On Sat, Feb 13, 2016 at 01:38:49PM +1100, Dave Chinner wrote: > On Fri, Feb 12, 2016 at 12:03:20PM -0700, Ross Zwisler wrote: > > On Thu, Feb 11, 2016 at 01:43:04PM +0100, Jan Kara wrote: > > > On Wed 10-02-16 13:48:54, Ross Zwisler wrote: > > > > 3) In filemap_write_and_wait() and filemap_write_and_wait_range(), continue > > > > the writeback in the case that DAX is enabled but we only have a nonzero > > > > mapping->nrpages. As with 1) and 2), I believe this is necessary to > > > > properly writeback metadata changes. If this sounds wrong, please let me > > > > know and I'll get more info. > > > > > > And I'm surprised here as well. If there are dax_mapping() inodes that have > > > pagecache pages, then we have issues with radix tree handling as well. So > > > how come dax_mapping() inodes have pages attached? If it is about block > > > device inodes, then I find it buggy, that S_DAX gets set for such inodes > > > when filesystem is mounted on them because in such cases we are IMO asking > > > for data corruption sooner rather than later... > > > > I think I've figured this one out, at least partially. > > > > For ext2 the issues I was seeing were due to the fact that directory inodes > > have S_DAX set, but have dirty page cache pages. In testing with > > generic/002, I see two ext2 inodes with S_DAX trying to do a writeback while > > they have dirty page cache pages. The first has i_ino=2, which is the > > EXT2_ROOT_INO. > .... > > As far as I can see, XFS does not have these issues - returning immediately > > having done just the DAX writeback in xfs_vm_writepages() lets all my xfstests > > pass. > > XFS will not have issues because it does not dirty directory inodes > at the VFS level, nor does it use the page cache for directory data. > However, looking at the code I think it does still set S_DAX on > directory inodes, which it shouldn't be doing. > > I've got a couple of fixes I need to do in this area - hopefully > I'll get it done on Monday. Cool. I've got a quick patch that stops S_DAX from being set on everything but regular inodes for ext2 and ext4. This solved a lot of my xfstests failures. Even after that I'm seeing two last failures with ext4 - I'll keep working on those. - Ross -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>