Hi, kernel is 5.10.2
cp --reflink hi hi2 This results in two EXTENT_DATA items with different offsets, therefore I think the data is duplicated in the leaf? Correct? Is it expected? item 9 key (257 EXTENT_DATA 0) itemoff 15673 itemsize 53 generation 435179 type 0 (inline) inline extent data size 32 ram_bytes 174 compression 3 (zstd) ... item 13 key (258 EXTENT_DATA 0) itemoff 15364 itemsize 53 generation 435179 type 0 (inline) inline extent data size 32 ram_bytes 174 compression 3 (zstd) The entire file tree containing only these two files follows: file tree key (394 ROOT_ITEM 0) leaf 26442252288 items 14 free space 15014 generation 435212 owner 394 leaf 26442252288 flags 0x1(WRITTEN) backref revision 1 item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160 generation 435123 transid 435212 size 10 nbytes 0 block group 0 mode 40755 links 1 uid 1000 gid 1000 rdev 0 sequence 5267 flags 0x0(none) atime 1608689569.708325037 (2020-12-22 19:12:49) ctime 1608694856.721370147 (2020-12-22 20:40:56) mtime 1608694856.721370147 (2020-12-22 20:40:56) otime 1608689569.708325037 (2020-12-22 19:12:49) item 1 key (256 INODE_REF 256) itemoff 16111 itemsize 12 index 0 namelen 2 name: .. item 2 key (256 DIR_ITEM 432062026) itemoff 16079 itemsize 32 location key (257 INODE_ITEM 0) type FILE transid 435124 data_len 0 name_len 2 name: hi item 3 key (256 DIR_ITEM 4216900732) itemoff 16046 itemsize 33 location key (258 INODE_ITEM 0) type FILE transid 435196 data_len 0 name_len 3 name: hi2 item 4 key (256 DIR_INDEX 2) itemoff 16014 itemsize 32 location key (257 INODE_ITEM 0) type FILE transid 435124 data_len 0 name_len 2 name: hi item 5 key (256 DIR_INDEX 4) itemoff 15981 itemsize 33 location key (258 INODE_ITEM 0) type FILE transid 435196 data_len 0 name_len 3 name: hi2 item 6 key (257 INODE_ITEM 0) itemoff 15821 itemsize 160 generation 435124 transid 435212 size 174 nbytes 174 block group 0 mode 100644 links 1 uid 1000 gid 1000 rdev 0 sequence 19 flags 0x0(none) atime 1608689574.394444809 (2020-12-22 19:12:54) ctime 1608694856.721370147 (2020-12-22 20:40:56) mtime 1608692923.231038818 (2020-12-22 20:08:43) otime 1608689574.394444809 (2020-12-22 19:12:54) item 7 key (257 INODE_REF 256) itemoff 15809 itemsize 12 index 2 namelen 2 name: hi item 8 key (257 XATTR_ITEM 3817753667) itemoff 15726 itemsize 83 location key (0 UNKNOWN.0 0) type XATTR transid 435124 data_len 37 name_len 16 name: security.selinux data unconfined_u:object_r:unlabeled_t:s0 item 9 key (257 EXTENT_DATA 0) itemoff 15673 itemsize 53 generation 435179 type 0 (inline) inline extent data size 32 ram_bytes 174 compression 3 (zstd) item 10 key (258 INODE_ITEM 0) itemoff 15513 itemsize 160 generation 435196 transid 435196 size 174 nbytes 174 block group 0 mode 100644 links 1 uid 1000 gid 1000 rdev 0 sequence 34 flags 0x0(none) atime 1608693921.97510335 (2020-12-22 20:25:21) ctime 1608693921.97510335 (2020-12-22 20:25:21) mtime 1608693921.97510335 (2020-12-22 20:25:21) otime 1608693921.97510335 (2020-12-22 20:25:21) item 11 key (258 INODE_REF 256) itemoff 15500 itemsize 13 index 4 namelen 3 name: hi2 item 12 key (258 XATTR_ITEM 3817753667) itemoff 15417 itemsize 83 location key (0 UNKNOWN.0 0) type XATTR transid 435196 data_len 37 name_len 16 name: security.selinux data unconfined_u:object_r:unlabeled_t:s0 item 13 key (258 EXTENT_DATA 0) itemoff 15364 itemsize 53 generation 435179 type 0 (inline) inline extent data size 32 ram_bytes 174 compression 3 (zstd) total bytes 31005392896 bytes used 20153282560 -- Chris Murphy