On 9/7/2021 12:58 AM, Pascal Hambourg wrote:
Actually, there is a 32 bit rev level defined in the superblock. However, it doesn't distinguish much and isn't the whole story. There are also feature bits that must be supported by any software attempting to read the disk. I think you are correct that incompatible features would cause any software trying to read the disk to fail. ext4 also supports 48 bit block numbers. It is therefore probable u-boot couldn't actually read an ext4 file system if the file sizes were such that extents were used. It doesn't actually matter, because u-boot see options it doesn't recognize and won't try.Hello, Le 05/09/2021 à 18:47, J. William Campbell a écrit :AFAIK, the on disk format for ext4 is the same as ext2. If the code can read an ext2 filesystem, it can read an ext4 filesystem.I am not sure about that. AFAIK, some ext4 features such as extents create a different on-disk format than ext2 or ext3. The ext2, ext3 and ext4 Linux drivers refuse to mount an ext4 filesystem as ext2 because of unsupported features.
Good question. I think it should be. Making the boot partition as simple as possible without adding problems accessing it from "normal" software seems like a good goal. All userspace programs can access ext2 file systems with ease equal to ext4. IMHO it should be a requirement that the file system be ext2. For sure, the boot partition doesn't need 48 bit block numbers an "largefile" support. The kernel/initrd is big but not that big😁.older u-boots didn't know about ext4, so when they check the version of the filesystem they see a number that they don't understand and give up.IIUC, an ext* filesystem does not have a version number. Instead it has a collection of "features", some of which are supported only by ext4.But IMO the real point is : if ext2 is mandatory for /boot when installing with LVM, why then is it not mandatory when installing without LVM ?