Re: [PATCH v2 12/21] block: Move qemu_fcntl_addfl() into osdep.c

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Jun 04, 2025 at 03:28:04PM +0200, Hanna Czenczek wrote:
> Move file-posix's helper to add a flag (or a set of flags) to an FD's
> existing set of flags into osdep.c for other places to use.
> 
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
> ---
>  include/qemu/osdep.h |  1 +
>  block/file-posix.c   | 17 +----------------
>  util/osdep.c         | 18 ++++++++++++++++++
>  3 files changed, 20 insertions(+), 16 deletions(-)

I was curious if putting POSIX fcntl(2) in osdep.c would work on
Windows. It does not:

x86_64-w64-mingw32-gcc -m64 -Ilibqemuutil.a.p -I. -I.. -Iqapi -Itrace -Iui -Iui/shader -I/usr/x86_64-w64-mingw32/sys-root/mingw/include/glib-2.0 -I/usr/x86_64-w64-mingw32/sys-root/mingw/lib/glib-2.0/include -fdiagnostics-color=auto -Wall -Winvalid-pch -Werror -std=gnu11 -O2 -g -fstack-protector-strong -Wempty-body -Wendif-labels -Wexpansion-to-defined -Wformat-security -Wformat-y2k -Wignored-qualifiers -Wimplicit-fallthrough=2 -Winit-self -Wmissing-format-attribute -Wmissing-prototypes -Wnested-externs -Wold-style-declaration -Wold-style-definition -Wredundant-decls -Wshadow=local -Wstrict-prototypes -Wtype-limits -Wundef -Wvla -Wwrite-strings -Wno-missing-include-dirs -Wno-psabi -Wno-shift-negative-value -iquote . -iquote /home/stefanha/qemu -iquote /home/stefanha/qemu/include -iquote /home/stefanha/qemu/host/include/x86_64 -iquote /home/stefanha/qemu/host/include/generic -iquote /home/stefanha/qemu/tcg/i386 -mms-bitfields -mms-bitfields -mcx16 -msse2 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing -fno-common -fwrapv -fno-pie -no-pie -ftrivial-auto-var-init=zero -fzero-call-used-regs=used-gpr -mms-bitfields -mms-bitfields -pthread -mms-bitfields -MD -MQ libqemuutil.a.p/util_osdep.c.obj -MF libqemuutil.a.p/util_osdep.c.obj.d -o libqemuutil.a.p/util_osdep.c.obj -c ../util/osdep.c
../util/osdep.c: In function 'qemu_fcntl_addfl':
../util/osdep.c:625:13: error: implicit declaration of function 'fcntl' [-Wimplicit-function-declaration]
  625 |     flags = fcntl(fd, F_GETFL);
      |             ^~~~~
../util/osdep.c:625:13: error: nested extern declaration of 'fcntl' [-Werror=nested-externs]
../util/osdep.c:625:23: error: 'F_GETFL' undeclared (first use in this function)
  625 |     flags = fcntl(fd, F_GETFL);
      |                       ^~~~~~~
../util/osdep.c:625:23: note: each undeclared identifier is reported only once for each function it appears in
../util/osdep.c:629:19: error: 'F_SETFL' undeclared (first use in this function)
  629 |     if (fcntl(fd, F_SETFL, flags | flag) == -1) {
      |                   ^~~~~~~
cc1: all warnings being treated as errors

> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 96fe51bc39..49b729edc1 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -774,6 +774,7 @@ static inline void qemu_reset_optind(void)
>  }
>  
>  int qemu_fdatasync(int fd);
> +int qemu_fcntl_addfl(int fd, int flag);
>  
>  /**
>   * qemu_close_all_open_fd:
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 9b5f08ccb2..045e94d54d 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -1047,21 +1047,6 @@ static int raw_handle_perm_lock(BlockDriverState *bs,
>      return ret;
>  }
>  
> -/* Sets a specific flag */
> -static int fcntl_setfl(int fd, int flag)
> -{
> -    int flags;
> -
> -    flags = fcntl(fd, F_GETFL);
> -    if (flags == -1) {
> -        return -errno;
> -    }
> -    if (fcntl(fd, F_SETFL, flags | flag) == -1) {
> -        return -errno;
> -    }
> -    return 0;
> -}
> -
>  static int raw_reconfigure_getfd(BlockDriverState *bs, int flags,
>                                   int *open_flags, uint64_t perm, Error **errp)
>  {
> @@ -1100,7 +1085,7 @@ static int raw_reconfigure_getfd(BlockDriverState *bs, int flags,
>          /* dup the original fd */
>          fd = qemu_dup(s->fd);
>          if (fd >= 0) {
> -            ret = fcntl_setfl(fd, *open_flags);
> +            ret = qemu_fcntl_addfl(fd, *open_flags);
>              if (ret) {
>                  qemu_close(fd);
>                  fd = -1;
> diff --git a/util/osdep.c b/util/osdep.c
> index 770369831b..ce5c6a7f59 100644
> --- a/util/osdep.c
> +++ b/util/osdep.c
> @@ -613,3 +613,21 @@ int qemu_fdatasync(int fd)
>      return fsync(fd);
>  #endif
>  }
> +
> +/**
> + * Set the given flag(s) (fcntl GETFL/SETFL) on the given FD, while retaining
> + * other flags.
> + */
> +int qemu_fcntl_addfl(int fd, int flag)
> +{
> +    int flags;
> +
> +    flags = fcntl(fd, F_GETFL);
> +    if (flags == -1) {
> +        return -errno;
> +    }
> +    if (fcntl(fd, F_SETFL, flags | flag) == -1) {
> +        return -errno;
> +    }
> +    return 0;
> +}
> -- 
> 2.49.0
> 

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