linux-ext4 - Re: Make huge files strictly contiguous (fallocate, bigalloc, e4defrag...)

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Date:	Sun, 20 Apr 2014 21:38:30 +0200
From:	Contact <neitsab@....fr>
To:	Theodore Ts'o <tytso@....edu>
CC:	Lukáš Czerner <lczerner@...hat.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: Make huge files strictly contiguous (fallocate, bigalloc, e4defrag...)

Le dim. 20 avril 2014 21:01:46 CEST, Theodore Ts'o a écrit :
>
> This requires recompiling e2fsprogs using the tip of the maint branch,
> as I had suggested earlier (and which you had ruled out because you
> didn't want to build your own e2fsprogs from source).
>
Thanks, that explains why I wasn't able to find this option in regular 
e2fsprogs.

> Once you do this, and you put the following in
>
> 	hugefiles = {
> 		features = extent,huge_file,flex_bg,uninit_bg,dir_nlink,extra_isize,^resize_inode,sparse_super2
> 		hash_alg = half_md4
> 		num_backup_sb = 0
> 		packed_meta_blocks = 1
> 		flex_bg_size = 262144
> 		inode_ratio = 4194304
> 		make_hugefiles = 1
> 		hugefiles_dir = /boot
> 		hugefiles_name = contig-files
> 		hugefiles_digits = 1
> 		hugefiles_size = 256M
> 		num_hugefiles = 3
> 	}
>
> Using the sparse_super2 feature and setting num_backup_sb=0 disables
> the backup superblocks.  Then setting flex_bg_size to a very large
> value (262144 in this case), will force all of the allocation bitmaps
> and inodetables to the very beginning of the file system.
>
The tip and stanza look very useful though, I'll reconsider retrieving 
and compiling maint branch to try, thanks.

> Note that because this uses a new compat feature, "sparse_super2", if
> you use the new mke2fs to create such a file system, you will also
> need to make sure the file system is checked using a version of e2fsck
> that supports this new feature as well.  No kernel changes are
> required to support this, though.
>
Any plans to get this feature into master at some point in the 
development?

--Bastien

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