Hi, On Monday, August 15, 2011, Jan Kara wrote: > Hello, > > On Mon 15-08-11 20:09:13, Rafael J. Wysocki wrote: > > On Monday, August 15, 2011, Jan Kara wrote: ... > > > It's not so simple as this. Ext3 relies on the mutex (the one hidden in > > > journal_lock_updates()) to make sure that new transaction cannot be started > > > while the filesystem is frozen - that's essentially what makes the > > > filesystem frozen. So if we want to get rid of the mutex we have to achieve > > > blocking by something else - ext4 uses vfs_check_frozen() in > > > ext4_journal_start(). > > > > I see. Still, freeze_bdev() may be called by user space through a syscall, > > as far as I can say, so it shouldn't leave the mutex locked. > Yes, I agree with you. That's an ugliness left over from a long time ago. > I'll have a look at fixing this... Thanks! > > > BTW, filesystem freezing never really worked for mmaped writes under > > > ext3 - ext3 would have to implement page_mkwrite() callback for that - so > > > if you want to rely on it for suspending, this will be non-trivial. > > > > At this point the purpose of freezing filesystems is basically to > > prevent XFS from deadlocking with hibernation's memory preallocation. > > For other filesystems it may or may not make a difference depending on > > their implementation of freeze/unfreeze_super(). > What's exactly the problem? Memory preallocation enters direct reclaim > and that deadlocks in the filesystem? Yes, that seems to be the case. Thanks, Rafael -- 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
