linux-kernel - Re: [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell"

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Date:   Wed, 5 Jan 2022 01:43:36 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Ard Biesheuvel <ardb@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Al Viro <viro@...iv.linux.org.uk>, llvm@...ts.linux.dev,
        ashimida <ashimida@...ux.alibaba.com>,
        Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree
 -v1: Eliminate the Linux kernel's "Dependency Hell"


* Nick Desaulniers <ndesaulniers@...gle.com> wrote:

> > Can this Clang warning be disabled?
> 
> Clang is warning that the attribute will be ignored because of that 
> positioning. If you disable the warning, code will probably stop working 
> as intended.  This warning has at least been helping us make the kernel 
> coding style more consistent.

Yeah, indeed, Clang is fully correct to warn here, and these changes in my 
tree are outright bugs (which bugs Clang found & reported :-).

See the fixes below - by doing it this way the 'spurious link failure' 
problem when a header include is missing should be fixed as well.

Thanks,

	Ingo
---
 include/linux/dcache.h        | 3 +--
 include/linux/fs_types.h      | 3 +--
 include/linux/netdevice_api.h | 2 +-
 include/net/xdp_types.h       | 2 +-
 4 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 520daf638d06..da7e77a7cede 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -127,8 +127,7 @@ enum dentry_d_lock_class
 	DENTRY_D_LOCK_NESTED
 };
 
-____cacheline_aligned
-struct dentry_operations {
+struct ____cacheline_aligned dentry_operations {
 	int (*d_revalidate)(struct dentry *, unsigned int);
 	int (*d_weak_revalidate)(struct dentry *, unsigned int);
 	int (*d_hash)(const struct dentry *, struct qstr *);
diff --git a/include/linux/fs_types.h b/include/linux/fs_types.h
index b53aadafab1b..e2e1c0827183 100644
--- a/include/linux/fs_types.h
+++ b/include/linux/fs_types.h
@@ -994,8 +994,7 @@ struct file_operations {
 	int (*fadvise)(struct file *, loff_t, loff_t, int);
 } __randomize_layout;
 
-____cacheline_aligned
-struct inode_operations {
+struct ____cacheline_aligned inode_operations {
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
 	const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
 	int (*permission) (struct user_namespace *, struct inode *, int);
diff --git a/include/linux/netdevice_api.h b/include/linux/netdevice_api.h
index 4a8d7688e148..0e5e08dcbb2a 100644
--- a/include/linux/netdevice_api.h
+++ b/include/linux/netdevice_api.h
@@ -49,7 +49,7 @@
 #endif
 
 /* This structure contains an instance of an RX queue. */
-____cacheline_aligned_in_smp struct netdev_rx_queue {
+struct ____cacheline_aligned_in_smp netdev_rx_queue {
 	struct xdp_rxq_info		xdp_rxq;
 #ifdef CONFIG_RPS
 	struct rps_map __rcu		*rps_map;
diff --git a/include/net/xdp_types.h b/include/net/xdp_types.h
index 442028626b35..accc12372bca 100644
--- a/include/net/xdp_types.h
+++ b/include/net/xdp_types.h
@@ -56,7 +56,7 @@ struct xdp_mem_info {
 struct page_pool;
 
 /* perf critical, avoid false-sharing */
-____cacheline_aligned struct xdp_rxq_info {
+struct ____cacheline_aligned xdp_rxq_info {
 	struct net_device *dev;
 	u32 queue_index;
 	u32 reg_state;