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Re: [Qemu-devel] [PATCH v8 04/36] osdep: Add qemu_lock_fd and qemu_unloc
From: |
Max Reitz |
Subject: |
Re: [Qemu-devel] [PATCH v8 04/36] osdep: Add qemu_lock_fd and qemu_unlock_fd |
Date: |
Fri, 21 Oct 2016 23:15:30 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 30.09.2016 14:09, Fam Zheng wrote:
> They are wrappers of POSIX fcntl "file private locking".
>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
> include/qemu/osdep.h | 2 ++
> util/osdep.c | 29 +++++++++++++++++++++++++++++
> 2 files changed, 31 insertions(+)
>
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 9e9fa61..f773f49 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -286,6 +286,8 @@ int qemu_close(int fd);
> #ifndef _WIN32
> int qemu_dup(int fd);
> #endif
> +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 06fb1cf..b85a490 100644
> --- a/util/osdep.c
> +++ b/util/osdep.c
> @@ -140,6 +140,35 @@ static int qemu_parse_fdset(const char *param)
> {
> return qemu_parse_fd(param);
> }
> +
> +static int qemu_lock_fcntl(int fd, int64_t start, int64_t len, int fl_type)
> +{
> +#ifdef F_OFD_SETLK
> + int ret;
> + struct flock fl = {
> + .l_whence = SEEK_SET,
> + .l_start = start,
> + .l_len = len,
> + .l_type = fl_type,
> + };
> + do {
> + ret = fcntl(fd, F_OFD_SETLK, &fl);
> + } while (ret == -1 && errno == EINTR);
Can EINTR happen? My fcntl() man page claims it's only possible with
F(_OFD)_SETLKW.
Max
> + return ret == -1 ? -errno : 0;
> +#else
> + return -ENOTSUP;
> +#endif
> +}
> +
> +int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive)
> +{
> + 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);
> +}
> #endif
>
> /*
>
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