On Mon, Mar 14, 2016 at 10:47:33PM +0100, Arnd Bergmann wrote: > The current_user_ns() macro currently returns &init_user_ns when > user namespaces are disabled, and that causes several warnings > when building with gcc-6.0 in code that compares the result of > the macro to &init_user_ns itself: > > fs/xfs/xfs_ioctl.c: In function 'xfs_ioctl_setattr_check_projid': > fs/xfs/xfs_ioctl.c:1249:22: error: self-comparison always evaluates to true > [-Werror=tautological-compare] > if (current_user_ns() == &init_user_ns) > > This is a legitimate warning in principle, but here it isn't > really helpful, so I'm reprasing the definition in a way that > shuts up the warning. Apparently gcc only warns when comparing > identical literals, but it can figure out that the result of > an inline function can be identical to a constant expression > in order to optimize a condition yet not warn about the fact > that the condition is known at compile time. This is exactly > what we want here, and it looks reasonable because we generally > prefer inline functions over macros anyway. > > Signed-off-by: Arnd Bergmann <[email protected]>
Was a bit worried about the first hunk since capability.h doesn't include cred.h explicitly, but I guess if that was a problem it would've not compiled long ago due to current_cred_xxx(). Acked-by: Serge Hallyn <[email protected]> > --- > include/linux/capability.h | 2 -- > include/linux/cred.h | 5 ++++- > 2 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/include/linux/capability.h b/include/linux/capability.h > index f314275d4e3f..00690ff92edf 100644 > --- a/include/linux/capability.h > +++ b/include/linux/capability.h > @@ -40,8 +40,6 @@ struct inode; > struct dentry; > struct user_namespace; > > -struct user_namespace *current_user_ns(void); > - > extern const kernel_cap_t __cap_empty_set; > extern const kernel_cap_t __cap_init_eff_set; > > diff --git a/include/linux/cred.h b/include/linux/cred.h > index 8d70e1361ecd..257db64562e5 100644 > --- a/include/linux/cred.h > +++ b/include/linux/cred.h > @@ -377,7 +377,10 @@ extern struct user_namespace init_user_ns; > #ifdef CONFIG_USER_NS > #define current_user_ns() (current_cred_xxx(user_ns)) > #else > -#define current_user_ns() (&init_user_ns) > +static inline struct user_namespace *current_user_ns(void) > +{ > + return &init_user_ns; > +} > #endif > > > -- > 2.7.0
