WARNING: 'an union' may be misspelled - perhaps 'a union'?
#18: 
Add a new (struct sock)sk_freeptr field, in an union
                                            ^^^^^^^^

CHECK: Alignment should match open parenthesis
#115: FILE: net/core/sock.c:4204:
+		prot->slab = kmem_cache_create(prot->name, prot->obj_size,
+					&args,

WARNING: line length of 82 exceeds 80 columns
#143: FILE: net/ipv6/tcp_ipv6.c:2336:
+					   tcp.inet_conn.icsk_inet.sk.sk_freeptr),

total: 0 errors, 2 warnings, 1 checks, 68 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

Commit 9407f090ead6 ("tcp: reduce tcp sockets size by one cache line") has style problems, please review.

NOTE: Ignored message types: ALLOC_SIZEOF_STRUCT BAD_REPORTED_BY_LINK CAMELCASE COMMIT_LOG_LONG_LINE FILE_PATH_CHANGES GIT_COMMIT_ID MACRO_ARG_REUSE NO_AUTHOR_SIGN_OFF

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.
total: 0 errors, 2 warnings, 1 checks, 68 lines checked