> On Jun 10, 2021, at 1:23 AM, Christophe Leroy <christophe.le...@csgroup.eu> > wrote: > > With a config having PAGE_SIZE set to 256K, BTRFS build fails > with the following message > > include/linux/compiler_types.h:326:38: error: call to > '__compiletime_assert_791' declared with attribute error: BUILD_BUG_ON > failed: (BTRFS_MAX_COMPRESSED % PAGE_SIZE) != 0 > > BTRFS_MAX_COMPRESSED being 128K, BTRFS cannot support platforms with > 256K pages at the time being. > > There are two platforms that can select 256K pages: > - hexagon > - powerpc > > Disable BTRFS when 256K page size is selected. >
We’ll have other subpage blocksize concerns with 256K pages, but this BTRFS_MAX_COMPRESSED #define is arbitrary. It’s just trying to have an upper bound on the amount of memory we’ll need to uncompress a single page’s worth of random reads. We could change it to max(PAGE_SIZE, 128K) or just bump to 256K. -chris
