29.03.2019 13:12, Kevin Wolf wrote: > Am 29.03.2019 um 10:53 hat Vladimir Sementsov-Ogievskiy geschrieben: >> 28.03.2019 21:40, Kevin Wolf wrote: >>> Am 28.03.2019 um 08:21 hat Vladimir Sementsov-Ogievskiy geschrieben: >>>> bdrv_replace_child() calls bdrv_check_perm() with error_abort on >>>> loosening permissions. However file-locking operations may fail even >>>> in this case, for example on NFS. And this leads to Qemu crash. >>>> >>>> Let's ignore such errors, as we do already on permission update commit >>>> and abort. >>>> >>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> >>> >>> I think this would better be fixed in block.c code so that unlock never >>> fails for any block driver. >> >> Hmm. We now only have one .bdrv_check_perm handler - raw_check_perm. And >> in this particular case, yes, the only thing we can do is ignoring error >> and do not fail on loosening permissions.. >> >> If we have more drivers with this callback, what should be the common >> behavior? >> >> Do you propose to ignore .bdrv_check_perm errors in common case? >> >> Isn't it better to require, that .bdrv_check_perm handler do not fail on >> loosening permissions, and abort if it fail in this case, like it actually >> works after this patch? > > Maybe an assertion in the common code is actually better, yes. > > I do think that the common behaviour we want is to ignore > .bdrv_check_perm errors for unlock, but it might be surprising for > drivers that .bdrv_set_perm is called when .bdrv_check_perm failed. So > we need the drivers to be aware of the problem anyway. > > Back to your patch: Why do you need to call raw_check_lock_bytes() in > the unlock case? We don't acquire any new permissions and hold the locks > for everything, so nobody else should have taken a conflicting lock. >
Hmm.. it check not same arguments, so I didn't drop it as raw_apply_lock_bytes. On the other hand, the only meaning of this raw_check_lock_bytes, is that we'll print error if it come (when it should not). Seems OK for me to drop it too and just return 0 immediately. -- Best regards, Vladimir
