On Sat, Nov 26, 2016 at 08:20:48PM -0800, Eric Biggers wrote: > > I guess I'm okay with that, since struct fscrypt_policy won't have any padding > bytes because its members are all bytes. Plus it's marked __packed, though I > think that was a mistake given that the struct isn't stored on disk directly. > It wouldn't have mattered if wasn't marked __packed, since the first four fields are __u8, and the master_key_descriptor is a 4 byte aligned __u8 array of size 8. The use of __packed in the fscrypt code came from Michael, and I suspect it's more of a Microsoft thing, since his previous experience was as the architect for Bitlocker. It's actually pretty rare that we use __packed in Linux kernel sources in general, and in ext4 specifically. Personally, I tend to depend on __uNN declaration and various assumptions that we make about "sane" packing rules which are assumed by the kernel. See how the on-disk ext4 superblock is defined; that's not the only place where we make assumptions about sane structure packing, and anyone who tried porting Linux to a 18-bit or 36-bit architecture would have lots of other problems, even if a modern Linux kernel could be made small enough to fit in the memory available to a PDP-10 or a PDP-15. :-) We probably could remove a few of them, but I haven't bothered, since in general they aren't doing any harm. Cheers, - Ted -- 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
