On Wed 27-03-19 18:59:48, Al Viro wrote: > On Wed, Mar 27, 2019 at 05:58:31PM +0100, Jan Kara wrote: > > On Tue 26-03-19 04:15:10, Al Viro wrote: > > > On Mon, Mar 25, 2019 at 08:18:25PM -0700, Mark Fasheh wrote: > > > > > > > Hey Al, > > > > > > > > It's been a while since I've looked at that bit of code but it looks like > > > > Ocfs2 is syncing the inode to disk and disposing of it's memory > > > > representation (which would include the cluster locks held) so that other > > > > nodes get a chance to delete the potentially orphaned inode. In Ocfs2 we > > > > won't delete an inode if it exists in another nodes cache. > > > > > > Wait a sec - what's the reason for forcing that write_inode_now(); why > > > doesn't the normal mechanism work? I'm afraid I still don't get it - > > > we do wait for writeback in evict_inode(), or the local filesystems > > > wouldn't work. > > > > I'm just guessing here but they don't want an inode cached once its last > > dentry goes away (it makes cluster wide synchronization easier for them and > > they do play tricks with cluster lock on dentries). > > Sure, but that's as simple as "return 1 from ->drop_inode()". Right. > > There is some info in > > 513e2dae9422 "ocfs2: flush inode data to disk and free inode when i_count > > becomes zero" which adds this ocfs2_drop_inode() implementation. So when > > the last inode reference is dropped, they want to flush any dirty data to > > disk and evict the inode. But AFAICT they should be fine with flushing the > > inode from their ->evict_inode method. I_FREEING just stops the flusher > > thread from touching the inode but explicit writeback through > > write_inode_now(inode, 1) should go through just fine. > > Umm... Why is that write_inode_now() needed in either place? I agree that > moving it to ->evict_inode() ought to be safe, but what makes it necessary > in the first place? Put it another way, what dirties the data and/or > metadata without marking it dirty? Well, the inode & pages are marked dirty and they are dirty when we get to iput_final(). But if ->drop_inode() returns 1 (which normally happens only for unlinked files), we will not write out the inode in iput_final() and the dirty data just gets discarded in ->evict_inode(). OCFS2 doesn't want this so they have to write-out by hand. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
