On Mar 18, 2006 22:01 +0900, [email protected] wrote:
> The unit of ext2/ext3_inode.i_blocks is sector(512B) and the variable
> size is 4bytes, so it limits the max file size to 2TB.
> I found that i_blocks is always counted with rounding up to the file
> system block size and does not have fractions. So we can change the
> unit of ext2/ext3_inode.i_blocks from sector to block size.
> This change extends the maximum file size as below.
>
> - Add new compatible flag "EXT2_FEATURE_INCOMPAT_LARGE_BLOCK".
> It indicates that the file size is extended.
>
> - If the flag is set in the super block, ext2_inode.i_blocks is
> translated into the number of sectors and set to i_blocks of VFS
> inode. And, if not, ext2_inode.i_blocks is passed to i_blocks
> of VFS inode as it is.
>
> - If the flag is set, the limit of the max file size defined in
> ext2_max_size() is set to block size * 2G-1(2^31-1).
Instead of breaking all filesystems that need to create large files,
the patch should instead set "i_flags | EXT2_LARGEBLK_FL" only on inodes
that are larger than 2TB and use "blocksize" i_blocks on those files.
This preserves compatibility with existing filesystems and doesn't
impose any breakage opon an existing filesystem for anyone who wants
to use this feature.
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.
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