Re: [Qemu-devel] [PATCH v5 08/27] osdep: Add qemu_lock_fd and qemu_unlock_fd

[Max Reitz <mreitz@redhat.com>]

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On 17.05.2016 09:35, Fam Zheng wrote:
> They are wrappers of POSIX fcntl "file private locking".
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  include/qemu/osdep.h |  2 ++
>  util/osdep.c         | 31 +++++++++++++++++++++++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 1e3221c..81913a7 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -265,6 +265,8 @@ int qemu_madvise(void *addr, size_t len, int advice);
>  
>  int qemu_open(const char *name, int flags, ...);
>  int qemu_close(int fd);
> +int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive);
> +int qemu_unlock_fd(int fd, int64_t start, int64_t len);
>  
>  #if defined(__HAIKU__) && defined(__i386__)
>  #define FMT_pid "%ld"
> diff --git a/util/osdep.c b/util/osdep.c
> index d56d071..9e5d7fa 100644
> --- a/util/osdep.c
> +++ b/util/osdep.c
> @@ -236,6 +236,37 @@ int qemu_close(int fd)
>      return close(fd);
>  }
>  
> +static int qemu_lock_fcntl(int fd, int64_t start, int64_t len, int fl_type)
> +{
> +#ifdef F_OFD_SETLK
> +    struct flock fl = (struct flock) {

The (struct flock) can be omitted here (since this is an
initialization), but that's up to you.

> +        .l_whence  = SEEK_SET,

One space too many?

> +        /* Locking byte 1 avoids interfereing with virtlockd. */

*interfering or *interference

But apart from that: This comment seems completely misplaced here. I
guess it's supposed to be in raw-posix.c instead (or just wherever
you're calling qemu_{un,}lock_fd()).

> +        .l_start = start,
> +        .l_len = len,
> +        .l_type = fl_type,
> +    };
> +    if (fcntl(fd, F_OFD_SETLK, &fl) == -1) {
> +        return -errno;
> +    } else {
> +        return 0;
> +    }
> +#else
> +    return -ENOTSUP;
> +#endif
> +}
> +
> +int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive)
> +{
> +

Superfluous empty line.

Max

> +    return qemu_lock_fcntl(fd, start, len, exclusive ? F_WRLCK : F_RDLCK);
> +}
> +
> +int qemu_unlock_fd(int fd, int64_t start, int64_t len)
> +{
> +    return qemu_lock_fcntl(fd, start, len, F_UNLCK);
> +}
> +
>  /*
>   * A variant of write(2) which handles partial write.
>   *
> 



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