Re: [PATCH v2] misc: Add support for Linux uio.h RWF_NOAPPEND flag

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 03/04/24 04:13, Stafford Horne wrote:
> In Linux 6.9 a new flag is added to allow for Per-io operations to
> disable append mode even if a file was opened with the flag O_APPEND.
> This is done with the new RWF_NOAPPEND flag.
> 
> This caused two test failures as these tests expected the flag 0x00000020
> to be unused.  Adding the flag definition now fixes these tests on Linux
> 6.9 (v6.9-rc1).
> 
>   FAIL: misc/tst-preadvwritev2
>   FAIL: misc/tst-preadvwritev64v2
> 
> This patch adds the flag, adjusts the test and adds details to
> documentation.
> 
> Link: https://lore.kernel.org/all/20200831153207.GO3265@brightrain.aerifal.cx/

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
> Since v1:
>  - Fix subject grammar
>  - Fix issue with build being broken due to having 2 @end vtable clauses
>    in the .texi file.
> 
> Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
> 
> As he mentioned he would be looking into it when this was mentioned in the
> LoongArch TLS patch.
> 
>    https://sourceware.org/pipermail/libc-alpha/2024-March/155323.html
> 
> This also was encountered during OpenRISC testing, and I found a fix.  This has
> been found before Linux 6.9 is actually released.  I guess we should not merge
> it to glibc until 6.9 is official.  What is the policy on this?
> 
> 
>  manual/llio.texi                       | 4 ++++
>  misc/tst-preadvwritev2-common.c        | 5 ++++-
>  sysdeps/unix/sysv/linux/bits/uio-ext.h | 1 +
>  3 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/manual/llio.texi b/manual/llio.texi
> index 0b61d491f5..fae49d1433 100644
> --- a/manual/llio.texi
> +++ b/manual/llio.texi
> @@ -1339,6 +1339,10 @@ will fail and set @code{errno} to @code{EAGAIN} if the operation would block.
>  
>  @item RWF_APPEND
>  Per-IO synchronization as if the file was opened with @code{O_APPEND} flag.
> +
> +@item RWF_NOAPPEND
> +This flag allows an offset to be honored, even if the file was opened with
> +@code{O_APPEND} flag.
>  @end vtable
>  
>  When the source file is compiled with @code{_FILE_OFFSET_BITS == 64} the
> diff --git a/misc/tst-preadvwritev2-common.c b/misc/tst-preadvwritev2-common.c
> index b5f19f002c..8e04ff7282 100644
> --- a/misc/tst-preadvwritev2-common.c
> +++ b/misc/tst-preadvwritev2-common.c
> @@ -34,8 +34,11 @@
>  #ifndef RWF_APPEND
>  # define RWF_APPEND 0
>  #endif
> +#ifndef RWF_NOAPPEND
> +# define RWF_NOAPPEND 0
> +#endif
>  #define RWF_SUPPORTED	(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT \
> -			 | RWF_APPEND)
> +			 | RWF_APPEND | RWF_NOAPPEND)
>  
>  /* Generic uio_lim.h does not define IOV_MAX.  */
>  #ifndef IOV_MAX
> diff --git a/sysdeps/unix/sysv/linux/bits/uio-ext.h b/sysdeps/unix/sysv/linux/bits/uio-ext.h
> index 7854cccef3..ead7a09156 100644
> --- a/sysdeps/unix/sysv/linux/bits/uio-ext.h
> +++ b/sysdeps/unix/sysv/linux/bits/uio-ext.h
> @@ -47,6 +47,7 @@ extern ssize_t process_vm_writev (pid_t __pid, const struct iovec *__lvec,
>  #define RWF_SYNC	0x00000004 /* per-IO O_SYNC.  */
>  #define RWF_NOWAIT	0x00000008 /* per-IO nonblocking mode.  */
>  #define RWF_APPEND	0x00000010 /* per-IO O_APPEND.  */
> +#define RWF_NOAPPEND	0x00000020 /* per-IO negation of O_APPEND */
>  
>  __END_DECLS
>