On Tue 25-08-20 10:11:29, yebin wrote:

Your patch certainly can fix the problem with my testcases, but I don't
think it's a good way. There are other paths that can call
do_invalidatepage , for instance block ioctl to discard and zero_range.

OK, good point! So my patch is a cleanup that stands on its own and we
should do it regardless. But I agree we need more to completely fix this.
I don't quite like the callback you've added just for this special case
(furthermore it grows size of every buffer_head and there can be lots of
those). But I agree with the general idea that we shouldn't discard buffers
that the filesystem is working with.

In fact I believe that fallocate(2) and zeroout/discard ioctls should
return EBUSY if they are run against a mounted device because with 99%
probability something went wrong and you're accidentally discarding the
wrong device. But maybe I'm wrong. I'll run this idea through other fs
developers.

								Honza

On 2020/8/24 23:51, Jan Kara wrote:

quoted

On Sat 22-08-20 16:22:16, Ye Bin wrote:

quoted

Ye Bin (2):
   ext4: Add comment to BUFFER_FLAGS_DISCARD for search code
   jbd2: Fix race between do_invalidatepage and init_page_buffers

  fs/buffer.c                 | 12 +++++++++++-
  fs/jbd2/journal.c           |  7 +++++++
  include/linux/buffer_head.h |  2 ++
  3 files changed, 20 insertions(+), 1 deletion(-)

Thanks for the good description of the problem and the analysis. I could
now easily understand what was really happening on your system. I think the
problem should be fixed differently through - it is a problem of
block_write_full_page() that it invalidates buffers while JBD2 is working
with them. Attached patch should also fix the problem. Can you please test
whether it fixes your testcase as well? Thanks!

								Honza

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