Am 22.06.2016 um 09:34 hat Fam Zheng geschrieben: > On Fri, 06/17 14:12, Kevin Wolf wrote: > > Am 03.06.2016 um 10:48 hat Fam Zheng geschrieben: > > > They are wrappers of POSIX fcntl "file private locking". > > > > > > Signed-off-by: Fam Zheng <[email protected]> > > > --- > > > 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 6937694..749214a 100644 > > > --- a/include/qemu/osdep.h > > > +++ b/include/qemu/osdep.h > > > @@ -280,6 +280,8 @@ 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 9a7a439..085ed52 100644 > > > --- a/util/osdep.c > > > +++ b/util/osdep.c > > > @@ -137,6 +137,35 @@ 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); > > > + return ret == -1 ? -errno : 0; > > > +#else > > > + return -ENOTSUP; > > > +#endif > > > +} > > > > This will return -ENOTSUP in the case that the function wasn't available > > at build time, but -EINVAL if it was available at build time but the > > kernel doesn't support it at runtime. Should we unify this? > > I'm not sure we can reliably distinguish "fcntl cmd not supported" and "fcntl > cmd supported but parameters have invalid value" out of -EINVAL.
Well, the other option is returning -EINVAL instead of -ENOTSUP in the #else branch. > Quoting the manual: > > > https://www.gnu.org/software/libc/manual/html_node/Open-File-Description-Locks.html > > > > Macro: int F_OFD_SETL > > > > EINVAL > > > > Either the lockp argument doesn’t specify valid lock information, the > > operating system kernel doesn’t support open file description locks, or > > the > > file associated with filedes doesn’t support locks. > > > > I'd expect the user to know what he's doing if he is using a kernel that is > much older than the one built QEMU, since this is relatively a very uncommon > thing to do. I'm talking about possible bugs if a caller of this function is checking for -ENOTSUP, it's easy to forget -EINVAL there. Fixing qemu isn't one of the things that we should expect even from a "user who knows what he's doing". Kevin
