Re: [PATCH] btrfs: disable zstd support for i386-pc

[David Sterba]

On Tue, Nov 05, 2019 at 09:19:59AM +0000, Michael Chang wrote:
> The zstd support in btrfs has dependenciy to zstd module and core.img
> grows its size significantly to 75KB on my system. The resulted image
> cannot be installed into btrfs bootloader area in the size of 64KB and
> eventually fails with following message.
> 
> /usr/sbin/grub-install: warning: your core.img is unusually large.  It
> won't fit in the embedding area.
> /usr/sbin/grub-install: error: filesystem `btrfs' doesn't support
> blocklists.
> 
> The patch disabled the zstd support of btrfs in pc-bios platform to
> avoid the regression. The resulting size is 56KB, albeit a bit too close
> to the 64KB but works. This is simple workaround until a proper fix
> landed upstream.

So combination zstd+btrfs+i386-pc never worked? Removing support for
zstd could lead to unbootable system, but if that has never worked
before it'd be ok to make the build conditional.

Looking at zstd code, does not seem to be easy to squeeze the asm to
something like 64-56=8K.