On Thu 30-08-12 14:54:33, Ashish Sangwan wrote: > On Wed, Aug 29, 2012 at 6:47 PM, Jan Kara <jack@xxxxxxx> wrote: > > On Wed 29-08-12 14:52:22, Ashish Sangwan wrote: > >> I have a query about orphan list and truncate. > >> Currently these steps are performed in ext4_ext_truncate(): > >> a) Start journal handle. > >> b) add inode to orphan list. > >> c) i_disksize is updated and inode is mark dirty. > >> d) actual truncate happen. > >> e) remove inode from orphan list. > >> f) handle stop. > >> > >> If system crash during step d) will i_disksize is actually updated on disk? > >> AFAIK i_disksize might be updated on the journal but not on its > >> original location because the transaction is not commited yet. > > Yes, that can happen. > > > Ok, > To test it, I inserted a 10 seconds sleep between d) and e) > I created a 10MB file on new ext4 partition and tried to truncate it to 10KB. > After waiting for 10 seconds, unplug the device. > On remount, the inode was not present on the orphan list. > No matter how many times I repeat this operation, result is same. Well, this is likely because inode is small and thus the whole truncate operation fits in a single transaction. So your sleep just held the transaction with add-to-orphan operation open. Try creating a big fragmented file - like: for ((i = 0; i < 5000; i++)); do dd if=/dev/urandom of=file bs=4096 count=1 conv=notrunc seek=$((i*2)); done fsync file Then try your above experiment and you should see inode on orphan list. > After that I inserted a call to ext4_journal_restart() between step c) > and d.) and repeat the above operation. > This time the inode was present on orphan list and i_disksize was > updated (10KB) correctly too. > Is it the correct thing to do? Yes. That's expected result. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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
