From: Christoph Lameter <clameter@sgi.com>
To: Andreas Dilger <adilger@clusterfs.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Christoph Hellwig <hch@lst.de>, Mel Gorman <mel@skynet.ie>,
William Lee Irwin III <wli@holomorphy.com>,
David Chinner <dgc@sgi.com>, Jens Axboe <jens.axboe@oracle.com>,
Badari Pulavarty <pbadari@gmail.com>,
Maxim Levitsky <maximlevitsky@gmail.com>,
linux-ext4@vger.kernel.org
Subject: Re: [36/37] Large blocksize support for ext2
Date: Wed, 20 Jun 2007 14:27:22 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0706201425050.31425@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <20070620205602.GI5181@schatzie.adilger.int>
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.
next prev parent reply other threads:[~2007-06-20 21:27 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-20 18:29 [00/37] Large Blocksize Support V4 clameter
2007-06-20 18:29 ` [01/37] Define functions for page cache handling clameter
2007-06-20 18:29 ` [02/37] Pagecache zeroing: zero_user_segment, zero_user_segments and zero_user clameter
2007-06-20 18:29 ` [03/37] Use page_cache_xxx function in mm/filemap.c clameter
2007-06-20 18:29 ` [04/37] Use page_cache_xxx in mm/page-writeback.c clameter
2007-06-20 18:29 ` [05/37] Use page_cache_xxx in mm/truncate.c clameter
2007-06-20 18:29 ` [06/37] Use page_cache_xxx in mm/rmap.c clameter
2007-06-20 18:29 ` [07/37] Use page_cache_xxx in mm/filemap_xip.c clameter
2007-06-20 18:29 ` [08/37] Use page_cache_xxx in mm/migrate.c clameter
2007-06-20 18:29 ` [09/37] Use page_cache_xxx in fs/libfs.c clameter
2007-06-20 18:29 ` [10/37] Use page_cache_xxx in fs/sync clameter
2007-06-20 18:29 ` [11/37] Use page_cache_xxx in fs/buffer.c clameter
2007-06-20 18:29 ` [12/37] Use page_cache_xxx in mm/mpage.c clameter
2007-06-20 18:29 ` [13/37] Use page_cache_xxx in mm/fadvise.c clameter
2007-06-20 18:29 ` [14/37] Use page_cache_xxx in fs/splice.c clameter
2007-06-20 18:29 ` [15/37] Use page_cache_xxx functions in fs/ext2 clameter
2007-06-20 18:29 ` [16/37] Use page_cache_xxx in fs/ext3 clameter
2007-06-20 18:29 ` [17/37] Use page_cache_xxx in fs/ext4 clameter
2007-06-20 18:29 ` [18/37] Use page_cache_xxx in fs/reiserfs clameter
2007-06-20 18:29 ` [19/37] Use page_cache_xxx for fs/xfs clameter
2007-06-20 18:29 ` [20/37] Fix PAGE SIZE assumption in miscellaneous places clameter
2007-06-20 18:29 ` [21/37] Use page_cache_xxx in drivers/block/loop.c clameter
2007-06-20 18:29 ` [22/37] Use page_cache_xxx in drivers/block/rd.c clameter
2007-06-20 18:29 ` [23/37] compound pages: PageHead/PageTail instead of PageCompound clameter
2007-06-20 18:29 ` [24/37] compound pages: Add new support functions clameter
2007-06-20 18:29 ` [25/37] compound pages: vmstat support clameter
2007-06-20 18:29 ` [26/37] compound pages: Use new compound vmstat functions in SLUB clameter
2007-06-20 18:29 ` [27/37] compound pages: Allow use of get_page_unless_zero with compound pages clameter
2007-06-20 18:29 ` [28/37] compound pages: Allow freeing of compound pages via pagevec clameter
2007-06-20 18:29 ` [29/37] Large blocksize support: Fix up reclaim counters clameter
2007-06-20 18:29 ` [30/37] Add VM_BUG_ONs to check for correct page order clameter
2007-06-20 18:29 ` [31/37] Large blocksize support: Core piece clameter
2007-06-21 0:20 ` Bob Picco
2007-06-21 5:26 ` Christoph Lameter
2007-06-20 18:29 ` [32/37] Readahead changes to support large blocksize clameter
2007-06-20 18:29 ` [33/37] Large blocksize: Compound page zeroing and flushing clameter
2007-06-20 18:29 ` [34/37] Large blocksize support in ramfs clameter
2007-06-20 20:50 ` Andreas Dilger
2007-06-20 21:29 ` Christoph Lameter
2007-06-20 18:29 ` [35/37] Large blocksize support in XFS clameter
2007-06-20 18:29 ` [36/37] Large blocksize support for ext2 clameter
2007-06-20 20:56 ` Andreas Dilger
2007-06-20 21:27 ` Christoph Lameter [this message]
2007-06-20 22:19 ` Andreas Dilger
2007-06-20 18:29 ` [37/37] Reiserfs: Fix up for mapping_set_gfp_mask clameter
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