On Wed, Oct 30, 2019 at 12:39:18PM +0100, Jan Kara wrote:
> On Wed 30-10-19 12:26:52, Jan Kara wrote:
> > On Wed 30-10-19 13:00:24, Matthew Bobrowski wrote:
> > > On Tue, Oct 29, 2019 at 07:34:01PM -0400, Theodore Y. Ts'o wrote:
> > > > On Tue, Oct 29, 2019 at 07:31:59PM -0400, Theodore Y. Ts'o wrote:
> > > > > Hi Matthew, it looks like there are a number of problems with this
> > > > > patch series when using the ext3 backwards compatibility mode (e.g.,
> > > > > no extents enabled).
> > > > >
> > > > > So the following configurations are failing:
> > > > >
> > > > > kvm-xfstests -c ext3 generic/091 generic/240 generic/263
> > >
> > > This is one mode that I didn't get around to testing. Let me take a
> > > look at the above and get back to you.
> >
> > If I should guess, I'd start looking at what that -ENOTBLK fallback from
> > direct IO ends up doing as we seem to be hitting that path...
>
> Hum, actually no. This write from fsx output:
>
> 24( 24 mod 256): WRITE 0x23000 thru 0x285ff (0x5600 bytes)
>
> should have allocated blocks to where the failed write was going (0x24000).
> But still I'd expect some interaction between how buffered writes to holes
> interact with following direct IO writes... One of the subtle differences
> we have introduced with iomap conversion is that the old code in
> __generic_file_write_iter() did fsync & invalidate written range after
> buffered write fallback and we don't seem to do that now (probably should
> be fixed regardless of relation to this bug).
After performing some debugging this afternoon, I quickly realised
that the fix for this is rather trivial. Within the previous direct
I/O implementation, we passed EXT4_GET_BLOCKS_CREATE to
ext4_map_blocks() for any writes to inodes without extents. I seem to
have missed that here and consequently block allocation for a write
wasn't performing correctly in such cases.
Also, I agree, the fsync + page cache invalidation bits need to be
implemented. I'm just thinking to branch out within
ext4_buffered_write_iter() and implement those bits there i.e.
...
ret = generic_perform_write();
if (ret > 0 && iocb->ki_flags & IOCB_DIRECT) {
err = filemap_write_and_wait_range();
if (!err)
invalidate_mapping_pages();
...
AFAICT, this would be the most appropriate place to put it? Or, did
you have something else in mind?
--<M>--
