On Fri, Dec 07, 2012 at 02:03:06PM -0500, Chris Mason wrote: > > That's not what happened though, and the right way forward from here is > to give the bit to the feature, maybe with a generic name like > FALLOCATE_WITHOUT_BEING_HORRIBLY_SLOW. I don't think that's a good idea, because the current name explicitly calls out the fact that we are making a tradeoff between what ***might*** be a security exposure in some cases (but which might be perfectly fine in others) for performance. Using the generic name would hide the fact that this tradeoff is being made, and the arguments (which I've never seen backed up with a specific design) is that it's possible to speed up random writes into preallocated space on a flash device without making any kind of tradeoff that might imply a security tradeoff. If indeed it is possible to speed up this particular workload without making any kind of no-hide-stale tradeoff, then we won't need the bit --- writes into fallocated space will just get faster, with or without the bit I am sure it will be possible to do this in some cases (for example if you have a device that supports persistent trim which can quickly zeroize the blocks in question), but I would be very surprised if it's possible to completely eliminate the performance degradation for all devices and workloads. (Not all storage devices support persistent trim, just for starters.) In answer's to Linus's question, the reason why people are hyperventilating so badly about this is that in some circles, revealing stale data is so horrible that anyone who even tries to suggest this should be excommunicated. The mere existence of the code, or that people are using it, horribly offends those people. (Witness how people reacted when Linus changed the default of ext3 to data=writeback many years ago in order to solve a performance problem that was impacting him and other desktop users very badly. At the time, I understood why he made that change, but I know a lot of people were horrified. These days we have a better solution which is used by ext4, but for desktop users at that time, it was a completely fair engineering choice to make.) - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
