On Fri, 6 Aug 2010, Dmitry Monakhov wrote: > Lukas Czerner <lczerner@xxxxxxxxxx> writes: > > > On Fri, 6 Aug 2010, Lukas Czerner wrote: > > > >> On Fri, 6 Aug 2010, Dmitry Monakhov wrote: > >> > >> > Lukas Czerner <lczerner@xxxxxxxxxx> writes: > >> > > >> > > Hi, all > >> > > > >> > > because people were worried about possibly long stalls appearing > >> > > when FITRIM ioctl is working, I have changed the FITRIM interface > >> > > as Dimitry suggested. Now you can choose whether to trim whole > >> > > file system or just a part of it, resp. you can specify the range > >> > > of Bytes to trim. > >> > Agree with whole patch-set, except minor note for ext4'th path. > >> > Please feel free to add > >> > Reviewed-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx> to the series > >> > > >> > The only thing what is still not obvious for me is that, there are > >> > several types of discard request possible > >> > 1) Simple discard > >> > 2) Secure discard which was proposed here http://lkml.org/lkml/2010/6/24/71 > >> > Should we specify which type should be used in ioctl flags? > >> > But i hope that we can just stick maximum security scenario > >> > Use secure discard if possible. > >> > >> First of all, thanks for you review Dimitry. And second, to be honest I > >> am not entirely familiar with the Secure discard implementation. Right > >> now it just doing the simple discard like "send TRIM command", so it > >> does work just for devices which supports it. I suppose we can just > >> check blk_queue_discard() at some level and then decide whether to do > >> simple discard (TRIM), or secure discard "Write zeroes", when the device > >> does not support TRIM - if it is what you mean by secure discard. > >> > >> Regards > >> -Lukas > >> > > > > When I am thinking about this, it may not be a bad idea to create a > > completely new ioctl for this purpose of "zeroing all free space". We > > do the trimming for completely different reasons, and the "secure" > Actually you may be right here. > For example it is usual to give some one an usb stick, > and always assumes what USB stick is WhatYouSeeIsWhatYouGet storage. > but this is obviously not true, a man now has full access to that > device, so stale data is almost transparently available. > Off course i can use SECRM but it has runtime overhead. > So i can easily call SECDISCARD (even in emulation mode) before umount > in order to be on safe side and then share my USB stick without any > fears. > > > thing is just an side effect, so we probably should not mix it together. > > > > The new ioclt (FISECER ?) and FITRIM can use the same infrastructure in > > ext3/4, but we should add a flag to distinguish what we need to do - > > TRIM or secure erase. What do you think ? > Or we can just add a behavior flags filed > DISCARD :will works only for SDD and return ENOTSUPP for others > SECURE_DEL :will guarantee that data will be zeroed on success. > > DISCARD -> (simple discard) send discard requests > SECURE_DEL -> (simple emulation) write free space with zeroes > (DISCARD|SECURE_DEL) -> send discards request with secure flag enabled. Ok, so lets finish this simple discard thing first and then, when there will be a "real" interest in this we can do something about it. Thanks, Dimitry. -Lukas > > > > Regards > > -lukas > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
