On Thu, Sep 4, 2025 at 8:22 AM Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote:
>
> Don't define the AT_RENAME_* macros at all since the kernel does not
> use them nor does the kernel need to provide them for userspace.
> Leave them as comments in <uapi/linux/fcntl.h> only as an example.
>
> The AT_RENAME_* macros have recently been added to glibc's <stdio.h>.
> For a kernel allmodconfig build, this made the macros be defined
> differently in 2 places (same values but different macro text),
> causing build errors/warnings (duplicate definitions) in both
> samples/watch_queue/watch_test.c and samples/vfs/test-statx.c.
> (<linux/fcntl.h> is included indirecty in both programs above.)
>
> Fixes: b4fef22c2fb9 ("uapi: explain how per-syscall AT_* flags should be allocated")
> Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> ---
> Cc: Amir Goldstein <amir73il@xxxxxxxxx>
> Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> Cc: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Cc: Alexander Aring <alex.aring@xxxxxxxxx>
> Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Cc: Aleksa Sarai <cyphar@xxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: David Howells <dhowells@xxxxxxxxxx>
> CC: linux-api@xxxxxxxxxxxxxxx
> To: linux-fsdevel@xxxxxxxxxxxxxxx
> ---
> include/uapi/linux/fcntl.h | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> --- linux-next-20250819.orig/include/uapi/linux/fcntl.h
> +++ linux-next-20250819/include/uapi/linux/fcntl.h
> @@ -155,10 +155,16 @@
> * as possible, so we can use them for generic bits in the future if necessary.
> */
>
> +/*
> + * Note: This is an example of how the AT_RENAME_* flags could be defined,
> + * but the kernel has no need to define them, so leave them as comments.
> + */
> /* Flags for renameat2(2) (must match legacy RENAME_* flags). */
> +/*
> #define AT_RENAME_NOREPLACE 0x0001
> #define AT_RENAME_EXCHANGE 0x0002
> #define AT_RENAME_WHITEOUT 0x0004
> +*/
>
I find this end result a bit odd, but I don't want to suggest another variant
I already proposed one in v2 review [1] that maybe you did not like.
It's fine.
I'll let Aleksa and Christian chime in to decide on if and how they want this
comment to look or if we should just delete these definitions and be done with
this episode.
Thanks,
Amir.
[1] https://lore.kernel.org/r/CAOQ4uxjXvYBsW1Nb2HKaoUg1qi8Pkq1XKtQEbnAvMUGcp7LrZA@xxxxxxxxxxxxxx/
