Re: [PATCH][next] net/smc: Avoid -Wflex-array-member-not-at-end warnings
From: Wen Gu
Date: Mon Mar 04 2024 - 04:01:45 EST
On 2024/3/2 02:40, Gustavo A. R. Silva wrote:
-Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.
There are currently a couple of objects in `struct smc_clc_msg_proposal_area`
that contain a couple of flexible structures:
struct smc_clc_msg_proposal_area {
...
struct smc_clc_v2_extension pclc_v2_ext;
...
struct smc_clc_smcd_v2_extension pclc_smcd_v2_ext;
...
};
So, in order to avoid ending up with a couple of flexible-array members
in the middle of a struct, we use the `struct_group_tagged()` helper to
separate the flexible array from the rest of the members in the flexible
structure:
struct smc_clc_smcd_v2_extension {
struct_group_tagged(smc_clc_smcd_v2_extension_hdr, hdr,
u8 system_eid[SMC_MAX_EID_LEN];
u8 reserved[16];
);
struct smc_clc_smcd_gid_chid gidchid[];
};
With the change described above, we now declare objects of the type of
the tagged struct without embedding flexible arrays in the middle of
another struct:
struct smc_clc_msg_proposal_area {
...
struct smc_clc_v2_extension_hdr pclc_v2_ext;
...
struct smc_clc_smcd_v2_extension_hdr pclc_smcd_v2_ext;
...
};
We also use `container_of()` when we need to retrieve a pointer to the
flexible structures.
So, with these changes, fix the following warnings:
In file included from net/smc/af_smc.c:42:
net/smc/smc_clc.h:186:49: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
186 | struct smc_clc_v2_extension pclc_v2_ext;
| ^~~~~~~~~~~
net/smc/smc_clc.h:188:49: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
188 | struct smc_clc_smcd_v2_extension pclc_smcd_v2_ext;
| ^~~~~~~~~~~~~~~~
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
net/smc/smc_clc.c | 5 +++--
net/smc/smc_clc.h | 24 ++++++++++++++----------
2 files changed, 17 insertions(+), 12 deletions(-)
diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
index e55026c7529c..3094cfa1c458 100644
--- a/net/smc/smc_clc.c
+++ b/net/smc/smc_clc.c
@@ -853,8 +853,9 @@ int smc_clc_send_proposal(struct smc_sock *smc, struct smc_init_info *ini)
pclc_smcd = &pclc->pclc_smcd;
pclc_prfx = &pclc->pclc_prfx;
ipv6_prfx = pclc->pclc_prfx_ipv6;
- v2_ext = &pclc->pclc_v2_ext;
- smcd_v2_ext = &pclc->pclc_smcd_v2_ext;
+ v2_ext = container_of(&pclc->pclc_v2_ext, struct smc_clc_v2_extension, _hdr);
+ smcd_v2_ext = container_of(&pclc->pclc_smcd_v2_ext,
+ struct smc_clc_smcd_v2_extension, hdr);
gidchids = pclc->pclc_gidchids;
trl = &pclc->pclc_trl;
diff --git a/net/smc/smc_clc.h b/net/smc/smc_clc.h
index 7cc7070b9772..5b91a1947078 100644
--- a/net/smc/smc_clc.h
+++ b/net/smc/smc_clc.h
@@ -134,12 +134,14 @@ struct smc_clc_smcd_gid_chid {
*/
struct smc_clc_v2_extension {
- struct smc_clnt_opts_area_hdr hdr;
- u8 roce[16]; /* RoCEv2 GID */
- u8 max_conns;
- u8 max_links;
- __be16 feature_mask;
- u8 reserved[12];
+ struct_group_tagged(smc_clc_v2_extension_hdr, _hdr,
+ struct smc_clnt_opts_area_hdr hdr;
+ u8 roce[16]; /* RoCEv2 GID */
+ u8 max_conns;
+ u8 max_links;
+ __be16 feature_mask;
+ u8 reserved[12];
+ );
u8 user_eids[][SMC_MAX_EID_LEN];
};
@@ -159,8 +161,10 @@ struct smc_clc_msg_smcd { /* SMC-D GID information */
};
struct smc_clc_smcd_v2_extension {
- u8 system_eid[SMC_MAX_EID_LEN];
- u8 reserved[16];
+ struct_group_tagged(smc_clc_smcd_v2_extension_hdr, hdr,
+ u8 system_eid[SMC_MAX_EID_LEN];
+ u8 reserved[16];
+ );
struct smc_clc_smcd_gid_chid gidchid[];
};
@@ -183,9 +187,9 @@ struct smc_clc_msg_proposal_area {
struct smc_clc_msg_smcd pclc_smcd;
struct smc_clc_msg_proposal_prefix pclc_prfx;
struct smc_clc_ipv6_prefix pclc_prfx_ipv6[SMC_CLC_MAX_V6_PREFIX];
- struct smc_clc_v2_extension pclc_v2_ext;
+ struct smc_clc_v2_extension_hdr pclc_v2_ext;
u8 user_eids[SMC_CLC_MAX_UEID][SMC_MAX_EID_LEN];
- struct smc_clc_smcd_v2_extension pclc_smcd_v2_ext;
+ struct smc_clc_smcd_v2_extension_hdr pclc_smcd_v2_ext;
struct smc_clc_smcd_gid_chid
pclc_gidchids[SMCD_CLC_MAX_V2_GID_ENTRIES];
struct smc_clc_msg_trail pclc_trl;
Thank you! Gustavo. This patch can fix this warning well, just the name
'*_hdr' might not be very accurate, but I don't have a good idea ATM.
Besides, I am wondering if this can be fixed by moving
user_eids of smc_clc_msg_proposal_area into smc_clc_v2_extension,
and
pclc_gidchids of smc_clc_msg_proposal_area into smc_clc_smcd_v2_extension.
so that we can avoid to use the flexible-array in smc_clc_v2_extension
and smc_clc_smcd_v2_extension.
diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
index e55026c7529c..971b4677b84d 100644
--- a/net/smc/smc_clc.c
+++ b/net/smc/smc_clc.c
@@ -855,7 +855,7 @@ int smc_clc_send_proposal(struct smc_sock *smc, struct smc_init_info *ini)
ipv6_prfx = pclc->pclc_prfx_ipv6;
v2_ext = &pclc->pclc_v2_ext;
smcd_v2_ext = &pclc->pclc_smcd_v2_ext;
- gidchids = pclc->pclc_gidchids;
+ gidchids = pclc->pclc_smcd_v2_ext.gidchid;
trl = &pclc->pclc_trl;
pclc_base->hdr.version = SMC_V2;
diff --git a/net/smc/smc_clc.h b/net/smc/smc_clc.h
index 7cc7070b9772..36c8432af73e 100644
--- a/net/smc/smc_clc.h
+++ b/net/smc/smc_clc.h
@@ -133,6 +133,14 @@ struct smc_clc_smcd_gid_chid {
* (https://www.ibm.com/support/pages/node/6326337)
*/
+#define SMC_CLC_MAX_V6_PREFIX 8
+#define SMC_CLC_MAX_UEID 8
+#define SMCD_CLC_MAX_V2_GID_ENTRIES 8 /* max # of CHID-GID entries in CLC
+ * proposal SMC-Dv2 extension.
+ * each ISM device takes one entry and
+ * each Emulated-ISM takes two entries
+ */
+
struct smc_clc_v2_extension {
struct smc_clnt_opts_area_hdr hdr;
u8 roce[16]; /* RoCEv2 GID */
@@ -140,7 +148,7 @@ struct smc_clc_v2_extension {
u8 max_links;
__be16 feature_mask;
u8 reserved[12];
- u8 user_eids[][SMC_MAX_EID_LEN];
+ u8 user_eids[SMC_CLC_MAX_UEID][SMC_MAX_EID_LEN];
};
struct smc_clc_msg_proposal_prefix { /* prefix part of clc proposal message*/
@@ -161,7 +169,7 @@ struct smc_clc_msg_smcd { /* SMC-D GID information */
struct smc_clc_smcd_v2_extension {
u8 system_eid[SMC_MAX_EID_LEN];
u8 reserved[16];
- struct smc_clc_smcd_gid_chid gidchid[];
+ struct smc_clc_smcd_gid_chid gidchid[SMCD_CLC_MAX_V2_GID_ENTRIES];
};
struct smc_clc_msg_proposal { /* clc proposal message sent by Linux */
@@ -170,24 +178,13 @@ struct smc_clc_msg_proposal { /* clc proposal message sent by Linux */
__be16 iparea_offset; /* offset to IP address information area */
} __aligned(4);
-#define SMC_CLC_MAX_V6_PREFIX 8
-#define SMC_CLC_MAX_UEID 8
-#define SMCD_CLC_MAX_V2_GID_ENTRIES 8 /* max # of CHID-GID entries in CLC
- * proposal SMC-Dv2 extension.
- * each ISM device takes one entry and
- * each Emulated-ISM takes two entries
- */
-
struct smc_clc_msg_proposal_area {
struct smc_clc_msg_proposal pclc_base;
struct smc_clc_msg_smcd pclc_smcd;
struct smc_clc_msg_proposal_prefix pclc_prfx;
struct smc_clc_ipv6_prefix pclc_prfx_ipv6[SMC_CLC_MAX_V6_PREFIX];
struct smc_clc_v2_extension pclc_v2_ext;
- u8 user_eids[SMC_CLC_MAX_UEID][SMC_MAX_EID_LEN];
struct smc_clc_smcd_v2_extension pclc_smcd_v2_ext;
- struct smc_clc_smcd_gid_chid
- pclc_gidchids[SMCD_CLC_MAX_V2_GID_ENTRIES];
struct smc_clc_msg_trail pclc_trl;
};
Thanks!
Wen Gu