> What's the answer? Easy and obvious, just (try to) overwrite the contents > of a file by request from userspace. Filesystems do know where on the > storage they have written the contents to, so why not just let them delete > that stuff themself instead? It's almost unbelievable that this was not > already done in the past 30 years. Easy, obvious and wrong 8) The last PC hard disks that were defined to do what you told them where ST-506 MFM and RLL devices. IDE disks are basically 'disk emulators', SSDs vastly more so. An IDE disk can do what it likes with your I/O so long as your requests and returns are what the standard expects. So for example if you zero a sector its perfectly entitled to set a bit in a master index of zeroed sectors. You can't tell the difference and externally it looks like an ST506 disc with extensions. Even simple devices may well move blocks around to deal with bad blocks, or high usage spots to avoid having to keep rewriting the tracks either side. An SSD internally has minimal relationship to a disc. If you have the tools to write a file, write over it, discard it and then dump the flash chips you'll probably find it's still there. If you plug a Raspberry Pi into a modern large hard disk, the chances are the smarter end of the cable is the disk. Alan -- 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
