On Wed, 24 July 2013 17:03:53 -0400, Dhaval Giani wrote:I am posting this series early in its development phase to solicit someAt this state, a good description of the format would be nice.
We are implementing transparent decompression with a focus on ext4. OneIt is not quite clear what you want to achieve here.
of the main usecases is that of Firefox on Android. Currently libxul.so
is compressed and it is loaded into memory by a custom linker on
demand. With the use of transparent decompression, we can make do
without the custom linker. More details (i.e. code) about the linker can
be found at https://github.com/glandium/faulty.lib
One approach isWhy? If it is going to only be a few applications who know the file is compressed, and read it to get decompressed data, why would it be painful? What about introducing a new flag, O_COMPR which tells the kernel, btw, we want this file to be decompressed if it can be. It can fallback to O_RDONLY or something like that? That gets rid of the chattr ugliness.
to create an empty file, chattr it to enable compression, then write
uncompressed data to it. Nothing in userspace will ever know the file
is compressed, unless you explicitly call lsattr.
If you want to follow some other approach where userspace has one
interface to write the compressed data to a file and some other
interface to read the file uncompressed, you are likely in a world of
Assuming you use the chattr approach, that pretty much comes down to
adding compression support to ext4. There have been old patches for
ext2 around that never got merged. Reading up on the problems
encountered by those patches might be instructive.