Re: [PATCH 0/1] cover-letter/lz4: Implement lz4 with dynamic offset length.

Sergey Senozhatsky
2018-03-21T06:41:36Z

On (03/21/18 10:10), Maninder Singh wrote:
> (Added cover letter to avoid much text in patch description)
>
> LZ4 specification defines 2 byte offset length for 64 KB data.
> But in case of ZRAM we compress data per page and in most of
> architecture PAGE_SIZE is 4KB. So we can decide offset length based
> on actual offset value. For this we can reserve 1 bit to decide offset
> length (1 byte or 2 byte). 2 byte required only if ofsset is greater than 127,
> else 1 byte is enough.

So what happens if I compress the data on a system with no dyn
offset and then send it over the network to a machine which has
dyn offset? Or, say, I have a USB stick with a compression enabled
FS, store files on a dyn offset enabled PC and then mount that USB
stick on a machine with no dyn offset support. And vice versa.

-ss