On Wed, 2007-10-17 at 21:09 -0700, Andrew Morton wrote: > On Thu, 11 Oct 2007 13:18:49 +0200 Jan Kara <jack@xxxxxxx> wrote: > > > With 64KB blocksize, a directory entry can have size 64KB which does not fit > > into 16 bits we have for entry lenght. So we store 0xffff instead and convert > > value when read from / written to disk. > > btw, this changes ext2's on-disk format. > Just to clarify this is only changes the directory entries format on ext2/3/4 fs with 64k block size. But currently without kernel changes ext2/3/4 does not support 64 block size. > a) is the ext2 format documented anywhere? If so, that document will > need updating. > The e2fsprogs needs to be changed to sync up with this change. Ted has a paper a while back to show ext2 disk format http://web.mit.edu/tytso/www/linux/ext2intro.html The Documentation/filesystems/ext2.txt doesn't have the ext2 format documented. That document is out-dated need to be reviewed and cleaned up. > b) what happens when an old ext2 driver tries to read and/or write this > directory entry? Do we need a compat flag for it? > > c) what happens when old and new ext3 or ext4 try to read/write this > directory entry? > Without the first patch in this series: ext2 large blocksize support patches, it fails to mount a ext2 filesystem with 64k block size. [PATCH 1/2] ext2: Support large blocksize up to PAGESIZE http://lkml.org/lkml/2007/10/1/361 So the old ext2/3/4 driver will not get access the directory entry with 64k block size format changes. Regards, Mingming > - > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
