Re: [Jfs-discussion] Truncated files after reboot

[Mikael L. <mik...@gm...>]

Hi again, I've tried to sync the file system but that does not seem to
help. I still get 0 byte files after a sync and a hard reboot.

I looked at the kernel source and found that jfs_sync_fs calls
jfs_flush_journal with wait <= 1 and jfs_syncpt with parameter hard_sync
set to 0. However, according to the comments to lmLogSync in jfs_logmgr.c
hard_sync = 1 means: "push dirty metapages out to disk".

As far as I can see this only happens when the log is closed via
lmLogShutdown which calls jfs_flush_journal(log, 2); This happens when
unmounting a rw file system, but it doesn't seem to happen for an ordinary
sync.

jfs_syncpt is also called with hard_sync = 1 from txEnd in jfs_txnmgr.c
under certain circumstances which I have not investigated yet, but I have
not found any connection to sync.

Plus, in jfs_umount_rw in jfs_umount.c the following is also done:

/*
* Make sure all metadata makes it to disk
*/
dbSync(sbi->ipbmap);
diSync(sbi->ipimap);

I'm not entirely sure what dbSync and diSync do or what the
filemap_fdatawrite(sbi->ipbmap->imapping) etc for a hard_sync=1 does. But
isn't that required to properly write everything to disk, which one would
want when doing a sync?

Perhaps a call to jfs_syncpt(log,1) in jfs_sync_fs could improve my
situation?

Regards
Mikael

2012/7/17 Mikael Liljeroth <mik...@gm...>

> Thanks for all the tips and pointers, much appreciated. I have a lot to
> learn, but I will try the fsync approach in the meantime.
>
> Regards
> Mikael
>