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osdep: Add qemu_lock_fd and qemu_unlock_fd

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They are wrappers of POSIX fcntl "file private locking", with a
convenient "try lock" wrapper implemented with F_OFD_GETLK.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Fam Zheng 2017-05-03 00:35:54 +08:00 committed by Kevin Wolf
parent fc0932fdcf
commit 13461fdba6
2 changed files with 51 additions and 0 deletions
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3
include/qemu/osdep.h
View File

@ -341,6 +341,9 @@ 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);
int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive);
#if defined(__HAIKU__) && defined(__i386__)
#define FMT_pid "%ld"

48
util/osdep.c
View File

@ -140,6 +140,54 @@ 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,
};
ret = fcntl(fd, F_OFD_SETLK, &fl);
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);
}
int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive)
{
#ifdef F_OFD_SETLK
int ret;
struct flock fl = {
.l_whence = SEEK_SET,
.l_start = start,
.l_len = len,
.l_type = exclusive ? F_WRLCK : F_RDLCK,
};
ret = fcntl(fd, F_OFD_GETLK, &fl);
if (ret == -1) {
return -errno;
} else {
return fl.l_type == F_UNLCK ? 0 : -EAGAIN;
}
#else
return -ENOTSUP;
#endif
}
#endif
/*