On Thu, Dec 25, 2008 at 10:52:48AM -0500, Theodore Tso wrote: > On Thu, Dec 25, 2008 at 12:35:35PM -0200, Alberto Bertogli wrote: > > - What is the reason behind the j_inode check in jbd2_journal_create()? > > jbd2_journal_create was only designed for creating inode-based > journals, and it's a deprecated function that will likely be removed > soon. Thanks, I didn't know that! > > - Does mke2fs -O journal_dev creates a journal that jbd2_journal_load() > > is supposed to read without any knowledge of ext2/3/4 stuff? If not, > > how can I create such a journal? I'll be looking at the e2fsprogs > > code for the answer to this question later today (I haven't looked at > > it yet). > > mke2fs -O journal_dev creates an external journal, but when you create > a filesystem, you need to specify need to specify location of the > external journal. Hence: > > mke2fs -O journal_dev /dev/extern_journal_dev > mke2fs -t ext4 -J device=/dev/extern_journal_dev /dev/filesystem_dev > > As I said in my last message. I've tested it, and it works Just Fine. I think I'm not explaining myself correctly. My code has _nothing_ to do with ext2/3/4 (or any other filesystem) whatsoever. I'm not using the journal as an external one for a filesystem. I want to use it to be able to do atomic writes in my own, filesystem independant, device-mapper code. After what you told me (both this and the deprecation of jbd2_journal_create()), I took a look at e2fsprogs' source. From what I could see, "mke2fs -O journal_dev" creates the external journal inside some ext2/3/4 structures, which caused my journal-loading code to fail (because it doesn't know about ext stuff). So, I wrote a small "mkjournal" utility that creates a journal on the block device without any ext2/3/4 stuff. It's based on e2fsprogs' mkjournal.c, except it doesn't have any ext2 stuff. And it worked great! I'm now able to load the journal just fine. Thanks a lot for all the help! Alberto -- 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
