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Sony Beefs up FAT for Consumer Devices
An anonymous reader points to a report at LinuxDevices which says that "Sony has created an enhanced version of the vFAT filesystem that it says works better in Linux-based consumer electronic devices with removable USB mass storage devices. Unlike vFAT, the xvFAT filesystem will not induce a kernel panic if a USB storage device is removed during a write operation, Sony says," and writes "For now, xvFAT is a patch to the Linux 2.4.20 source tree maintained by CELF, an industry group of consumer electronics giants working to improve Linux for CE devices. Sony intends to submit the filesystem for inclusion in the mainstream 2.6 Linux tree as well."
This is the same company that sues DVD decryption software authors, sues restaurant owners who's name happens to be Sony, sues people using old Sony cases for iPod mods.
So apparently it's OK to "vigorously defend their IP", while blatantly violating everybody else's. I wonder if the same big bucks and lawyers that force little people to bow to their corporate steamroller had anything to do with voiding Microsoft's patent of the FAT filesystem?
Don't misunderstand me; pulling out that particular stupid patent after all these years was a dirty stunt, and certainly deserved to get shot down, but that doesn't make Sony any cleaner. Two rabid pit bulls aren't any better than one.
Everything you've said here is correct, and I agree with you, but you haven't mentioned the fact that in general, dealing with transient filesystems is an enormously hard problem on any real OS. There is no quick fix for this.
The problem is that you have to make sure that the filesystem on disk is consistent when the media is removed --- but by the time you know that the media is being removed, it's too late to do anything!
Unix deals with this problem by simply refusing to deal with it: it requires you to dismount all filesystems before disconnecting the media. Which is fine if you're dealing with hard disks, but less fine on USB devices and floppies. (There's a good reason why most serious Unix hardware have software floppy drive eject mechanisms.)
(Unix has the particularly unpleasant issue of the unified VM and I/O system; what do you do if you want to page in a block from a file system that's gone away? Seg fault? Block until it comes back again? Wave your arms in the air and run around in small circles? Different implementations do all three...)
Windows and DOS attempt to deal with the problem by using write-through cacheing on anything it thinks is transient. This kills performance. (Try switching off write-through cacheing on your floppy disk sometime.) But even Windows wants you to dismount USB devices before removing them.
Even CP/M had a variation of this problem --- there were specific system calls to detect disk changes and discard its caches. You were supposed to call this every time your program stopped for user input. Not all programs did, which meant that if you changed disks at the wrong time, you could end up with a corrupted disk...