On Fri 27-10-17 08:43:01, Christoph Hellwig wrote:

On Thu, Oct 26, 2017 at 05:48:04PM +0200, Jan Kara wrote:

quoted

But now that I look at XFS implementation again, it misses handling
of VM_FAULT_NEEDSYNC in xfs_filemap_pfn_mkwrite() (ext4 gets this right).
I'll fix this by using __xfs_filemap_fault() for xfs_filemap_pfn_mkwrite()
as well since it mostly duplicates it anyway... Thanks for inquiring!

My first patches move xfs_filemap_pfn_mkwrite to use __xfs_filemap_fault,
but that didn't work.  Wish I'd remember why, though.

Maybe due to the additional check on IS_DAX(inode) in __xfs_filemap_fault()
which could do the wrong thing if per-inode DAX flag is switched? Because
otherwise __xfs_filemap_fault(vmf, PE_SIZE_PTE, true) does exactly the same
thing as xfs_filemap_pfn_mkwrite() did.

If we do care about per-inode DAX flag switching, I can just fixup
xfs_filemap_pfn_mkwrite() but my understanding was that we ditched the idea
at least until someone comes up with a reliable way to implement that...

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