On Mon, Oct 12, 2015 at 03:41:35PM -0600, Ross Zwisler wrote: > On Mon, Oct 12, 2015 at 10:14:43AM +1100, Dave Chinner wrote: > > On Fri, Oct 09, 2015 at 04:02:08PM -0600, Ross Zwisler wrote: > > > Add locking to ensure that DAX faults are isolated from ext2 operations > > > that modify the data blocks allocation for an inode. This is intended to > > > be analogous to the work being done in XFS by Dave Chinner: > > > > > > http://www.spinics.net/lists/linux-fsdevel/msg90260.html > > > > > > Compared with XFS the ext2 case is greatly simplified by the fact that ext2 > > > already allocates and zeros new blocks before they are returned as part of > > > ext2_get_block(), so DAX doesn't need to worry about getting unmapped or > > > unwritten buffer heads. > > > > > > This means that the only work we need to do in ext2 is to isolate the DAX > > > faults from inode block allocation changes. I believe this just means that > > > we need to isolate the DAX faults from truncate operations. > > > > Why limit this just to DAX page faults? > > Yep, I see that XFS uses the same locking to protect both DAX and non-DAX > faults. I'll add this protection to non-DAX ext2 faults as well. > > One quick question - it looks like that dax_pmd_fault() only grabs the > pagefault lock and updates the file_update_time() if the FAULT_WRITE_FLAG is > set. In xfs_filemap_pfn_mkwrite(), though, these two steps are taken for read > faults as well. Is this intentional? xfs_filemap_pfn_mkwrite() should not be called for read faults. We've already had to have a fault that maps the page to pfn for us to get a pfn based fault, and hence that code is correct. Or are you talking about xfs_filemap_pmd_fault()? In which case, I refer you to the commit log and it should be obvious that it was committed without me even looking at it. I have another patch in my current series for 4.4 that will fix this. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- 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
