Date: Mon, 31 Oct 2005 19:53:40 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Brian Bergstrand <freebsd@classicalguitar.net> Cc: freebsd-fs@freebsd.org, Ivan Voras <ivoras@fer.hr> Subject: Re: ext2 large_file Message-ID: <20051031191139.J38757@delplex.bde.org> In-Reply-To: <46D894BD-16E0-4CBA-B40A-EEBAAC2547D2@classicalguitar.net> References: <20051030183340.B19470@geri.cc.fer.hr> <46D894BD-16E0-4CBA-B40A-EEBAAC2547D2@classicalguitar.net>
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On Sun, 30 Oct 2005, Brian Bergstrand wrote:
> I ported the FreeBSD driver to Mac OS X / Darwin a few years ago and added
> large file support in the process. Here's the patch, as you can see it's a
> rather simple patch (as long as the in core i_size member is 64bit which I
> think is true for FreeBSD):
tjr implemented it in FreeBSD almost 2 years ago:
% RCS file: /home/ncvs/src/sys/gnu/ext2fs/ext2_fs.h,v
% Working file: ext2_fs.h
% head: 1.13
% ...
% ----------------------------
% revision 1.13
% date: 2004/02/18 14:08:25; author: tjr; state: Exp; lines: +2 -1
% Add partial support for large (>4GB) files on ext2 filesystems. This
% support is partial in that it will refuse to create large files on
% filesystems that haven't been upgraded to EXT2_DYN_REV or that don't
% have the EXT2_FEATURE_RO_COMPAT_LARGE_FILE flag set in the superblock.
%
% MFC after: 2 weeks
% ----------------------------
I don't don't know if block allocation actually works for large files.
> I doubt this patch will apply cleanly as my tree has diverged from FreeBSD in
> a non-compatible way quite a while ago -- but it should give you a start:
I prefer tjr's version.
> Index: ext2_inode_cnv.c
> ===================================================================
> RCS file: /cvsroot/ext2fsx/src/gnu/ext2fs/ext2_inode_cnv.c,v
> retrieving revision 1.6
> retrieving revision 1.7
> diff -u -b -r1.6 -r1.7
> - --- ext2_inode_cnv.c 3 May 2003 23:54:39 -0000 1.6
> +++ ext2_inode_cnv.c 9 Jul 2003 23:09:24 -0000 1.7
> ...
> @@ -182,6 +214,31 @@
> raw_inode->i_uid_high = 0;
> raw_inode->i_gid_high = 0;
> }*/
> + if (S_ISREG(ip->i_mode)) {
> + ei->i_size_high = cpu_to_le32(ip->i_size >> 32);
> + if (ip->i_size > 0x7fffffffULL) {
> + struct ext2_sb_info *sb = ip->i_e2fs;
> + if (!EXT2_HAS_RO_COMPAT_FEATURE(sb,
> + EXT2_FEATURE_RO_COMPAT_LARGE_FILE) ||
> + EXT2_SB(sb)->s_es->s_rev_level == cpu_to_le32
> (EXT2_GOOD_OLD_REV)) {
> + /* First large file, add the flag to the superblock. */
Compatibility flags shouldn't be forced on IMO. Linux does it for this
flag, but this is a bug IMO. It breaks subsequent remounting r/w on
old or other kernels that don't support large files.
Changes are also needed to at least ext2_fs.h (to indicate that the kernel
supports large files), ext2_vfsops.c (to set fs_maxfilesize according to
the compatibility flag), and ext2_readwrite.c (to actually use the ifdefed
out code that checks fs_maxfilesize, and fix minor bitrot in that code).
> On Oct 30, 2005, at 11:37 AM, Ivan Voras wrote:
>
>> I recently tried to use ext2 on FreeBSD but have decided not to when I saw
>> that the support for large files is missing (and went with msdosfs
>> instead).
msdosfs is physically incapable of supporting large files. Its maximum
file size is the constant 0xffffffff.
>> Now I accidentaly noticed that large_file support is present in latest
>> NetBSD (and maybe OpenBSD). Is anyone interested in porting the support to
>> FreeBSD? :)
I prefer FreeBSD's version.
NetBSD got it 9 months ago, only a year after FreeBSD. It refuses to
create files larger than 2G-1 if the ext2fs rev number is old, and says
in a comment that Linux silently upgrades the rev number. It silently
clobbers the compat flag like Linux. Someone has an off-by-power-of-2
error -- the corresponding limit in FreeBSD is 4G-1.
Bruce
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