| Message ID | 20200821172105.608752-4-berrange@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | block: improve error reporting for unsupported O_DIRECT | expand |
Daniel P. Berrangé <berrange@redhat.com> 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 <berrange@redhat.com> > --- > 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)) {
On Tue, Aug 25, 2020 at 05:14:21PM +0200, Markus Armbruster wrote: > Daniel P. Berrangé <berrange@redhat.com> 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 <berrange@redhat.com> > > --- > > 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
Daniel P. Berrangé <berrange@redhat.com> writes: > On Tue, Aug 25, 2020 at 05:14:21PM +0200, Markus Armbruster wrote: >> Daniel P. Berrangé <berrange@redhat.com> 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 <berrange@redhat.com> >> > --- >> > 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
On Wed, Aug 26, 2020 at 01:03:19PM +0200, Markus Armbruster wrote: > Daniel P. Berrangé <berrange@redhat.com> writes: > > > On Tue, Aug 25, 2020 at 05:14:21PM +0200, Markus Armbruster wrote: > >> Daniel P. Berrangé <berrange@redhat.com> 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 <berrange@redhat.com> > >> > --- > >> > 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
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)) {
Instead of relying on the limited information from errno, we can now also provide detailed error messages. Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- util/osdep.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)