Messages in this thread | | | Date | Wed, 20 Jun 2007 14:27:22 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [36/37] Large blocksize support for ext2 |
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On Wed, 20 Jun 2007, Andreas Dilger wrote:
> On Jun 20, 2007 11:29 -0700, clameter@sgi.com wrote: > > This adds support for a block size of up to 64k on any platform. > > It enables the mounting filesystems that have a larger blocksize > > than the page size. > > Might have been good to CC the ext2/3/4 maintainers here? I definitely > have been waiting for a patch like this for ages (so definitely no > objection from me), but there are a few caveats before this will work > on ext2/3/4.
The CC list is already big so I thought those would be monitoring linux-fsdevel.
> > Hmmm... Actually there is nothing additional to be done after the earlier > > cleanup of the macros. So just modify copyright. > > It is NOT possible to have 64kB blocksize on ext2/3/4 without some small > changes to the directory handling code. The reason is that an empty 64kB > directory block would have a rec_len == (__u16)2^16 == 0, and this would > cause an error to be hit in the filesystem. What is needed is to put > 2 empty records in such a directory, or to special-case an impossible > value like rec_len = 0xffff to handle this. > > There was a patch to fix the 64kB blocksize directory problem, but it > hasn't been merged anywhere yet seeing as there wasn't previously a > patch to allow larger blocksize...
mke2fs allows to specify a 64kb blocksize and IA64 can run with 64kb PAGE_SIZE. So this is a bug in ext2fs that needs to be fixed regardless.
> Having 32kB blocksize has no problems that I'm aware of. Also, I'm not > sure how it happened, but ext2 SHOULD have an explicit check (as > ext3/4 does) limiting it to EXT2_MAX_BLOCK_SIZE. Otherwise it appears > that there would be no error reported if the superblock reports e.g. 16MB > blocksize, and all kinds of things would break.
mke2fs fails for blocksizes > 64k so you are safe there. I'd like to see that limit lifted?
> There shouldn't be a problem with increasing EXT{2,3,4}_MAX_BLOCK_SIZE to > 32kB (AFAIK), but I haven't looked into this in a while.
I'd love to see such a patch. That is also useful for arches that have PAGE_SIZE > 4kb without this patchset.
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