Currently, there are 3 different macros, namely sizeof_field, SIZEOF_FIELD
and FIELD_SIZEOF which are used to calculate the size of a member of
structure, so to bring uniformity in entire kernel source tree lets use
FIELD_SIZEOF and replace all occurrences of other two macros with this.
For this purpose, redefine FIELD_SIZEOF in include/linux/stddef.h and
tools/testing/selftests/bpf/bpf_util.h and remove its defination from
include/linux/kernel.h
In favour of FIELD_SIZEOF, this patch also deprecates other two similar
macros sizeof_field and SIZEOF_FIELD.
For code compatibility reason, retain sizeof_field macro as a wrapper macro
to FIELD_SIZEOF
Signed-off-by: Shyam Saini <[email protected]>
---
Changelog:
V1->V2
- Consolidate previous patch 1 and 2 into single patch
- For code compatibility reason, retain sizeof_field macro as a
wrapper macro to FIELD_SIZEOF
arch/arm64/include/asm/processor.h | 10 +++++-----
arch/mips/cavium-octeon/executive/cvmx-bootmem.c | 9 +--------
drivers/gpu/drm/i915/gvt/scheduler.c | 2 +-
drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c | 4 ++--
fs/befs/linuxvfs.c | 2 +-
fs/ext2/super.c | 2 +-
fs/ext4/super.c | 2 +-
fs/freevxfs/vxfs_super.c | 2 +-
fs/orangefs/super.c | 2 +-
fs/ufs/super.c | 2 +-
include/linux/kernel.h | 9 ---------
include/linux/slab.h | 2 +-
include/linux/stddef.h | 17 ++++++++++++++---
kernel/fork.c | 2 +-
kernel/utsname.c | 2 +-
net/caif/caif_socket.c | 2 +-
net/core/skbuff.c | 2 +-
net/ipv4/raw.c | 2 +-
net/ipv6/raw.c | 2 +-
net/sctp/socket.c | 4 ++--
tools/testing/selftests/bpf/bpf_util.h | 22 +++++++++++++++++++---
virt/kvm/kvm_main.c | 2 +-
22 files changed, 58 insertions(+), 47 deletions(-)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index fcd0e691b1ea..ace906d887cc 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -164,13 +164,13 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset,
unsigned long *size)
{
/* Verify that there is no padding among the whitelisted fields: */
- BUILD_BUG_ON(sizeof_field(struct thread_struct, uw) !=
- sizeof_field(struct thread_struct, uw.tp_value) +
- sizeof_field(struct thread_struct, uw.tp2_value) +
- sizeof_field(struct thread_struct, uw.fpsimd_state));
+ BUILD_BUG_ON(FIELD_SIZEOF(struct thread_struct, uw) !=
+ FIELD_SIZEOF(struct thread_struct, uw.tp_value) +
+ FIELD_SIZEOF(struct thread_struct, uw.tp2_value) +
+ FIELD_SIZEOF(struct thread_struct, uw.fpsimd_state));
*offset = offsetof(struct thread_struct, uw);
- *size = sizeof_field(struct thread_struct, uw);
+ *size = FIELD_SIZEOF(struct thread_struct, uw);
}
#ifdef CONFIG_COMPAT
diff --git a/arch/mips/cavium-octeon/executive/cvmx-bootmem.c b/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
index ba8f82a29a81..44b506a14666 100644
--- a/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
+++ b/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
@@ -45,13 +45,6 @@ static struct cvmx_bootmem_desc *cvmx_bootmem_desc;
/* See header file for descriptions of functions */
/**
- * This macro returns the size of a member of a structure.
- * Logically it is the same as "sizeof(s::field)" in C++, but
- * C lacks the "::" operator.
- */
-#define SIZEOF_FIELD(s, field) sizeof(((s *)NULL)->field)
-
-/**
* This macro returns a member of the
* cvmx_bootmem_named_block_desc_t structure. These members can't
* be directly addressed as they might be in memory not directly
@@ -65,7 +58,7 @@ static struct cvmx_bootmem_desc *cvmx_bootmem_desc;
#define CVMX_BOOTMEM_NAMED_GET_FIELD(addr, field) \
__cvmx_bootmem_desc_get(addr, \
offsetof(struct cvmx_bootmem_named_block_desc, field), \
- SIZEOF_FIELD(struct cvmx_bootmem_named_block_desc, field))
+ FIELD_SIZEOF(struct cvmx_bootmem_named_block_desc, field))
/**
* This function is the implementation of the get macros defined
diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
index 0f919f0a43d4..820f95a52542 100644
--- a/drivers/gpu/drm/i915/gvt/scheduler.c
+++ b/drivers/gpu/drm/i915/gvt/scheduler.c
@@ -1243,7 +1243,7 @@ int intel_vgpu_setup_submission(struct intel_vgpu *vgpu)
sizeof(struct intel_vgpu_workload), 0,
SLAB_HWCACHE_ALIGN,
offsetof(struct intel_vgpu_workload, rb_tail),
- sizeof_field(struct intel_vgpu_workload, rb_tail),
+ FIELD_SIZEOF(struct intel_vgpu_workload, rb_tail),
NULL);
if (!s->workloads) {
diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
index 46baf3b44309..c0447bf07fbb 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
@@ -49,13 +49,13 @@ struct mlxsw_sp_fid_8021d {
};
static const struct rhashtable_params mlxsw_sp_fid_ht_params = {
- .key_len = sizeof_field(struct mlxsw_sp_fid, fid_index),
+ .key_len = FIELD_SIZEOF(struct mlxsw_sp_fid, fid_index),
.key_offset = offsetof(struct mlxsw_sp_fid, fid_index),
.head_offset = offsetof(struct mlxsw_sp_fid, ht_node),
};
static const struct rhashtable_params mlxsw_sp_fid_vni_ht_params = {
- .key_len = sizeof_field(struct mlxsw_sp_fid, vni),
+ .key_len = FIELD_SIZEOF(struct mlxsw_sp_fid, vni),
.key_offset = offsetof(struct mlxsw_sp_fid, vni),
.head_offset = offsetof(struct mlxsw_sp_fid, vni_ht_node),
};
diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
index 462d096ff3e9..06ffd4829e2e 100644
--- a/fs/befs/linuxvfs.c
+++ b/fs/befs/linuxvfs.c
@@ -438,7 +438,7 @@ befs_init_inodecache(void)
SLAB_ACCOUNT),
offsetof(struct befs_inode_info,
i_data.symlink),
- sizeof_field(struct befs_inode_info,
+ FIELD_SIZEOF(struct befs_inode_info,
i_data.symlink),
init_once);
if (befs_inode_cachep == NULL)
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 1d7ab73b1014..d9a6c81f4a47 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -220,7 +220,7 @@ static int __init init_inodecache(void)
(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
SLAB_ACCOUNT),
offsetof(struct ext2_inode_info, i_data),
- sizeof_field(struct ext2_inode_info, i_data),
+ FIELD_SIZEOF(struct ext2_inode_info, i_data),
init_once);
if (ext2_inode_cachep == NULL)
return -ENOMEM;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 4079605d437a..b1b5856248bd 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1148,7 +1148,7 @@ static int __init init_inodecache(void)
(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
SLAB_ACCOUNT),
offsetof(struct ext4_inode_info, i_data),
- sizeof_field(struct ext4_inode_info, i_data),
+ FIELD_SIZEOF(struct ext4_inode_info, i_data),
init_once);
if (ext4_inode_cachep == NULL)
return -ENOMEM;
diff --git a/fs/freevxfs/vxfs_super.c b/fs/freevxfs/vxfs_super.c
index a89f68c3cbed..ffd22f85bbe0 100644
--- a/fs/freevxfs/vxfs_super.c
+++ b/fs/freevxfs/vxfs_super.c
@@ -329,7 +329,7 @@ vxfs_init(void)
sizeof(struct vxfs_inode_info), 0,
SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
offsetof(struct vxfs_inode_info, vii_immed.vi_immed),
- sizeof_field(struct vxfs_inode_info,
+ FIELD_SIZEOF(struct vxfs_inode_info,
vii_immed.vi_immed),
NULL);
if (!vxfs_inode_cachep)
diff --git a/fs/orangefs/super.c b/fs/orangefs/super.c
index ee5efdc35cc1..30f625059ad9 100644
--- a/fs/orangefs/super.c
+++ b/fs/orangefs/super.c
@@ -646,7 +646,7 @@ int orangefs_inode_cache_initialize(void)
ORANGEFS_CACHE_CREATE_FLAGS,
offsetof(struct orangefs_inode_s,
link_target),
- sizeof_field(struct orangefs_inode_s,
+ FIELD_SIZEOF(struct orangefs_inode_s,
link_target),
orangefs_inode_cache_ctor);
diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index 3d247c0d92aa..1e8bcd950f6d 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -1469,7 +1469,7 @@ static int __init init_inodecache(void)
(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
SLAB_ACCOUNT),
offsetof(struct ufs_inode_info, i_u1.i_symlink),
- sizeof_field(struct ufs_inode_info,
+ FIELD_SIZEOF(struct ufs_inode_info,
i_u1.i_symlink),
init_once);
if (ufs_inode_cachep == NULL)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 74b1ee9027f5..4672391cdb5b 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -79,15 +79,6 @@
*/
#define round_down(x, y) ((x) & ~__round_mask(x, y))
-/**
- * FIELD_SIZEOF - get the size of a struct's field
- * @t: the target struct
- * @f: the target struct's field
- * Return: the size of @f in the struct definition without having a
- * declared instance of @t.
- */
-#define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
-
#define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP
#define DIV_ROUND_DOWN_ULL(ll, d) \
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 9449b19c5f10..8bdfdd389b37 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -175,7 +175,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *);
sizeof(struct __struct), \
__alignof__(struct __struct), (__flags), \
offsetof(struct __struct, __field), \
- sizeof_field(struct __struct, __field), NULL)
+ FIELD_SIZEOF(struct __struct, __field), NULL)
/*
* Common kmalloc functions provided by all allocators
diff --git a/include/linux/stddef.h b/include/linux/stddef.h
index 998a4ba28eba..a5960e2b4a8b 100644
--- a/include/linux/stddef.h
+++ b/include/linux/stddef.h
@@ -20,12 +20,23 @@ enum {
#endif
/**
- * sizeof_field(TYPE, MEMBER)
+ * FIELD_SIZEOF - get the size of a struct's field
+ * @t: the target struct
+ * @f: the target struct's field
+ * Return: the size of @f in the struct definition without having a
+ * declared instance of @t.
+ */
+#define FIELD_SIZEOF(t, f) (sizeof(((t *)0)->f))
+
+/*
+ * For code compatibility
*
+ * sizeof_field(TYPE, MEMBER)
* @TYPE: The structure containing the field of interest
* @MEMBER: The field to return the size of
*/
-#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+
+#define sizeof_field(TYPE, MEMBER) FIELD_SIZEOF(TYPE, MEMBER)
/**
* offsetofend(TYPE, MEMBER)
@@ -34,6 +45,6 @@ enum {
* @MEMBER: The member within the structure to get the end offset of
*/
#define offsetofend(TYPE, MEMBER) \
- (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
+ (offsetof(TYPE, MEMBER) + FIELD_SIZEOF(TYPE, MEMBER))
#endif
diff --git a/kernel/fork.c b/kernel/fork.c
index 75675b9bf6df..ef40b95bf82c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2553,7 +2553,7 @@ void __init proc_caches_init(void)
mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
offsetof(struct mm_struct, saved_auxv),
- sizeof_field(struct mm_struct, saved_auxv),
+ FIELD_SIZEOF(struct mm_struct, saved_auxv),
NULL);
vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
mmap_init();
diff --git a/kernel/utsname.c b/kernel/utsname.c
index f0e491193009..28257c571553 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -174,6 +174,6 @@ void __init uts_ns_init(void)
"uts_namespace", sizeof(struct uts_namespace), 0,
SLAB_PANIC|SLAB_ACCOUNT,
offsetof(struct uts_namespace, name),
- sizeof_field(struct uts_namespace, name),
+ FIELD_SIZEOF(struct uts_namespace, name),
NULL);
}
diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
index 13ea920600ae..3306bbed77eb 100644
--- a/net/caif/caif_socket.c
+++ b/net/caif/caif_socket.c
@@ -1033,7 +1033,7 @@ static int caif_create(struct net *net, struct socket *sock, int protocol,
.owner = THIS_MODULE,
.obj_size = sizeof(struct caifsock),
.useroffset = offsetof(struct caifsock, conn_req.param),
- .usersize = sizeof_field(struct caifsock, conn_req.param)
+ .usersize = FIELD_SIZEOF(struct caifsock, conn_req.param)
};
if (!capable(CAP_SYS_ADMIN) && !capable(CAP_NET_ADMIN))
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 47c1aa9ee045..816bea0c4a8e 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3983,7 +3983,7 @@ void __init skb_init(void)
0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC,
offsetof(struct sk_buff, cb),
- sizeof_field(struct sk_buff, cb),
+ FIELD_SIZEOF(struct sk_buff, cb),
NULL);
skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
sizeof(struct sk_buff_fclones),
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 0b8e06ca75d6..efa4c745f7b9 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -977,7 +977,7 @@ struct proto raw_prot = {
.unhash = raw_unhash_sk,
.obj_size = sizeof(struct raw_sock),
.useroffset = offsetof(struct raw_sock, filter),
- .usersize = sizeof_field(struct raw_sock, filter),
+ .usersize = FIELD_SIZEOF(struct raw_sock, filter),
.h.raw_hash = &raw_v4_hashinfo,
#ifdef CONFIG_COMPAT
.compat_setsockopt = compat_raw_setsockopt,
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 70693bc7ad9d..257c71e22d74 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -1292,7 +1292,7 @@ struct proto rawv6_prot = {
.unhash = raw_unhash_sk,
.obj_size = sizeof(struct raw6_sock),
.useroffset = offsetof(struct raw6_sock, filter),
- .usersize = sizeof_field(struct raw6_sock, filter),
+ .usersize = FIELD_SIZEOF(struct raw6_sock, filter),
.h.raw_hash = &raw_v6_hashinfo,
#ifdef CONFIG_COMPAT
.compat_setsockopt = compat_rawv6_setsockopt,
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 39ea0a37af09..6b648a6033b9 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9377,7 +9377,7 @@ struct proto sctp_prot = {
.useroffset = offsetof(struct sctp_sock, subscribe),
.usersize = offsetof(struct sctp_sock, initmsg) -
offsetof(struct sctp_sock, subscribe) +
- sizeof_field(struct sctp_sock, initmsg),
+ FIELD_SIZEOF(struct sctp_sock, initmsg),
.sysctl_mem = sysctl_sctp_mem,
.sysctl_rmem = sysctl_sctp_rmem,
.sysctl_wmem = sysctl_sctp_wmem,
@@ -9419,7 +9419,7 @@ struct proto sctpv6_prot = {
.useroffset = offsetof(struct sctp6_sock, sctp.subscribe),
.usersize = offsetof(struct sctp6_sock, sctp.initmsg) -
offsetof(struct sctp6_sock, sctp.subscribe) +
- sizeof_field(struct sctp6_sock, sctp.initmsg),
+ FIELD_SIZEOF(struct sctp6_sock, sctp.initmsg),
.sysctl_mem = sysctl_sctp_mem,
.sysctl_rmem = sysctl_sctp_rmem,
.sysctl_wmem = sysctl_sctp_wmem,
diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
index a29206ebbd13..571c35aac90f 100644
--- a/tools/testing/selftests/bpf/bpf_util.h
+++ b/tools/testing/selftests/bpf/bpf_util.h
@@ -58,13 +58,29 @@ static inline unsigned int bpf_num_possible_cpus(void)
# define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
#endif
-#ifndef sizeof_field
-#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
+/*
+ * FIELD_SIZEOF - get the size of a struct's field
+ * @t: the target struct
+ * @f: the target struct's field
+ * Return: the size of @f in the struct definition without having a
+ * declared instance of @t.
+ */
+#ifndef FIELD_SIZEOF
+#define FIELD_SIZEOF(t, f) (sizeof(((t *)0)->f))
#endif
+/*
+ * For code compatibility
+ *
+ * sizeof_field(TYPE, MEMBER)
+ * @TYPE: The structure containing the field of interest
+ * @MEMBER: The field to return the size of
+ */
+#define sizeof_field(TYPE, MEMBER) FIELD_SIZEOF(TYPE, MEMBER)
+
#ifndef offsetofend
#define offsetofend(TYPE, MEMBER) \
- (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
+ (offsetof(TYPE, MEMBER) + FIELD_SIZEOF(TYPE, MEMBER))
#endif
#endif /* __BPF_UTIL__ */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ca54b09adf5b..e43e3a26f6ab 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4275,7 +4275,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
kmem_cache_create_usercopy("kvm_vcpu", vcpu_size, vcpu_align,
SLAB_ACCOUNT,
offsetof(struct kvm_vcpu, arch),
- sizeof_field(struct kvm_vcpu, arch),
+ FIELD_SIZEOF(struct kvm_vcpu, arch),
NULL);
if (!kvm_vcpu_cache) {
r = -ENOMEM;
--
2.11.0
On Jun 11, 2019, at 2:48 PM, Andrew Morton <[email protected]> wrote:
>
> On Wed, 12 Jun 2019 01:08:36 +0530 Shyam Saini <[email protected]> wrote:
>
>> Currently, there are 3 different macros, namely sizeof_field, SIZEOF_FIELD
>> and FIELD_SIZEOF which are used to calculate the size of a member of
>> structure, so to bring uniformity in entire kernel source tree lets use
>> FIELD_SIZEOF and replace all occurrences of other two macros with this.
>>
>> For this purpose, redefine FIELD_SIZEOF in include/linux/stddef.h and
>> tools/testing/selftests/bpf/bpf_util.h and remove its defination from
>> include/linux/kernel.h
>>
>> In favour of FIELD_SIZEOF, this patch also deprecates other two similar
>> macros sizeof_field and SIZEOF_FIELD.
>>
>> For code compatibility reason, retain sizeof_field macro as a wrapper macro
>> to FIELD_SIZEOF
>
> As Alexey has pointed out, C structs and unions don't have fields -
> they have members. So this is an opportunity to switch everything to
> a new member_sizeof().
>
> What do people think of that and how does this impact the patch footprint?
I did a check, and FIELD_SIZEOF() is used about 350x, while sizeof_field()
is about 30x, and SIZEOF_FIELD() is only about 5x.
That said, I'm much more in favour of "sizeof_field()" or "sizeof_member()"
than FIELD_SIZEOF(). Not only does that better match "offsetof()", with
which it is closely related, but is also closer to the original "sizeof()".
Since this is a rather trivial change, it can be split into a number of
patches to get approval/landing via subsystem maintainers, and there is no
huge urgency to remove the original macros until the users are gone. It
would make sense to remove SIZEOF_FIELD() and sizeof_field() quickly so
they don't gain more users, and the remaining FIELD_SIZEOF() users can be
whittled away as the patches come through the maintainer trees.
Cheers, Andreas
Hi Kees,
Cc'ing William Kucharski,
> On Wed, Jun 12, 2019 at 01:08:36AM +0530, Shyam Saini wrote:
> > In favour of FIELD_SIZEOF, this patch also deprecates other two similar
> > macros sizeof_field and SIZEOF_FIELD.
> >
> > For code compatibility reason, retain sizeof_field macro as a wrapper macro
> > to FIELD_SIZEOF
>
> Can you explain this part? First sentence says you want to remove
> sizeof_field, and the second says you're keeping it? I thought the point
> was to switch all of these to FIELD_SIZEOF()?
Previously, William [1] suggested to retain sizeof_field as macro to
FIELD_SIZEOF
for code compatibility reason. I have removed all the usage of
sizeof_field apart from retained
wrapper macro definition.
[1] https://patchwork.ozlabs.org/patch/1085275/
Thanks,
Shyam
> >
> > arch/arm64/include/asm/processor.h | 10 +++++-----
> > arch/mips/cavium-octeon/executive/cvmx-bootmem.c | 9 +--------
> > drivers/gpu/drm/i915/gvt/scheduler.c | 2 +-
> > drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c | 4 ++--
> > fs/befs/linuxvfs.c | 2 +-
> > fs/ext2/super.c | 2 +-
> > fs/ext4/super.c | 2 +-
> > fs/freevxfs/vxfs_super.c | 2 +-
> > fs/orangefs/super.c | 2 +-
> > fs/ufs/super.c | 2 +-
> > include/linux/kernel.h | 9 ---------
> > include/linux/slab.h | 2 +-
> > include/linux/stddef.h | 17 ++++++++++++++---
> > kernel/fork.c | 2 +-
> > kernel/utsname.c | 2 +-
> > net/caif/caif_socket.c | 2 +-
> > net/core/skbuff.c | 2 +-
> > net/ipv4/raw.c | 2 +-
> > net/ipv6/raw.c | 2 +-
> > net/sctp/socket.c | 4 ++--
> > tools/testing/selftests/bpf/bpf_util.h | 22 +++++++++++++++++++---
> > virt/kvm/kvm_main.c | 2 +-
> > 22 files changed, 58 insertions(+), 47 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> > index fcd0e691b1ea..ace906d887cc 100644
> > --- a/arch/arm64/include/asm/processor.h
> > +++ b/arch/arm64/include/asm/processor.h
> > @@ -164,13 +164,13 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset,
> > unsigned long *size)
> > {
> > /* Verify that there is no padding among the whitelisted fields: */
> > - BUILD_BUG_ON(sizeof_field(struct thread_struct, uw) !=
> > - sizeof_field(struct thread_struct, uw.tp_value) +
> > - sizeof_field(struct thread_struct, uw.tp2_value) +
> > - sizeof_field(struct thread_struct, uw.fpsimd_state));
> > + BUILD_BUG_ON(FIELD_SIZEOF(struct thread_struct, uw) !=
> > + FIELD_SIZEOF(struct thread_struct, uw.tp_value) +
> > + FIELD_SIZEOF(struct thread_struct, uw.tp2_value) +
> > + FIELD_SIZEOF(struct thread_struct, uw.fpsimd_state));
> >
> > *offset = offsetof(struct thread_struct, uw);
> > - *size = sizeof_field(struct thread_struct, uw);
> > + *size = FIELD_SIZEOF(struct thread_struct, uw);
> > }
> >
> > #ifdef CONFIG_COMPAT
> > diff --git a/arch/mips/cavium-octeon/executive/cvmx-bootmem.c b/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
> > index ba8f82a29a81..44b506a14666 100644
> > --- a/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
> > +++ b/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
> > @@ -45,13 +45,6 @@ static struct cvmx_bootmem_desc *cvmx_bootmem_desc;
> > /* See header file for descriptions of functions */
> >
> > /**
> > - * This macro returns the size of a member of a structure.
> > - * Logically it is the same as "sizeof(s::field)" in C++, but
> > - * C lacks the "::" operator.
> > - */
> > -#define SIZEOF_FIELD(s, field) sizeof(((s *)NULL)->field)
> > -
> > -/**
> > * This macro returns a member of the
> > * cvmx_bootmem_named_block_desc_t structure. These members can't
> > * be directly addressed as they might be in memory not directly
> > @@ -65,7 +58,7 @@ static struct cvmx_bootmem_desc *cvmx_bootmem_desc;
> > #define CVMX_BOOTMEM_NAMED_GET_FIELD(addr, field) \
> > __cvmx_bootmem_desc_get(addr, \
> > offsetof(struct cvmx_bootmem_named_block_desc, field), \
> > - SIZEOF_FIELD(struct cvmx_bootmem_named_block_desc, field))
> > + FIELD_SIZEOF(struct cvmx_bootmem_named_block_desc, field))
> >
> > /**
> > * This function is the implementation of the get macros defined
> > diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
> > index 0f919f0a43d4..820f95a52542 100644
> > --- a/drivers/gpu/drm/i915/gvt/scheduler.c
> > +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
> > @@ -1243,7 +1243,7 @@ int intel_vgpu_setup_submission(struct intel_vgpu *vgpu)
> > sizeof(struct intel_vgpu_workload), 0,
> > SLAB_HWCACHE_ALIGN,
> > offsetof(struct intel_vgpu_workload, rb_tail),
> > - sizeof_field(struct intel_vgpu_workload, rb_tail),
> > + FIELD_SIZEOF(struct intel_vgpu_workload, rb_tail),
> > NULL);
> >
> > if (!s->workloads) {
> > diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
> > index 46baf3b44309..c0447bf07fbb 100644
> > --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
> > +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
> > @@ -49,13 +49,13 @@ struct mlxsw_sp_fid_8021d {
> > };
> >
> > static const struct rhashtable_params mlxsw_sp_fid_ht_params = {
> > - .key_len = sizeof_field(struct mlxsw_sp_fid, fid_index),
> > + .key_len = FIELD_SIZEOF(struct mlxsw_sp_fid, fid_index),
> > .key_offset = offsetof(struct mlxsw_sp_fid, fid_index),
> > .head_offset = offsetof(struct mlxsw_sp_fid, ht_node),
> > };
> >
> > static const struct rhashtable_params mlxsw_sp_fid_vni_ht_params = {
> > - .key_len = sizeof_field(struct mlxsw_sp_fid, vni),
> > + .key_len = FIELD_SIZEOF(struct mlxsw_sp_fid, vni),
> > .key_offset = offsetof(struct mlxsw_sp_fid, vni),
> > .head_offset = offsetof(struct mlxsw_sp_fid, vni_ht_node),
> > };
> > diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
> > index 462d096ff3e9..06ffd4829e2e 100644
> > --- a/fs/befs/linuxvfs.c
> > +++ b/fs/befs/linuxvfs.c
> > @@ -438,7 +438,7 @@ befs_init_inodecache(void)
> > SLAB_ACCOUNT),
> > offsetof(struct befs_inode_info,
> > i_data.symlink),
> > - sizeof_field(struct befs_inode_info,
> > + FIELD_SIZEOF(struct befs_inode_info,
> > i_data.symlink),
> > init_once);
> > if (befs_inode_cachep == NULL)
> > diff --git a/fs/ext2/super.c b/fs/ext2/super.c
> > index 1d7ab73b1014..d9a6c81f4a47 100644
> > --- a/fs/ext2/super.c
> > +++ b/fs/ext2/super.c
> > @@ -220,7 +220,7 @@ static int __init init_inodecache(void)
> > (SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
> > SLAB_ACCOUNT),
> > offsetof(struct ext2_inode_info, i_data),
> > - sizeof_field(struct ext2_inode_info, i_data),
> > + FIELD_SIZEOF(struct ext2_inode_info, i_data),
> > init_once);
> > if (ext2_inode_cachep == NULL)
> > return -ENOMEM;
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index 4079605d437a..b1b5856248bd 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -1148,7 +1148,7 @@ static int __init init_inodecache(void)
> > (SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
> > SLAB_ACCOUNT),
> > offsetof(struct ext4_inode_info, i_data),
> > - sizeof_field(struct ext4_inode_info, i_data),
> > + FIELD_SIZEOF(struct ext4_inode_info, i_data),
> > init_once);
> > if (ext4_inode_cachep == NULL)
> > return -ENOMEM;
> > diff --git a/fs/freevxfs/vxfs_super.c b/fs/freevxfs/vxfs_super.c
> > index a89f68c3cbed..ffd22f85bbe0 100644
> > --- a/fs/freevxfs/vxfs_super.c
> > +++ b/fs/freevxfs/vxfs_super.c
> > @@ -329,7 +329,7 @@ vxfs_init(void)
> > sizeof(struct vxfs_inode_info), 0,
> > SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
> > offsetof(struct vxfs_inode_info, vii_immed.vi_immed),
> > - sizeof_field(struct vxfs_inode_info,
> > + FIELD_SIZEOF(struct vxfs_inode_info,
> > vii_immed.vi_immed),
> > NULL);
> > if (!vxfs_inode_cachep)
> > diff --git a/fs/orangefs/super.c b/fs/orangefs/super.c
> > index ee5efdc35cc1..30f625059ad9 100644
> > --- a/fs/orangefs/super.c
> > +++ b/fs/orangefs/super.c
> > @@ -646,7 +646,7 @@ int orangefs_inode_cache_initialize(void)
> > ORANGEFS_CACHE_CREATE_FLAGS,
> > offsetof(struct orangefs_inode_s,
> > link_target),
> > - sizeof_field(struct orangefs_inode_s,
> > + FIELD_SIZEOF(struct orangefs_inode_s,
> > link_target),
> > orangefs_inode_cache_ctor);
> >
> > diff --git a/fs/ufs/super.c b/fs/ufs/super.c
> > index 3d247c0d92aa..1e8bcd950f6d 100644
> > --- a/fs/ufs/super.c
> > +++ b/fs/ufs/super.c
> > @@ -1469,7 +1469,7 @@ static int __init init_inodecache(void)
> > (SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
> > SLAB_ACCOUNT),
> > offsetof(struct ufs_inode_info, i_u1.i_symlink),
> > - sizeof_field(struct ufs_inode_info,
> > + FIELD_SIZEOF(struct ufs_inode_info,
> > i_u1.i_symlink),
> > init_once);
> > if (ufs_inode_cachep == NULL)
> > diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> > index 74b1ee9027f5..4672391cdb5b 100644
> > --- a/include/linux/kernel.h
> > +++ b/include/linux/kernel.h
> > @@ -79,15 +79,6 @@
> > */
> > #define round_down(x, y) ((x) & ~__round_mask(x, y))
> >
> > -/**
> > - * FIELD_SIZEOF - get the size of a struct's field
> > - * @t: the target struct
> > - * @f: the target struct's field
> > - * Return: the size of @f in the struct definition without having a
> > - * declared instance of @t.
> > - */
> > -#define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
> > -
> > #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP
> >
> > #define DIV_ROUND_DOWN_ULL(ll, d) \
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 9449b19c5f10..8bdfdd389b37 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -175,7 +175,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *);
> > sizeof(struct __struct), \
> > __alignof__(struct __struct), (__flags), \
> > offsetof(struct __struct, __field), \
> > - sizeof_field(struct __struct, __field), NULL)
> > + FIELD_SIZEOF(struct __struct, __field), NULL)
> >
> > /*
> > * Common kmalloc functions provided by all allocators
> > diff --git a/include/linux/stddef.h b/include/linux/stddef.h
> > index 998a4ba28eba..a5960e2b4a8b 100644
> > --- a/include/linux/stddef.h
> > +++ b/include/linux/stddef.h
> > @@ -20,12 +20,23 @@ enum {
> > #endif
> >
> > /**
> > - * sizeof_field(TYPE, MEMBER)
> > + * FIELD_SIZEOF - get the size of a struct's field
> > + * @t: the target struct
> > + * @f: the target struct's field
> > + * Return: the size of @f in the struct definition without having a
> > + * declared instance of @t.
> > + */
> > +#define FIELD_SIZEOF(t, f) (sizeof(((t *)0)->f))
> > +
> > +/*
> > + * For code compatibility
> > *
> > + * sizeof_field(TYPE, MEMBER)
> > * @TYPE: The structure containing the field of interest
> > * @MEMBER: The field to return the size of
> > */
> > -#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
> > +
> > +#define sizeof_field(TYPE, MEMBER) FIELD_SIZEOF(TYPE, MEMBER)
> >
> > /**
> > * offsetofend(TYPE, MEMBER)
> > @@ -34,6 +45,6 @@ enum {
> > * @MEMBER: The member within the structure to get the end offset of
> > */
> > #define offsetofend(TYPE, MEMBER) \
> > - (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
> > + (offsetof(TYPE, MEMBER) + FIELD_SIZEOF(TYPE, MEMBER))
> >
> > #endif
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 75675b9bf6df..ef40b95bf82c 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -2553,7 +2553,7 @@ void __init proc_caches_init(void)
> > mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
> > SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
> > offsetof(struct mm_struct, saved_auxv),
> > - sizeof_field(struct mm_struct, saved_auxv),
> > + FIELD_SIZEOF(struct mm_struct, saved_auxv),
> > NULL);
> > vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
> > mmap_init();
> > diff --git a/kernel/utsname.c b/kernel/utsname.c
> > index f0e491193009..28257c571553 100644
> > --- a/kernel/utsname.c
> > +++ b/kernel/utsname.c
> > @@ -174,6 +174,6 @@ void __init uts_ns_init(void)
> > "uts_namespace", sizeof(struct uts_namespace), 0,
> > SLAB_PANIC|SLAB_ACCOUNT,
> > offsetof(struct uts_namespace, name),
> > - sizeof_field(struct uts_namespace, name),
> > + FIELD_SIZEOF(struct uts_namespace, name),
> > NULL);
> > }
> > diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
> > index 13ea920600ae..3306bbed77eb 100644
> > --- a/net/caif/caif_socket.c
> > +++ b/net/caif/caif_socket.c
> > @@ -1033,7 +1033,7 @@ static int caif_create(struct net *net, struct socket *sock, int protocol,
> > .owner = THIS_MODULE,
> > .obj_size = sizeof(struct caifsock),
> > .useroffset = offsetof(struct caifsock, conn_req.param),
> > - .usersize = sizeof_field(struct caifsock, conn_req.param)
> > + .usersize = FIELD_SIZEOF(struct caifsock, conn_req.param)
> > };
> >
> > if (!capable(CAP_SYS_ADMIN) && !capable(CAP_NET_ADMIN))
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 47c1aa9ee045..816bea0c4a8e 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -3983,7 +3983,7 @@ void __init skb_init(void)
> > 0,
> > SLAB_HWCACHE_ALIGN|SLAB_PANIC,
> > offsetof(struct sk_buff, cb),
> > - sizeof_field(struct sk_buff, cb),
> > + FIELD_SIZEOF(struct sk_buff, cb),
> > NULL);
> > skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
> > sizeof(struct sk_buff_fclones),
> > diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
> > index 0b8e06ca75d6..efa4c745f7b9 100644
> > --- a/net/ipv4/raw.c
> > +++ b/net/ipv4/raw.c
> > @@ -977,7 +977,7 @@ struct proto raw_prot = {
> > .unhash = raw_unhash_sk,
> > .obj_size = sizeof(struct raw_sock),
> > .useroffset = offsetof(struct raw_sock, filter),
> > - .usersize = sizeof_field(struct raw_sock, filter),
> > + .usersize = FIELD_SIZEOF(struct raw_sock, filter),
> > .h.raw_hash = &raw_v4_hashinfo,
> > #ifdef CONFIG_COMPAT
> > .compat_setsockopt = compat_raw_setsockopt,
> > diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
> > index 70693bc7ad9d..257c71e22d74 100644
> > --- a/net/ipv6/raw.c
> > +++ b/net/ipv6/raw.c
> > @@ -1292,7 +1292,7 @@ struct proto rawv6_prot = {
> > .unhash = raw_unhash_sk,
> > .obj_size = sizeof(struct raw6_sock),
> > .useroffset = offsetof(struct raw6_sock, filter),
> > - .usersize = sizeof_field(struct raw6_sock, filter),
> > + .usersize = FIELD_SIZEOF(struct raw6_sock, filter),
> > .h.raw_hash = &raw_v6_hashinfo,
> > #ifdef CONFIG_COMPAT
> > .compat_setsockopt = compat_rawv6_setsockopt,
> > diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> > index 39ea0a37af09..6b648a6033b9 100644
> > --- a/net/sctp/socket.c
> > +++ b/net/sctp/socket.c
> > @@ -9377,7 +9377,7 @@ struct proto sctp_prot = {
> > .useroffset = offsetof(struct sctp_sock, subscribe),
> > .usersize = offsetof(struct sctp_sock, initmsg) -
> > offsetof(struct sctp_sock, subscribe) +
> > - sizeof_field(struct sctp_sock, initmsg),
> > + FIELD_SIZEOF(struct sctp_sock, initmsg),
> > .sysctl_mem = sysctl_sctp_mem,
> > .sysctl_rmem = sysctl_sctp_rmem,
> > .sysctl_wmem = sysctl_sctp_wmem,
> > @@ -9419,7 +9419,7 @@ struct proto sctpv6_prot = {
> > .useroffset = offsetof(struct sctp6_sock, sctp.subscribe),
> > .usersize = offsetof(struct sctp6_sock, sctp.initmsg) -
> > offsetof(struct sctp6_sock, sctp.subscribe) +
> > - sizeof_field(struct sctp6_sock, sctp.initmsg),
> > + FIELD_SIZEOF(struct sctp6_sock, sctp.initmsg),
> > .sysctl_mem = sysctl_sctp_mem,
> > .sysctl_rmem = sysctl_sctp_rmem,
> > .sysctl_wmem = sysctl_sctp_wmem,
> > diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
> > index a29206ebbd13..571c35aac90f 100644
> > --- a/tools/testing/selftests/bpf/bpf_util.h
> > +++ b/tools/testing/selftests/bpf/bpf_util.h
> > @@ -58,13 +58,29 @@ static inline unsigned int bpf_num_possible_cpus(void)
> > # define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> > #endif
> >
> > -#ifndef sizeof_field
> > -#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
> > +/*
> > + * FIELD_SIZEOF - get the size of a struct's field
> > + * @t: the target struct
> > + * @f: the target struct's field
> > + * Return: the size of @f in the struct definition without having a
> > + * declared instance of @t.
> > + */
> > +#ifndef FIELD_SIZEOF
> > +#define FIELD_SIZEOF(t, f) (sizeof(((t *)0)->f))
> > #endif
> >
> > +/*
> > + * For code compatibility
> > + *
> > + * sizeof_field(TYPE, MEMBER)
> > + * @TYPE: The structure containing the field of interest
> > + * @MEMBER: The field to return the size of
> > + */
> > +#define sizeof_field(TYPE, MEMBER) FIELD_SIZEOF(TYPE, MEMBER)
> > +
> > #ifndef offsetofend
> > #define offsetofend(TYPE, MEMBER) \
> > - (offsetof(TYPE, MEMBER) + sizeof_field(TYPE, MEMBER))
> > + (offsetof(TYPE, MEMBER) + FIELD_SIZEOF(TYPE, MEMBER))
> > #endif
> >
> > #endif /* __BPF_UTIL__ */
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index ca54b09adf5b..e43e3a26f6ab 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -4275,7 +4275,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
> > kmem_cache_create_usercopy("kvm_vcpu", vcpu_size, vcpu_align,
> > SLAB_ACCOUNT,
> > offsetof(struct kvm_vcpu, arch),
> > - sizeof_field(struct kvm_vcpu, arch),
> > + FIELD_SIZEOF(struct kvm_vcpu, arch),
> > NULL);
> > if (!kvm_vcpu_cache) {
> > r = -ENOMEM;
> > --
> > 2.11.0
> >
>
> --
> Kees Cook
On Jun 11, 2019, at 3:09 PM, Andrew Morton <[email protected]> wrote:
>
> On Tue, 11 Jun 2019 15:00:10 -0600 Andreas Dilger <[email protected]> wrote:
>
>>>> to FIELD_SIZEOF
>>>
>>> As Alexey has pointed out, C structs and unions don't have fields -
>>> they have members. So this is an opportunity to switch everything to
>>> a new member_sizeof().
>>>
>>> What do people think of that and how does this impact the patch footprint?
>>
>> I did a check, and FIELD_SIZEOF() is used about 350x, while sizeof_field()
>> is about 30x, and SIZEOF_FIELD() is only about 5x.
>
> Erk. Sorry, I should have grepped.
>
>> That said, I'm much more in favour of "sizeof_field()" or "sizeof_member()"
>> than FIELD_SIZEOF(). Not only does that better match "offsetof()", with
>> which it is closely related, but is also closer to the original "sizeof()".
>>
>> Since this is a rather trivial change, it can be split into a number of
>> patches to get approval/landing via subsystem maintainers, and there is no
>> huge urgency to remove the original macros until the users are gone. It
>> would make sense to remove SIZEOF_FIELD() and sizeof_field() quickly so
>> they don't gain more users, and the remaining FIELD_SIZEOF() users can be
>> whittled away as the patches come through the maintainer trees.
>
> In that case I'd say let's live with FIELD_SIZEOF() and remove
> sizeof_field() and SIZEOF_FIELD().
The real question is whether we want to live with a sub-standard macro for
the next 20 years rather than taking the opportunity to clean it up now?
> I'm a bit surprised that the FIELD_SIZEOF() definition ends up in
> stddef.h rather than in kernel.h where such things are normally
> defined. Why is that?
Cheers, Andreas
On Tue, Jun 11, 2019 at 03:00:10PM -0600, Andreas Dilger wrote:
> On Jun 11, 2019, at 2:48 PM, Andrew Morton <[email protected]> wrote:
> >
> > On Wed, 12 Jun 2019 01:08:36 +0530 Shyam Saini <[email protected]> wrote:
> I did a check, and FIELD_SIZEOF() is used about 350x, while sizeof_field()
> is about 30x, and SIZEOF_FIELD() is only about 5x.
>
> That said, I'm much more in favour of "sizeof_field()" or "sizeof_member()"
> than FIELD_SIZEOF(). Not only does that better match "offsetof()", with
> which it is closely related, but is also closer to the original "sizeof()".
>
> Since this is a rather trivial change, it can be split into a number of
> patches to get approval/landing via subsystem maintainers, and there is no
> huge urgency to remove the original macros until the users are gone. It
> would make sense to remove SIZEOF_FIELD() and sizeof_field() quickly so
> they don't gain more users, and the remaining FIELD_SIZEOF() users can be
> whittled away as the patches come through the maintainer trees.
The signature should be
sizeof_member(T, m)
it is proper English,
it is lowercase, so is easier to type,
it uses standard term (member, not field),
it blends in with standard "sizeof" operator,