| Message ID | 1463608420-26837-2-git-send-email-jsnow@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 05/18/2016 03:53 PM, John Snow wrote: > If you use HMP's eject but the CDROM tray is locked, you may get a > confusing error message informing you that the "tray isn't open." > > As this is the point of eject, we can do a little better and help > clarify that the tray was locked and that it (might) open up later, > so try again. > > It's not ideal, but it makes the semantics of the (legacy) eject > command more understandable to end users when they try to use it. > > Signed-off-by: John Snow <jsnow@redhat.com> > --- > blockdev.c | 51 ++++++++++++++++++++++++++++++++++++++++----------- > 1 file changed, 40 insertions(+), 11 deletions(-) Still somewhat complicated, but this time the complication is documented, and the clean <0, 0, and >0 semantics make parsing the return value a bit easier to understand. And I don't see any cleaner way to do it. Reviewed-by: Eric Blake <eblake@redhat.com>
On Wed, 05/18 17:53, John Snow wrote: > If you use HMP's eject but the CDROM tray is locked, you may get a > confusing error message informing you that the "tray isn't open." > > As this is the point of eject, we can do a little better and help > clarify that the tray was locked and that it (might) open up later, > so try again. > > It's not ideal, but it makes the semantics of the (legacy) eject > command more understandable to end users when they try to use it. > > Signed-off-by: John Snow <jsnow@redhat.com> Thanks for addressing my comments! And I like the new message a lot. Reviewed-by: Fam Zheng <famz@redhat.com>
John Snow <jsnow@redhat.com> writes: > If you use HMP's eject but the CDROM tray is locked, you may get a > confusing error message informing you that the "tray isn't open." > > As this is the point of eject, we can do a little better and help > clarify that the tray was locked and that it (might) open up later, > so try again. > > It's not ideal, but it makes the semantics of the (legacy) eject > command more understandable to end users when they try to use it. > > Signed-off-by: John Snow <jsnow@redhat.com> [...] > @@ -2327,35 +2340,36 @@ void qmp_block_passwd(bool has_device, const char *device, > aio_context_release(aio_context); > } > > -void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, > - Error **errp) > +/** > + * returns -errno on fatal error, +errno for non-fatal situations. > + * errp will always be set when the return code is negative. > + * May return +ENOSYS if the device has no tray, > + * or +EINPROGRESS if the tray is locked and the guest has been notified. > + */ Returning or testing for positive errno instead of a negative one is a fairly common error. The more we can restrict use of positive errno codes to errno itself, the less likely such errors are. Moreover, I feel fatal vs. non-fatal is not for this function to decide. It's the caller's business. I'd return -errno on any error. If you need this function to also set an error, because it can do a better job than its callers, then set it on any error. If a caller wants to suppress a certain error, it can simply free the error. Clean separation of concerns, and a simpler interface. > +static int do_open_tray(const char *device, bool force, Error **errp) > { > BlockBackend *blk; > bool locked; > > - if (!has_force) { > - force = false; > - } > - > blk = blk_by_name(device); > if (!blk) { > error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND, > "Device '%s' not found", device); > - return; > + return -ENODEV; > } > > if (!blk_dev_has_removable_media(blk)) { > error_setg(errp, "Device '%s' is not removable", device); > - return; > + return -ENOTSUP; > } > > if (!blk_dev_has_tray(blk)) { > /* Ignore this command on tray-less devices */ > - return; > + return ENOSYS; > } > > if (blk_dev_is_tray_open(blk)) { > - return; > + return 0; > } > > locked = blk_dev_is_medium_locked(blk); > @@ -2366,6 +2380,21 @@ void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, > if (!locked || force) { > blk_dev_change_media_cb(blk, false); > } > + > + if (locked && !force) { > + return EINPROGRESS; > + } > + > + return 0; > +} > + > +void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, > + Error **errp) > +{ > + if (!has_force) { > + force = false; > + } > + do_open_tray(device, force, errp); > } > > void qmp_blockdev_close_tray(const char *device, Error **errp)
On 05/20/2016 10:48 AM, Markus Armbruster wrote: > John Snow <jsnow@redhat.com> writes: > >> If you use HMP's eject but the CDROM tray is locked, you may get a >> confusing error message informing you that the "tray isn't open." >> >> As this is the point of eject, we can do a little better and help >> clarify that the tray was locked and that it (might) open up later, >> so try again. >> >> It's not ideal, but it makes the semantics of the (legacy) eject >> command more understandable to end users when they try to use it. >> >> Signed-off-by: John Snow <jsnow@redhat.com> > [...] >> @@ -2327,35 +2340,36 @@ void qmp_block_passwd(bool has_device, const char *device, >> aio_context_release(aio_context); >> } >> >> -void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, >> - Error **errp) >> +/** >> + * returns -errno on fatal error, +errno for non-fatal situations. >> + * errp will always be set when the return code is negative. >> + * May return +ENOSYS if the device has no tray, >> + * or +EINPROGRESS if the tray is locked and the guest has been notified. >> + */ > > Returning or testing for positive errno instead of a negative one is a > fairly common error. The more we can restrict use of positive errno > codes to errno itself, the less likely such errors are. > > Moreover, I feel fatal vs. non-fatal is not for this function to decide. > It's the caller's business. I'd return -errno on any error. If you > need this function to also set an error, because it can do a better job > than its callers, then set it on any error. If a caller wants to > suppress a certain error, it can simply free the error. Clean > separation of concerns, and a simpler interface. > >> +static int do_open_tray(const char *device, bool force, Error **errp) >> { >> BlockBackend *blk; >> bool locked; >> >> - if (!has_force) { >> - force = false; >> - } >> - >> blk = blk_by_name(device); >> if (!blk) { >> error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND, >> "Device '%s' not found", device); >> - return; >> + return -ENODEV; >> } >> >> if (!blk_dev_has_removable_media(blk)) { >> error_setg(errp, "Device '%s' is not removable", device); >> - return; >> + return -ENOTSUP; >> } >> >> if (!blk_dev_has_tray(blk)) { >> /* Ignore this command on tray-less devices */ >> - return; >> + return ENOSYS; >> } >> >> if (blk_dev_is_tray_open(blk)) { >> - return; >> + return 0; >> } >> >> locked = blk_dev_is_medium_locked(blk); >> @@ -2366,6 +2380,21 @@ void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, >> if (!locked || force) { >> blk_dev_change_media_cb(blk, false); >> } >> + >> + if (locked && !force) { >> + return EINPROGRESS; >> + } >> + >> + return 0; >> +} >> + >> +void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, >> + Error **errp) >> +{ >> + if (!has_force) { >> + force = false; >> + } >> + do_open_tray(device, force, errp); >> } >> >> void qmp_blockdev_close_tray(const char *device, Error **errp) It already got applied, but I can change it to your preference. (Always return an -errno and an Error, delete-and-free when we don't care about it...) --js
John Snow <jsnow@redhat.com> writes: > It already got applied, but I can change it to your preference. (Always > return an -errno and an Error, delete-and-free when we don't care about > it...) I think that would be an improvement. This is advice, not a demand :)
diff --git a/blockdev.c b/blockdev.c index 1892b8e..4bd94b7 100644 --- a/blockdev.c +++ b/blockdev.c @@ -2290,16 +2290,29 @@ exit: block_job_txn_unref(block_job_txn); } +static int do_open_tray(const char *device, bool force, Error **errp); + void qmp_eject(const char *device, bool has_force, bool force, Error **errp) { Error *local_err = NULL; + int rc; - qmp_blockdev_open_tray(device, has_force, force, &local_err); + if (!has_force) { + force = false; + } + + rc = do_open_tray(device, force, &local_err); if (local_err) { error_propagate(errp, local_err); return; } + if (rc == EINPROGRESS) { + error_setg(errp, "Device '%s' is locked and force was not specified, " + "wait for tray to open and try again", device); + return; + } + qmp_x_blockdev_remove_medium(device, errp); } @@ -2327,35 +2340,36 @@ void qmp_block_passwd(bool has_device, const char *device, aio_context_release(aio_context); } -void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, - Error **errp) +/** + * returns -errno on fatal error, +errno for non-fatal situations. + * errp will always be set when the return code is negative. + * May return +ENOSYS if the device has no tray, + * or +EINPROGRESS if the tray is locked and the guest has been notified. + */ +static int do_open_tray(const char *device, bool force, Error **errp) { BlockBackend *blk; bool locked; - if (!has_force) { - force = false; - } - blk = blk_by_name(device); if (!blk) { error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND, "Device '%s' not found", device); - return; + return -ENODEV; } if (!blk_dev_has_removable_media(blk)) { error_setg(errp, "Device '%s' is not removable", device); - return; + return -ENOTSUP; } if (!blk_dev_has_tray(blk)) { /* Ignore this command on tray-less devices */ - return; + return ENOSYS; } if (blk_dev_is_tray_open(blk)) { - return; + return 0; } locked = blk_dev_is_medium_locked(blk); @@ -2366,6 +2380,21 @@ void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, if (!locked || force) { blk_dev_change_media_cb(blk, false); } + + if (locked && !force) { + return EINPROGRESS; + } + + return 0; +} + +void qmp_blockdev_open_tray(const char *device, bool has_force, bool force, + Error **errp) +{ + if (!has_force) { + force = false; + } + do_open_tray(device, force, errp); } void qmp_blockdev_close_tray(const char *device, Error **errp)
If you use HMP's eject but the CDROM tray is locked, you may get a confusing error message informing you that the "tray isn't open." As this is the point of eject, we can do a little better and help clarify that the tray was locked and that it (might) open up later, so try again. It's not ideal, but it makes the semantics of the (legacy) eject command more understandable to end users when they try to use it. Signed-off-by: John Snow <jsnow@redhat.com> --- blockdev.c | 51 ++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 40 insertions(+), 11 deletions(-)