Re: [PATCH v3 2/3] fs: record I_DIRTY_TIME even if inode already has I_DIRTY_INODE

On Sat 20-08-22 23:14:37, Christoph Hellwig wrote:

On Tue, Aug 16, 2022 at 01:21:24PM +0200, Jan Kara wrote:

quoted

2) I_DIRTY_TIME flag passed to ->dirty_inode() callback. This is admittedly
bit of a hack. Currently XFS relies on the fact that the only time its
->dirty_inode() callback needs to do anything is when VFS decides it is
time to writeback timestamps and XFS detects this situation by checking for
I_DIRTY_TIME in inode->i_state. Now to fix the race, we need to first clear
I_DIRTY_TIME in inode->i_state and only then call the ->dirty_inode()
callback (otherwise timestamp update can get lost). So the solution I've
suggested was to propagate the information "timestamp update needed" to XFS
through I_DIRTY_TIME in flags passed to ->dirty_inode().

Maybe we should just add a separate update_lazy_time method to make this
a little more clear?

Yes, we could do that if people prefer this. Although I'd say that good
documentation at the place in __mark_inode_dirty() where this gets used and
in documentation of .dirty_inode might clear the confusion as well.

								Honza
-- 
Jan Kara [off-list ref]
SUSE Labs, CR