Re: [PATCH v4 3/6] util: add Error object for qemu_open_internal error reporting
On Wed, Aug 26, 2020 at 01:03:19PM +0200, Markus Armbruster wrote:
> Daniel P. Berrangé writes:
>
> > On Tue, Aug 25, 2020 at 05:14:21PM +0200, Markus Armbruster wrote:
> >> Daniel P. Berrangé writes:
> >>
> >> > Instead of relying on the limited information from errno, we can now
> >> > also provide detailed error messages.
> >>
> >> The more detailed error messages are currently always ignored, but the
> >> next patches will fix that.
> >>
> >> > Signed-off-by: Daniel P. Berrangé
> >> > ---
> >> > util/osdep.c | 21 +++--
> >> > 1 file changed, 19 insertions(+), 2 deletions(-)
> >> >
> >> > diff --git a/util/osdep.c b/util/osdep.c
> >> > index 9ff92551e7..9c7118d3cb 100644
> >> > --- a/util/osdep.c
> >> > +++ b/util/osdep.c
> >> > @@ -284,7 +284,7 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t
> >> > len, bool exclusive)
> >> > * Opens a file with FD_CLOEXEC set
> >> > */
> >> > static int
> >> > -qemu_open_internal(const char *name, int flags, mode_t mode)
> >> > +qemu_open_internal(const char *name, int flags, mode_t mode, Error
> >> > **errp)
> >> > {
> >> > int ret;
> >> >
> >> > @@ -298,24 +298,31 @@ qemu_open_internal(const char *name, int flags,
> >> > mode_t mode)
> >> >
> >> > fdset_id = qemu_parse_fdset(fdset_id_str);
> >> > if (fdset_id == -1) {
> >> > +error_setg(errp, "Could not parse fdset %s", name);
> >> > errno = EINVAL;
> >> > return -1;
> >> > }
> >> >
> >> > fd = monitor_fdset_get_fd(fdset_id, flags);
> >> > if (fd < 0) {
> >> > +error_setg_errno(errp, -fd, "Could not 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, "Could not 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, "Could not save FD for %s flags %x",
> >> > + name, flags);
> >>
> >> Can this happen?
> >
> > Well there's code in monitor_fdset_dup_fd_add that can return -1.
>
> It fails when
>
> * @fdset_id contains @dupfd
>
> @dupfd is a fresh file descriptor. If @fdset_id already contains it,
> it's stale there. That would be a programming error. Recommend to
> assert.
>
> * @fdset_id is not in @mon_fdsets
>
> monitor_fdset_get_fd() fails the same way. monitor_fdset_dup_fd_add()
> can fail that way after monitor_fdset_get_fd() succeed only if the fd
> set went away between the two. Could that happen? Would it be safe?
>
> This is the only user of monitor_fdset_dup_fd_add(). Why not remove
> the awkward failure mode by making monitor_fdset_dup_fd_add() dup the
> fd and add?
Once we push the qemu_dup call into monitor_fdset_dup_fd_add, we
might as well go the whole way and merge monitor_fdset_get_fd
into it too. So I've done that, turning 3 calls into 1.
Regards,
Daniel
--
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Re: [PATCH v4 3/6] util: add Error object for qemu_open_internal error reporting
Daniel P. Berrangé writes:
> On Tue, Aug 25, 2020 at 05:14:21PM +0200, Markus Armbruster wrote:
>> Daniel P. Berrangé writes:
>>
>> > Instead of relying on the limited information from errno, we can now
>> > also provide detailed error messages.
>>
>> The more detailed error messages are currently always ignored, but the
>> next patches will fix that.
>>
>> > Signed-off-by: Daniel P. Berrangé
>> > ---
>> > util/osdep.c | 21 +++--
>> > 1 file changed, 19 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/util/osdep.c b/util/osdep.c
>> > index 9ff92551e7..9c7118d3cb 100644
>> > --- a/util/osdep.c
>> > +++ b/util/osdep.c
>> > @@ -284,7 +284,7 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t
>> > len, bool exclusive)
>> > * Opens a file with FD_CLOEXEC set
>> > */
>> > static int
>> > -qemu_open_internal(const char *name, int flags, mode_t mode)
>> > +qemu_open_internal(const char *name, int flags, mode_t mode, Error **errp)
>> > {
>> > int ret;
>> >
>> > @@ -298,24 +298,31 @@ qemu_open_internal(const char *name, int flags,
>> > mode_t mode)
>> >
>> > fdset_id = qemu_parse_fdset(fdset_id_str);
>> > if (fdset_id == -1) {
>> > +error_setg(errp, "Could not parse fdset %s", name);
>> > errno = EINVAL;
>> > return -1;
>> > }
>> >
>> > fd = monitor_fdset_get_fd(fdset_id, flags);
>> > if (fd < 0) {
>> > +error_setg_errno(errp, -fd, "Could not 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, "Could not 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, "Could not save FD for %s flags %x",
>> > + name, flags);
>>
>> Can this happen?
>
> Well there's code in monitor_fdset_dup_fd_add that can return -1.
It fails when
* @fdset_id contains @dupfd
@dupfd is a fresh file descriptor. If @fdset_id already contains it,
it's stale there. That would be a programming error. Recommend to
assert.
* @fdset_id is not in @mon_fdsets
monitor_fdset_get_fd() fails the same way. monitor_fdset_dup_fd_add()
can fail that way after monitor_fdset_get_fd() succeed only if the fd
set went away between the two. Could that happen? Would it be safe?
This is the only user of monitor_fdset_dup_fd_add(). Why not remove
the awkward failure mode by making monitor_fdset_dup_fd_add() dup the
fd and add?
>> > errno = EINVAL;
>> > return -1;
>> > }
>> > @@ -336,6 +343,16 @@ qemu_open_internal(const char *name, int flags,
>> > mode_t mode)
>> > }
>> > #endif /* ! O_CLOEXEC */
>> >
>> > +if (ret == -1) {
>> > +const char *action = "open";
>> > +if (flags & O_CREAT) {
>> > +action = "create";
>> > +}
>> > +error_setg_errno(errp, errno, "Could not %s '%s' flags 0x%x",
>> > + action, name, flags);
>>
>> Not a good user experience:
>>
>> Could not open '/etc/shadow' flags 0x0: Permission denied
>>
>> Better:
>>
>> Could not open '/etc/shadow' for reading: Permission denied
>>
>> Are you sure flags other than the access mode (O_RDONLY, O_WRONLY,
>> O_RDWR) must be included in the error message?
>
> It was the flags other than access mode that I was thinking were
> more important to log. I'm ambivalent htough, so can drop the
> flags if it is thought to be overkill.
Hexadecimal flags are borderline useless even for developers: to make
sense of them, you have to grep -R /usr/include/. For mere mortals,
they are confusing in addition to useless.
>> If you must report flags in hexadecimal, then please reporting them more
>> consistently. Right now you have
>>
>> for %s flags 0x%x
>> '%s' flags %x
>>
>> Perhaps '%s' with flags 0x%x
>>
>> > +}
>> > +
>> > +
>> > return ret;
>> > }
>> >
>> > @@ -352,7 +369,7 @@ int qemu_open_old(const char *name, int flags, ...)
>> > }
>> > va_end(ap);
>> >
>> > -ret = qemu_open_internal(name, flags, mode);
>> > +ret = qemu_open_internal(name, flags, mode, NULL);
>> >
>> > #ifdef O_DIRECT
>> > if (ret == -1 && errno == EINVAL && (flags & O_DIRECT)) {
>>
>>
>
> Regards,
> Daniel
Re: [PATCH v4 3/6] util: add Error object for qemu_open_internal error reporting
On Tue, Aug 25, 2020 at 05:14:21PM +0200, Markus Armbruster wrote:
> Daniel P. Berrangé writes:
>
> > Instead of relying on the limited information from errno, we can now
> > also provide detailed error messages.
>
> The more detailed error messages are currently always ignored, but the
> next patches will fix that.
>
> > Signed-off-by: Daniel P. Berrangé
> > ---
> > util/osdep.c | 21 +++--
> > 1 file changed, 19 insertions(+), 2 deletions(-)
> >
> > diff --git a/util/osdep.c b/util/osdep.c
> > index 9ff92551e7..9c7118d3cb 100644
> > --- a/util/osdep.c
> > +++ b/util/osdep.c
> > @@ -284,7 +284,7 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t
> > len, bool exclusive)
> > * Opens a file with FD_CLOEXEC set
> > */
> > static int
> > -qemu_open_internal(const char *name, int flags, mode_t mode)
> > +qemu_open_internal(const char *name, int flags, mode_t mode, Error **errp)
> > {
> > int ret;
> >
> > @@ -298,24 +298,31 @@ qemu_open_internal(const char *name, int flags,
> > mode_t mode)
> >
> > fdset_id = qemu_parse_fdset(fdset_id_str);
> > if (fdset_id == -1) {
> > +error_setg(errp, "Could not parse fdset %s", name);
> > errno = EINVAL;
> > return -1;
> > }
> >
> > fd = monitor_fdset_get_fd(fdset_id, flags);
> > if (fd < 0) {
> > +error_setg_errno(errp, -fd, "Could not 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, "Could not 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, "Could not save FD for %s flags %x",
> > + name, flags);
>
> Can this happen?
Well there's code in monitor_fdset_dup_fd_add that can return -1.
>
> > errno = EINVAL;
> > return -1;
> > }
> > @@ -336,6 +343,16 @@ qemu_open_internal(const char *name, int flags, mode_t
> > mode)
> > }
> > #endif /* ! O_CLOEXEC */
> >
> > +if (ret == -1) {
> > +const char *action = "open";
> > +if (flags & O_CREAT) {
> > +action = "create";
> > +}
> > +error_setg_errno(errp, errno, "Could not %s '%s' flags 0x%x",
> > + action, name, flags);
>
> Not a good user experience:
>
> Could not open '/etc/shadow' flags 0x0: Permission denied
>
> Better:
>
> Could not open '/etc/shadow' for reading: Permission denied
>
> Are you sure flags other than the access mode (O_RDONLY, O_WRONLY,
> O_RDWR) must be included in the error message?
It was the flags other than access mode that I was thinking were
more important to log. I'm ambivalent htough, so can drop the
flags if it is thought to be overkill.
>
> If you must report flags in hexadecimal, then please reporting them more
> consistently. Right now you have
>
> for %s flags 0x%x
> '%s' flags %x
>
> Perhaps '%s' with flags 0x%x
>
> > +}
> > +
> > +
> > return ret;
> > }
> >
> > @@ -352,7 +369,7 @@ int qemu_open_old(const char *name, int flags, ...)
> > }
> > va_end(ap);
> >
> > -ret = qemu_open_internal(name, flags, mode);
> > +ret = qemu_open_internal(name, flags, mode, NULL);
> >
> > #ifdef O_DIRECT
> > if (ret == -1 && errno == EINVAL && (flags & O_DIRECT)) {
>
>
Regards,
Daniel
--
|: https://berrange.com -o-https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o-https://fstop138.berrange.com :|
|: https://entangle-photo.org-o-https://www.instagram.com/dberrange :|
Re: [PATCH v4 3/6] util: add Error object for qemu_open_internal error reporting
Daniel P. Berrangé writes:
> Instead of relying on the limited information from errno, we can now
> also provide detailed error messages.
The more detailed error messages are currently always ignored, but the
next patches will fix that.
> Signed-off-by: Daniel P. Berrangé
> ---
> util/osdep.c | 21 +++--
> 1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/util/osdep.c b/util/osdep.c
> index 9ff92551e7..9c7118d3cb 100644
> --- a/util/osdep.c
> +++ b/util/osdep.c
> @@ -284,7 +284,7 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len,
> bool exclusive)
> * Opens a file with FD_CLOEXEC set
> */
> static int
> -qemu_open_internal(const char *name, int flags, mode_t mode)
> +qemu_open_internal(const char *name, int flags, mode_t mode, Error **errp)
> {
> int ret;
>
> @@ -298,24 +298,31 @@ qemu_open_internal(const char *name, int flags, mode_t
> mode)
>
> fdset_id = qemu_parse_fdset(fdset_id_str);
> if (fdset_id == -1) {
> +error_setg(errp, "Could not parse fdset %s", name);
> errno = EINVAL;
> return -1;
> }
>
> fd = monitor_fdset_get_fd(fdset_id, flags);
> if (fd < 0) {
> +error_setg_errno(errp, -fd, "Could not 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, "Could not 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, "Could not save FD for %s flags %x",
> + name, flags);
Can this happen?
> errno = EINVAL;
> return -1;
> }
> @@ -336,6 +343,16 @@ qemu_open_internal(const char *name, int flags, mode_t
> mode)
> }
> #endif /* ! O_CLOEXEC */
>
> +if (ret == -1) {
> +const char *action = "open";
> +if (flags & O_CREAT) {
> +action = "create";
> +}
> +error_setg_errno(errp, errno, "Could not %s '%s' flags 0x%x",
> + action, name, flags);
Not a good user experience:
Could not open '/etc/shadow' flags 0x0: Permission denied
Better:
Could not open '/etc/shadow' for reading: Permission denied
Are you sure flags other than the access mode (O_RDONLY, O_WRONLY,
O_RDWR) must be included in the error message?
If you must report flags in hexadecimal, then please reporting them more
consistently. Right now you have
for %s flags 0x%x
'%s' flags %x
Perhaps '%s' with flags 0x%x
> +}
> +
> +
> return ret;
> }
>
> @@ -352,7 +369,7 @@ int qemu_open_old(const char *name, int flags, ...)
> }
> va_end(ap);
>
> -ret = qemu_open_internal(name, flags, mode);
> +ret = qemu_open_internal(name, flags, mode, NULL);
>
> #ifdef O_DIRECT
> if (ret == -1 && errno == EINVAL && (flags & O_DIRECT)) {
[PATCH v4 3/6] util: add Error object for qemu_open_internal error reporting
Instead of relying on the limited information from errno, we can now
also provide detailed error messages.
Signed-off-by: Daniel P. Berrangé
---
util/osdep.c | 21 +++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/util/osdep.c b/util/osdep.c
index 9ff92551e7..9c7118d3cb 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -284,7 +284,7 @@ int qemu_lock_fd_test(int fd, int64_t start, int64_t len,
bool exclusive)
* Opens a file with FD_CLOEXEC set
*/
static int
-qemu_open_internal(const char *name, int flags, mode_t mode)
+qemu_open_internal(const char *name, int flags, mode_t mode, Error **errp)
{
int ret;
@@ -298,24 +298,31 @@ qemu_open_internal(const char *name, int flags, mode_t
mode)
fdset_id = qemu_parse_fdset(fdset_id_str);
if (fdset_id == -1) {
+error_setg(errp, "Could not parse fdset %s", name);
errno = EINVAL;
return -1;
}
fd = monitor_fdset_get_fd(fdset_id, flags);
if (fd < 0) {
+error_setg_errno(errp, -fd, "Could not 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, "Could not 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, "Could not save FD for %s flags %x",
+ name, flags);
errno = EINVAL;
return -1;
}
@@ -336,6 +343,16 @@ qemu_open_internal(const char *name, int flags, mode_t
mode)
}
#endif /* ! O_CLOEXEC */
+if (ret == -1) {
+const char *action = "open";
+if (flags & O_CREAT) {
+action = "create";
+}
+error_setg_errno(errp, errno, "Could not %s '%s' flags 0x%x",
+ action, name, flags);
+}
+
+
return ret;
}
@@ -352,7 +369,7 @@ int qemu_open_old(const char *name, int flags, ...)
}
va_end(ap);
-ret = qemu_open_internal(name, flags, mode);
+ret = qemu_open_internal(name, flags, mode, NULL);
#ifdef O_DIRECT
if (ret == -1 && errno == EINVAL && (flags & O_DIRECT)) {
--
2.26.2
