[syslinux] 3.36-pre2 without msdos filesystem

[H. Peter Anvin]

Tomas M wrote:

> 
> I'm happy you were able to track it down and fix it.
> 
> BTW: Is there any particular reason to run syslinux on unmounted 
> filesystem only? (As you mentioned in previous mail.)
> 
> I can't see this IMPORTANT fact anywhere in documentation 
> (syslinux.doc), moreover it works for me to run 'syslinux /dev/whatever' 
> while the device is already mounted read-write.
> 

Well, it's one of those things that wouldn't have been mattered until 
recently, because you simply couldn't have done it.

Earlier versions of Linux would simply have rejected the attempt to 
mount it, so it wouldn't have mattered.  Current versions allow a 
filesystem to be mounted more than once, but syslinux assumes the 
filesystem is quiescent.

There is no doubt the documentation is in shambles, and have been for 13 
years.

> I believe syslinux only modifies boot sector (after copying 
> ldlinux.sys), so it shouldn't cause any problems IMHO.

It's probably less destructive on the current version, as it only 
patches ldlinux.sys and is pretty careful about syncing excessively; 
earlier versions patch the root directory, and if you have any activity 
in the filesystem you would have a multiple-write problem.

It's still not a guarantee that the page cache and the block cache don't 
end up stepping on each other.

The boot sector in FAT is also the superblock, which means that (unlike, 
for example, ext2), it's not safe to assume that a mounted filesystem 
itself won't poke the boot sector.

	-hpa