[PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Alejandro Colomar]

Hi all,

I simplified some xxxof() macros,
by adding a new macro memberof(),
which implements a common operation in many of them.

I also splitted many of those macros into tiny headers,
since I noticed that touching those headers implied
recompiling almost the whole kernel.

Hopefully after this patch there will be less
things to recompile after touching one of those.

Having simpler headers means that now one can
include one of those without pulling too much stuff
that might break other stuff.

I removed some unnecessary casts too.

Every few commits in this series
and of course after the last commit
I rebuilt the kernel and run for a while with it without any problems.

Please note that I have written very few kernel code
and for example some files wouldn't let me include some of these files,
so I didn't change those.

What I mean is that,
even though this is super obvious and shouldn't break stuff,
and I'm not new to C,
I'm quite new to the kernel,
and ask that reviewers take deep look, please.


In the first and second commits
I changed a lot of stuff in many parts,
and that's why I CCd so many people (also in this cover letter).
However, to avoid spamming,
and since it would be a nightmare to
find all the relevant people affected in so many different areas,
I only CCd in 01, 02 and in the cover letter.
If anyone is interested in reading the full patch set,
I sent it to the LKML.


Thanks,
Alex


Alejandro Colomar (17):
  linux/container_of.h: Add memberof(T, m)
  Use memberof(T, m) instead of explicit NULL dereference
  Replace some uses of memberof() by its wrappers
  linux/memberof.h: Move memberof() to separate header
  linux/typeof_member.h: Move typeof_member() to a separate header
  Simplify sizeof(typeof_member()) to sizeof_field()
  linux/NULL.h: Move NULL to a separate header
  linux/offsetof.h: Move offsetof(T, m) to a separate header
  linux/offsetof.h: Implement offsetof() in terms of memberof()
  linux/container_of.h: Implement container_of_safe() in terms of
    container_of()
  linux/container_of.h: Cosmetic
  linux/container_of.h: Remove unnecessary cast to (void *)
  linux/sizeof_field.h: Move sizeof_field(T, m) to a separate header
  include/linux/: Include a smaller header if just for NULL
  linux/offsetofend.h: Move offsetofend(T, m) to a separate header
  linux/array_size.h: Move ARRAY_SIZE(arr) to a separate header
  include/: Include <linux/array_size.h> for ARRAY_SIZE()

 arch/x86/include/asm/bootparam_utils.h        |  3 +-
 arch/x86/kernel/signal_compat.c               |  5 ++--
 drivers/gpu/drm/i915/i915_sw_fence.c          |  1 +
 drivers/gpu/drm/i915/i915_utils.h             |  5 ++--
 drivers/gpu/drm/i915/intel_runtime_pm.h       |  3 +-
 drivers/net/ethernet/emulex/benet/be.h        | 10 +++----
 drivers/net/ethernet/i825xx/ether1.c          |  7 +++--
 drivers/platform/x86/wmi.c                    |  3 +-
 drivers/scsi/be2iscsi/be.h                    | 12 ++++----
 drivers/scsi/be2iscsi/be_cmds.h               |  5 +++-
 fs/btrfs/ctree.h                              |  5 ++--
 fs/proc/inode.c                               |  1 +
 include/acpi/actypes.h                        |  4 ++-
 include/crypto/internal/blake2b.h             |  1 +
 include/crypto/internal/blake2s.h             |  1 +
 include/crypto/internal/chacha.h              |  1 +
 include/drm/drm_mipi_dbi.h                    |  1 +
 include/drm/drm_mode_object.h                 |  1 +
 include/kunit/test.h                          |  1 +
 include/linux/NULL.h                          | 10 +++++++
 include/linux/arm_ffa.h                       |  1 +
 include/linux/array_size.h                    | 15 ++++++++++
 include/linux/blk_types.h                     |  1 +
 include/linux/can/core.h                      |  1 +
 include/linux/clk-provider.h                  |  1 +
 include/linux/container_of.h                  | 28 ++++++++++-------
 include/linux/counter.h                       |  1 +
 include/linux/crash_core.h                    |  1 +
 include/linux/efi.h                           |  1 +
 include/linux/extable.h                       |  2 +-
 include/linux/f2fs_fs.h                       |  1 +
 include/linux/filter.h                        |  3 ++
 include/linux/fs.h                            |  1 +
 include/linux/genl_magic_func.h               |  1 +
 include/linux/hashtable.h                     |  1 +
 include/linux/ieee80211.h                     |  1 +
 include/linux/kbuild.h                        |  3 ++
 include/linux/kernel.h                        |  7 +----
 include/linux/kfifo.h                         |  1 +
 include/linux/kvm_host.h                      |  3 ++
 include/linux/libata.h                        |  1 +
 include/linux/llist.h                         |  1 +
 include/linux/memberof.h                      | 11 +++++++
 include/linux/mlx5/device.h                   |  1 +
 include/linux/mlx5/driver.h                   |  1 +
 include/linux/mm_types.h                      |  1 +
 include/linux/moduleparam.h                   |  3 ++
 include/linux/mtd/rawnand.h                   |  1 +
 include/linux/netdevice.h                     |  1 +
 include/linux/netfilter.h                     |  1 +
 include/linux/nvme-fc.h                       |  2 ++
 include/linux/offsetof.h                      | 17 +++++++++++
 include/linux/offsetofend.h                   | 19 ++++++++++++
 include/linux/pagemap.h                       |  1 +
 include/linux/phy.h                           |  1 +
 include/linux/phy_led_triggers.h              |  1 +
 include/linux/pinctrl/machine.h               |  1 +
 include/linux/property.h                      |  1 +
 include/linux/rcupdate.h                      |  1 +
 include/linux/rcupdate_wait.h                 |  1 +
 include/linux/regmap.h                        |  1 +
 include/linux/sched/task.h                    |  1 +
 include/linux/sizeof_field.h                  | 14 +++++++++
 include/linux/skb_array.h                     |  1 +
 include/linux/skbuff.h                        |  1 +
 include/linux/skmsg.h                         |  3 ++
 include/linux/slab.h                          |  2 ++
 include/linux/spinlock_types.h                |  1 +
 include/linux/stddef.h                        | 30 +++----------------
 include/linux/string.h                        |  5 +++-
 include/linux/surface_aggregator/controller.h |  1 +
 include/linux/surface_aggregator/serial_hub.h |  1 +
 include/linux/swap.h                          |  1 +
 include/linux/ti-emif-sram.h                  |  1 +
 include/linux/typeof_member.h                 | 11 +++++++
 include/linux/ucs2_string.h                   |  2 +-
 include/linux/vdpa.h                          |  1 +
 include/linux/virtio_config.h                 | 17 ++++++-----
 include/linux/wireless.h                      |  2 ++
 include/net/bond_3ad.h                        |  1 +
 include/net/dsa.h                             |  1 +
 include/net/ip_vs.h                           |  1 +
 include/net/netfilter/nf_conntrack_tuple.h    |  1 +
 include/net/netfilter/nf_tables.h             |  1 +
 include/net/netlink.h                         |  1 +
 include/rdma/uverbs_ioctl.h                   |  1 +
 include/rdma/uverbs_named_ioctl.h             |  1 +
 include/scsi/scsi_host.h                      |  1 +
 include/sound/soc-dapm.h                      |  1 +
 include/sound/soc.h                           |  1 +
 include/trace/events/wbt.h                    |  1 +
 include/uapi/linux/netfilter/xt_sctp.h        |  1 +
 include/xen/hvm.h                             |  1 +
 kernel/kallsyms.c                             |  3 +-
 94 files changed, 255 insertions(+), 79 deletions(-)
 create mode 100644 include/linux/NULL.h
 create mode 100644 include/linux/array_size.h
 create mode 100644 include/linux/memberof.h
 create mode 100644 include/linux/offsetof.h
 create mode 100644 include/linux/offsetofend.h
 create mode 100644 include/linux/sizeof_field.h
 create mode 100644 include/linux/typeof_member.h

-- 
2.33.1

[PATCH 02/17] Use memberof(T, m) instead of explicit NULL dereference

[Alejandro Colomar]

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Cc: Ajit Khaparde <ajit.khaparde@broadcom.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Corey Minyard <cminyard@mvista.com>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: John S. Gruber <JohnSGruber@gmail.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ketan Mukadam <ketan.mukadam@broadcom.com>
Cc: Len Brown <lenb@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Somnath Kotur <somnath.kotur@broadcom.com>
Cc: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Cc: Subbu Seetharaman <subbu.seetharaman@broadcom.com>
Cc: <intel-gfx@lists.freedesktop.org>
Cc: <linux-acpi@vger.kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: <linux-btrfs@vger.kernel.org>
Cc: <linux-scsi@vger.kernel.org>
Cc: <netdev@vger.kernel.org>
Cc: <virtualization@lists.linux-foundation.org>
---
 arch/x86/include/asm/bootparam_utils.h  |  3 ++-
 arch/x86/kernel/signal_compat.c         |  5 +++--
 drivers/gpu/drm/i915/i915_utils.h       |  5 ++---
 drivers/gpu/drm/i915/intel_runtime_pm.h |  2 +-
 drivers/net/ethernet/emulex/benet/be.h  |  7 ++++---
 drivers/net/ethernet/i825xx/ether1.c    |  7 +++++--
 drivers/scsi/be2iscsi/be.h              |  7 ++++---
 drivers/scsi/be2iscsi/be_cmds.h         |  5 ++++-
 fs/btrfs/ctree.h                        |  5 +++--
 include/acpi/actypes.h                  |  4 +++-
 include/linux/container_of.h            |  6 +++---
 include/linux/virtio_config.h           | 14 +++++++-------
 12 files changed, 41 insertions(+), 29 deletions(-)

diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h
index 981fe923a59f..71b28b5fb088 100644
--- a/arch/x86/include/asm/bootparam_utils.h
+++ b/arch/x86/include/asm/bootparam_utils.h
@@ -3,6 +3,7 @@
 #define _ASM_X86_BOOTPARAM_UTILS_H
 
 #include <asm/bootparam.h>
+#include <linux/container_of.h>
 
 /*
  * This file is included from multiple environments.  Do not
@@ -19,7 +20,7 @@
  * private magic, so it is better to leave it unchanged.
  */
 
-#define sizeof_mbr(type, member) ({ sizeof(((type *)0)->member); })
+#define sizeof_mbr(type, member) ({ sizeof(memberof(type, member)); })
 
 #define BOOT_PARAM_PRESERVE(struct_member)				\
 	{								\
diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
index b52407c56000..28420a7df056 100644
--- a/arch/x86/kernel/signal_compat.c
+++ b/arch/x86/kernel/signal_compat.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/compat.h>
+#include <linux/container_of.h>
 #include <linux/uaccess.h>
 #include <linux/ptrace.h>
 
@@ -69,8 +70,8 @@ static inline void signal_compat_build_tests(void)
 	 * structure stays within the padding size (checked
 	 * above).
 	 */
-#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
-#define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
+#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(memberof(compat_siginfo_t ,_sifields.name)))
+#define CHECK_SI_SIZE(name, size)  BUILD_BUG_ON(size != sizeof(memberof(siginfo_t, _sifields.name)))
 
 	CHECK_CSI_OFFSET(_kill);
 	CHECK_CSI_SIZE  (_kill, 2*sizeof(int));
diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
index 7a5925072466..2e3ec28f4f1b 100644
--- a/drivers/gpu/drm/i915/i915_utils.h
+++ b/drivers/gpu/drm/i915/i915_utils.h
@@ -25,6 +25,7 @@
 #ifndef __I915_UTILS_H
 #define __I915_UTILS_H
 
+#include <linux/container_of.h>
 #include <linux/list.h>
 #include <linux/overflow.h>
 #include <linux/sched.h>
@@ -192,8 +193,6 @@ __check_struct_size(size_t base, size_t arr, size_t count, size_t *size)
 #define page_pack_bits(ptr, bits) ptr_pack_bits(ptr, bits, PAGE_SHIFT)
 #define page_unpack_bits(ptr, bits) ptr_unpack_bits(ptr, bits, PAGE_SHIFT)
 
-#define struct_member(T, member) (((T *)0)->member)
-
 #define ptr_offset(ptr, member) offsetof(typeof(*(ptr)), member)
 
 #define fetch_and_zero(ptr) ({						\
@@ -215,7 +214,7 @@ static __always_inline ptrdiff_t ptrdiff(const void *a, const void *b)
  */
 #define container_of_user(ptr, type, member) ({				\
 	void __user *__mptr = (void __user *)(ptr);			\
-	BUILD_BUG_ON_MSG(!__same_type(*(ptr), struct_member(type, member)) && \
+	BUILD_BUG_ON_MSG(!__same_type(*(ptr), memberof(type, member)) && \
 			 !__same_type(*(ptr), void),			\
 			 "pointer type mismatch in container_of()");	\
 	((type __user *)(__mptr - offsetof(type, member))); })
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.h b/drivers/gpu/drm/i915/intel_runtime_pm.h
index 47a85fab4130..6cb04bef62ad 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.h
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.h
@@ -73,7 +73,7 @@ struct intel_runtime_pm {
 };
 
 #define BITS_PER_WAKEREF	\
-	BITS_PER_TYPE(struct_member(struct intel_runtime_pm, wakeref_count))
+	BITS_PER_TYPE(memberof(struct intel_runtime_pm, wakeref_count))
 #define INTEL_RPM_WAKELOCK_SHIFT	(BITS_PER_WAKEREF / 2)
 #define INTEL_RPM_WAKELOCK_BIAS		(1 << INTEL_RPM_WAKELOCK_SHIFT)
 #define INTEL_RPM_RAW_WAKEREF_MASK	(INTEL_RPM_WAKELOCK_BIAS - 1)
diff --git a/drivers/net/ethernet/emulex/benet/be.h b/drivers/net/ethernet/emulex/benet/be.h
index 8689d4a51fe5..dc790bae2451 100644
--- a/drivers/net/ethernet/emulex/benet/be.h
+++ b/drivers/net/ethernet/emulex/benet/be.h
@@ -14,6 +14,7 @@
 #ifndef BE_H
 #define BE_H
 
+#include <linux/container_of.h>
 #include <linux/pci.h>
 #include <linux/etherdevice.h>
 #include <linux/delay.h>
@@ -824,7 +825,7 @@ extern const struct ethtool_ops be_ethtool_ops;
 
 /* Returns bit offset within a DWORD of a bitfield */
 #define AMAP_BIT_OFFSET(_struct, field)  				\
-		(((size_t)&(((_struct *)0)->field))%32)
+		(((size_t)&(memberof(_struct, field)))%32)
 
 /* Returns the bit mask of the field that is NOT shifted into location. */
 static inline u32 amap_mask(u32 bitsize)
@@ -843,7 +844,7 @@ amap_set(void *ptr, u32 dw_offset, u32 mask, u32 offset, u32 value)
 #define AMAP_SET_BITS(_struct, field, ptr, val)				\
 		amap_set(ptr,						\
 			offsetof(_struct, field)/32,			\
-			amap_mask(sizeof(((_struct *)0)->field)),	\
+			amap_mask(sizeof(memberof(_struct, field))),	\
 			AMAP_BIT_OFFSET(_struct, field),		\
 			val)
 
@@ -856,7 +857,7 @@ static inline u32 amap_get(void *ptr, u32 dw_offset, u32 mask, u32 offset)
 #define AMAP_GET_BITS(_struct, field, ptr)				\
 		amap_get(ptr,						\
 			offsetof(_struct, field)/32,			\
-			amap_mask(sizeof(((_struct *)0)->field)),	\
+			amap_mask(sizeof(memberof(_struct, field))),	\
 			AMAP_BIT_OFFSET(_struct, field))
 
 #define GET_RX_COMPL_V0_BITS(field, ptr)				\
diff --git a/drivers/net/ethernet/i825xx/ether1.c b/drivers/net/ethernet/i825xx/ether1.c
index c612ef526d16..4dece3476d31 100644
--- a/drivers/net/ethernet/i825xx/ether1.c
+++ b/drivers/net/ethernet/i825xx/ether1.c
@@ -28,6 +28,7 @@
  * 1.07	RMK	13/05/2000	Updated for 2.3.99-pre8
  */
 
+#include <linux/containerof.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
@@ -80,8 +81,10 @@ static char version[] = "ether1 ethernet driver (c) 2000 Russell King v1.07\n";
 #define DISABLEIRQS 1
 #define NORMALIRQS  0
 
-#define ether1_readw(dev, addr, type, offset, svflgs) ether1_inw_p (dev, addr + (int)(&((type *)0)->offset), svflgs)
-#define ether1_writew(dev, val, addr, type, offset, svflgs) ether1_outw_p (dev, val, addr + (int)(&((type *)0)->offset), svflgs)
+#define ether1_readw(dev, addr, type, offset, svflgs) \
+	ether1_inw_p(dev, addr + (int)(&(memberof(type, offset))), svflgs)
+#define ether1_writew(dev, val, addr, type, offset, svflgs) \
+	ether1_outw_p(dev, val, addr + (int)(&(memberof(type, offset))), svflgs)
 
 static inline unsigned short
 ether1_inw_p (struct net_device *dev, int addr, int svflgs)
diff --git a/drivers/scsi/be2iscsi/be.h b/drivers/scsi/be2iscsi/be.h
index 4c58a02590c7..6830e07fd37a 100644
--- a/drivers/scsi/be2iscsi/be.h
+++ b/drivers/scsi/be2iscsi/be.h
@@ -10,6 +10,7 @@
 #ifndef BEISCSI_H
 #define BEISCSI_H
 
+#include <linux/container_of.h>
 #include <linux/pci.h>
 #include <linux/if_vlan.h>
 #include <linux/irq_poll.h>
@@ -153,7 +154,7 @@ struct be_ctrl_info {
 
 /* Returns bit offset within a DWORD of a bitfield */
 #define AMAP_BIT_OFFSET(_struct, field)					\
-		(((size_t)&(((_struct *)0)->field))%32)
+		(((size_t)&(memberof(_struct, field)))%32)
 
 /* Returns the bit mask of the field that is NOT shifted into location. */
 static inline u32 amap_mask(u32 bitsize)
@@ -172,7 +173,7 @@ static inline void amap_set(void *ptr, u32 dw_offset, u32 mask,
 #define AMAP_SET_BITS(_struct, field, ptr, val)				\
 		amap_set(ptr,						\
 			offsetof(_struct, field)/32,			\
-			amap_mask(sizeof(((_struct *)0)->field)),	\
+			amap_mask(sizeof(memberof(_struct, field))),	\
 			AMAP_BIT_OFFSET(_struct, field),		\
 			val)
 
@@ -185,7 +186,7 @@ static inline u32 amap_get(void *ptr, u32 dw_offset, u32 mask, u32 offset)
 #define AMAP_GET_BITS(_struct, field, ptr)				\
 		amap_get(ptr,						\
 			offsetof(_struct, field)/32,			\
-			amap_mask(sizeof(((_struct *)0)->field)),	\
+			amap_mask(sizeof(memberof(_struct, field))),	\
 			AMAP_BIT_OFFSET(_struct, field))
 
 #define be_dws_cpu_to_le(wrb, len) swap_dws(wrb, len)
diff --git a/drivers/scsi/be2iscsi/be_cmds.h b/drivers/scsi/be2iscsi/be_cmds.h
index 5f9f0b18ddf3..bb6ee43769d5 100644
--- a/drivers/scsi/be2iscsi/be_cmds.h
+++ b/drivers/scsi/be2iscsi/be_cmds.h
@@ -10,6 +10,9 @@
 #ifndef BEISCSI_CMDS_H
 #define BEISCSI_CMDS_H
 
+
+#include <linux/container_of.h>
+
 /**
  * The driver sends configuration and managements command requests to the
  * firmware in the BE. These requests are communicated to the processor
@@ -1300,7 +1303,7 @@ struct be_cmd_get_port_name {
 
 /* Returns the number of items in the field array. */
 #define BE_NUMBER_OF_FIELD(_type_, _field_)	\
-	(sizeof_field(_type_, _field_)/sizeof((((_type_ *)0)->_field_[0])))\
+	(sizeof_field(_type_, _field_) / sizeof(memberof(_type_, _field_[0])))
 
 /**
  * Different types of iSCSI completions to host driver for both initiator
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 7553e9dc5f93..442b6f937b22 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -6,6 +6,7 @@
 #ifndef BTRFS_CTREE_H
 #define BTRFS_CTREE_H
 
+#include <linux/container_of.h>
 #include <linux/mm.h>
 #include <linux/sched/signal.h>
 #include <linux/highmem.h>
@@ -1575,13 +1576,13 @@ static inline void put_unaligned_le8(u8 val, void *p)
 	read_extent_buffer(eb, (char *)(result),			\
 			   ((unsigned long)(ptr)) +			\
 			    offsetof(type, member),			\
-			   sizeof(((type *)0)->member)))
+			   sizeof(memberof(type, member))))
 
 #define write_eb_member(eb, ptr, type, member, result) (\
 	write_extent_buffer(eb, (char *)(result),			\
 			   ((unsigned long)(ptr)) +			\
 			    offsetof(type, member),			\
-			   sizeof(((type *)0)->member)))
+			   sizeof(memberof(type, member))))
 
 #define DECLARE_BTRFS_SETGET_BITS(bits)					\
 u##bits btrfs_get_token_##bits(struct btrfs_map_token *token,		\
diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index ff8b3c913f21..c3b0eccb3377 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -10,6 +10,8 @@
 #ifndef __ACTYPES_H__
 #define __ACTYPES_H__
 
+#include <linux/container_of.h>
+
 /* acpisrc:struct_defs -- for acpisrc conversion */
 
 /*
@@ -508,7 +510,7 @@ typedef u64 acpi_integer;
 
 #define ACPI_TO_POINTER(i)              ACPI_CAST_PTR (void, (acpi_size) (i))
 #define ACPI_TO_INTEGER(p)              ACPI_PTR_DIFF (p, (void *) 0)
-#define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
+#define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(memberof(d, f)), (void *) 0)
 #define ACPI_PHYSADDR_TO_PTR(i)         ACPI_TO_POINTER(i)
 #define ACPI_PTR_TO_PHYSADDR(i)         ACPI_TO_INTEGER(i)
 
diff --git a/include/linux/container_of.h b/include/linux/container_of.h
index 199c78a3bf29..227418cb8c99 100644
--- a/include/linux/container_of.h
+++ b/include/linux/container_of.h
@@ -8,7 +8,7 @@
 
 #define memberof(T, m)   (((T *) NULL)->m)
 
-#define typeof_member(T, m)	typeof(((T*)0)->m)
+#define typeof_member(T, m)	typeof(memberof(T, m))
 
 /**
  * container_of - cast a member of a structure out to the containing structure
@@ -19,7 +19,7 @@
  */
 #define container_of(ptr, type, member) ({				\
 	void *__mptr = (void *)(ptr);					\
-	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
+	static_assert(__same_type(*(ptr), memberof(type, member)) ||	\
 		      __same_type(*(ptr), void),			\
 		      "pointer type mismatch in container_of()");	\
 	((type *)(__mptr - offsetof(type, member))); })
@@ -34,7 +34,7 @@
  */
 #define container_of_safe(ptr, type, member) ({				\
 	void *__mptr = (void *)(ptr);					\
-	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
+	static_assert(__same_type(*(ptr), memberof(type, member)) ||	\
 		      __same_type(*(ptr), void),			\
 		      "pointer type mismatch in container_of_safe()");	\
 	IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) :			\
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 4d107ad31149..a1e656c0d94a 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -328,12 +328,12 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 		)
 
 #define __virtio_native_type(structname, member) \
-	typeof(virtio_to_cpu(NULL, ((structname*)0)->member))
+	typeof(virtio_to_cpu(NULL, memberof(structname, member)))
 
 /* Config space accessors. */
 #define virtio_cread(vdev, structname, member, ptr)			\
 	do {								\
-		typeof(((structname*)0)->member) virtio_cread_v;	\
+		typeof(memberof(structname, member)) virtio_cread_v;	\
 									\
 		might_sleep();						\
 		/* Sanity check: must match the member's type */	\
@@ -362,8 +362,8 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 /* Config space accessors. */
 #define virtio_cwrite(vdev, structname, member, ptr)			\
 	do {								\
-		typeof(((structname*)0)->member) virtio_cwrite_v =	\
-			cpu_to_virtio(vdev, *(ptr), ((structname*)0)->member); \
+		typeof(memberof(structname, member)) virtio_cwrite_v =	\
+			cpu_to_virtio(vdev, *(ptr), memberof(structname, member)); \
 									\
 		might_sleep();						\
 		/* Sanity check: must match the member's type */	\
@@ -397,7 +397,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 /* LE (e.g. modern) Config space accessors. */
 #define virtio_cread_le(vdev, structname, member, ptr)			\
 	do {								\
-		typeof(((structname*)0)->member) virtio_cread_v;	\
+		typeof(memberof(structname, member)) virtio_cread_v;	\
 									\
 		might_sleep();						\
 		/* Sanity check: must match the member's type */	\
@@ -425,8 +425,8 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
 
 #define virtio_cwrite_le(vdev, structname, member, ptr)			\
 	do {								\
-		typeof(((structname*)0)->member) virtio_cwrite_v =	\
-			virtio_cpu_to_le(*(ptr), ((structname*)0)->member); \
+		typeof(memberof(structname, member)) virtio_cwrite_v =	\
+			virtio_cpu_to_le(*(ptr), memberof(structname, member)); \
 									\
 		might_sleep();						\
 		/* Sanity check: must match the member's type */	\
-- 
2.33.1

Re: [PATCH 02/17] Use memberof(T, m) instead of explicit NULL dereference

[Rafael J. Wysocki]

On Fri, Nov 19, 2021 at 12:37 PM Alejandro Colomar
<alx.manpages@gmail.com> wrote:
>
> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
> Cc: Ajit Khaparde <ajit.khaparde@broadcom.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Corey Minyard <cminyard@mvista.com>
> Cc: Chris Mason <clm@fb.com>
> Cc: Christian Brauner <christian.brauner@ubuntu.com>
> Cc: David Sterba <dsterba@suse.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: John S. Gruber <JohnSGruber@gmail.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Josef Bacik <josef@toxicpanda.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Ketan Mukadam <ketan.mukadam@broadcom.com>
> Cc: Len Brown <lenb@kernel.org>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Miguel Ojeda <ojeda@kernel.org>
> Cc: Mike Rapoport <rppt@linux.ibm.com>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Somnath Kotur <somnath.kotur@broadcom.com>
> Cc: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
> Cc: Subbu Seetharaman <subbu.seetharaman@broadcom.com>
> Cc: <intel-gfx@lists.freedesktop.org>
> Cc: <linux-acpi@vger.kernel.org>
> Cc: <linux-arm-kernel@lists.infradead.org>
> Cc: <linux-btrfs@vger.kernel.org>
> Cc: <linux-scsi@vger.kernel.org>
> Cc: <netdev@vger.kernel.org>
> Cc: <virtualization@lists.linux-foundation.org>
> ---
>  arch/x86/include/asm/bootparam_utils.h  |  3 ++-
>  arch/x86/kernel/signal_compat.c         |  5 +++--
>  drivers/gpu/drm/i915/i915_utils.h       |  5 ++---
>  drivers/gpu/drm/i915/intel_runtime_pm.h |  2 +-
>  drivers/net/ethernet/emulex/benet/be.h  |  7 ++++---
>  drivers/net/ethernet/i825xx/ether1.c    |  7 +++++--
>  drivers/scsi/be2iscsi/be.h              |  7 ++++---
>  drivers/scsi/be2iscsi/be_cmds.h         |  5 ++++-
>  fs/btrfs/ctree.h                        |  5 +++--
>  include/acpi/actypes.h                  |  4 +++-

The change in actypes.h would need to be submitted to the upstream
ACPICA project via https://github.com/acpica/acpica/

Thanks!

>  include/linux/container_of.h            |  6 +++---
>  include/linux/virtio_config.h           | 14 +++++++-------
>  12 files changed, 41 insertions(+), 29 deletions(-)

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Jani Nikula]

On Fri, 19 Nov 2021, Alejandro Colomar <alx.manpages@gmail.com> wrote:
> Hi all,
>
> I simplified some xxxof() macros,
> by adding a new macro memberof(),
> which implements a common operation in many of them.
>
> I also splitted many of those macros into tiny headers,
> since I noticed that touching those headers implied
> recompiling almost the whole kernel.
>
> Hopefully after this patch there will be less
> things to recompile after touching one of those.
>
> Having simpler headers means that now one can
> include one of those without pulling too much stuff
> that might break other stuff.
>
> I removed some unnecessary casts too.
>
> Every few commits in this series
> and of course after the last commit
> I rebuilt the kernel and run for a while with it without any problems.
>
> Please note that I have written very few kernel code
> and for example some files wouldn't let me include some of these files,
> so I didn't change those.
>
> What I mean is that,
> even though this is super obvious and shouldn't break stuff,
> and I'm not new to C,
> I'm quite new to the kernel,
> and ask that reviewers take deep look, please.
>
>
> In the first and second commits
> I changed a lot of stuff in many parts,
> and that's why I CCd so many people (also in this cover letter).
> However, to avoid spamming,
> and since it would be a nightmare to
> find all the relevant people affected in so many different areas,
> I only CCd in 01, 02 and in the cover letter.
> If anyone is interested in reading the full patch set,
> I sent it to the LKML.

I think with the patch split you have this would be a nightmare to get
merged. Please consider refactoring the headers first, and once those
are reviewed and merged, you can proceed with using them elsewhere. For
example, we'd want the drm/i915 changes in patches separate from changes
to other drivers or the core headers.

BR,
Jani.



>
>
> Thanks,
> Alex
>
>
> Alejandro Colomar (17):
>   linux/container_of.h: Add memberof(T, m)
>   Use memberof(T, m) instead of explicit NULL dereference
>   Replace some uses of memberof() by its wrappers
>   linux/memberof.h: Move memberof() to separate header
>   linux/typeof_member.h: Move typeof_member() to a separate header
>   Simplify sizeof(typeof_member()) to sizeof_field()
>   linux/NULL.h: Move NULL to a separate header
>   linux/offsetof.h: Move offsetof(T, m) to a separate header
>   linux/offsetof.h: Implement offsetof() in terms of memberof()
>   linux/container_of.h: Implement container_of_safe() in terms of
>     container_of()
>   linux/container_of.h: Cosmetic
>   linux/container_of.h: Remove unnecessary cast to (void *)
>   linux/sizeof_field.h: Move sizeof_field(T, m) to a separate header
>   include/linux/: Include a smaller header if just for NULL
>   linux/offsetofend.h: Move offsetofend(T, m) to a separate header
>   linux/array_size.h: Move ARRAY_SIZE(arr) to a separate header
>   include/: Include <linux/array_size.h> for ARRAY_SIZE()
>
>  arch/x86/include/asm/bootparam_utils.h        |  3 +-
>  arch/x86/kernel/signal_compat.c               |  5 ++--
>  drivers/gpu/drm/i915/i915_sw_fence.c          |  1 +
>  drivers/gpu/drm/i915/i915_utils.h             |  5 ++--
>  drivers/gpu/drm/i915/intel_runtime_pm.h       |  3 +-
>  drivers/net/ethernet/emulex/benet/be.h        | 10 +++----
>  drivers/net/ethernet/i825xx/ether1.c          |  7 +++--
>  drivers/platform/x86/wmi.c                    |  3 +-
>  drivers/scsi/be2iscsi/be.h                    | 12 ++++----
>  drivers/scsi/be2iscsi/be_cmds.h               |  5 +++-
>  fs/btrfs/ctree.h                              |  5 ++--
>  fs/proc/inode.c                               |  1 +
>  include/acpi/actypes.h                        |  4 ++-
>  include/crypto/internal/blake2b.h             |  1 +
>  include/crypto/internal/blake2s.h             |  1 +
>  include/crypto/internal/chacha.h              |  1 +
>  include/drm/drm_mipi_dbi.h                    |  1 +
>  include/drm/drm_mode_object.h                 |  1 +
>  include/kunit/test.h                          |  1 +
>  include/linux/NULL.h                          | 10 +++++++
>  include/linux/arm_ffa.h                       |  1 +
>  include/linux/array_size.h                    | 15 ++++++++++
>  include/linux/blk_types.h                     |  1 +
>  include/linux/can/core.h                      |  1 +
>  include/linux/clk-provider.h                  |  1 +
>  include/linux/container_of.h                  | 28 ++++++++++-------
>  include/linux/counter.h                       |  1 +
>  include/linux/crash_core.h                    |  1 +
>  include/linux/efi.h                           |  1 +
>  include/linux/extable.h                       |  2 +-
>  include/linux/f2fs_fs.h                       |  1 +
>  include/linux/filter.h                        |  3 ++
>  include/linux/fs.h                            |  1 +
>  include/linux/genl_magic_func.h               |  1 +
>  include/linux/hashtable.h                     |  1 +
>  include/linux/ieee80211.h                     |  1 +
>  include/linux/kbuild.h                        |  3 ++
>  include/linux/kernel.h                        |  7 +----
>  include/linux/kfifo.h                         |  1 +
>  include/linux/kvm_host.h                      |  3 ++
>  include/linux/libata.h                        |  1 +
>  include/linux/llist.h                         |  1 +
>  include/linux/memberof.h                      | 11 +++++++
>  include/linux/mlx5/device.h                   |  1 +
>  include/linux/mlx5/driver.h                   |  1 +
>  include/linux/mm_types.h                      |  1 +
>  include/linux/moduleparam.h                   |  3 ++
>  include/linux/mtd/rawnand.h                   |  1 +
>  include/linux/netdevice.h                     |  1 +
>  include/linux/netfilter.h                     |  1 +
>  include/linux/nvme-fc.h                       |  2 ++
>  include/linux/offsetof.h                      | 17 +++++++++++
>  include/linux/offsetofend.h                   | 19 ++++++++++++
>  include/linux/pagemap.h                       |  1 +
>  include/linux/phy.h                           |  1 +
>  include/linux/phy_led_triggers.h              |  1 +
>  include/linux/pinctrl/machine.h               |  1 +
>  include/linux/property.h                      |  1 +
>  include/linux/rcupdate.h                      |  1 +
>  include/linux/rcupdate_wait.h                 |  1 +
>  include/linux/regmap.h                        |  1 +
>  include/linux/sched/task.h                    |  1 +
>  include/linux/sizeof_field.h                  | 14 +++++++++
>  include/linux/skb_array.h                     |  1 +
>  include/linux/skbuff.h                        |  1 +
>  include/linux/skmsg.h                         |  3 ++
>  include/linux/slab.h                          |  2 ++
>  include/linux/spinlock_types.h                |  1 +
>  include/linux/stddef.h                        | 30 +++----------------
>  include/linux/string.h                        |  5 +++-
>  include/linux/surface_aggregator/controller.h |  1 +
>  include/linux/surface_aggregator/serial_hub.h |  1 +
>  include/linux/swap.h                          |  1 +
>  include/linux/ti-emif-sram.h                  |  1 +
>  include/linux/typeof_member.h                 | 11 +++++++
>  include/linux/ucs2_string.h                   |  2 +-
>  include/linux/vdpa.h                          |  1 +
>  include/linux/virtio_config.h                 | 17 ++++++-----
>  include/linux/wireless.h                      |  2 ++
>  include/net/bond_3ad.h                        |  1 +
>  include/net/dsa.h                             |  1 +
>  include/net/ip_vs.h                           |  1 +
>  include/net/netfilter/nf_conntrack_tuple.h    |  1 +
>  include/net/netfilter/nf_tables.h             |  1 +
>  include/net/netlink.h                         |  1 +
>  include/rdma/uverbs_ioctl.h                   |  1 +
>  include/rdma/uverbs_named_ioctl.h             |  1 +
>  include/scsi/scsi_host.h                      |  1 +
>  include/sound/soc-dapm.h                      |  1 +
>  include/sound/soc.h                           |  1 +
>  include/trace/events/wbt.h                    |  1 +
>  include/uapi/linux/netfilter/xt_sctp.h        |  1 +
>  include/xen/hvm.h                             |  1 +
>  kernel/kallsyms.c                             |  3 +-
>  94 files changed, 255 insertions(+), 79 deletions(-)
>  create mode 100644 include/linux/NULL.h
>  create mode 100644 include/linux/array_size.h
>  create mode 100644 include/linux/memberof.h
>  create mode 100644 include/linux/offsetof.h
>  create mode 100644 include/linux/offsetofend.h
>  create mode 100644 include/linux/sizeof_field.h
>  create mode 100644 include/linux/typeof_member.h

-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Alejandro Colomar (man-pages)]

Hi Jani,

On 11/19/21 13:47, Jani Nikula wrote:
> On Fri, 19 Nov 2021, Alejandro Colomar <alx.manpages@gmail.com> wrote:
>> In the first and second commits
>> I changed a lot of stuff in many parts,
>> and that's why I CCd so many people (also in this cover letter).
>> However, to avoid spamming,
>> and since it would be a nightmare to
>> find all the relevant people affected in so many different areas,
>> I only CCd in 01, 02 and in the cover letter.
>> If anyone is interested in reading the full patch set,
>> I sent it to the LKML.
> 
> I think with the patch split you have this would be a nightmare to get
> merged. Please consider refactoring the headers first, and once those
> are reviewed and merged, you can proceed with using them elsewhere. For
> example, we'd want the drm/i915 changes in patches separate from changes
> to other drivers or the core headers.

So,
would it be preferable something like this?:

Patch set 1:
- Add <linux/memberof.h> with memberof()
- Split offsetof() to <linux/offsetof.h>
- Split offsetofend() to <linux/offsetofend.h>
- Split typeof_member() to <linux/typeof_member.h>
- Split sizeof_field() to <linux/sizeof_field.h>
- Split NULL to <linux/NULL.h>
- Split ARRAY_SIZE() to <linux/array_size.h>
- Implement offsetof() in terms of memberof()
- Implement typeof_member() in terms of memberof()
- Implement sizeof_field() in terms of memberof()
- Implement container_of_safe() in terms of container_of()
- Remove unnecessary cast from container_of[_safe]()
- Cosmetic changes

Patch set 2:
- And in a different patch set, fix all other files
   that make use of these macros.


Patch 1 without editing any other files except for the basic ones,
and adding includes where the definition had been previously,
to not break stuff.

And then,
start patching individual subsystems and
send tiny patch sets to each of them?


For the first part,
I agree it is better.
I'll change it to do that.
I'll send an v2 with less changes and more organized.


For the second part,
I'll see what I can do after the first one has been reviewed.
I'll do tiny patches with a few changes to one or few files,
so that I can reorganize them easily with a rebase -i afterwards,
and then decide.


Thanks,
Alex

> 
>>
>>
>> Alejandro Colomar (17):
>>    linux/container_of.h: Add memberof(T, m)
>>    Use memberof(T, m) instead of explicit NULL dereference
>>    Replace some uses of memberof() by its wrappers
>>    linux/memberof.h: Move memberof() to separate header
>>    linux/typeof_member.h: Move typeof_member() to a separate header
>>    Simplify sizeof(typeof_member()) to sizeof_field()
>>    linux/NULL.h: Move NULL to a separate header
>>    linux/offsetof.h: Move offsetof(T, m) to a separate header
>>    linux/offsetof.h: Implement offsetof() in terms of memberof()
>>    linux/container_of.h: Implement container_of_safe() in terms of
>>      container_of()
>>    linux/container_of.h: Cosmetic
>>    linux/container_of.h: Remove unnecessary cast to (void *)
>>    linux/sizeof_field.h: Move sizeof_field(T, m) to a separate header
>>    include/linux/: Include a smaller header if just for NULL
>>    linux/offsetofend.h: Move offsetofend(T, m) to a separate header
>>    linux/array_size.h: Move ARRAY_SIZE(arr) to a separate header
>>    include/: Include <linux/array_size.h> for ARRAY_SIZE()
>>
>>   arch/x86/include/asm/bootparam_utils.h        |  3 +-
>>   arch/x86/kernel/signal_compat.c               |  5 ++--
>>   drivers/gpu/drm/i915/i915_sw_fence.c          |  1 +
>>   drivers/gpu/drm/i915/i915_utils.h             |  5 ++--
>>   drivers/gpu/drm/i915/intel_runtime_pm.h       |  3 +-
>>   drivers/net/ethernet/emulex/benet/be.h        | 10 +++----
>>   drivers/net/ethernet/i825xx/ether1.c          |  7 +++--
>>   drivers/platform/x86/wmi.c                    |  3 +-
>>   drivers/scsi/be2iscsi/be.h                    | 12 ++++----
>>   drivers/scsi/be2iscsi/be_cmds.h               |  5 +++-
>>   fs/btrfs/ctree.h                              |  5 ++--
>>   fs/proc/inode.c                               |  1 +
>>   include/acpi/actypes.h                        |  4 ++-
>>   include/crypto/internal/blake2b.h             |  1 +
>>   include/crypto/internal/blake2s.h             |  1 +
>>   include/crypto/internal/chacha.h              |  1 +
>>   include/drm/drm_mipi_dbi.h                    |  1 +
>>   include/drm/drm_mode_object.h                 |  1 +
>>   include/kunit/test.h                          |  1 +
>>   include/linux/NULL.h                          | 10 +++++++
>>   include/linux/arm_ffa.h                       |  1 +
>>   include/linux/array_size.h                    | 15 ++++++++++
>>   include/linux/blk_types.h                     |  1 +
>>   include/linux/can/core.h                      |  1 +
>>   include/linux/clk-provider.h                  |  1 +
>>   include/linux/container_of.h                  | 28 ++++++++++-------
>>   include/linux/counter.h                       |  1 +
>>   include/linux/crash_core.h                    |  1 +
>>   include/linux/efi.h                           |  1 +
>>   include/linux/extable.h                       |  2 +-
>>   include/linux/f2fs_fs.h                       |  1 +
>>   include/linux/filter.h                        |  3 ++
>>   include/linux/fs.h                            |  1 +
>>   include/linux/genl_magic_func.h               |  1 +
>>   include/linux/hashtable.h                     |  1 +
>>   include/linux/ieee80211.h                     |  1 +
>>   include/linux/kbuild.h                        |  3 ++
>>   include/linux/kernel.h                        |  7 +----
>>   include/linux/kfifo.h                         |  1 +
>>   include/linux/kvm_host.h                      |  3 ++
>>   include/linux/libata.h                        |  1 +
>>   include/linux/llist.h                         |  1 +
>>   include/linux/memberof.h                      | 11 +++++++
>>   include/linux/mlx5/device.h                   |  1 +
>>   include/linux/mlx5/driver.h                   |  1 +
>>   include/linux/mm_types.h                      |  1 +
>>   include/linux/moduleparam.h                   |  3 ++
>>   include/linux/mtd/rawnand.h                   |  1 +
>>   include/linux/netdevice.h                     |  1 +
>>   include/linux/netfilter.h                     |  1 +
>>   include/linux/nvme-fc.h                       |  2 ++
>>   include/linux/offsetof.h                      | 17 +++++++++++
>>   include/linux/offsetofend.h                   | 19 ++++++++++++
>>   include/linux/pagemap.h                       |  1 +
>>   include/linux/phy.h                           |  1 +
>>   include/linux/phy_led_triggers.h              |  1 +
>>   include/linux/pinctrl/machine.h               |  1 +
>>   include/linux/property.h                      |  1 +
>>   include/linux/rcupdate.h                      |  1 +
>>   include/linux/rcupdate_wait.h                 |  1 +
>>   include/linux/regmap.h                        |  1 +
>>   include/linux/sched/task.h                    |  1 +
>>   include/linux/sizeof_field.h                  | 14 +++++++++
>>   include/linux/skb_array.h                     |  1 +
>>   include/linux/skbuff.h                        |  1 +
>>   include/linux/skmsg.h                         |  3 ++
>>   include/linux/slab.h                          |  2 ++
>>   include/linux/spinlock_types.h                |  1 +
>>   include/linux/stddef.h                        | 30 +++----------------
>>   include/linux/string.h                        |  5 +++-
>>   include/linux/surface_aggregator/controller.h |  1 +
>>   include/linux/surface_aggregator/serial_hub.h |  1 +
>>   include/linux/swap.h                          |  1 +
>>   include/linux/ti-emif-sram.h                  |  1 +
>>   include/linux/typeof_member.h                 | 11 +++++++
>>   include/linux/ucs2_string.h                   |  2 +-
>>   include/linux/vdpa.h                          |  1 +
>>   include/linux/virtio_config.h                 | 17 ++++++-----
>>   include/linux/wireless.h                      |  2 ++
>>   include/net/bond_3ad.h                        |  1 +
>>   include/net/dsa.h                             |  1 +
>>   include/net/ip_vs.h                           |  1 +
>>   include/net/netfilter/nf_conntrack_tuple.h    |  1 +
>>   include/net/netfilter/nf_tables.h             |  1 +
>>   include/net/netlink.h                         |  1 +
>>   include/rdma/uverbs_ioctl.h                   |  1 +
>>   include/rdma/uverbs_named_ioctl.h             |  1 +
>>   include/scsi/scsi_host.h                      |  1 +
>>   include/sound/soc-dapm.h                      |  1 +
>>   include/sound/soc.h                           |  1 +
>>   include/trace/events/wbt.h                    |  1 +
>>   include/uapi/linux/netfilter/xt_sctp.h        |  1 +
>>   include/xen/hvm.h                             |  1 +
>>   kernel/kallsyms.c                             |  3 +-
>>   94 files changed, 255 insertions(+), 79 deletions(-)
>>   create mode 100644 include/linux/NULL.h
>>   create mode 100644 include/linux/array_size.h
>>   create mode 100644 include/linux/memberof.h
>>   create mode 100644 include/linux/offsetof.h
>>   create mode 100644 include/linux/offsetofend.h
>>   create mode 100644 include/linux/sizeof_field.h
>>   create mode 100644 include/linux/typeof_member.h
> 

-- 
Alejandro Colomar
Linux man-pages comaintainer; http://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Jani Nikula]

On Fri, 19 Nov 2021, "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com> wrote:
> Hi Jani,
>
> On 11/19/21 13:47, Jani Nikula wrote:
>> On Fri, 19 Nov 2021, Alejandro Colomar <alx.manpages@gmail.com> wrote:
>>> In the first and second commits
>>> I changed a lot of stuff in many parts,
>>> and that's why I CCd so many people (also in this cover letter).
>>> However, to avoid spamming,
>>> and since it would be a nightmare to
>>> find all the relevant people affected in so many different areas,
>>> I only CCd in 01, 02 and in the cover letter.
>>> If anyone is interested in reading the full patch set,
>>> I sent it to the LKML.
>> 
>> I think with the patch split you have this would be a nightmare to get
>> merged. Please consider refactoring the headers first, and once those
>> are reviewed and merged, you can proceed with using them elsewhere. For
>> example, we'd want the drm/i915 changes in patches separate from changes
>> to other drivers or the core headers.
>
> So,
> would it be preferable something like this?:
>
> Patch set 1:
> - Add <linux/memberof.h> with memberof()
> - Split offsetof() to <linux/offsetof.h>
> - Split offsetofend() to <linux/offsetofend.h>
> - Split typeof_member() to <linux/typeof_member.h>
> - Split sizeof_field() to <linux/sizeof_field.h>
> - Split NULL to <linux/NULL.h>
> - Split ARRAY_SIZE() to <linux/array_size.h>
> - Implement offsetof() in terms of memberof()
> - Implement typeof_member() in terms of memberof()
> - Implement sizeof_field() in terms of memberof()
> - Implement container_of_safe() in terms of container_of()
> - Remove unnecessary cast from container_of[_safe]()
> - Cosmetic changes
>
> Patch set 2:
> - And in a different patch set, fix all other files
>    that make use of these macros.
>
>
> Patch 1 without editing any other files except for the basic ones,
> and adding includes where the definition had been previously,
> to not break stuff.
>
> And then,
> start patching individual subsystems and
> send tiny patch sets to each of them?
>
>
> For the first part,
> I agree it is better.
> I'll change it to do that.
> I'll send an v2 with less changes and more organized.
>
>
> For the second part,
> I'll see what I can do after the first one has been reviewed.
> I'll do tiny patches with a few changes to one or few files,
> so that I can reorganize them easily with a rebase -i afterwards,
> and then decide.

Sounds about right. I presume just the first series is going to generate
quite a bit of discussion, in particular <linux/NULL.h> looks like
everyone's going to have an opinion. And for that, you really don't need
or want all the users (patch series 2) Cc'd.


BR,
Jani.



>
>
> Thanks,
> Alex
>
>> 
>>>
>>>
>>> Alejandro Colomar (17):
>>>    linux/container_of.h: Add memberof(T, m)
>>>    Use memberof(T, m) instead of explicit NULL dereference
>>>    Replace some uses of memberof() by its wrappers
>>>    linux/memberof.h: Move memberof() to separate header
>>>    linux/typeof_member.h: Move typeof_member() to a separate header
>>>    Simplify sizeof(typeof_member()) to sizeof_field()
>>>    linux/NULL.h: Move NULL to a separate header
>>>    linux/offsetof.h: Move offsetof(T, m) to a separate header
>>>    linux/offsetof.h: Implement offsetof() in terms of memberof()
>>>    linux/container_of.h: Implement container_of_safe() in terms of
>>>      container_of()
>>>    linux/container_of.h: Cosmetic
>>>    linux/container_of.h: Remove unnecessary cast to (void *)
>>>    linux/sizeof_field.h: Move sizeof_field(T, m) to a separate header
>>>    include/linux/: Include a smaller header if just for NULL
>>>    linux/offsetofend.h: Move offsetofend(T, m) to a separate header
>>>    linux/array_size.h: Move ARRAY_SIZE(arr) to a separate header
>>>    include/: Include <linux/array_size.h> for ARRAY_SIZE()
>>>
>>>   arch/x86/include/asm/bootparam_utils.h        |  3 +-
>>>   arch/x86/kernel/signal_compat.c               |  5 ++--
>>>   drivers/gpu/drm/i915/i915_sw_fence.c          |  1 +
>>>   drivers/gpu/drm/i915/i915_utils.h             |  5 ++--
>>>   drivers/gpu/drm/i915/intel_runtime_pm.h       |  3 +-
>>>   drivers/net/ethernet/emulex/benet/be.h        | 10 +++----
>>>   drivers/net/ethernet/i825xx/ether1.c          |  7 +++--
>>>   drivers/platform/x86/wmi.c                    |  3 +-
>>>   drivers/scsi/be2iscsi/be.h                    | 12 ++++----
>>>   drivers/scsi/be2iscsi/be_cmds.h               |  5 +++-
>>>   fs/btrfs/ctree.h                              |  5 ++--
>>>   fs/proc/inode.c                               |  1 +
>>>   include/acpi/actypes.h                        |  4 ++-
>>>   include/crypto/internal/blake2b.h             |  1 +
>>>   include/crypto/internal/blake2s.h             |  1 +
>>>   include/crypto/internal/chacha.h              |  1 +
>>>   include/drm/drm_mipi_dbi.h                    |  1 +
>>>   include/drm/drm_mode_object.h                 |  1 +
>>>   include/kunit/test.h                          |  1 +
>>>   include/linux/NULL.h                          | 10 +++++++
>>>   include/linux/arm_ffa.h                       |  1 +
>>>   include/linux/array_size.h                    | 15 ++++++++++
>>>   include/linux/blk_types.h                     |  1 +
>>>   include/linux/can/core.h                      |  1 +
>>>   include/linux/clk-provider.h                  |  1 +
>>>   include/linux/container_of.h                  | 28 ++++++++++-------
>>>   include/linux/counter.h                       |  1 +
>>>   include/linux/crash_core.h                    |  1 +
>>>   include/linux/efi.h                           |  1 +
>>>   include/linux/extable.h                       |  2 +-
>>>   include/linux/f2fs_fs.h                       |  1 +
>>>   include/linux/filter.h                        |  3 ++
>>>   include/linux/fs.h                            |  1 +
>>>   include/linux/genl_magic_func.h               |  1 +
>>>   include/linux/hashtable.h                     |  1 +
>>>   include/linux/ieee80211.h                     |  1 +
>>>   include/linux/kbuild.h                        |  3 ++
>>>   include/linux/kernel.h                        |  7 +----
>>>   include/linux/kfifo.h                         |  1 +
>>>   include/linux/kvm_host.h                      |  3 ++
>>>   include/linux/libata.h                        |  1 +
>>>   include/linux/llist.h                         |  1 +
>>>   include/linux/memberof.h                      | 11 +++++++
>>>   include/linux/mlx5/device.h                   |  1 +
>>>   include/linux/mlx5/driver.h                   |  1 +
>>>   include/linux/mm_types.h                      |  1 +
>>>   include/linux/moduleparam.h                   |  3 ++
>>>   include/linux/mtd/rawnand.h                   |  1 +
>>>   include/linux/netdevice.h                     |  1 +
>>>   include/linux/netfilter.h                     |  1 +
>>>   include/linux/nvme-fc.h                       |  2 ++
>>>   include/linux/offsetof.h                      | 17 +++++++++++
>>>   include/linux/offsetofend.h                   | 19 ++++++++++++
>>>   include/linux/pagemap.h                       |  1 +
>>>   include/linux/phy.h                           |  1 +
>>>   include/linux/phy_led_triggers.h              |  1 +
>>>   include/linux/pinctrl/machine.h               |  1 +
>>>   include/linux/property.h                      |  1 +
>>>   include/linux/rcupdate.h                      |  1 +
>>>   include/linux/rcupdate_wait.h                 |  1 +
>>>   include/linux/regmap.h                        |  1 +
>>>   include/linux/sched/task.h                    |  1 +
>>>   include/linux/sizeof_field.h                  | 14 +++++++++
>>>   include/linux/skb_array.h                     |  1 +
>>>   include/linux/skbuff.h                        |  1 +
>>>   include/linux/skmsg.h                         |  3 ++
>>>   include/linux/slab.h                          |  2 ++
>>>   include/linux/spinlock_types.h                |  1 +
>>>   include/linux/stddef.h                        | 30 +++----------------
>>>   include/linux/string.h                        |  5 +++-
>>>   include/linux/surface_aggregator/controller.h |  1 +
>>>   include/linux/surface_aggregator/serial_hub.h |  1 +
>>>   include/linux/swap.h                          |  1 +
>>>   include/linux/ti-emif-sram.h                  |  1 +
>>>   include/linux/typeof_member.h                 | 11 +++++++
>>>   include/linux/ucs2_string.h                   |  2 +-
>>>   include/linux/vdpa.h                          |  1 +
>>>   include/linux/virtio_config.h                 | 17 ++++++-----
>>>   include/linux/wireless.h                      |  2 ++
>>>   include/net/bond_3ad.h                        |  1 +
>>>   include/net/dsa.h                             |  1 +
>>>   include/net/ip_vs.h                           |  1 +
>>>   include/net/netfilter/nf_conntrack_tuple.h    |  1 +
>>>   include/net/netfilter/nf_tables.h             |  1 +
>>>   include/net/netlink.h                         |  1 +
>>>   include/rdma/uverbs_ioctl.h                   |  1 +
>>>   include/rdma/uverbs_named_ioctl.h             |  1 +
>>>   include/scsi/scsi_host.h                      |  1 +
>>>   include/sound/soc-dapm.h                      |  1 +
>>>   include/sound/soc.h                           |  1 +
>>>   include/trace/events/wbt.h                    |  1 +
>>>   include/uapi/linux/netfilter/xt_sctp.h        |  1 +
>>>   include/xen/hvm.h                             |  1 +
>>>   kernel/kallsyms.c                             |  3 +-
>>>   94 files changed, 255 insertions(+), 79 deletions(-)
>>>   create mode 100644 include/linux/NULL.h
>>>   create mode 100644 include/linux/array_size.h
>>>   create mode 100644 include/linux/memberof.h
>>>   create mode 100644 include/linux/offsetof.h
>>>   create mode 100644 include/linux/offsetofend.h
>>>   create mode 100644 include/linux/sizeof_field.h
>>>   create mode 100644 include/linux/typeof_member.h
>> 

-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Andy Shevchenko]

On Fri, Nov 19, 2021 at 02:16:03PM +0100, Alejandro Colomar (man-pages) wrote:
> On 11/19/21 13:47, Jani Nikula wrote:
> > On Fri, 19 Nov 2021, Alejandro Colomar <alx.manpages@gmail.com> wrote:

...

> Patch set 1:
> - Add <linux/memberof.h> with memberof()
> - Split offsetof() to <linux/offsetof.h>
> - Split offsetofend() to <linux/offsetofend.h>
> - Split typeof_member() to <linux/typeof_member.h>
> - Split sizeof_field() to <linux/sizeof_field.h>
> - Split NULL to <linux/NULL.h>
> - Split ARRAY_SIZE() to <linux/array_size.h>

Isn't it way too small granularity? I agree on having the separate header
for ARRAY_SIZE() and it was discussed, but the rest...

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Arnd Bergmann]

On Fri, Nov 19, 2021 at 12:36 PM Alejandro Colomar
<alx.manpages@gmail.com> wrote:
>
> Alejandro Colomar (17):
>   linux/container_of.h: Add memberof(T, m)
>   Use memberof(T, m) instead of explicit NULL dereference
>   Replace some uses of memberof() by its wrappers
>   linux/memberof.h: Move memberof() to separate header
>   linux/typeof_member.h: Move typeof_member() to a separate header
>   Simplify sizeof(typeof_member()) to sizeof_field()
>   linux/NULL.h: Move NULL to a separate header
>   linux/offsetof.h: Move offsetof(T, m) to a separate header
>   linux/offsetof.h: Implement offsetof() in terms of memberof()
>   linux/container_of.h: Implement container_of_safe() in terms of
>     container_of()
>   linux/container_of.h: Cosmetic
>   linux/container_of.h: Remove unnecessary cast to (void *)

My feeling is that this takes the separation too far: by having this many header
files that end up being included from practically every single .c file
in the kernel,
I think you end up making compile speed worse overall.

If your goal is to avoid having to recompile as much of the kernel
after touching
a header, I think a better approach is to help untangle the dependencies, e.g.
by splitting out type definitions from headers with inline functions (most
indirect header dependencies are on type definitions) and by focusing on
linux/fs.h, linux/sched.h, linux/mm.h and how they interact with the rest of the
headers. At the moment, these are included in most .c files and they in turn
include a ton of other headers.

          Arnd

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Alejandro Colomar (man-pages)]

Hi Arnd,

On 11/19/21 15:47, Arnd Bergmann wrote:
> On Fri, Nov 19, 2021 at 12:36 PM Alejandro Colomar
> <alx.manpages@gmail.com> wrote:
>>
>> Alejandro Colomar (17):
>>   linux/container_of.h: Add memberof(T, m)
>>   Use memberof(T, m) instead of explicit NULL dereference
>>   Replace some uses of memberof() by its wrappers
>>   linux/memberof.h: Move memberof() to separate header
>>   linux/typeof_member.h: Move typeof_member() to a separate header
>>   Simplify sizeof(typeof_member()) to sizeof_field()
>>   linux/NULL.h: Move NULL to a separate header
>>   linux/offsetof.h: Move offsetof(T, m) to a separate header
>>   linux/offsetof.h: Implement offsetof() in terms of memberof()
>>   linux/container_of.h: Implement container_of_safe() in terms of
>>     container_of()
>>   linux/container_of.h: Cosmetic
>>   linux/container_of.h: Remove unnecessary cast to (void *)
> 
> My feeling is that this takes the separation too far: by having this many header
> files that end up being included from practically every single .c file
> in the kernel,
> I think you end up making compile speed worse overall.
> 
> If your goal is to avoid having to recompile as much of the kernel
> after touching
> a header, I think a better approach is to help untangle the dependencies, e.g.
> by splitting out type definitions from headers with inline functions (most
> indirect header dependencies are on type definitions) and by focusing on
> linux/fs.h, linux/sched.h, linux/mm.h and how they interact with the rest of the
> headers. At the moment, these are included in most .c files and they in turn
> include a ton of other headers.

Yes, I would like to untangle the dependencies.

The main reason I started doing this splitting
is because I wouldn't be able to include
<linux/stddef.h> in some headers,
because it pulled too much stuff that broke unrelated things.

So that's why I started from there.

I for example would like to get NULL in memberof()
without puling anything else,
so <linux/NULL.h> makes sense for that.

It's clear that every .c wants NULL,
but it's not so clear that every .c wants
everything that <linux/stddef.h> pulls indirectly.

But I'll note that linux/fs.h, linux/sched.h, linux/mm.h are
interesting headers for further splitting.


BTW, I also have a longstanding doubt about
how header files are organized in the kernel,
and which headers can and cannot be included
from which other files.

For example I see that files in samples or scripts or tools,
that redefine many things such as offsetof() or ARRAY_SIZE(),
and I don't know if there's a good reason for that,
or if I should simply remove all that stuff and
include <linux/offsetof.h> everywhere I see offsetof() being used.



Thanks,
Alex

-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Andy Shevchenko]

On Fri, Nov 19, 2021 at 04:06:27PM +0100, Alejandro Colomar (man-pages) wrote:
> Hi Arnd,
> 
> On 11/19/21 15:47, Arnd Bergmann wrote:
> > On Fri, Nov 19, 2021 at 12:36 PM Alejandro Colomar
> > <alx.manpages@gmail.com> wrote:
> >>
> >> Alejandro Colomar (17):
> >>   linux/container_of.h: Add memberof(T, m)
> >>   Use memberof(T, m) instead of explicit NULL dereference
> >>   Replace some uses of memberof() by its wrappers
> >>   linux/memberof.h: Move memberof() to separate header
> >>   linux/typeof_member.h: Move typeof_member() to a separate header
> >>   Simplify sizeof(typeof_member()) to sizeof_field()
> >>   linux/NULL.h: Move NULL to a separate header
> >>   linux/offsetof.h: Move offsetof(T, m) to a separate header
> >>   linux/offsetof.h: Implement offsetof() in terms of memberof()
> >>   linux/container_of.h: Implement container_of_safe() in terms of
> >>     container_of()
> >>   linux/container_of.h: Cosmetic
> >>   linux/container_of.h: Remove unnecessary cast to (void *)
> > 
> > My feeling is that this takes the separation too far: by having this many header
> > files that end up being included from practically every single .c file
> > in the kernel,
> > I think you end up making compile speed worse overall.
> > 
> > If your goal is to avoid having to recompile as much of the kernel
> > after touching
> > a header, I think a better approach is to help untangle the dependencies, e.g.
> > by splitting out type definitions from headers with inline functions (most
> > indirect header dependencies are on type definitions) and by focusing on
> > linux/fs.h, linux/sched.h, linux/mm.h and how they interact with the rest of the
> > headers. At the moment, these are included in most .c files and they in turn
> > include a ton of other headers.
> 
> Yes, I would like to untangle the dependencies.
> 
> The main reason I started doing this splitting
> is because I wouldn't be able to include
> <linux/stddef.h> in some headers,
> because it pulled too much stuff that broke unrelated things.
> 
> So that's why I started from there.
> 
> I for example would like to get NULL in memberof()
> without puling anything else,
> so <linux/NULL.h> makes sense for that.

I don't believe that the code that uses NULL won't include types.h.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Alejandro Colomar (man-pages)]

Hi Andy,

On 11/19/21 16:34, Andy Shevchenko wrote:
> On Fri, Nov 19, 2021 at 04:06:27PM +0100, Alejandro Colomar (man-pages) wrote:
>> Yes, I would like to untangle the dependencies.
>>
>> The main reason I started doing this splitting
>> is because I wouldn't be able to include
>> <linux/stddef.h> in some headers,
>> because it pulled too much stuff that broke unrelated things.
>>
>> So that's why I started from there.
>>
>> I for example would like to get NULL in memberof()
>> without puling anything else,
>> so <linux/NULL.h> makes sense for that.
> 
> I don't believe that the code that uses NULL won't include types.h.

I'm not sure about the error I got (I didn't write it down),
but I got a compilation error.
That's why I split NULL.

If one could anwer my doubt,
I would be in better position to learn how to avoid them.
See below.

On 11/19/21 16:06, Alejandro Colomar (man-pages) wrote:
> BTW, I also have a longstanding doubt about
> how header files are organized in the kernel,
> and which headers can and cannot be included
> from which other files.
>
> For example I see that files in samples or scripts or tools,
> that redefine many things such as offsetof() or ARRAY_SIZE(),
> and I don't know if there's a good reason for that,
> or if I should simply remove all that stuff and
> include <linux/offsetof.h> everywhere I see offsetof() being used.

Thanks,
Alex



-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Arnd Bergmann]

On Fri, Nov 19, 2021 at 4:06 PM Alejandro Colomar (man-pages)
<alx.manpages@gmail.com> wrote:
> On 11/19/21 15:47, Arnd Bergmann wrote:
> > On Fri, Nov 19, 2021 at 12:36 PM Alejandro Colomar
>
> Yes, I would like to untangle the dependencies.
>
> The main reason I started doing this splitting
> is because I wouldn't be able to include
> <linux/stddef.h> in some headers,
> because it pulled too much stuff that broke unrelated things.
>
> So that's why I started from there.
>
> I for example would like to get NULL in memberof()
> without puling anything else,
> so <linux/NULL.h> makes sense for that.
>
> It's clear that every .c wants NULL,
> but it's not so clear that every .c wants
> everything that <linux/stddef.h> pulls indirectly.

From what I can tell, linux/stddef.h is tiny, I don't think it's really
worth optimizing this part. I have spent some time last year
trying to untangle some of the more interesting headers, but ended
up not completing this as there are some really hard problems
once you start getting to the interesting bits.

The approach I tried was roughly:

- For each header in the kernel, create a preprocessed version
  that includes all the indirect includes, from that start a set
  of lookup tables that record which header is eventually included
  by which ones, and the size of each preprocessed header in
  bytes

- For a given kernel configuration (e.g. defconfig or allmodconfig)
  that I'm most interested in, look at which files are built, and what
  the direct includes are in the source files.

- Sort the headers by the product of the number of direct includes
  and the preprocessed size: the largest ones are those that are
  worth looking at first.

- use graphviz to visualize the directed graph showing the includes
  between the top 100 headers in that list. You get something like
  I had in [1], or the version afterwards at [2].

- split out unneeded indirect includes from the headers in the center
  of that graph, typically by splitting out struct definitions.

- repeat.

The main problem with this approach is that as soon as you start
actually reducing the unneeded indirect includes, you end up with
countless .c files that no longer build because they are missing a
direct include for something that was always included somewhere
deep underneath, so I needed a second set of scripts to add
direct includes to every .c file.

On the plus side, I did see something on the order of a 30%
compile speed improvement with clang, which is insane
given that this only removed dead definitions.

> But I'll note that linux/fs.h, linux/sched.h, linux/mm.h are
> interesting headers for further splitting.
>
>
> BTW, I also have a longstanding doubt about
> how header files are organized in the kernel,
> and which headers can and cannot be included
> from which other files.
>
> For example I see that files in samples or scripts or tools,
> that redefine many things such as offsetof() or ARRAY_SIZE(),
> and I don't know if there's a good reason for that,
> or if I should simply remove all that stuff and
> include <linux/offsetof.h> everywhere I see offsetof() being used.

The main issue here is that user space code should not
include anything outside of include/uapi/ and arch/*/include/uapi/

offsetof() is defined in include/linux/stddef.h, so this is by
definition not accessible here. It appears that there is also
an include/uapi/linux/stddef.h that is really strange because
it includes linux/compiler_types.h, which in turn is outside
of uapi/. This should probably be fixed.

      Arnd

[1] https://drive.google.com/file/d/14IKifYDadg2W5fMsefxr4373jizo9bLl/view?usp=sharing
[2] https://drive.google.com/file/d/1pWQcv3_ZXGqZB8ogV-JOfoV-WJN2UNnd/view?usp=sharing

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Andy Shevchenko]

On Fri, Nov 19, 2021 at 04:57:46PM +0100, Arnd Bergmann wrote:
> On Fri, Nov 19, 2021 at 4:06 PM Alejandro Colomar (man-pages)
> <alx.manpages@gmail.com> wrote:
> > On 11/19/21 15:47, Arnd Bergmann wrote:
> > > On Fri, Nov 19, 2021 at 12:36 PM Alejandro Colomar
> >
> > Yes, I would like to untangle the dependencies.
> >
> > The main reason I started doing this splitting
> > is because I wouldn't be able to include
> > <linux/stddef.h> in some headers,
> > because it pulled too much stuff that broke unrelated things.
> >
> > So that's why I started from there.
> >
> > I for example would like to get NULL in memberof()
> > without puling anything else,
> > so <linux/NULL.h> makes sense for that.
> >
> > It's clear that every .c wants NULL,
> > but it's not so clear that every .c wants
> > everything that <linux/stddef.h> pulls indirectly.
> 
> From what I can tell, linux/stddef.h is tiny, I don't think it's really
> worth optimizing this part. I have spent some time last year
> trying to untangle some of the more interesting headers, but ended
> up not completing this as there are some really hard problems
> once you start getting to the interesting bits.
> 
> The approach I tried was roughly:
> 
> - For each header in the kernel, create a preprocessed version
>   that includes all the indirect includes, from that start a set
>   of lookup tables that record which header is eventually included
>   by which ones, and the size of each preprocessed header in
>   bytes
> 
> - For a given kernel configuration (e.g. defconfig or allmodconfig)
>   that I'm most interested in, look at which files are built, and what
>   the direct includes are in the source files.
> 
> - Sort the headers by the product of the number of direct includes
>   and the preprocessed size: the largest ones are those that are
>   worth looking at first.
> 
> - use graphviz to visualize the directed graph showing the includes
>   between the top 100 headers in that list. You get something like
>   I had in [1], or the version afterwards at [2].
> 
> - split out unneeded indirect includes from the headers in the center
>   of that graph, typically by splitting out struct definitions.
> 
> - repeat.
> 
> The main problem with this approach is that as soon as you start
> actually reducing the unneeded indirect includes, you end up with
> countless .c files that no longer build because they are missing a
> direct include for something that was always included somewhere
> deep underneath, so I needed a second set of scripts to add
> direct includes to every .c file.

Can't it be done with cocci support?

> On the plus side, I did see something on the order of a 30%
> compile speed improvement with clang, which is insane
> given that this only removed dead definitions.

Thumb up!

> > But I'll note that linux/fs.h, linux/sched.h, linux/mm.h are
> > interesting headers for further splitting.
> >
> >
> > BTW, I also have a longstanding doubt about
> > how header files are organized in the kernel,
> > and which headers can and cannot be included
> > from which other files.
> >
> > For example I see that files in samples or scripts or tools,
> > that redefine many things such as offsetof() or ARRAY_SIZE(),
> > and I don't know if there's a good reason for that,
> > or if I should simply remove all that stuff and
> > include <linux/offsetof.h> everywhere I see offsetof() being used.
> 
> The main issue here is that user space code should not
> include anything outside of include/uapi/ and arch/*/include/uapi/
> 
> offsetof() is defined in include/linux/stddef.h, so this is by
> definition not accessible here. It appears that there is also
> an include/uapi/linux/stddef.h that is really strange because
> it includes linux/compiler_types.h, which in turn is outside
> of uapi/. This should probably be fixed.
> 
>       Arnd
> 
> [1] https://drive.google.com/file/d/14IKifYDadg2W5fMsefxr4373jizo9bLl/view?usp=sharing
> [2] https://drive.google.com/file/d/1pWQcv3_ZXGqZB8ogV-JOfoV-WJN2UNnd/view?usp=sharing

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Arnd Bergmann]

On Fri, Nov 19, 2021 at 5:10 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
> On Fri, Nov 19, 2021 at 04:57:46PM +0100, Arnd Bergmann wrote:

> > The main problem with this approach is that as soon as you start
> > actually reducing the unneeded indirect includes, you end up with
> > countless .c files that no longer build because they are missing a
> > direct include for something that was always included somewhere
> > deep underneath, so I needed a second set of scripts to add
> > direct includes to every .c file.
>
> Can't it be done with cocci support?

There are many ways of doing it, but they all tend to suffer from the
problem of identifying which headers are actually needed based on
the contents of a file, and also figuring out where to put the extra
#include if there are complex #ifdefs.

For reference, see below for the naive pattern matching I tried.
This is obviously incomplete and partially wrong.

    Arnd

---
#!/bin/bash

GITARGS="$@"
declare HEADER
declare SEARCH
declare FILES
declare OTHERHEADERS

# insert <foo/baz.h> alphabetically after the nearest <foo/bar.h>
insertafter() {
MYFILES=`git grep -l "#include.*<${HEADER%/*}/.*>" $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
MYFILES=`grep -wL $HEADER $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
echo after $HEADER $MYFILES
echo $OTHERHEADERS | tr '[:space:]' '\n' | sort -ru | grep
^${HEADER%/*} | grep -A10000 ^$HEADER | grep -v ^$HEADER | tr / . |
while read i ; do

if [ -z "$MYFILES" ] ; then return ; fi
echo AFTER $i
echo $MYFILES | xargs sed -i '/include.*<'$i'>/ a #include '"<$HEADER>"
MYFILES=`grep -wL $HEADER $MYFILES`
done
}

# insert <foo/bar.h> alphabetically after the nearest <foo/baz.h>
insertbefore() {
MYFILES=`git grep -l "#include.*<${HEADER%/*}/.*>" $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
MYFILES=`grep -wL $HEADER $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
echo before $HEADER $MYFILES
echo $OTHERHEADERS | tr '[:space:]' '\n' | sort -u | grep
^${HEADER%/*} | grep -A10000 ^$HEADER | grep -v ^$HEADER | tr / . |
while read i ; do
if [ -z "$MYFILES" ] ; then return ; fi
echo BEFORE $i
echo $MYFILES | xargs sed -i '/include.*<'$i'>/ i #include '"<$HEADER>"
MYFILES=`grep -wL $HEADER $MYFILES`
done
}

# insert <foo/bar.h> before first <qux/quux.h>
insertcategory() {
MYFILES=`git grep -l "#include.*<.*/.*>" $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
MYFILES=`grep -wL $HEADER $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
for f in $MYFILES ; do
sed -i -e "/^#include.*<.*\/.*>/ { i #include <$HEADER>" -e " ; :L; n;
bL; } " $f
done
}

insertafterlocal() {
MYFILES=`git grep -l "#include.*\".*\"" $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
MYFILES=`grep -wL $HEADER $FILES`
if [ -z "$MYFILES" ] ; then return ; fi
for f in $MYFILES ; do
sed -i -e "/^#include.*\".*\/.*\"/ { a #include <$HEADER>" -e " ; :L;
n; bL; } " $f
done
}

x() {
HEADER="$1"
SEARCH="$2"
echo $HEADER
FILES=`git grep -wl "$SEARCH" | grep -v
"^\(Documentation\|include\|tools\|arch/.*/include\|arch/.*/boot/dts\|scripts\|samples\|arch/*/\(kernel/\|vdso\)\|lib/vdso\)\|classmap.h$"
| grep -v "\.S\>"`
if [ -z "$FILES" ] ; then return ; fi
        FILES=`echo $FILES | xargs grep $HEADER -L `
if [ -z "$FILES" ] ; then return ; fi
OTHERHEADERS=`echo $FILES | xargs grep -h  "include.*\<.*/.*\>" | cut
-f 2 -d\< | cut -f 1 -d \> | grep ^[-_a-zA-Z0-9]*/ ; echo $HEADER`

insertafter
insertbefore
insertcategory
# insertafterlocal
}

# error: implicit declaration of function 'skb_tunnel_rx'
[-Werror,-Wimplicit-function-declaration]
#x linux/debug_locks.h "\(__\|\)debug_locks_off"
#x linux/stat.h
"S_I\(R\|W\|X\)\(USR\|GRP\|OTH\|UGO\)\|S_IRWX\(UGO\|U\|G\|O\)\|S_IALLUGO"
#x linux/stat.h "[A-Z0-9_]*ATTR_\(RW\|RO\|WO\)"
#x linux/dev_printk.h "dev_\(debug\|info\|warn\|err\|notice\|alert\)"
x net/scheduler.h "dev_init_scheduler\|dev_activate"
x linux/sysfs.h
"sysfs_\(create\|remove\|update\|merge\|add_file_to\)_\(\(bin_\|\)file\|file_self\|group\|link\|mount_point\)\(\|s\|_ns\|\)\|sysfs_\(ops\|notify\|chmod_file\|get_dirent\|notify_dirent\|put\)"
x linux/kref.h "kref_get_unless_zero\|kref_get\|kref_init\|kref_read\|kref_put"
x linux/skb_alloc.h
"\(dev\|netdev\|__dev\|__netdev\)_alloc_skb\(\|_ip_align\)\|skb_frag_must_loop\|skb_fill_page_desc\|skb_queue_purge\|skb_rbtree_purge\|netdev_alloc_frag\|skb_frag_address_safe"
x linux/mutex.h
"DEFINE_MUTEX\|\(device\|mutex\|tty\)_\(lock\|unlock\|is_locked\|is_writelocked\)\|usb_\(un\|\)lock_device\|BLOCKING_INIT_NOTIFIER_HEAD\|mutex_init"
x linux/page.h "PAGE_ALIGN\|PAGE_ALIGNED\|dma_map_single\|offset_in_page\|page_address\|virt_to_head_page"
x linux/pgtable.h
"PAGE_\(KERNEL_EXEC\|KERNEL_RO\|KERNEL\|READONLY\)\|pgprot_\(writecombine\|device\|noncached\)"
x linux/if_vlan.h "is_vlan_dev\|vlan_dev_vlan_id\|vlan_get_protocol"
x linux/skb_alloc.h
"skb_frag_must_loop\|\(__\|\)skb_\(fill_page_desc\|queue_purge\|frag_\(address\|ref\|unref_\)\)\|\(__\|\)\(dev\|netdev\|napi\)_alloc_\(page\|pages\|skb\)\|napi_consume_skb\|skb_free_frag"
x linux/gfp.h "__page_frag_cache_drain\|page_frag_alloc"
x linux/skbuff.h "skb_\(copy\|get\|put\)\|skb_queue_[a-z]*"
x linux/iopoll.h
"\(phy_read_mmd\|phy_read\|regmap_field_read\|regmap_read\|read[bwl]\)_poll_timeout\(_atomic\|\)"
x linux/in.h "IPPROTO_\(IP\|TCP\|UDP\|SCTP\)\|struct\ sockaddr_in"
x net/sock.h "\(RCV\|SEND\)_SHUTDOWN\|sk_pacing_shift_update\|sk_capable\|sk_user_ns\|sock_queue_err_skb"
x net/sock.h "SOCKET_I\|\(bh_\|\)\(un\|\)lock_sock\(_nested\|\|_fast\)\|skb_set_owner_w\|skb_orphan_partial"
x linux/bitops.h
"\(__\|\)\(assign\|set\|clear\|test\)_bit\|sign_extend32\|sign_extend64\|for_each_\(set\|clear\)_bit\|get_count_order"
x linux/fs.h "\(un\|\)register_chrdev\(_region\|\)\|compat_ptr_ioctl\|file_clone_open\|filp_open\|filp_close"
x linux/mem_encrypt.h "mem_encrypt_active"
x linux/backlight.h "struct\
\(backlight_ops\|backlight_properties\|backlight_device\)\|backlight_\(enable\|disable\)"
x linux/sched.h "task_pid\(_nr\|\)"
x linux/fb.h "KHZ2PICOS\|PICOS2KHZ\|fb_get_options"
x linux/fcntl.h "O_CLOEXEC\|O_NONBLOCK"
x linux/dma-mapping.h
"\(dma\|dmam\)_\(\(alloc\|free\)_\(coherent\|attrs\)\|\(un\|\)map_\(single\|sg\|page\)\(\_attrs\|\)\)\|dma_set_mask\(_and_coherent\)\|DMA_\(BIT_MASK\|TO_DEVICE\|FROM_DEVICE\|BIDIRECTIONAL\)\|dma_set_max_seg_\(size\|boundary\)\|dma_debug_add_bus"
x linux/file_operations.h
"\(noop\|default\)_llseek\|\(static\|extern\|const\).*struct\
file_operations\|DEFINE_\(SHOW\|SEQ\|DEBUGFS\)_ATTRIBUTE\|iminor\|imajor\|DEFINE_\(SIMPLE\|DEBUGFS\)_ATTRIBUTE\|DEFINE_DRM_[A-Z_]*_FOPS"
x linux/file_operations.h
"\(file\|vm_file\|filp\)->\(private_data\|f_mapping\|f_cred\)\|file_inode"
x linux/bitmap.h
"\(__\|\)bitmap_\(fill\|copy\|zero\|alloc\|zalloc\|and\|or\|xor\|set\|weight\|clear\)"
x linux/mm_types.h "mm->mmap_lock"
x linux/wait.h "\(wait_event\|wake_up\)\(_interruptible\|_killable\|\)\|init_waitqueue_head"
x linux/workqueue.h "DEFINE_STATIC_SRCU\|DEFINE_SRCU\|INIT_WORK"
x linux/timex.h "get_cycles\|random_get_entropy\|struct\
__kernel_timex\|do_adjtimex\|shift_right"
x linux/lockdep.h
"lockdep_assert_irqs_disabled\|lockdep_init_map[_a-z]*\|INIT_DELAYED_WORK"
x linux/kobject_ns.h "kobj_ns_\(drop\|ops\|grab_current\)"
x linux/sched/signal.h "rlimit\(.*\)"
x linux/wait_bit.h
"wake_up_bit\|wait_on_bit\(_timeout\|_io\|_lock\|_lock_io\|_action\|\)\|wait_var_event[a-z_]*"
x linux/io.h "\(__raw_\|\)\(in\|out\|read\|write\)\(b\|w\|l\|q\)\(_p\|_relaxed\|\)\|\(ioread\|iowrite\)\(8\|16\|32\)\(\|_be\)\|wr32\|memset_io"
x linux/mm.h "\(get\|pin\)_user_pages\(_fast\|_locked\|_remote\|unlocked\|\)"
x linux/interrupt.h
"\(free_\|request_\|devm_request_\|enable_\|disable_\)\(threaded_\|\)irq"
x linux/completion.h
"\(re\|\)init_completion\|wait_for_completion\([a-z_]*\)\|struct\
completion\|complete(.*)\|DECLARE_COMPLETION_ONSTACK"
x linux/scatterlist.h
"sg_copy_to_buffer\|sg_nents_for_len\|sg_set_buf\|sg_chain\|sg_pcopy_to_buffer\|for_each_sg\|sg_next\|sg_init_table\|sg_virt\|sg_page\|sg_alloc_table\|sg_set_page\|sg_init_one\|sg_zero_buffer\|sg_dma_page_iter\|for_each_sg_dma_page\|sg_free_table"
x linux/hash.h "hash\(32_ptr\|ptr\|\(_32\|_64\)\(\|_generic\)\)"
x linux/bitmap.h "DECLARE_BITMAP\|bitmap_\(find\|allocate\|release\)_region"
x linux/rwsem.h
"\(up\|down\|downgrade\)_\(read\|write\)\(_killable\|\)\|BLOCKING_INIT_NOTIFIER_HEAD"
x linux/smp.h "get_cpu\|put_cpu\|smp_processor_id"
x linux/if_ether.h "sysfs_format_mac"
x linux/pgtable.h "swapper_pg_dir\|ZERO_PAGE"
x linux/jiffies.h
"jiffies\|get_jiffies_64\|SHIFT_HZ\|jiffies_to_.secs\|preset_lpj\|.secs_to_jiffies"
x linux/page.h "PAGE_ALIGN\|get_page\|put_page\|unpin_user_page\|page_maybe_dma_pinned\|page_to_nid\|page_zone\|page_zonenum\|unpin_user_pages_dirty_lock"
x linux/page.h "PageHighMem"
x linux/pid.h "pid_task\|get_pid\|find_vpid\|find_pid_ns\|put_pid"
x linux/sched.h
"\(wait_event\|wake_up\|wake_up_all\)\(_interruptible\|_killable\|_process\|_timeout\|\)\|current_cred\|kthread_run\|current_euid\|current_user_ns\|lockdep_assert_irqs_disabled"
x linux/of.h "of_parse_phandle[a-z_]*\|of_node->phandle"
x linux/sched/prio.h "MAX_RT_PRIO"
x linux/sched.h "SCHED_FIFO"
x linux/kdev_t.h "\(MINOR\|MAJOR\)(.*)"
x linux/idr.h "\(ida\|idr\)_\(alloc\|simple_get\|find\|for_each[a-z_]*\|destroy\|get_next\|get_cursor\)"
x linux/sched/signal.h "signal_pending"
x linux/math64.h
"\(div_\|div64_\)\(s64\|u64\)\(_rem\|\)\|div64_long\|div64_ul\|DIV64_U64_ROUND_\(UP\|CLOSEST\)\|DIV_ROUND_CLOSEST_ULL\|mul_u64_u32_div"
x linux/eventfd.h "eventfd_\(signal\|ctx_fdget\|ctx_put\)"
x linux/mm.h "find_vma\(_prev\|\)\|put_vaddr_frames\|frame_vector_pages\|frame_vector_to_pages\|frame_vector_destroy\|set_page_dirty\(_lock\|\)\|try_to_release_page\|write_one_page"
x linux/fs.h "AOP_TRUNCATED_PAGE\|AOP_WRITEPAGE_ACTIVATE\|AOP_FLAG_CONT_EXPAND"
x linux/vmalloc.h
"\(vm\|kv\|kvz\)\(free\|alloc\)\|vmalloc_to_page\|is_vmalloc_addr\|dma_map_single\(_attrs\|\)"
x linux/memory.h "high_memory\|virt_addr_valid"
x linux/percpu.h "DEFINE_PER_CPU[A-Z_]*\|per_cpu_ptr"
x linux/percpu-rwsem.h
"DEFINE_PER_CPU[A-Z_]*\|per_cpu_ptr\|percpu_\(down\|up\)_\(read\|write\)\(\|_trylock\)\|percpu_init_rwsem"
x linux/errno.h "EPROBE_DEFER\|EINVAL\|ENOMEM"
x linux/mmap_lock.h
"mmap_\(read\|write\|init\)_\(un\|try\|\)lock\(_non_owner\|_killable\|\)"
x net/net_namespace.h "get_net\|maybe_get_net\|put_net\|check_net\|net_eq"
x linux/nsproxy.h "current->nsproxy\|get_nsproxy\|put_nsproxy"
x linux/sched/task.h "\(put\|get\)_task_struct"
x linux/seq_file.h "seq_open\|single_open\|seq_printf\|seq->private"
x linux/page-flags.h "PG_\(buddy\|lru\|slab\|private\|swapcache\|swapmasked\)"
x linux/crash_core.h "VMCOREINFO_[A-Z]*"
x linux/nodemask.h "\(for_each\|first\)_\(memory_\|online_\|\)node"
x linux/interrupt.h "tasklet_\(init\|schedule\|disable\|enable\|unlock\|kill\)"
x linux/security.h "security_\(path_mknod\|bpf[a-z_]*\)"
x asm/byteorder.h
"\(be\|le\)\(16\|32\|64\)_to_cpu\|cpu_to_\(be\|le\)\(16\|32\|64\)\|\(ntoh\|hton\)\(s\|l\)"
x net/flow_dissector.h "struct flow_keys"
x linux/filter.h "sk_filter\|bpf_dump_raw_ok\|bpf_jit_enable"
x linux/mm.h "truncate_setsize\|truncate_pagecache"
x asm/unaligned.h "\(get\|put\)_unaligned\(\|_le\|_be\)\(16\|32\|64\|\)"
x linux/srcu.h "DEFINE_STATIC_SRCU\|DEFINE_SRCU"
x linux/seq_file_net.h "seq_file_\(single_\|\)net"
x linux/netdevice.h "struct\ napi_struct"
x asm/processor.h "cpu_relax"
x linux/fs.h "deactivate_locked_super\|file_dentry\|alloc_chrdev_region\|init_sync_kiocb\|get_file\|get_dma_buf\|rw_copy_check_uvector"
x linux/spinlock.h
"\(raw_\|arch_\|\)spin_\(try\|un\|\)lock\(_irq\|_irqsave\|_init\|\)\|dsb_sev\|ATOMIC_INIT_NOTIFIER_HEAD\|DEFINE_MUTEX"
x asm/tlbflush.h "flush_tlb_all"
x linux/workqueue.h "\(schedule\|queue\|cancel\)_\(delayed_\|\)work"
x linux/thread_info.h "current->[a-z_]*"
x linux/sched.h "current->[a-z_]*"
x linux/dcache.h "d_backing_dentry\|d_backing_inode\|d_path"
x linux/shrinker.h "register_shrinker\|prealloc_shrinker\|struct\
shrink_control"
x linux/fs_types.h "mapping->i_mmap\(\|rwsem\)"
x linux/fs.h "IOP_\(XATTR\|FASTPERM\|LOOKUP\|NOFOLLOW\|DEFAULT_READLINK\)"
x linux/mm.h "vmf_error\|filemap_fault\|clear_page_dirty_for_io\|vm_operations_struct"
x linux/pagemap.h "read_mapping_page\|read_cache_page\(_gfp\|\)"
x linux/slab.h "ZERO_SIZE_PTR"
x linux/capability.h "capable(.*)"
x linux/mm.h "truncate_inode_page[a-z_]*\|truncate_pageche"
x linux/fs.h "bdevname\|\(un\|\)register_blkdev\|revalidate_disk\|inode_\(un\|\)lock\|i_size_\(write\|read\)\|kill_fasync\|kernel_read_file_from_path"
x linux/fs.h "FMODE_\(WRITE\|READ\|EXEC\)"
x linux/fs_types.h "ATTR_MODE\|struct\ iattr"
x linux/fs_types.h
"\(bd_\|anon_\|\)inode->\(i_uid\|i_gid\|i_mmap\|i_generation\|i_sb\|i_opflags\|i_mmap_rwsem\|i_size\|i_data\|i_mapping\)"
x linux/path.h "path_get\|path_put"
x linux/file_operations.h
"simple_\(read_from_buffer\|write_to_buffer\|open\)\|nonseekable_open"
x linux/spinlock.h
"rwlock_init\|\(read\|write\)_\(lock\|unlock\)\(\|_irq\|\_bh\|_irqsave\)"
x linux/mod_devicetable.h
"\(platform\|of\|dmi\|mdio\|ispnp\|typec\|wmi\|i2c\|i3c\|spi\|slim\|sdio\|input\|pci\|pcmcia\|hda\|pnp\|acpi\|ccw\|ap\|hid\|usb\)_device_id"
x linux/filter.h "struct\ sk_filter\|bpf_compute_data_pointers\|struct bpf_prog"
x linux/if_ether.h "eth_hdr"
x linux/etherdevice.h "ether_addr_copy"
#inet_request_bound_dev_if
x linux/if_addr.h
"IFA_F_PERMANENT\|IFA_F_SECONDARY\|IFA_F_TENTATIVE\|IFA_F_OPTIMISTIC\|IFA_F_DEPRECATED\|IFA_MAX\|IFA_LOCAL\|struct\
ifaddrmsg"
x net/l3mdev.h "l3mdev_master_ifindex_rcu\|inet_sk_bound_l3mdev\|l3mdev_ip6_out"
x net/rtnetlink.h "struct\
rtnl_link_ops\|rtnl_link_register\|rtnl_lock\|MODULE_ALIAS_RTNL_LINK\|RTNL_FLAG_DOIT_UNLOCKED"
x linux/netdevice.h "enum\ tc_setup_type"
x linux/netlink.h "NL_SET_ERR_MSG_MOD"
x net/netlink.h
"nlmsg_parse_deprecated\|nlmsg_\(cancel\|data\|end\|msg_size\|attrlen\)\|nla_data\|nla_get_u32\|nla_put_in6_addr\|nla_total_size"
x linux/if_addrlabel.h "ifaddrlblmsg"
x linux/dcache.h "d_lookup_done\|file_dentry\|d_parent\|dget\|dput\|d_sb"
#inet_sk_bound_l3mdev
x net/netprio_cgroup.h
"sock_update_netprioidx\|task_netprioidx\|struct\ netprio_map"
x linux/device.h "\(get\|put\)_device"
x linux/kernel.h ARRAY_SIZE
x linux/bits.h "BIT(.*)\|GENMASK\|BITS_PER_BYTE"
x linux/of.h "of_get_property\|of_match_node\|of_get_child_by_name\|of_match_ptr\|of_property_read_[a-z0-9_]*"
x linux/pci-dma-compat.h
"PCI_DMA_FROMDEVICE\|PCI_DMA_TODEVICE\|PCI_DMA_NONE\|PCI_DMA_BIDIRECTIONAL\|pci_map_\(single\|sg\|page\)\|pci_\(zalloc\|alloc\|free\)_consistent\|pci_dma_mapping_error\|pci_set_\(dma_mask\|consistent_dma_mask\)"
x asm/compiler.h "__asmeq"
x asm/cpuidle.h "cpu_do_idle"
x crypto/hash.h
"SHASH_DESC_ON_STACK\|crypto_\(shash\|ahash\)_\(digest\|update\)\|ahash_request_set_crypt"
x linux/acpi.h "ACPI_PTR"
x linux/atomic.h
"INIT_WORK\|atomic\(\|64\|_long\)_\(get\|set\|add\|inc\|dec\|sub\|init\)"
x linux/bitops.h
"\(ror\|rol\|hweight\)\(8\|16\|32\|64\)\(fls\|ffs\)\(\|64\|_long\)\|__fls\|__ffs"
x linux/bpf-cgroup.h "bpf_cgroup_[a-z_]*\|cgroup_storage_type"
x linux/cgroup.h "cgroup_id\|task_dfl_cgroup\|cgroup_ancestor"
x linux/cpumask.h
"for_each_\(online\|possible\|present\)_cpu\|cpumask_\(of_node\|of_pci\)\|nr_cpu_ids"
x linux/cpumask.h "num_online_cpus"
x linux/debugobjects.h "debug_object_\(init\|activate\|free\|destroy\)"
x linux/device.h
"device_\(create\|remove\|update\)_\(\(bin_\|\)file\|group\|link\)\(\|s\|_ns\|\)"
x linux/device.h "devm_\(kfree\|kzalloc\|kmalloc\|kcalloc\)"
x linux/err.h "ERR_PTR\|PTR_ERR\|PTR_ERR_OR_ZERO\|IS_ERR\|MAX_ERRNO"
x linux/filter.h "bpf_stats_enabled_key"
x linux/gfp.h "\(__\|\)\(alloc\|free\|get_free\|get_zeroed\)_page\(s\|\)\(_exact\|_node\|\)"
x linux/gfp.h "pm_restore_gfp_mask\|gfpflags_allow_blocking"
x linux/gpio.h "\(devm_\|\)gpio_\(\(set_value\|get_value\)\(_cansleep\|\)\|request\(_one\|\)\|to_irq\|is_valid\|direction_[a-z]*\|free\)"
x linux/gpio/consumer.h
"GPIOD_\(ASIS\|IN\|OUT[A-Z_]*\)\|\(devm_\|\)gpiod_get\(\|_index\|_array\)\(_optional\)\|gpio_\(free\|request\direction_output\|direction_input\)"
x linux/hardirq.h "rcu_nmi_exit"
x linux/i2c.h "struct\ i2c_board_info"
x linux/if_link.h "ifla_vf_info"
x linux/ioctl.h "\(_IO\|_IOR\|_IOW\|_IOWR\)"
x linux/ioprio.h
"get_current_ioprio\|task_nice_io\(class\|prio\)\|init_sync_kiocb"
x linux/kobject.h "\(mm\|kernel\|hypervisor\|fs\)_kobj"
x linux/kobject.h "kernel_kobj"
x linux/kobject.h
"kobject_\(get\|put\|uevent\|get_path\|uevent_env\|set_name\|del\|create\|create_and_add\)\|add_uevent_var"
x linux/log2.h "is_power_of_2\|ilog2"
x linux/math64.h "do_div\|DIV_ROUND_UP_ULL\|DIV_ROUND_DOWN_ULL"
x linux/memcontrol.h "lock_page_memcg\|get_mem_cgroup_from_page\|mem_cgroup_put"
x linux/memory_hotplug.h
"get_online_mems\|put_online_mems\|movable_node_is_enabled\|pfn_to_online_page\|try_online_node"
x linux/mm.h "VMALLOC_START\|VMALLOC_END\|VMALLOC_TOTAL\|unmap_mapping_range\|si_meminfo\|totalram_pages"
x linux/mm.h "VM_READ\|VM_WRITE\|VM_EXEC\|VM_NONE\|VM_SHARED\|VM_DONTDUMP\|VM_DONTEXPAND\|VM_DONTCOPY\|\(io_\|\)remap_pfn_range"
x linux/mm.h "truncate_inode_pages_final\|truncate_inode_pages_range\|vma_pages\|set_page_dirty\|want_init_on_\(alloc\|free\)"
x linux/mmzone.h "MAX_ORDER\|KMALLOC_MAX_SIZE"
x linux/module.h
"MODULE_\(LICENSE\|AUTHOR\|DESCRIPTION\|PARM_DESC\|ALIAS.*\|DEVICE_TABLE\)"
x linux/module.h
"register_module_notifier\|MODULE_STATE_COMING\|MODULE_STATE_GOING\|try_module_get\|lookup_module_symbol_attrs\|lookup_module_symbol_attrs\|module_put\|__module_get"
x linux/notifier.h "struct\
notifier_block\|NOTIFY_DONE\|NOTIFY_OK\|\(atomic\|blocking\|raw\|srcu\)_notifier_chain_\(\(un\|\)register\|call_chain\)\|\(ATOMIC\|BLOCKING\|RAW\)_INIT_NOTIFIER_HEAD"
x linux/of_platform.h
"\(devm_\|\)of_platform_\(populate\|register_reconfig_notifier\|default_populate\|depopulate\)"
x linux/of_platform.h "of_find_device_by_node"
x linux/osq_lock.h "osq_\(lock_init\|lock\|unlock\|is_locked\)"
x linux/pagemap.h "page_endio\|mapping_\(set_\|\)gfp_mask"
x linux/poll.h "poll_wait"
x linux/proc_fs.h "struct\
proc_ops\|proc_mkdir\|proc_create\|remove_proc_\(entry\|file\)"
x linux/ptrace.h "instruction_pointer"
x linux/radix-tree.h "radix_tree_[a-z_]*\|RADIX_TREE_MAX_TAGS"
x linux/random.h "\(get_random_\|prandom\_\)\(u32\|u64\|long\|bytes\)"
x linux/ratelimit.h
"ratelimit_\(state_init\|set_flags\)\|WARN_ON_RATELIMIT\|WARN_RATELIMIT\|pr_[a-z]*_ratelimited"
x linux/rbtree.h
"rb_\(prev\|erase\|link_node\|first\|insert_color\|root\|node\)"
x linux/rbtree_latch.h "latch_tree_[a-z]*"
x linux/rculist.h
"\(list\|__hlist\|hlist\)_\(for_each_[a-z_]*\|next\|first\|tail\|add\|add_tail\|del\|del_init\|entry\)_rcu"
x linux/rcupdate.h "synchronize_rcu"
x linux/rcuwait.h "rcuwait_init\|rcuwait_wait_event"
x linux/regmap.h "regmap_read_poll_timeout\(_atomic\|\)"
x linux/sched.h "TASK_\(\(UN\|\)INTERRUPTIBLE\|NORMAL\|KILLABLE\)"
x linux/sched.h
"cond_resched\|set_current_state\|current->comm\|need_resched\|schedule_timeout\(_killable\|_interruptible\|_idle\|\)\|schedule()"
x linux/sched/pagefault.h "pagefault_\(en\|dis\)able"
x linux/semaphore.h "struct\
semaphore\|down_\(interruptible\|killable\|timeout\|trylock\)\|sema_init"
x linux/seqlock.h "\(__\|raw_\|\)\(read\|write\)_seqcount_begin"
x linux/skbuff.h
"skb_\(push\|pull\|tailroom\|trim\|shinfo\|share_check\|reserve\|queue_[a-z_]*\|headlen\|cloned\)"
x linux/slab.h "\(kfree\|kzalloc\|kmalloc\|kcalloc\)"
x linux/spinlock.h "vcpu_is_preempted"
x linux/string.h
"memcpy\|memcmp\|strcmp\|strncmp\|kmemdup\|memset\|strcat\|strncat\|strlcat\|strstr\|strlen"
x linux/swap.h "mark_page_accessed\|nr_free_buffer_pages"
x linux/swap.h "si_swapinfo\|shrink_all_memory"
x linux/sysctl.h
"proc_do\(string\|\(long\|int\|uint\)vec\)[a-z_]*\|proc_handler\|ctl_table\|register_sysctl[a-z_]*"
x linux/timekeeping.h
"ktime_get[_a-z0-9]*\|ktime_mono_to_real\|JFFS2_NOW\|getboottime64"
x linux/topology.h "cpu_to_node\|node_distance"
x linux/u64_stats_sync.h "u64_stats_\(init\|update_begin\)"
x linux/uaccess.h "\(__\|\)\(get\|put\|copy_from\|copy_to\)_user"
x linux/uprobes.h "uprobe_\(munmap\|mmap\)"
x linux/watch_queue.h
"watch_sizeof\|add_watch_to_object\|put_watch_queue\|remove_watch_list"
x linux/xarray.h "xa_\(alloc\|linux_32b\|erase\|load\|for_each\)\|XA_CHUNK_SIZE"
x net/gro.h "skb_gro_[a-z_0-z]*"
x net/gso.h "skb_gso_[a-z_0-z]*"
x sound/soc-component.h
"snd_soc_component\(_driver\|_set_sysclk\|_set_pll\|\)\|snd_soc_dapm_to_component"

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Alejandro Colomar (man-pages)]

On 11/19/21 17:18, Arnd Bergmann wrote:
> On Fri, Nov 19, 2021 at 5:10 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
>> On Fri, Nov 19, 2021 at 04:57:46PM +0100, Arnd Bergmann wrote:
> 
>>> The main problem with this approach is that as soon as you start
>>> actually reducing the unneeded indirect includes, you end up with
>>> countless .c files that no longer build because they are missing a
>>> direct include for something that was always included somewhere
>>> deep underneath, so I needed a second set of scripts to add
>>> direct includes to every .c file.
>>
>> Can't it be done with cocci support?
> 
> There are many ways of doing it, but they all tend to suffer from the
> problem of identifying which headers are actually needed based on
> the contents of a file, and also figuring out where to put the extra
> #include if there are complex #ifdefs.
> 
> For reference, see below for the naive pattern matching I tried.
> This is obviously incomplete and partially wrong.

FYI, if you may not know the tool,
theres include-what-you-use(1) (a.k.a. iwyu(1))[1],
although it is still not mature,
and I'm helping improve it a bit.

If I understood better the kernel Makefiles,
I'd try it.

You can try it yourselves.
I still can't use it for my own code,
since it has a lot of false positives.

Cheers,
Alex

[1]: <https://include-what-you-use.org/>


-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Arnd Bergmann]

On Fri, Nov 19, 2021 at 5:22 PM Alejandro Colomar (man-pages)
<alx.manpages@gmail.com> wrote:
> On 11/19/21 17:18, Arnd Bergmann wrote:
> > On Fri, Nov 19, 2021 at 5:10 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> >> On Fri, Nov 19, 2021 at 04:57:46PM +0100, Arnd Bergmann wrote:
> >
> >>> The main problem with this approach is that as soon as you start
> >>> actually reducing the unneeded indirect includes, you end up with
> >>> countless .c files that no longer build because they are missing a
> >>> direct include for something that was always included somewhere
> >>> deep underneath, so I needed a second set of scripts to add
> >>> direct includes to every .c file.
> >>
> >> Can't it be done with cocci support?
> >
> > There are many ways of doing it, but they all tend to suffer from the
> > problem of identifying which headers are actually needed based on
> > the contents of a file, and also figuring out where to put the extra
> > #include if there are complex #ifdefs.
> >
> > For reference, see below for the naive pattern matching I tried.
> > This is obviously incomplete and partially wrong.
>
> FYI, if you may not know the tool,
> theres include-what-you-use(1) (a.k.a. iwyu(1))[1],
> although it is still not mature,
> and I'm helping improve it a bit.

Yes, I know that one, I tried using it as well, but it did not really
scale to the size of the kernel as it requires having all files to use
the correct set of #include, and to know about all the definitions.

       Arnd

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Andy Shevchenko]

On Fri, Nov 19, 2021 at 05:22:48PM +0100, Alejandro Colomar (man-pages) wrote:
> 
> 
> On 11/19/21 17:18, Arnd Bergmann wrote:
> > On Fri, Nov 19, 2021 at 5:10 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> >> On Fri, Nov 19, 2021 at 04:57:46PM +0100, Arnd Bergmann wrote:
> > 
> >>> The main problem with this approach is that as soon as you start
> >>> actually reducing the unneeded indirect includes, you end up with
> >>> countless .c files that no longer build because they are missing a
> >>> direct include for something that was always included somewhere
> >>> deep underneath, so I needed a second set of scripts to add
> >>> direct includes to every .c file.
> >>
> >> Can't it be done with cocci support?
> > 
> > There are many ways of doing it, but they all tend to suffer from the
> > problem of identifying which headers are actually needed based on
> > the contents of a file, and also figuring out where to put the extra
> > #include if there are complex #ifdefs.
> > 
> > For reference, see below for the naive pattern matching I tried.
> > This is obviously incomplete and partially wrong.
> 
> FYI, if you may not know the tool,
> theres include-what-you-use(1) (a.k.a. iwyu(1))[1],
> although it is still not mature,
> and I'm helping improve it a bit.

Yes, I know the tool, but it produces insanity. Jonathan (maintainer
of IIO subsystem) actually found it useful after manual work applied.
Perhaps you can chat with him about usage of it in the Linux kernel.

> If I understood better the kernel Makefiles,
> I'd try it.
> 
> You can try it yourselves.
> I still can't use it for my own code,
> since it has a lot of false positives.

> [1]: <https://include-what-you-use.org/>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Jonathan Cameron]

On Fri, 19 Nov 2021 18:35:26 +0200
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Fri, Nov 19, 2021 at 05:22:48PM +0100, Alejandro Colomar (man-pages) wrote:
> > 
> > 
> > On 11/19/21 17:18, Arnd Bergmann wrote:  
> > > On Fri, Nov 19, 2021 at 5:10 PM Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com> wrote:  
> > >> On Fri, Nov 19, 2021 at 04:57:46PM +0100, Arnd Bergmann wrote:  
> > >   
> > >>> The main problem with this approach is that as soon as you start
> > >>> actually reducing the unneeded indirect includes, you end up with
> > >>> countless .c files that no longer build because they are missing a
> > >>> direct include for something that was always included somewhere
> > >>> deep underneath, so I needed a second set of scripts to add
> > >>> direct includes to every .c file.  
> > >>
> > >> Can't it be done with cocci support?  
> > > 
> > > There are many ways of doing it, but they all tend to suffer from the
> > > problem of identifying which headers are actually needed based on
> > > the contents of a file, and also figuring out where to put the extra
> > > #include if there are complex #ifdefs.
> > > 
> > > For reference, see below for the naive pattern matching I tried.
> > > This is obviously incomplete and partially wrong.  
> > 
> > FYI, if you may not know the tool,
> > theres include-what-you-use(1) (a.k.a. iwyu(1))[1],
> > although it is still not mature,
> > and I'm helping improve it a bit.  
> 
> Yes, I know the tool, but it produces insanity. Jonathan (maintainer
> of IIO subsystem) actually found it useful after manual work applied.
> Perhaps you can chat with him about usage of it in the Linux kernel.

IIO drivers use a fairly limited subset of headers, so it wasn't implausible
to produce a mapping file to get to fairly sane results.

https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=iio-iwyu-cleanups&id=8bc7ff8d5385e89a5199e792fda18dbf2ca8f2e5

If we did head towards a general mapping file that 'more or less made sense'
then maybe this tool can be fairly useful kernel wide.

Typical patch that results in clean checks with that mapping file is:
https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=iio-iwyu-cleanups&id=0eff2dd097add84c464710003c3bc9929f646427

There are always going to be questions of how many of the really low level
direct includes make sense though which was the stumbling block.

It is nice to get rid of the pointless includes though for things that due
to refactors etc are no longer used in a file, or were cut and paste from
another driver.

I've paused efforts on this front for now given series like this one can
have significant impact and it seems to be an active area at the moment.
Might revisit later this cycle.

Jonathan

> 
> > If I understood better the kernel Makefiles,
> > I'd try it.
> > 
> > You can try it yourselves.
> > I still can't use it for my own code,
> > since it has a lot of false positives.  
> 
> > [1]: <https://include-what-you-use.org/>  
> 

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Alejandro Colomar (man-pages)]

Hi Arnd,

On 11/19/21 16:57, Arnd Bergmann wrote:
> 
> From what I can tell, linux/stddef.h is tiny, I don't think it's really
> worth optimizing this part. I have spent some time last year
> trying to untangle some of the more interesting headers, but ended
> up not completing this as there are some really hard problems
> once you start getting to the interesting bits.

In this case it was not about being worth it or not,
but that the fact that adding memberof() would break,
unless I use 0 instead of NULL for the implementation of memberof(),
which I'm against,
or I split stddef.

If I don't do either of those,
I'm creating a circular dependency,
and it doesn't compile.

> 
> The approach I tried was roughly:
> 
> - For each header in the kernel, create a preprocessed version
>   that includes all the indirect includes, from that start a set
>   of lookup tables that record which header is eventually included
>   by which ones, and the size of each preprocessed header in
>   bytes
> 
> - For a given kernel configuration (e.g. defconfig or allmodconfig)
>   that I'm most interested in, look at which files are built, and what
>   the direct includes are in the source files.
> 
> - Sort the headers by the product of the number of direct includes
>   and the preprocessed size: the largest ones are those that are
>   worth looking at first.
> 
> - use graphviz to visualize the directed graph showing the includes
>   between the top 100 headers in that list. You get something like
>   I had in [1], or the version afterwards at [2].
> 
> - split out unneeded indirect includes from the headers in the center
>   of that graph, typically by splitting out struct definitions.
> 
> - repeat.
> 
> The main problem with this approach is that as soon as you start
> actually reducing the unneeded indirect includes, you end up with
> countless .c files that no longer build because they are missing a
> direct include for something that was always included somewhere
> deep underneath, so I needed a second set of scripts to add
> direct includes to every .c file.
> 
> On the plus side, I did see something on the order of a 30%
> compile speed improvement with clang, which is insane
> given that this only removed dead definitions.

Huh!

I'd like to see the kernel some day
not having _any_ hidden dependencies.

For the moment,
since my intent is familiarizing with kernel programming,
and not necessarily improving performance considerably
(at least not in the first rounds of changes),
I prefer starting where it more directly affects
what I initially intended to change in the kernel,
which in this case was adding memberof().

> 
>> But I'll note that linux/fs.h, linux/sched.h, linux/mm.h are
>> interesting headers for further splitting.
>>
>>
>> BTW, I also have a longstanding doubt about
>> how header files are organized in the kernel,
>> and which headers can and cannot be included
>> from which other files.
>>
>> For example I see that files in samples or scripts or tools,
>> that redefine many things such as offsetof() or ARRAY_SIZE(),
>> and I don't know if there's a good reason for that,
>> or if I should simply remove all that stuff and
>> include <linux/offsetof.h> everywhere I see offsetof() being used.
> 
> The main issue here is that user space code should not
> include anything outside of include/uapi/ and arch/*/include/uapi/

Okay.  That's good to know.

So everything can use uapi code,
and uapi code can only use uapi code,
right?

Every duplicate definition of something outside of uapi
should/could be removed.

> 
> offsetof() is defined in include/linux/stddef.h, so this is by
> definition not accessible here. It appears that there is also
> an include/uapi/linux/stddef.h that is really strange because
> it includes linux/compiler_types.h, which in turn is outside
> of uapi/. This should probably be fixed.

I see.
Then,
perhaps it would be better to define offsetof() _only_ inside uapi/,
and use that definition from everywhere else,
and therefore remove the non-uapi version,
right?

Thanks,
Alex


-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Arnd Bergmann]

On Fri, Nov 19, 2021 at 5:12 PM Alejandro Colomar (man-pages)
<alx.manpages@gmail.com> wrote:
>
> On 11/19/21 16:57, Arnd Bergmann wrote:
> >
> > From what I can tell, linux/stddef.h is tiny, I don't think it's really
> > worth optimizing this part. I have spent some time last year
> > trying to untangle some of the more interesting headers, but ended
> > up not completing this as there are some really hard problems
> > once you start getting to the interesting bits.
>
> In this case it was not about being worth it or not,
> but that the fact that adding memberof() would break,
> unless I use 0 instead of NULL for the implementation of memberof(),
> which I'm against, or I split stddef.
>
> If I don't do either of those,
> I'm creating a circular dependency,
> and it doesn't compile.

Sorry for missing the background here, but I don't see what that
dependency is. If memberof() is a macro, then including the definition
should not require having the NULL definition first, you just need to
have both at the time you use it.

> > The main issue here is that user space code should not
> > include anything outside of include/uapi/ and arch/*/include/uapi/
>
> Okay.  That's good to know.
>
> So everything can use uapi code,
> and uapi code can only use uapi code,
> right?

Correct.

> > offsetof() is defined in include/linux/stddef.h, so this is by
> > definition not accessible here. It appears that there is also
> > an include/uapi/linux/stddef.h that is really strange because
> > it includes linux/compiler_types.h, which in turn is outside
> > of uapi/. This should probably be fixed.
>
> I see.
> Then,
> perhaps it would be better to define offsetof() _only_ inside uapi/,
> and use that definition from everywhere else,
> and therefore remove the non-uapi version,
> right?

No, because the user-space <stddef.h> provided by the compiler
also includes an offsetof() definition. In the uapi/ namespace, the
kernel must only provide definitions that do not clash with anything
in user space.

        Arnd

Re: [PATCH 00/17] Add memberof(), split some headers, and slightly simplify code

[Andy Shevchenko]

On Fri, Nov 19, 2021 at 05:12:19PM +0100, Alejandro Colomar (man-pages) wrote:
> On 11/19/21 16:57, Arnd Bergmann wrote:

...

> > On the plus side, I did see something on the order of a 30%
> > compile speed improvement with clang, which is insane
> > given that this only removed dead definitions.
> 
> Huh!
> 
> I'd like to see the kernel some day
> not having _any_ hidden dependencies.

It's neither feasible nor practical. If we know the hard dependencies between
headers, why should we not use implicit inclusion?

We all know that bitmap.h includes bitops.h and this is good and a must, why
to avoid this?

-- 
With Best Regards,
Andy Shevchenko