On Thu, Jul 02, 2020 at 07:13:08AM +0200, Markus Armbruster wrote:
> Daniel P. Berrangé <berra...@redhat.com> writes:
>
> > Create a "qemu_open_err" method which does the same as "qemu_open",
> > but with a "Error **errp" for error reporting. There should be no
> > behavioural difference for existing callers at this stage.
> >
> > Signed-off-by: Daniel P. Berrangé <berra...@redhat.com>
> > ---
> > include/qemu/osdep.h | 1 +
> > util/osdep.c | 71 +++++++++++++++++++++++++++++++++++---------
> > 2 files changed, 58 insertions(+), 14 deletions(-)
> >
> > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> > index 0d26a1b9bd..e41701a308 100644
> > --- a/include/qemu/osdep.h
> > +++ b/include/qemu/osdep.h
> > @@ -483,6 +483,7 @@ int qemu_madvise(void *addr, size_t len, int advice);
> > int qemu_mprotect_rwx(void *addr, size_t size);
> > int qemu_mprotect_none(void *addr, size_t size);
> >
> > +int qemu_open_err(const char *name, int flags, Error **errp, ...);
> > int qemu_open(const char *name, int flags, ...);
> > int qemu_close(int fd);
> > int qemu_unlink(const char *name);
> > diff --git a/util/osdep.c b/util/osdep.c
> > index 4bdbe81cec..450b3a5da3 100644
> > --- a/util/osdep.c
> > +++ b/util/osdep.c
> > @@ -22,6 +22,7 @@
> > * THE SOFTWARE.
> > */
> > #include "qemu/osdep.h"
> > +#include "qapi/error.h"
> >
> > /* Needed early for CONFIG_BSD etc. */
> >
> > @@ -282,7 +283,7 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t
> > len, bool exclusive)
> > /*
> > * Opens a file with FD_CLOEXEC set
> > */
> > -int qemu_open(const char *name, int flags, ...)
> > +static int qemu_openv(const char *name, int flags, Error **errp, va_list
> > ap)
> > {
> > int ret;
> > int mode = 0;
> > @@ -297,24 +298,31 @@ int qemu_open(const char *name, int flags, ...)
> >
> > fdset_id = qemu_parse_fdset(fdset_id_str);
> > if (fdset_id == -1) {
> > + error_setg(errp, "Unable to parse fdset %s", name);
> > errno = EINVAL;
> > return -1;
> > }
> >
> > fd = monitor_fdset_get_fd(fdset_id, flags);
> > if (fd < 0) {
> > + error_setg_errno(errp, -fd, "Unable acquire FD for %s flags
> > %x",
> > + name, flags);
> > errno = -fd;
> > return -1;
> > }
> >
> > dupfd = qemu_dup_flags(fd, flags);
> > if (dupfd == -1) {
> > + error_setg_errno(errp, errno, "Unable dup FD for %s flags %x",
> > + name, flags);
> > return -1;
> > }
> >
> > ret = monitor_fdset_dup_fd_add(fdset_id, dupfd);
> > if (ret == -1) {
> > close(dupfd);
> > + error_setg(errp, "Unable save FD for %s flags %x",
> > + name, flags);
> > errno = EINVAL;
> > return -1;
> > }
> > @@ -324,11 +332,7 @@ int qemu_open(const char *name, int flags, ...)
> > #endif
> >
> > if (flags & O_CREAT) {
> > - va_list ap;
> > -
> > - va_start(ap, flags);
> > mode = va_arg(ap, int);
> > - va_end(ap);
> > }
> >
> > #ifdef O_CLOEXEC
> > @@ -340,25 +344,64 @@ int qemu_open(const char *name, int flags, ...)
> > }
> > #endif
> >
> > + if (ret == -1) {
> > + const char *action = "open";
> > + if (flags & O_CREAT) {
> > + action = "create";
> > + }
> > #ifdef O_DIRECT
> > - if (ret == -1 && errno == EINVAL && (flags & O_DIRECT)) {
> > - int newflags = flags & ~O_DIRECT;
> > + if (errno == EINVAL && (flags & O_DIRECT)) {
> > + int newflags = flags & ~O_DIRECT;
> > # ifdef O_CLOEXEC
> > - ret = open(name, newflags | O_CLOEXEC, mode);
> > + ret = open(name, newflags | O_CLOEXEC, mode);
> > # else
> > - ret = open(name, newflags, mode);
> > + ret = open(name, newflags, mode);
> > # endif
> > - if (ret != -1) {
> > - close(ret);
> > - error_report("file system does not support O_DIRECT");
> > - errno = EINVAL;
> > + if (ret != -1) {
> > + close(ret);
> > + error_setg(errp, "Unable to %s '%s' flags 0x%x: "
> > + "filesystem does not support O_DIRECT",
> > + action, name, flags);
> > + if (!errp) {
>
> If the caller ignores errors, ...
>
> > + error_report("file system does not support O_DIRECT");
>
> ... we report this error to stderr (but not any of the other ones).
> This is weird. I figure you do it here to reproduce the weirdness of
> qemu_open() before the patch. Goes back to
>
> commit a5813077aac7865f69b7ee46a594f3705429f7cd
> Author: Stefan Hajnoczi <stefa...@redhat.com>
> Date: Thu Aug 22 11:29:03 2013 +0200
>
> osdep: warn if open(O_DIRECT) on fails with EINVAL
>
> Print a warning when opening a file O_DIRECT fails with EINVAL. This
> saves users a lot of time trying to figure out the EINVAL error, which
> is typical when attempting to open a file O_DIRECT on Linux tmpfs.
>
> Reported-by: Deepak C Shetty <deepa...@linux.vnet.ibm.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> Reviewed-by: Eric Blake <ebl...@redhat.com>
>
> The message isn't phrased as a warning, though. Should it use
> warn_report()? Stefan?
I was really in two minds as to whether to keep this error_report or
not. It depends depends on whether any other callers of qemu_open
still need it. In fact if nothing outside the block layer uses O_DIRECT
then I think we can remove the error_report line.
> > +int qemu_open_err(const char *name, int flags, Error **errp, ...)
> > +{
> > + va_list ap;
> > + int rv;
> > +
> > + va_start(ap, errp);
> > + rv = qemu_openv(name, flags, errp, ap);
> > + va_end(ap);
> > +
> > + return rv;
> > +}
> > +
> > +int qemu_open(const char *name, int flags, ...)
> > +{
> > + va_list ap;
> > + int rv;
> > +
> > + va_start(ap, flags);
> > + rv = qemu_openv(name, flags, NULL, ap);
> > + va_end(ap);
> > +
> > + return rv;
> > +}
>
> I'd rename this to qemu_open_with_bad_error_messages().
My goal was to avoid a big bang conversion of all callers.
>
> For better ones, callers can use
>
> if (qemu_open_err(name, flags, &err) < 0) {
> error_report_err(err);
> ...
> }
>
> or, where the error is fatal
>
> qemu_open_err(name, flags, &error_fatal);
>
> If you prefer not to rename it now, please add a comment why it should
> not be used in new code, and existing uses should be converted.
>
> If you rename, call the new one qemu_open().
Maybe it is better to rename upfront though, instead of waiting till
everything uses the qemu_open_err and then renaming back to qemu_open.
Regards,
Daniel
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