From: Andreas Dilger <adilger@clusterfs.com>
To: clameter@sgi.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 14:56:02 -0600 [thread overview]
Message-ID: <20070620205602.GI5181@schatzie.adilger.int> (raw)
In-Reply-To: <20070620183014.438784820@sgi.com>
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.
> 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...
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.
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.
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.
next prev parent reply other threads:[~2007-06-20 20:56 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 [this message]
2007-06-20 21:27 ` Christoph Lameter
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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