On 3/7/24 02:17, Jan Karcher wrote:
On 04/03/2024 10:00, Wen Gu wrote:
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:
Thank you Gustavo for the proposal.
I had to do some reading to better understand what's happening and how your patch solves this.
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.
I agree. Should we chose this option we should come up for a better name.
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.
I like the idea and put some thought into it. The only thing that is not perfectly clean IMO is the following:
By the current definition it is easily visible that we are dealing with a variable sized array. If we move them into the structs one could think they are always
at their MAX size which they are not.
E.g.: An incoming proposal can have 0 UEIDs indicated by the eid_cnt.
That said nothing a comment can't fix.
From what i have seen the offset and length calculations regarding the "real" size of those structs is fine with your proposal.
Can you verify that your changes also resolve the warnings?
I can confirm that the changes Wen Gu is proposing also resolve the warnings.
Wen,
If you send a proper patch, you can include the following tags:
Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Build-tested-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Thanks!
--
Gustavo
[...]
};
Thanks!
Wen Gu
Thanks you
- Jan
