, we can create different profiles for metadata/data for
+ * converted fs.
+ *
+ * We must reserve and relocate 3 ranges for btrfs:
+ * * [0, 1M) - area never used for any data except the first
+ * superblock
+ * * [btrfs_sb_offset(1), +64K) - 1st superblock backup copy
+ * * [btrfs_sb_offset(2), +64K) - 2nd, dtto
+ *
+ * Most work is spent handling corner cases around these reserved ranges.
+ *
+ * Detailed workflow is:
+ * 1) Scan old fs used space and calculate data chunk layout
+ * 1.1) Scan old fs
+ * We can a map used space of old fs
+ *
+ * 1.2) Calculate data chunk layout - this is the hard part
+ * New data chunks must meet 3 conditions using result fomr 1.1
+ * a. Large enough to be a chunk
+ * b. Doesn't intersect reserved ranges
+ * c. Covers all the remaining old fs used space
+ *
+ * NOTE: This can be simplified if we don't need to handle backup supers
+ *
+ * 1.3) Calculate usable space for new btrfs chunks
+ * Btrfs chunk usable space must meet 3 conditions using result from 1.2
+ * a. Large enough to be a chunk
+ * b. Doesn't intersect reserved ranges
+ * c. Doesn't cover any data chunks in 1.1
+ *
+ * 2) Create basic btrfs filesystem structure
+ * Initial metadata and sys chunks are inserted in the first availabe
+ * space found in step 1.3
+ * Then insert all data chunks into the basic btrfs
+ *
+ * 3) Create convert image
+ * We need to relocate reserved ranges here.
+ * After this step, the convert image is done, and we can use the image
+ * as reflink source to create old files
+ *
+ * 4) Iterate old fs to create files
+ * We just reflink file extents from old fs to newly created files on
+ * btrfs.
+ */
+
#include "kerncompat.h"
#include <stdio.h>