The following companies have contributed and/or contribute to Btrfs (sorted alphabetically):

Statistics

Version	Contributors	SLOC	Raw lines	Patches	Diffstat
4.1	24	86683	113825	119	+2411 -1058
4.2	19	87064	114360	119	+2392 -1800
4.3	23	87513	115146	74	+1516 -730
4.4	26	88592	116891	138	+3071 -1304
4.5	26	90756	119092	127	+4368 -1461

Legend:

Files: fs/btrfs/*.[ch], include/uapi/linux/btrfs.h
Version: mainline version
Contributors: number of people that sent patches that modified Files, direct btrfs development or originating from other tree-wide changes
SLOC: lines of code, http://dwheeler.com/sloccount/ (generated by version 2.26)
Raw lines: counted by wc -l over Files
Patches: number of patches from Contributors
Diffstat: lines added and deleted in Files

Statistics for 3.x series

Version	Contributors	SLOC	Raw lines	Patches
3.0	25	48665	65192	127
3.1	24	48647	65248	107
3.2	28	51574	69552	184
3.3	24	56216	75485	131
3.4	23	57865	77671	118
3.5	19	59683	79983	108
3.6	24	65894	88123	104
3.7	29	67348	90171	151
3.8	23	70289	93916	161
3.9	29	73414	98602	162
3.10	21	74449	99980	134
3.11	19	74875	100657	100
3.12	29	76265	102068	158
3.13	24	77532	102120	125
3.14	25	79879	105081	171
3.15	26	80308	105556	152
3.16	28	82292	107794	137
3.17	17	82625	108304	44
3.18	23	83910	109855	149
3.19	17	85420	111980	82

Version	Contributors	SLOC	Raw lines	Patches
2.6.30	21	33866	45377	71
2.6.31	18	38853	51693	68
2.6.32	14	40239	53515	95
2.6.33	17	40436	53806	45
2.6.34	17	41128	54715	54
2.6.35	12	43042	57082	50
2.6.36	3	43044	57088	6
2.6.37	16	44809	59491	83
2.6.38	22	46601	61980	90
2.6.39	25	47234	62859	146